Examining Macroecological Patterns in Mammals: Space Use, Diet and Energetics.
Marlee Tucker
Evolution and Ecology Research Centre School of Biological, Earth and Environmental Sciences University of New South Wales Sydney, N.S.W 2052, Australia
______Thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy within the University of New South Wales September 2014 THE UNIVERSITY OF NEW SOUTH WALES Thesis/Dissertation Sheet
Surname or Family name: Tucker
First name: Marlee Other name/s: Anne
Abbreviation for degree as given in the University calendar: PhD
School: Biological, Earth and Environmental Sciences Faculty: Science
Title: Examining Macroecological Patterns in Mammals: Space Use, Diet and Energetics.
Investigating large-scale patterns in ecology, biogeography and evolution is important to aid our knowledge of species diversity. With the current natural and anthropogenic environmental changes, it is necessary to gather information that can be used for developing models of global ecosystems to assist with conservation. To achieve this, we need to establish basic ecological theories and re-examine older theories to ensure that our current understanding—which is often based on small datasets consisting of a couple of individuals or species—is applicable when expanded across communities, populations and species. The aim of this thesis was to examine the driving influences behind macroecological patterns in mammals, including spatial behaviour and foraging ecology. The investigation of spatial behaviour and foraging ecology will provide useful information on the area required by species, trophic interactions and community structure. More specifically, I was interested in how behavioural changes that have occurred following the colonisation of the marine environment has influenced patterns in home range size, predator-prey relationships and trophic level position. Using published and empirical data and comparative methodologies, I examine the effect of body size, diet, energetics and environment upon home range size, predator-prey relationships and trophic position across mammals. I identify that body mass has been the key factor driving of home range size, prey size, energetics and trophic position in mammals, explaining between 46 and 85% of the variance. However, whether a species lives within the marine or terrestrial environment has also influenced macroecological patterns, with marine mammals having home ranges 1.2 times larger, sitting 1.3 trophic levels higher and have evolved two distinct feeding strategies compared to their terrestrial counterparts. I demonstrate the ability to utilise published data to re-examine ecological theories and highlights that when developing integrative models, we need to incorporate the possibility of phylogenetic effects, a range of ecological variables, and species representative of the diversity within a group should be included. I identify the driving influences of macroecological patterns and show how living in different environments has impacted upon mammalian spatial behaviour, foraging, food web structure and energetics.
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I dedicate this thesis to my mother, Jenny, who has believed in me
since day one.
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Acknowledgements
Firstly, I would like to sincerely thank Tracey for all of your help, support and guidance throughout my PhD. I genuinely appreciate this opportunity to work with you. To Terry, a huge thank you for your invaluable assistance with statistical analyses, revisions, the crash course into phylogenetic trees/analyses and providing me a space when I had forgotten my keys! I would like to thank everyone on my panel; Alistair Poore, Adriana
Verges and Gerry Cassis, for your suggestions and input throughout my PhD.
Especially to Alistair for his statistical advice, providing feedback and for always making time to see me. Also to Angela Moles and Rob Brooks for your support and advice.
This thesis has been primarily based upon data from other researchers. The majority of the data were collected from published studies and are open access. However, I would like to acknowledge and thank Douglas Kelt (UC Davis), Dirk van Vuren (UC Davis),
Horst Bornemann (AWI), Joachim Plötz (AWI), Nick Gales (AAD), PJ Nico deBruyn
(U.Pretoria), Cheryl Tosh (U.Pretoria), Colin Southwell (AAD) and Iain Staniland (BAS) for making their datasets available to me (Chapter 2). All research related to animal handling (Chapter 2) was approved by the University of New South Wales Animal Care and Ethics Committee (08/103B and 11/112A). Some of the data used Chapter 2 were obtained from the Australian Antarctic Data Centre (IDN Node AMD/AU), a part of the
Australian Antarctic Division (Commonwealth of Australia). The data are described in the ARGOS satellite tracking record "1994 to 2000 - Antarctic Pack Ice Seals (APIS)
Survey" (Southwell, 2007). I wish to thank the personnel from the Instituto Antártico
Argentino IAA at Primavera Station in the years 2007-2011 for field work support.
Logistics support was provided by a grant from the IAA to my collaborator Alejandro
Carlini. The research (Chapters 2-5) was supported by an Australian Research Council
(ARC) grant LP0989933 awarded to my PhD supervisor Tracey Rogers.
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Thank you to everyone in the lab (both past and current) - Michaela, Jess, Tempe,
Naysa, Alicia, Kobé, Belinda, Jeff, Lisa, Tiffanie, Nadine, Marie and Joy for providing valuable advice and feedback. I have enjoyed our cake and questions sessions as well as lab discussions, workshops and the occasional fieldtrips/extreme walks.
To my fellow Beesians (Rhiannon, Habacuc, Rachel, Sam, Andy, Flo, Tom, Melanie,
Angela and Ellie, among numerous others), who have helped along the way including coffee meetings, beverages, and of course serious work involving discussion groups and workshops. A big thank you to Jonathan, with his endless wealth of knowledge, has helped immensely with the administration side of my PhD.
To my fellow Antarctic adventurers who have taught me so much and have helped to keep me safe and well: Fernando Isla, Diego Gonzalez Zevallos, Jorge Gomez, Victor
Hugo Merlo Alvarez, Jorge Augusto Mennucci, Victor Llampa, Walter Edgardo Varela,
Edgardo Hector Toso, Ricardo Ceferino Larrea, Miguel Angel Schell, Fabian Villalba,
Carla Asti, David Slip, Ben Wallis, Skye Marr-Whelan, Magnus, Nicky, Dick, Mari,
Wouter and Rod.
Thank you to my friends who have helped to keep my social skills alive, especially
Alison, Theresa, Emma, Sam, Nicole, DR and Mary. Also a big thank you to everyone on my roller derby teammates who have helped me to keep me active and sane during the last year and a half.
And last but by no means least, a huge and heartfelt thank you to my parents. You have supported and encouraged me throughout my PhD and have experienced every low and high with me; especially during the several months I was down south with no means of contact.
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Preface
Several chapters from my thesis have been published elsewhere:
Chapter 2 has been previously published as:
Tucker, M.A., Ord, T.J. & Rogers, T.L. (2014) Evolutionary predictors of mammalian home range size: body mass, diet and the environment. Global Ecology and Biogeography, 23, 1105-1114. (Appendix 1).
MAT, TLR and TJO conceived the study. MAT and TLR collected and compiled the data. MAT conducted the analyses. MAT, TJO and TLR wrote the paper.
Chapter 3 has been previously published as:
Tucker M.A. and Rogers T.L. (2014) Examining the Prey Mass of Terrestrial and Aquatic Carnivorous Mammals: Minimum, Maximum and Range. PLoS ONE 9(8): e106402. doi:10.1371/journal.pone.0106402
MAT and TLR conceived the study. MAT collected and compiled the data. MAT conducted the analyses. MAT and TLR wrote the paper.
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Abstract
Investigating large-scale patterns in ecology, biogeography and evolution is important to aid our knowledge of species diversity. With the current natural and anthropogenic environmental changes, it is necessary to gather information that can be used for developing models of global ecosystems to assist with conservation. To achieve this, we need to establish basic ecological theories and re-examine older theories to ensure that our current understanding—which is often based on small datasets consisting of a couple of individuals or species—is applicable when expanded across communities, populations and species.
The aim of this thesis was to examine the driving influences behind macroecological patterns in mammals, including spatial behaviour and foraging ecology. The investigation of spatial behaviour and foraging ecology will provide useful information on the area required by species, trophic interactions and community structure. More specifically, I was interested in how behavioural changes that have occurred following the colonisation of the marine environment has influenced patterns in home range size, predator-prey relationships and trophic level position.
Using published and empirical data and comparative methodologies, I examine the effect of body size, diet, energetics and environment upon home range size, predator-prey relationships and trophic position across mammals. I identify that body mass has been the key factor driving of home range size, prey size, energetics and trophic position in mammals, explaining between 46 and 85% of the variance. However, whether a species lives within the marine or terrestrial environment has also influenced macroecological patterns, with marine mammals having home ranges 1.2 times larger, sitting 1.3 trophic levels higher and have evolved two distinct feeding strategies compared to their terrestrial counterparts. I
1 demonstrate the ability to utilise published data to re-examine ecological theories and highlights that when developing integrative models, we need to incorporate the possibility of phylogenetic effects, a range of ecological variables, and species representative of the diversity within a group.
I identify the driving influences of macroecological patterns and show how living in different environments has impacted upon mammalian spatial behaviour, foraging, food web structure and energetics.
2
Table of Contents
Dedication ...... iv Acknowledgements ...... v Preface ...... vii Abstract...... viii Table of Contents ...... x List of Tables ...... xii List of Figures ...... xiv Appendices ...... xv
Chapter 1: General Introduction ...... 1 1.1 Body Size ...... 2 1.2 Spatial Behaviour ...... 10 1.3 Carnivory in Mammals ...... 11 1.4 Trophic Level ...... 12 1.5 Phylogenetic Data ...... 13 1.6 Phylogenetic Comparative Analyses ...... 13 1.7 Thesis Outline ...... 15
Chapter 2: Evolutionary predictors of mammalian home range size: body size, diet and the environment ...... 17 2.1 Summary ...... 17 2.2 Introduction ...... 18 2.3 Methods and Materials ...... 22 2.4 Results ...... 27 2.5 Discussion ...... 35 2.6 Conclusion ...... 39
Chapter 3: Examining the prey mass of terrestrial and aquatic carnivorous mammals: minimum, maximum and range...... 41 3.1 Summary ...... 41 3.2 Introduction ...... 42 3.3 Methods and Materials ...... 44 3.4 Results ...... 48 3.5 Discussion ...... 54 3.6 Conclusion ...... 59
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Chapter 4: The cost of carnivory revisited ...... 61 4.1 Summary ...... 61 4.2 Introduction ...... 62 4.3 Methods and Materials ...... 66 4.4 Results ...... 70 4.5 Discussion ...... 78 4.6 Conclusion ...... 84
Chapter 5: Examining predator-prey body size, trophic level and body mass across marine and terrestrial mammals ...... 85 5.1 Summary ...... 85 5.2 Introduction ...... 86 5.3 Methods and Materials ...... 89 5.4 Results ...... 91 5.5 Discussion ...... 96 5.6 Conclusion ...... 105
Chapter 6: General Discussion ...... 107 6.1 Home Range Size ...... 108 6.2 Minimum, Maximum and Range of Prey Mass ...... 109 6.3 Carnivorous Strategies ...... 110 6.4 Trophic Level ...... 112 6.5 General Findings ...... 113 6.6 Conclusion ...... 115
References ...... 116 Appendix 1 ...... 133 Appendix 2 ...... 144 Appendix 3 ...... 195 Appendix 4 ...... 203 Appendix 5 ...... 219 Appendix 6 ...... 241
Frontispiece: All silhouettes were downloaded from http://phylopic.org.
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List of Tables
Table 2.1 Model estimates and confidence intervals for the β0+βmass+βenvironment+βmethodology model across 312 mammals ...... 25
Table 2.2 Level of support for explanatory models of home range size evolution in terrestrial mammals ...... 28
Table 2.3 Level of support for explanatory models of home range size evolution in marine and terrestrial mammals ...... 31
Table 2.4 Level of support for explanatory models of home range size evolution in carnivorous mammals ...... 33
Table 3.1 Summary of the orders and families included in the study sample ...... 45
Table 3.2 Level of support for explanatory models of prey mass evolution in carnivorous mammals ...... 48
Table 3.3 Variance components analysis of prey mass across 108 carnivorous mammal species ...... 51
Table 3.4 Descriptive statistics for the prey mass distributions across 108 carnivorous mammals ...... 52
Table 3.5 Descriptive statistics for the prey mass distributions across 51 carnivorous terrestrial mammals ...... 54
Table 3.6 Descriptive statistics for the prey mass distributions across 57 carnivorous aquatic mammals ...... 54
Table 4.1 Best supported breakpoint models and associated coefficients for daily energetic intake (DEI) and daily energetic expenditure (DEE) in relation to predator mass (M) ...... 72
Table 4.2 Best supported breakpoint models and associated coefficients for prey mass (P) against predator mass (M) ...... 73
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Table 4.3 Level of support for explanatory models of prey mass of predatory mammals. Results are from phylogenetic regression analyses ...... 77
Table 5.1 Level of support for explanatory models of trophic level evolution in mammals .. 92
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List of Figures
Figure 2.1 Home range size as a function of species body mass compared for terrestrial carnivorous, herbivorous and omnivorous species (n=429 species) ...... 29
Figure 2.2 Home range size as a function of species body mass compared for carnivorous, herbivorous and omnivorous species (n=462 species) ...... 32
Figure 2.3 Carnivore home range size as a function of species body mass compared for species occupying terrestrial and marine environments (n=134 species) ...... 34
Figure 3.1 Minimum prey mass (A), maximum prey mass (B) and prey mass range (C) as a function of carnivore body mass compared for terrestrial and aquatic species ...... 50
Figure 3.2 Distributions of the minimum prey mass for (A) terrestrial carnivorous mammals and (B) aquatic carnivorous mammals, and the maximum prey mass for (C) for terrestrial carnivorous mammals and (D) for aquatic carnivorous mammals ...... 53
Figure 4.1 Estimates of (A) Daily energy intake (DEI) against carnivore body mass (n=48) and (B) daily energy expenditure (DEE) against carnivore body mass (n=27) in marine and terrestrial mammals combined ...... 71
Figure 4.2 Mean prey body mass as a function of carnivore body mass for 107 species across the marine and terrestrial environments ...... 75
Figure 5.1 (A) Trophic level as a function of species body mass compared for species occupying terrestrial and marine (n=107 species). (B) Schematic of general trophic level patterns for terrestrial mammals and marine mammals ...... 93
Figure 5.2 (A) The relationship between log10 predator-prey ratio as a function of predator trophic level, across marine and terrestrial mammals (n=107 species). (B) Examples of feeding strategies used by marine and terrestrial carnivorous mammals ...... 95
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Appendices
Appendix 1: Tucker, M.A., Ord, T.J. & Rogers, T.L. (2014) Evolutionary predictors of mammalian home range size: body mass, diet and the environment. Global Ecology and Biogeography, 23, 1105-1114...... 133
Appendix 2: Supplementary information for Chapter 2 ...... 144
Appendix 3: Tucker, M.A, and Rogers, T.L. (2014) Examining the prey mass of terrestrial and aquatic carnivorous mammals: minimum, maximum and range PLoS ONE 9(8): e106402 ...... 195
Appendix 4: Supplementary information for Chapter 3 ...... 203
Appendix 5: Supplementary information for Chapter 4 ...... 219
Appendix 6: Supplementary information for Chapter 5 ...... 241
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Chapter 1 General Introduction
Investigating large scale patterns in ecology, biogeography and evolution is important to aid our knowledge of species’ vulnerability to changing environments. Due to the current natural and anthropogenic environmental changes, it is necessary to gather information that can be used for developing models of whole ecosystems and global processes to assist with conservation. To achieve this, we need to establish ecological theories and re-examine older theories to ensure that our current understanding— which is often based on small datasets consisting of a few individuals or species—is applicable when expanded across communities, populations and species.
Macroecology uses statistical analyses to investigate the relationship between organisms and their environment at broad scales (Brown, 1995). Whilst small-scale investigations focus on a single species or on localised patterns, the focus of ecological studies is on ecological and evolutionary patterns that occur over large temporal or spatial scales (Smith & Lyons, 2011). Macroecology has enhanced our understanding of the mechanisms behind broad-scale patterns including species richness (Gotelli et al., 2009), species distribution (Pautasso et al., 2011), species-energy relationships
(Anderson & Jetz, 2005) and spatial behaviour (Jetz et al., 2004). One key area of study within macroecology is animal body size evolution and the broad effects that body size has on animal life history, ecology, abundance and assemblages (Peters,
1983; Gaston & Blackburn, 1996; Sibly & Brown, 2007; Chown & Gaston, 2010;
Cooper & Purvis, 2010; Smith & Lyons, 2011).
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Chapter 1 – Introduction
1.1 BODY SIZE
Over the past 70 million years, evolution has led to huge variation in the evolution of mammalian body sizes. Body size has undergone a large transformation resulting in a broad range of sizes, from the 20g mouse to the 2,000,000g elephant (Evans et al.,
2012). Mammals are an ideal model to examine the drivers of macroecological patterns. They are a diverse group of species that have colonised a range of habitats across the terrestrial and marine environments, and fill a variety of feeding niches
(Smith & Lyons, 2011; Price et al., 2012). Additionally, mammals have evolved a range of locomotion behaviours including running and swimming, which has aided the exploitation of these different environments and associated resource niches. For example, mammals have colonised the marine ecosystem on seven separate occasions, with five extant groups still remaining (Uhen, 2007). The successful colonisation of new environments (e.g. water) provided access to new ecological resources, but also exposure to a system with completely different physical properties.
Living in an aquatic environment has resulted in altered morphology (e.g. body shape;
Gatesy et al., 2012), physiology (e.g. increased levels of globins for more efficient oxygen transfer; Williams et al., 2008) and behaviour (e.g. altered locomotion; Gatesy et al., 2012).
A large amount of research effort has been dedicated to examining the patterns of body size in animals and attempting to tease apart the drivers behind these patterns.
There is extensive variation in body size across mammals, both temporally (going back in time) and spatially (across continents) (Smith & Lyons, 2013). It has been shown that variation in body size is influenced by a range of factors including physiology
(acquisition and allocation constraints), evolution (selection and diversification forces) and ecology (biotic and abiotic setting) (Maurer & Marquet, 2013). Physiological factors include biomechanical and thermoregulatory constraints on maximum body size
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Chapter 1 – Introduction
(Schmidt-Nielsen, 1984), and the trade-off between energy acquisition and allocation for reproduction and its effects on the shape of the body size distribution of mammals
(Brown et al., 1993). Evolutionary factors include higher extinction risk in larger mammals limiting the maximum size that can be obtained (Dial & Marzluff, 1989;
Cardillo et al., 2005) and constraints on natural selection that influence the structure of body size patterns (e.g. constraints on the ability of individuals to transform resources into offspring; Maurer, 1998). Ecological factors include competition between species or individual impacting upon minimum body size (Brown et al., 1978) and the interaction between space use, land mass area and energetic requirements impacting upon both minimum and maximum sizes (Marquet & Taper, 1998).
Several ‘rules’ have been developed in order to explain the patterns in body size across mammals. Bergmann’s rule attempts to explain one of the ‘general’ patterns in body size where individuals of a species have larger body size in colder environments
(i.e. away from the equator) (Bergmann, 1847). There have been several suggestions as to why this pattern is expected. First it was suggested that variation in body size is driven by ectothermic thermoregulation and geometric heat loss, where species with large body size have a smaller surface area to volume ratio compared to smaller species, meaning that smaller species would lose more heat per unit mass than those with larger body sizes (Mayr, 1963). However, it was later suggested that due to the greater importance of insulation and heat-conserving properties for large-bodied mammals, that pelage characteristics (i.e. hair and its insulation properties) were more important than body size (McNab, 1971; Steudel et al., 1994). The results from studies examining the validity of Bergmann’s rule suggested that the majority of mammals follow this pattern. Today Bergmann’s rule is accepted as an ecological generalisation for mammals (Ashton et al., 2000; Meiri & Dayan, 2003; Meiri, 2011).
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Chapter 1 – Introduction
Cope’s rule is another ecological generalisation related to body size and attempts to explain patterns whereby organisms within a lineage evolve towards a larger body size
(Cope, 1986). There are benefits associated with large body size including decreased predation risk, extended longevity and resistance to climatic variation or extremes
(Hone & Benton, 2005). However, the evolution of increased body size is only advantageous when these benefits outweigh the negatives (e.g. increased extinction rate, increased resource requirements and low fecundity). Cope’s rule has been demonstrated across taxa including birds, plants, insects and mammals (Kingsolver &
Pfennig, 2004).
Rensch’s rule describes sexual dimorphism in species, where the magnitude of sexual dimorphism increases with body size (Rensch, 1950). This pattern is explained by a combination of life history and energetic drivers associated with body size, and are observed in herbivorous mammals such as bovids. For example, small species such as
Kirk's dik-dik (Madoqua kirkii) live in pairs, mature rapidly at similar sizes across the sexes and males have small weaponry, compared with large species such as Spanish ibex (Capra pyrenaica) where time to maturity is slower, male weaponry and body size is larger, and polygyny increases (Jarman, 1983). In addition, a relationship has been identified between female groups size (i.e. size of herd) and the body size of males in mammals (Sibly et al., 2012). Large polygynous males tend to have larger weaponry, which means that they can outcompete smaller males for access to large groups of females (and potentially increase the number of offspring sired). This suggests that female group size is an important parameter for Rensch’s rule (Sibly et al., 2012).
The island rule describes the phenomenon of insular species (isolated on islands) evolving body sizes which differ significantly from their mainland relatives (Van Valen,
1973; Lomolino, 1985; Lomolino, 2005). For example, the Sardinian dhole
(Cynotherium sardous) had evolved towards a smaller body size compared with its
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Chapter 1 – Introduction
mainland relatives (Lyras et al., 2010). These changes in body size are thought to be driven by the reduction in predation pressure and lower competition for resources.
Measuring body size patterns between mainland and island species for birds, lizards and mammals has produced mixed results (Lomolino, 2005; Meiri et al., 2005; Raia et al., 2010). The most recent studies suggest that the island effect can be detected at the genus level for mammals, where large species have become smaller, but there was no evidence of small insular species becoming larger (Meiri et al., 2011).
There is a relationship between body size and life history traits in mammals, with large species generally having low productivity and long lifespans (slow life-history continuum) compared to small species which have high production rates and short lifespans (fast life-history continuum) (Sibly & Brown, 2007; Okie et al., 2013). This relationship between body size and life history is driven by the physiological factors impacting upon birth and death rates (e.g. mass-specific metabolic rate). Lifestyle, the interaction between physiology, ecology and anatomy, also has a substantial impact on a species’ life history (Sibly & Brown, 2007). For example, species that specialise on an abundant resource such as grazing herbivores or marine mammals often have higher production rates due to their access to abundant and reliable resources which can support higher mass-specific productivity (Okie et al., 2013). An example of how death rate impacts the life history of mammalian species is the evolution of behaviours that minimise predation. Adaptations including the evolution of flight (e.g. bats), an arboreal lifestyle (e.g. primates) or extreme body size (e.g. megaherbivores) have all increased the longevity of various species due to the reduced predation risk associated with these adaptations, resulting in a lower mass-specific productions rate (Sibly & Brown, 2007).
Birth rate is another driver impacting mammal life history, where the size and frequency of litters has been shaped by a range of factors including body mass constraints and offspring success rates (Sibly & Brown, 2009). Species with large body mass tend to produce large single offspring (or few large offspring) compared with smaller mammals
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Chapter 1 – Introduction
that produce small and numerous offspring. Species that produce numerous offspring face greater predation risk and have evolved behaviours to minimise this risk. For example, species that produce large litters often utilise a burrow which provides protection for the offspring from predation (e.g. lagomorphs). In comparison, species that experience high exposure to predation (e.g. pinnipeds), or those that need to transport their young (e.g. primates) often produce few or single offspring. Marsupials provide an interesting example as they can alter their reproductive capabilities according to the resource availability. For example, kangaroos and wallabies can pause the development of the embryo when environmental conditions are poor (e.g. a drought) and then can continue the development process when conditions have improved (Clark & Poole, 1967).
There have been extensive investigations into the relationship between body size and abundance (Damuth, 1981; Damuth, 1993; Marquet et al., 1995; Ernest et al., 2003a;
White et al., 2007). There are four main measures of abundance including global size– density relationships (GSDR), local size-density relationships (LSDR), individual size distributions (ISD) and cross-community scaling relationships (CCSR) (White et al.,
2007). GSDRs are one of the most studied relationships and is a measure of body size and species population densities calculated from global aggregates (White et al.,
2007). GSDRs demonstrate that population densities decrease with increasing body mass because of underlying energetic processes such as resource use and availability, energy transfer between trophic levels and metabolic constraints (Damuth, 1981). This has been deemed the energy-equivalence rule (EER) because as population density declines with increasing body mass, individual energy demands of populations increase with body mass, resulting in the energy use of local populations to be approximately independent of body size (Nee et al., 1991). However, there is debate over whether the EER is a valid ‘rule’ and if global patterns in abundance are actually driven by resources and/or energetics because resources are driven by local
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Chapter 1 – Introduction
processes, not a global process (Blackburn & Gaston, 1999; Isaac et al., 2013). It is currently thought that both ecological and evolutionary drivers have had a role in
GSDRs (Damuth, 2007; Isaac et al., 2013).
It is well established that metabolic rate, whether it be basal, field or maximal metabolic rate, increases with body size (Nagy, 1987; Karasov, 1992; Ernest et al., 2003b; Nagy,
2005; Clarke et al., 2010). The metabolic theory of ecology (MTE) describes how metabolism varies with body size and temperature, and is used to link ecological patterns and processes to various constraints placed upon individuals (e.g. biological, physical and chemical) (Brown et al., 2004a; Humphries & McCann, 2014). Patterns explained range from life history traits such as life span, to population interactions including patterns of species diversity, and ecosystem processes such as biomass production (Brown et al., 2004b; Humphries & McCann, 2014). Body size accounts for a large portion of the variation in metabolism (in addition to temperature), which further demonstrates the fundamental importance of size on ecology and biology. An example of this is the relationship between body size, metabolism and animal behaviour. Across animal taxa, including mammals, birds, fish and invertebrates, it has been demonstrated that variation in migration distance can be explained by metabolic rate and therefore the energetic costs of migration (Hein et al., 2012), where flying animals generally travel further than swimming and walking animals of a similar body mass
(Hein et al., 2012).
Behavioural impacts of body size can be observed in the foraging behaviour of animals. In herbivorous mammals, body size influences diet type and distribution
(Hopcraft et al., 2012). When herbivores are small, they tend to feed on high quality resources and are found in areas of low predation risk, compared to large herbivores that feed on resources of mixed quality and in areas of mixed predation risk (Clauss et al., 2003; Hopcraft et al., 2012; Clauss et al., 2013). These patterns explain why
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Chapter 1 – Introduction
herbivore assemblages generally consist of species with varying body sizes to minimise the competition between species while maximising the available energy. The foraging and escape behaviour of animals is also influenced by body size. An example is the reaction time and response of an individual to approaching heterospecific individuals of differing sizes. In some species, such as the Yarrow's Spiny Lizard
(Sceloporus jarrovii) and Striped Plateau Lizard (Sceloporus virgatus), when the approaching individual is larger than the individual being approached, this will invoke a fear response (i.e. the individual being approached will flee), but when the approaching species is smaller, the individual being approached will wait and attack (assuming the approaching species to be prey; Cooper & Stankowich, 2010). Also, when mammals reach a certain size (e.g. elephants or giraffes), predation risk often decreases because it is too energetically expensive and often dangerous for predators to attack. However, there are exceptions with the juveniles of these large species still susceptible to predation, as well as the threat that humans pose to all mammals due to technological advances (i.e. guns).
There are numerous questions which need to be addressed about the evolution of body mass and the effects of body mass on behaviours and traits of animals. One of these questions is whether there is a general rule or a single process that is driving the broad-scale macroecological patterns we see in mammals. Body size is a fundamental trait for a broad suite of patterns including metabolic rate, longevity, life history traits and spatial patterns (Jetz et al., 2004; Sibly & Brown, 2007; Litchman et al., 2009;
Shattuck & Williams, 2010). Understanding allometric patterns and how they have evolved, will not only enhance our current knowledge of ecological theories (from individuals and their environment to entire ecosystems), but will also aid the development of models to predict how these patterns may change in the future
(Hendriks, 2007; Freckleton & Jetz, 2009).
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Chapter 1 – Introduction
For mammals experiencing environmental changes that are altering their habitats and resources, it is necessary to gain an understanding of how these changes are influencing the mammal guild. Animal extinction risk is the focus of many current investigations (Bromham et al., 2012; Hanna & Cardillo, 2013; Dulvy et al., 2014;
McCain & King, 2014; Murray et al., 2014), with investigations encompassing a wide range of measurable traits or processes including life history traits, longevity, geographic range and ecosystem structure. Life history traits fall within a fast-slow continuum (Bielby et al., 2007) and species with traits at the slower end of this continuum (low reproductive rates) have a higher risk of extinction, both historically and at present (Johnson, 2002; García et al., 2008). As life history traits are often inherited from common ancestors, these traits are often similar among species that belong to specific taxa, meaning that extinction risk can be similar across related taxa (Davidson et al., 2012). Geographic range is another factor influencing the vulnerability of animals, with species restricted to small ranges highly susceptible to changes (e.g. anthropogenic impacts) within that range (Ceballos & Ehrlich, 2002; Laliberte & Ripple,
2004; Davidson et al., 2009). The trophic structure and productivity of an environment can influence the structure of an ecosystem and the susceptibility of the species within this system to extinction (Worm & Duffy, 2003). For example, species at higher trophic levels have higher extinction threats (e.g. carnivores; Borrvall et al., 2000; Duffy, 2003).
Additionally, it has been identified that the majority of models that predict extinction risk in mammals tend to treat all species as equally likely to respond to environmental changes (Moritz et al., 2008; McCain & Colwell, 2011). It was further demonstrated that this is an unrealistic assumption due to the body size and activity time of a species mediating their response to climate change (McCain & King, 2014). It is likely that other predictors, such as the physical environment, energetic requirements and diet will influence a species response to changes in their ecosystem. Through the examination of basic ecological theories of space use, feeding strategies and trophic structure, we
9
Chapter 1 – Introduction
can gather key information such as the drivers behind these macroecological patterns.
We can then incorporate this information into management plans and strategies, as well as providing base information for more complicated global models such as correlates of mammal extinction (Cardillo et al., 2008) or latitudinal gradients in diversity (Brown, 2014).
In this thesis, I have focused upon investigating spatial behaviour (home range) and foraging ecology (predator-prey relationships and trophic patterns) of mammals, all of which provide useful information on the area required by species, trophic interactions, and community structure.
1.2 SPATIAL BEHAVIOUR
Spatial behaviour provides information on how species interact with their environment
(Börger et al., 2006a). It is necessary to gain an understanding of the areas utilised and required by species if we wish to predict how environmental changes will impact mammalian species. A method used to characterise spatial behaviour is home range, which is the area covered by an individual during activities that allow it to survive and reproduce (Burt, 1943). Spatial movement patterns such as home range are tangible behavioural traits which can be monitored over time and result from the interaction of a range of predictors including environment and resource use (Börger et al., 2006a).
Average individual home range size at the species level is an ideal trait to examine as it has been demonstrated to have a strong relationship with body size within the terrestrial environment (Jetz et al., 2004) and ranges of different species can differ by several orders of magnitude, for example, the woodland vole, Microtus pinetorum, has a range less than 1 km2 (Gettle, 1975), compared with the polar bear (Ursus maritimus), which has a range of 125 100 km2 (Ferguson et al., 1999). In addition, across species of similar mass, home range can vary significantly (Kelt & van Vuren,
10
Chapter 1 – Introduction
2001), raising questions on what could be driving these differences and whether these drivers are uniform across all mammals.
1.3 CARNIVORY IN MAMMALS
Carnivorous mammal populations are highly vulnerable to extinction (Cardillo et al.,
2005; Carbone et al., 2011). This is due to the high energetic requirements of carnivores (Nagy, 2005), and therefore the need for a readily available and steady source of prey to sustain these populations. This is particularly pertinent for carnivorous mammals that experience energetic constraints caused by the amount of energy expended whilst locating and hunting sparsely distributed prey species (Carbone et al.,
1999). If prey populations decline, carnivores must spend more time and energy hunting and have less energy for reproduction, resulting in population declines of carnivores. It is therefore necessary to examine carnivorous strategies across the entire guild of carnivorous mammals in order to better predict how species will respond to changes within their environment.
We can utilise predator-prey relationships to gain insights into carnivore requirements
(e.g. prey and energetics) and their role within their ecosystem. More specifically, by studying the size of prey consumed by predators we can gather information on predation pressure (e.g. on specific size guilds; Hayward & Kerley, 2005) and the potential for trophic cascades (Fortin et al., 2005). It is important that when we investigate prey size we examine both the mean and the extremes (i.e. the minimum and maximum). Mean prey size patterns provide information on general patterns of prey size consumed by predators and this information is often used for predicting the susceptibility of carnivores to population declines and the role of carnivores within community structure (Carbone et al., 2007a). The extremes of prey size indicates the upper and lower limits of carnivore prey selection and this information is used to build
11
Chapter 1 – Introduction
our knowledge of how species respond to variation in the availability of food resources and optimal foraging theory (Costa et al., 2008). There has been little research on prey size patterns outside of the terrestrial environment (mean or extremes). This has limited the information we have on the entire guild of carnivorous mammals and whether they all follow similar foraging strategies regardless of the ecosystem they inhabit and the trophic structure of that ecosystem.
1.4 TROPHIC LEVEL
Understanding ecosystem structure and energy flow provides information useful for monitoring changes within a particular ecosystem (Jennings et al., 2002). The primary productivity of an ecosystem drives the amount of energy available to the organisms within that system (Arendt & Reznick, 2005). Additionally, the ecosystem characteristics (i.e. physical structure (Almany, 2004) and diversity (Duffy &
Stachowicz, 2006) influence the strength of biological interactions. Both energy availability and biological interactions play a role in the life history of an organism, highlighting the importance of understanding food web structure and trophic position.
We can use body size to model trophic position and food web interactions (e.g. predator-prey relationships), because energetic requirements and metabolic function dictate the flow of energy through an ecosystem (Petchey et al., 2008). In addition, information about food web complexity, ecosystem stability and community structure can be gathered using predator-prey body-mass ratios (Weitz & Levin, 2006; Petchey et al., 2008). Ecosystem stability is achieved when large species consume small species, leading to size structured trophic levels and food webs (Jennings &
Mackinson, 2003; Brose et al., 2006). As slight changes within a food web can result in trophic cascades (e.g. whales–otter–urchins–kelp; Pace et al., 1999; Estes et al.,
2011), we need to understand how trophic-level body-mass patterns in mammals have evolved, to better predict how the system may respond to such changes.
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Chapter 1 – Introduction
1.5 PHYLOGENETIC DATA
When using standard statistical analyses to make comparisons across multiple species, issues related to non-independence can arise. This is caused by the fact that most standard statistical methods, such as analysis of variance, have key assumptions that the data points are independent. Generally, the data will not be independent if the species share a common evolutionary history (Ricklefs & Starck, 1996). Ignoring species relationships can result in the detection of relationships based upon non- independent points or the masking of within group relationships by phylogenetic differences across groups (Type II error; Orme et al., 2012). To overcome the issue of non-independence, it has been suggested that studies examining cross species patterns should include phylogenetic information, as traits are not randomly distributed across species (Harvey, 1996). Very few previous investigations of home range, predator-prey relationships and trophic level patterns have actually considered the possible bias of phylogenetic relatedness when examining traits. Mammals are a well- studied clade and this has aided the construction of a phylogeny that is relatively well resolved compared with other taxa (e.g. reptiles). To overcome statistical issues and to examine the effect of phylogeny upon mammalian spatial and foraging patterns, I have incorporated analyses that combine both trait and phylogenetic data into each data chapter of this thesis.
1.6 PHYLOGENETIC COMPARATIVE ANALYSES
The presence of large datasets and phylogenetic trees have led to numerous high impact studies investigating broad patterns in ecology and evolution at both the temporal and spatial scales, including species richness, biogeography and extinction risk (Fritz et al., 2009; Huang et al., 2012; Price et al., 2012; FitzJohn et al., 2014; Liow
& Finarelli, 2014). When combining phylogenetic information with species trait data we can use comparative methods to examine a large range of questions including
13
Chapter 1 – Introduction
examining character diversification across species, investigate convergent evolution, examine the tempo and mode of evolutionary traits and traits simulation (e.g. reconstruct ancestral states).
As my focus is to examine the relationships between traits and environments, the main analysis I use is phylogenetic regression. This type of analysis incorporates different sources of error including within-species variation and measurement error, error due to the evolutionary process, and error due to unknown or uncertain phylogenetic information (Martins & Hansen, 1997). Additionally, phylogenetic regression also allows for the estimation of phylogenetic signal within the data. This can be measured in various ways depending on the hypothesis. As I am interested in the correlation between species’ traits and their evolutionary history, I will use both alpha (α) and lambda (λ). α estimates the extent phenotypic variation among species is correlated to phylogeny. When α is close to 0, phenotypic differentiation among present-day taxa reflects the phylogenetic relationships among those species and is the product of
Brownian evolution. Brownian motion is a model of evolution that assumes that trait evolution proceeds as a random walk through trait space and Brownian motion has been proposed as a null model of evolution for testing hypotheses of trait evolution
(Felsenstein, 1985). When α is large (e.g., 15.50) phenotypic differentiation is unrelated to phylogeny (Martins & Hansen, 1997). Similarly, λ can also be used to quantify phylogenetic signal in the data and the extent to which correlations in traits reflect their shared evolutionary history (Pagel, 1999). The values of λ sit between 0 and 1, where values of 1 suggest a strong correlation between traits and their evolutionary history and 0 suggests there is no correlation.
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Chapter 1 – Introduction
1.7 THESIS OUTLINE
Previous macroecology studies have examined whether there are general rules in ecology spanning spatial behaviour, feeding strategies and trophic structure (Brown,
1995; Carbone et al., 2007b; Boyer et al., 2010; Meiri, 2011). However, the majority of this previous research has either used data from predominantly terrestrial mammal species or have not included representatives across the entire span of mammal body mass (2 to 200,000,000 g). As a result, ecologists have an incomplete knowledge of general ecological patterns across all mammals. Including data on species from environments other than the terrestrial system, thereby including the full range of body sizes, can provide information on the driving factors behind large-scale patterns and general ecological rules. The aim of this thesis is to examine the effect of environment on spatial behaviour, carnivorous strategies and trophic structure of mammals in relation to body size and phylogenetic relatedness.
In Chapter 2 I investigate the driving factors of mammal home range size using data from the literature along with empirically derived values on home range size. First, I examine the relationship between diet, body mass and home range size in terrestrial mammals within an explicit phylogenetic framework. Second, I used a more comprehensive dataset that includes data on marine as well as terrestrial species to examine the effect of diet, body mass and environment (marine versus terrestrial) on home range size evolution across all mammals. Chapter 2 has been published in
Global Ecology and Biogeography, and a reprint of the published article is included in
Appendix 1 at the end of this thesis.
In Chapter 3 I examine the relationship between predator body mass and the minimum, maximum and range of their prey’s body mass. To achieve this, I test whether mammals show a positive relationship between prey and predator body mass, as found
15
Chapter 1 – Introduction
across reptiles and birds and predicted by optimal foraging strategy. I then examine the role that environment (i.e. aquatic and terrestrial) and phylogenetic relatedness have had in these predator-prey relationships. Chapter 3 has been published in PloS one, and a reprint of the published article is included in Appendix 3 at the end of this thesis.
In Chapter 4 I investigate the effects of living within the marine environment on carnivorous mammal feeding strategies. I first establish the energetic requirements of mammals on land and in water by examining the relationships between daily energy intake and body mass, and daily energetic expenditure and body mass. I then determine whether changes in energy intake and expenditure are associated with corresponding changes in feeding ecology.
Using diet information and trophic level data for terrestrial and marine mammals, I investigate how the colonisation of the marine and terrestrial environments has impacted the relationship between body size, trophic level and predator-prey ratio across mammals (Chapter 5). I also examine how differences between consumers within terrestrial and marine environments have influenced the trophic and food web structure of mammals. Here I had three objectives: (1) to determine what has driven the evolution of trophic-level body-mass patterns in mammals; (2) to determine whether living in different environments has resulted in the diversification of particular diet categories among mammalian taxa; and (3) to identify the drivers behind these patterns.
16
Chapter 2
Evolutionary predictors of mammalian
home range size: body size, diet and the
environment
This chapter has been published in Global Ecology and Biogeography (Appendix 1): Tucker, M.A., Ord, T.J. & Rogers, T.L. (2014) Evolutionary predictors of mammalian home range size: body mass, diet and the environment. 23, 1105-1114.
2.1 SUMMARY
Mammalian home range patterns provide information on spatial behaviour and ecological patterns, such as resource use, that is often used by conservation managers in a variety of contexts. However, there has been little research on home range patterns outside of the terrestrial environment, potentially limiting the relevance of current home range models for marine mammals, a group of particular conservation concern. To address this gap, I investigated how variation in mammalian home range size among marine and terrestrial species was related to diet, environment and body mass. I compiled data on home range size, environment (marine and terrestrial), diet and body mass from the literature and empirical studies to obtain a dataset covering
462 mammalian species. I then used phylogenetic regression analyses (to address non-independence between species) to examine the relative contribution of these factors to home range size variation among species. Body size explained the majority of differences among species in home range size (53-85%), with larger species occupying larger home ranges. The type of food exploited by species was also an 17
Chapter 2 – Mammalian Home Range
important predictor of home range size (an additional 15% of variation), as was the environment, but to a much lesser degree (1.7%). The factors contributing to home range evolution have been more complex than assumed. I demonstrate that both diet and body size are influential factors on home range patterns, but differ in their relative contribution, and show that the colonisation of the marine environment has resulted in the expansion of home range size. Broad-scale models are often used to inform conservation strategies. I propose that future integrative models incorporate the possibility of phylogenetic effects, a range of ecological variables, and that they include species representative of the diversity within a group.
2.2 INTRODUCTION
In animals, a broad range of physiological, ecological and behavioural factors scale with body size (Peters, 1983). Body mass, a measure of body size, accounts for a large proportion of the variation in home range size among terrestrial mammals (Kelt & van
Vuren, 2001; Jetz et al., 2004). Of all the potential consequences of allometry, the size of an animal’s home range provides valuable information on a variety of ecological variables, including resource use, social behaviour and other activities (Knight et al.,
2009). The strong positive relationship between home range size and body mass reflects the balance between the cost of locomotion and metabolic requirements with increasing body mass (McNab, 1963). Larger individuals can travel further than smaller individuals, but larger individuals have higher absolute energetic demands and need to travel further to gain the resources to meet those demands (McNab, 1963).
In addition to an animal’s size, diet is another important factor believed to dictate home range patterns. Carnivores, omnivores and herbivores have differences in their foraging costs (i.e., food acquisition and processing costs) due to their reliance on different food resources, which are also temporally and spatially different in distribution.
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Chapter 2 – Mammalian Home Range
Carnivores feed on resources that are sparsely distributed, mobile and unpredictable across the landscape, requiring a large home range (Kelt & van Vuren, 2001; Carbone et al., 2007a). There are also additional costs for carnivores such as the time and energy required to hunt for food (Carbone et al., 1999). In contrast, herbivores tend to have the smallest home ranges because they feed on vegetation which is fixed in time and space and is generally abundant. However, there are additional energetic costs associated with processing plant material (e.g. Clauss et al., 2003), which limits their ability to forage widely. Omnivores have an intermediate-sized home range that reflects their mixed diet (meat and vegetation) (Kelt & van Vuren, 2001) and the intermediate costs associated with processing these foods (McNab, 1986).
Despite the large body of work on the physiological and ecological variables that might impact an animal’s home range size (e.g., body mass and diet), gaps remain in our understanding of which factors (or combination of factors) actually drive mammalian home range patterns. While it is clear that diet and body mass are important, past studies have examined these factors separately (Kelt & van Vuren, 2001; Jetz et al.,
2004) and we have little idea of the relative contribution each has on mammalian home range size. Furthermore, home range data have been historically biased towards terrestrial mammals, resulting in the exclusion of the larger mammals (>4000 kg).
Marine mammals represent a prominent group of large carnivores. It is also unclear whether the factors driving home range size in mammals are the same in terrestrial and marine environments. Furthermore, previous studies have failed to consider the phylogeny of species being studied. On methodological grounds, not incorporating information on the phylogenetic relatedness among species violates the statistical assumption that data points are independent of one another. This results in inflated
Type I error rates and correlations between variables that may not actually exist (Stone et al., 2011). On biological grounds, while closely related species are more likely to share characteristics through common ancestry (and are therefore not independent of 19
Chapter 2 – Mammalian Home Range
one another), variation among species can also be generated through the inherently stochastic process of evolutionary differentiation (e.g., drift) or phenotypic correlations that track the phylogeny and indirectly effect home range rather than adaptation in home range specifically. That is, variation in home range size among mammals may have little adaptive significance and might simply reflect a history of stochastic differentiation or other factors associated with phylogeny.
In this study, I set out to clarify these issues by conducting an inclusive analyses across both terrestrial and marine mammals to test the diet and the body mass hypotheses alongside each other (i.e., that home ranges will increase with increasing meat in diets in addition to—and independently of—increasing body mass) and against an evolutionary null model (stochastic variation). As part of these analyses, I also examined whether the same relative contribution of these factors has impacted home range evolution in the same way in both terrestrial and marine mammals.
The colonisation of the marine environment has been accompanied by fundamental shifts in physiology and ecology that may have changed the way in which body mass and diet affect home range size in marine species. One example of this is the ability of marine mammals to utilise buoyancy. Marine mammals have evolved various mechanisms to achieve neutral buoyancy such as increases in bone density and large blubber stores (Wall, 1983). Buoyancy is a key strategy for marine mammals to minimise costs associated with diving. An example of this is the North Atlantic right whale (Eubalaena glacialis) which utilises positive buoyancy when ascending
(Nowacek et al., 2001). Marine mammals have also evolved other adaptations that allow them to survive in the ocean and decrease their cost of transport (COT) per unit weight (Williams, 1999). These include a mixture of adaptations that are physiological
(e.g. increased levels of globins for more efficient oxygen transfer; Williams et al.,
2008) and behavioural (e.g. alternate forms of locomotion during diving; Williams, 20
Chapter 2 – Mammalian Home Range
1999) . The subsequent decrease in COT per unit weight, combined with passive movement via oceanic currents (Tremblay et al., 2006), results in the relaxation of energetic costs in marine environments compared with the terrestrial environment.
Given that marine COT is approximately half that of land COT (e.g. Californian sea lion
2.5 J kg-1m-1 (Williams, 1999) vs. grey wolf 4.6 J kg-1m-1 (Pontzer, 2007)), marine mammals on average should have home ranges at least twice as large as terrestrial mammals for any given body mass. Moreover, as the marine system is fluid with few boundaries to limit movement, food resources tend to be highly mobile across the ecosystem (Sims et al., 2008). In response, marine mammals are highly mobile, and this should result in further increases in home range size. Therefore, I anticipated that a regression of home range size on body mass should compute a higher intercept for marine mammals (larger home ranges) compared to terrestrial mammals. However, as the COT per unit weight decreases with body mass at a similar rate in both marine and terrestrial mammals (Hildebrand & Goslow, 1995; Pontzer, 2007), the scaling relationship of home range size and body mass should remain the same across both environments.
This study was conducted in two parts. First, I revisited the relationship between diet, body mass and home range size in terrestrial mammals within an explicit phylogenetic framework and assessed the relative contribution of each factor in shaping home range size. Second, I combined data on marine and terrestrial species to examine the effect of diet and body mass on home range size evolution across non-flying mammals, while also evaluating the role of the environment (marine versus terrestrial). Each of the factors—diet, environment and body mass—were formulated into mathematical functions and tested against an evolutionary null model. This null model provides a biological benchmark to establish the extent “neutral” evolutionary differentiation in home range evolution can be excluded. In this second part of the study, I tested two main hypotheses: (1) diet type underpins home range patterns in mammals because of 21
Chapter 2 – Mammalian Home Range
differences in the distribution and assimilation of food types; and (2) the home range- body mass relationship differs between marine and terrestrial mammals because of differences in the physiology of species and the physical properties of the two environments. However, I predicted that body mass would be the primary variable determining home range size evolution across all species. This is due to the metabolic and energetic costs associated with body mass driving the food requirements of individuals, which are a key determinant of spatial movements in mammals (Kelt & van
Vuren, 2001). Given this overarching effect of body mass, I then predicted that the environment would have an important secondary effect on home range size because it influences both the physiology of animals and the distribution of resources. Finally, within a given environment (e.g., terrestrial), I predict that diet type would generate additional variation in home range size among species, reflecting the interaction of diet with the metabolic and energetic costs associated with a given body mass.
2.3 MATERIALS AND METHODS
2.3.1 Database
A database of 462 mammalian species, representing 293 genera, 89 families and 24 orders, was collated. I collected body mass and home range values, physical environment (marine versus terrestrial) and diet (carnivore, omnivore and herbivore) information. The home range values for individual species were calculated as weighted averages which included both sexes, but did not incorporate sex ratios or averaged population densities. All body mass and home range data for terrestrial mammals was obtained from Kelt and van Vuren (2001) and the panTHERIA database (Jones et al.,
2009). Body mass and home range data for marine species was collected from published literature and unpublished empirical data (Appendix 2, Table 2.1). Home range was defined as the area covered by an animal during its daily activities such as mating and foraging (Burt, 1943), and used across the marine and terrestrial
22
Chapter 2 – Mammalian Home Range
environments. Marine mammals were defined as species that rely upon the ocean to survive (e.g. foraging etc.). Carnivores were defined as those species with diets comprising of at least 90% meat, herbivores at least 90% vegetation, and omnivores between 10 and 90% vegetation (Kelt & van Vuren, 2001). Insectivores were classified as “carnivores”, while frugivores and folivores were classified as “herbivores”. Home range and body mass data were log10 transformed prior to analysis.
To supplement data for six species not well represented in the published literature, I calculated home range size from satellite tracking data. These species were the leopard seal (Hydrurga leptonyx), Weddell seal (Leptonychotes weddellii), crabeater seal (Lobodon carcinophaga), southern elephant sela (Mirounga leonina), Subantarctic fur seal (Arctocephalus tropicalis) and Antarctic fur seal (Arctocephalus gazella). For information on sample size, data collection and sampling protocols see Appendix 2,
Tables S2.2 - S2.5. The satellite tracking data were filtered using a Speed-Distance-
Angle-filter (Freitas & Lydersen, 2008), resulting in the use of location classes A, B, 1,
2, 3. These classes represent the accuracy of the positional data where 3 has an accuracy of 0.49 km, 2 with 1.01 km, 1 with 4.18 km, A with 6.19 km and B with 10.28 km (Costa et al., 2010). The average daily position was calculated for each individual based upon all location data for a given day and only adult individuals were used.
Home range was calculated via the fixed kernel density method (KDE) (Seaman &
Powell, 1996) using the ArcGIS extension Hawth’s Tools (Beyer, 2004). I chose kernel density estimation to calculate home range size, as reviews into the benefits and bias’ of home range methods including kernels and minimum convex polygons (Laver &
Kelly, 2008) suggest that kernels are preferable over polygons which are biased by outliers and low numbers of location fixes (Börger et al., 2006b).
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Chapter 2 – Mammalian Home Range
2.3.2 Phylogenetic Information
Due to the absence of a single phylogeny including all species of interest, a composite tree was created by combining information from several sources. The majority of the phylogeny was based on the mammalian supertree from Fritz et al. (2009) in which branch lengths were proportional to time since divergence. The following species were added to the Fritz et al. (2009) supertree using Mesquite ver 2.74 (Maddison &
Maddison, 2010) and species were positioned based on the topologies of the following sources; Callosciurus erythraeus (Steppan et al., 2004); Canis familiaris (Agnarsson et al., 2010); Eremitalpa granti (Kuntner et al., 2011); Orcaella heinsohni (McGowen,
2011); Sciurus aberti (Grill et al., 2009); and Sotalia guianensis (Caballero et al., 2008).
The Fritz et al. (2009) supertree included polytomies which are defined as a node where more than two species diverge at a single point in time (multifurcations). In this instance, these are soft polytomies due to insufficient phylogenetic information. To resolve the branch lengths and the polytomies present, I randomly generated 1,000 alternative branch lengths using the ‘randomly resolve polytomies’ function in Mesquite ver 2.74 (Maddison & Maddison, 2010). This produced 1000 alternative phylogenies and provided the basis for all of the phylogenetic comparative analyses.
2.3.3 Home Range Methodology
I have made an attempt to minimise any effects from different tracking methods (e.g.,
GPS, satellite and radio telemetry), analysis methodologies (kernels and polygons) and environments (terrestrial and marine) (Börger et al., 2006b; Frair et al., 2010), yet published studies differ in the methods used, resulting in the final database including mixed home range values by necessity. To examine the potential effect of different home range methodologies on a study of this scale (incorporating over 100 species), I ran a phylogenetic least squares (PGLS) regression analysis using the home range data collected (including a mixture of the home range estimation methods; kernel density estimation (n=26) and minimum convex polygons (n=286) and the phylogenetic 24
Chapter 2 – Mammalian Home Range
trees compiled (see above). Body mass and environment (i.e. marine or terrestrial) was included in this analysis as body size is a key driver of home range size (McNab, 1963;
Jetz et al., 2004) and the incorporation both marine and terrestrial species. PGLS analysis (β0+βmass+βenvironment+βmethodology) was then run across the 1000 trees including home range size (β0), body mass (βmass), environment (βenvironment, binary coded as 0 for terrestrial species and 1 for marine species) and estimation method (βmethodology, binary coded as 0 for MCP and 1 for KDE). The results from the phylogenetic regression demonstrate that methodology had no effect on home range size when comparing data on mammalian species from the marine and terrestrial environments (Table 2.1).
However, body mass and environment have a significant effect (Table 2.1) on home range size in mammals. This suggests that methodology has no effect on home range comparisons across a large number of species and physical environments.
Table 2.1 Model estimates and confidence intervals for the
β0+βmass+βenvironment+βmethodology model across 312 mammals. Results are from phylogenetic regressions computed for 1000 alternative resolutions of the mammalian phylogeny.
Model Term β(lower 95% CI, upper 95% CI) β0 -1.07 (-1.25,-0.89)* βmass 1.04 (0.93,1.16)* βenvironment 1.31 (0.54,2.08)* βmethodology 0.43 (-0.26,1.13) *Confidence intervals statistically different from zero and equivalent to p<0.05.
2.3.4 Analysis
I applied a model selection approach to test the level of support for alternative models of home range evolution. The best model was selected using second-order Akaike’s information criterion with a correction for sample size (AICc; Johnson & Omland, 2004).
The model with the lowest AICc value reflects the model with the highest support,
25
Chapter 2 – Mammalian Home Range
although any other model within two units of the lowest AICc value was also considered to be likely candidates (i.e. ∆AIC < 2.0; Burnham & Anderson, 2002). To compute AICc values, I applied each model as a phylogenetic generalized least squares (PGLS) regression using COMPARE ver 4.6b (Martins, 2004) to each of the
1000 trees (see previous section). Computed log-likelihood estimates from these analyses were converted into AICc values using equations presented in (Burnham &
Anderson, 2002). PGLS regression also computes an α parameter using maximum likelihood that estimates the extent phenotypic variation among species (e.g., mean body mass and associated home range size) is correlated to phylogeny. When α is close to 0, phenotypic differentiation among present-day taxa reflects the phylogenetic relationships among those species and is the product of Brownian evolution. When α is large (e.g., 15.50) phenotypic differentiation is unrelated to phylogeny and might be the outcome of adaptive evolution (Martins & Hansen, 1997; but also see; Revell et al.,
2008).
First, I assessed the level of support for the relationship between diet and home range among 429 species of terrestrial mammals relative to the level of variation in home range size generated solely by body mass or the evolutionary null model. These models were formulated as: (a) β0+βmass+βdiet_H+βdiet_O, where diet was scored as binary dummy variables with the resulting parameters β0, βdiet_H and βdiet_O corresponding to carnivores, herbivores, and omnivores, respectively (this was effectively a phylogenetic
ANCOVA); (b) β0+βmass, which predicted that differences in home range size among species were exclusively explained by body mass; and (c) β0, the evolutionary null model in which no predictor variable was included and therefore modelled variance in species home range size as the outcome of Brownian evolution and stochastic factors associated with evolutionary differentiation.
26
Chapter 2 – Mammalian Home Range
Second, I expanded the analyses to cover both marine and terrestrial species in order to examine the relationship between environment and home range, and the extent to which environment overrides the influence of diet. This analysis included new empirical data on several marine species (see ‘Database’ above) and covered 462 species.
Models were formulated as: (a) β0+βmass+βenvironment, where environment was entered as a binary variable in which species were coded as living in either a terrestrial (0) or marine (1) environment; (b) β0+βmass+βdiet_H+βdiet_O, the diet model which is described above for the terrestrial mammal analysis; (c) β0+βmass+βdiet_H+βdiet_O+βenvironment, where both diet and environment were included together in the same model; (d) β0+βmass, which assumed body mass was the only variable predicting home range size; and (e)
β0, the evolutionary null model described above for the terrestrial mammal analysis.
2.4 RESULTS
I found that diet and body mass together accounted for a portion of the variation in home range size observed among terrestrial mammals (Table 2.2, Fig. 2.1).
Carnivores, omnivores and herbivores demonstrated the predicted difference in intercept values. Carnivores showed the predicted large home ranges with an intercept that was significantly higher than omnivores and herbivores. Omnivores had the intermediate home range sizes that were significantly larger than herbivores and herbivores had the smallest home ranges across the three diet categories (Fig. 2.1).
However, where body mass accounted for 52% of the variance in home range size among terrestrial species (r = 0.72), the inclusion of diet improved the explanatory power of the model by 15% (r = 0.82). There was also a substantial improvement in the computed AICc value between the diet model and the body mass only model (∆AICc
40.6). The inclusion of phylogeny was important for these analyses as the estimated phylogenetic signal in home range size among species was high (the null model,
α=2.9; NB: values approaching 0 indicate high phylogenetic signal in species data).
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Chapter 2 – Mammalian Home Range
That is, closely related species tended to share similar home range sizes and this could not be explained by phylogenetic inertia in body mass (i.e., α is a combined estimate of phylogenetic signal across all the variables entered into the model, and when body mass was included α was 8.36 suggesting that the level of phylogenetic signal exhibited by body mass was potentially lower than for home range size, otherwise the estimate would be similar or even lower than that estimated by the null model).
Table 2.2 Level of support for explanatory models of home range size evolution in land mammals. Results are from phylogenetic generalized least squares (PGLS) regression computed for 1000 alternative resolutions of the mammalian phylogeny. Model terms include herbivores (diet_H), omnivores (diet_O), body mass (mass) and intercept (0).
Model ∆AICc ∆AICc 95% CI PGLS Effect (upper, lower) α size (r) β0+βmass+βdiet_H+βdiet_O 0.0 NA 14.8 0.82 β0+βmass 40.6 34.8, 51.0 8.4 0.72 β0 281.5 268.5, 298.4 2.9 -
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Chapter 2 – Mammalian Home Range
Figure 2.1 Home range size as a function of species body mass compared for terrestrial carnivorous (red circles), herbivorous (yellow circles) and omnivorous species (blue circles). Each datum represents a species mean value (n=429 species).
The solid red line is the phylogenetic regression of carnivorous mammals: logY=1.12(logX)-0.48, the dashed black line is the phylogenetic regression of omnivorous mammals: logY=1.12(logX)-0.94, while the solid blue line is the phylogenetic regression of herbivorous mammals: logY=1.12(logX)-1.45. Bottom right insert: intercept values and confidence intervals (CI) for terrestrial herbivores, omnivores and carnivores. Values were calculated from phylogenetic least squares
(PGLS) regression analyses applied to 1000 alternative resolutions of the mammalian phylogeny.
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Chapter 2 – Mammalian Home Range
When the analysis was expanded to all mammals in both terrestrial and marine environments, the model that included environment, diet and body mass was by far the best-supported model and explained 74% of the variance in home range size among species (r = 0.86; Table 2.3). There was virtually no support for any of the alternative models (∆AICc > 10), although it was noteworthy that the second best model of diet and mass provided a similarly high level of explanatory power (72% variance explained; r = 0.85; Table 2.3). The majority of marine species are large and carnivorous (~95% carnivorous species) and this lead us to question whether the environment specifically influenced the best supported model or whether it was the inclusion of larger carnivores into the data set. To explore this, I examined the parameter estimates for the second best supported model which included only diet and body mass. These estimates confirmed the expected positive relationship between home range and body mass and showed that each of the diet categories were significantly different from one another: carnivores had the largest home ranges, omnivores had intermediate home ranges and herbivores had the smallest home ranges (Fig.2.2). That is, with the inclusion of the marine mammals, the primary effect seems to have been a divergence in intercept values between the carnivores and omnivores (compare Figs 2.1 and 2.2).
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Chapter 2 – Mammalian Home Range
Table 2.3 Level of support for explanatory models of home range size evolution in mammals. Results are from phylogenetic generalized least squares (PGLS) regression computed for 1000 alternative resolutions of the mammalian phylogeny. Model terms include herbivores (diet_H), omnivores (diet_O), environment (marine or terrestrial), body mass (mass) and intercept (0).
Model ∆AICc ∆AICc 95% CI PGLS Effect (upper, lower) α size (r) β0+βmass+βdiet_H+βdiet_O+βenvironment 0.0 NA 14.6 0.86 β0+βmass+βdiet_H+βdiet_O 21.3 7.0, 44.3 14.1 0.85 β0+βmass+βenvironment 43.9 24.2, 61.8 8.9 0.79 β0+βmass 77.9 58.8, 100.8 7.2 0.73 β0 322.9 302.3, 354.2 2.4 -
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Chapter 2 – Mammalian Home Range
Figure 2.2 Home range size as a function of species body mass compared for carnivorous (red circles), herbivorous (yellow circles) and omnivorous species (blue circles). Each datum represents a species mean value (n=462 species). The red line is the phylogenetic regression of carnivorous mammals: logY=1.19(logX)-0.29, the blue line is the phylogenetic regression of omnivorous mammals: logY=1.19(logX)-0.91, while the yellow line is the phylogenetic regression of herbivorous mammals: logY=1.19(logX)-1.47. Bottom right insert: intercept values and confidence intervals
(CI) for carnivores (C), omnivores (O) and herbivores (H). Values were calculated from phylogenetic least squares (PGLS) regression analyses applied to 1000 alternative resolutions of the mammalian phylogeny. Panthera and Macaca silhouettes are uncredited and the Loxodonta silhouette is by Steven Traver, all images are available for reuse under the Public Domain Mark 1.0 license.
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Chapter 2 – Mammalian Home Range
To examine whether the environment has had any impact on home range size, I restricted the analyses to only carnivorous marine and terrestrial mammals and refitted the environment and body mass model (β0+βmass+βenvironment), the body mass only model
(β0+βmass) and evolutionary null model (β0). The environment model was the best supported model of the three, but only explained an additional 1.7% of the variance in home range size above the 72% explained by body mass only (Table 2.4). In general, however, marine carnivores have home ranges 1.2 times larger than terrestrial species of a similar mass (Fig. 2.3).
Table 2.4 Level of support for explanatory models of home range size evolution in carnivorous mammals. Results are from phylogenetic generalized least squares
(PGLS) regression computed for 1000 alternative resolutions of the mammalian phylogeny. Model terms include environment (marine or terrestrial), body mass (mass) and intercept (0).
Model ∆AICc ∆AICc 95% CI PGLS Effect (upper, lower) α size (r) β0+βmass+βenvironment 0.0 NA 11.6 0.86 β0+βmass 4.0 3.6, 4.6 11.0 0.85 β0 93.7 90.3, 101.5 1.5 -
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Chapter 2 – Mammalian Home Range
Figure 2.3 Carnivore home range size as a function of species body mass compared for species occupying terrestrial (green circles) and marine (blue circles) environments.
Each datum represents a species mean value (n=134 species). The green line is the phylogenetic regression of terrestrial mammals: logY=1.2(logX)+0.39, while the blue line is the PGLS phylogenetic regression line of marine mammals: logY=1.2(logX)-
0.44. The river otter (9kg) and Southern humpback whale (32 000kg) are the smallest and largest marine mammal, while the masked shrew (4.2g) and lion (204kg) are the smallest and largest terrestrial mammals. Bottom right insert: intercept values and confidence intervals (CI) for terrestrial and marine mammals. Values were calculated from phylogenetic least squares (PGLS) regression analyses applied to 1000 alternative resolutions of the mammalian phylogeny. Eubalaena silhouette by Chris
Huh and available for reuse under the Creative Commons Attribution-ShareAlike 3.0
Unported license; Panthera silhouette is uncredited and is available for reuse under the
Public Domain Mark 1.0 license.
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Chapter 2 – Mammalian Home Range
Overall, the results confirmed the overarching effect of body mass on mammalian home range size. In addition to body mass, diet and the physical environment both explained additional variance in home range size among species, but their influence was less than that of body mass. There was evidence to suggest that diet might have had a greater impact on home range size than the physical environment (19% additional variance explained for diet compared to 9% for the environment). In no instance was the evolutionary null model a compelling alternative explanation for differences in home range size among species, but home range size was found to exhibit a strong phylogenetic signal in all analyses (α =1.50-2.90; Tables 2.2-2.4).
2.5 DISCUSSION
Body mass was the principal predictor of home range size in mammals, accounting for
53-85% of the observed variation in home range size among species. The evolution of home range size appears to have been driven, for the most part, by the energetic requirements and costs or benefits associated with a given body mass. Energetic requirements, such as metabolic rate (kJ day-1), are positively correlated with body mass (Nagy, 2005). As large species have higher absolute energy needs, they must consume more resources and cover larger areas in order to gain enough resources to meet their energetic demands (McNab, 1963). In contrast, energetic costs associated with movement are greater in smaller species (Pontzer, 2007), which tends to constrain their movements and results in smaller home range sizes. In addition to the effects of body mass, I found the amount of meat included in diets was a second-order predictor of home range, followed closely by the physical environment (terrestrial versus marine).
However, while providing significant improvements in the level of support for models, there were varying effects of diet and physical environment on home range size. Both could only explain a further 1-19% of the variation in home range size among species beyond the effect of body mass. Such a small effect was surprising for diet as several
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Chapter 2 – Mammalian Home Range
past studies have concluded diet as the key determinant of the home range-body mass relationship among terrestrial mammals (Swihart et al., 1988; Kelt & van Vuren, 2001).
This seems reasonable considering that what species eat has a direct impact on both the energetic requirements species and the type of costs incurred in obtaining and processing food resources. However, while the results confirm that diet has been a factor shaping mammalian home ranges (support was high for models that included a parameter for diet), it has nevertheless been far less influential. Previous studies of diet and home range use were based on datasets with limited species coverage across physical environments (i.e. marine and terrestrial), which can result in model bias and cause issues when these models are extrapolated over a broader range of species
(Sibly et al., 2012). Furthermore, phylogenetic information was not incorporated into previous analyses and the results showed that home range size does exhibit a large amount of phylogenetic signal (and this was not likely the by-product of phylogenetic inertia in body mass).
When the analyses were applied to all species, an apparent dual role of both diet and the environment seemed to be supported (Table 2.3). However, the precise relationship with the physical environment was unclear because the majority of marine mammals were large carnivores with very large home ranges. The specific relevance of the marine environment on home range evolution was therefore unclear. When the effect of diet was controlled for by focusing on carnivorous mammals across terrestrial and marine environments, I found that home ranges were significantly larger in marine environments for a given body mass than they were on land (Table 2.4), but the effect was arguably smaller than diet (environment only accounted for an additional 1.7% of the variation in home range size among species over body mass). The combination of living in an open environment, feeding on mobile resources and lower transport costs have resulted in the evolution of large home range sizes in marine carnivorous mammals (roughly 1.2 times larger), but the impact of these factors have been minimal 36
Chapter 2 – Mammalian Home Range
compared to the energetic requirements/costs driven by body mass. Unfortunately I was unable to examine the relationship between home range, diet and environment more closely for herbivores and omnivores, due to the predominance of carnivory within the marine environment.
Large carnivorous mammals have high daily energetic requirements and one strategy to meet these requirements is to utilise pack hunting (Carbone et al., 2007a). Pack hunting enables prey with large body mass to be hunted whilst minimising energy expended during the hunt. There is potential that pack hunting may alter home range size due to the increased density of individuals within an area. The data did not suggest any difference in home range size between carnivores that utilise pack hunting and those that do not (Appendix 2, Table S2.6 and Fig. S2.4). It would be ideal to have more complete home range information on whales. With the addition of more whale species, I would expect to see a different home range relationship with body mass, such as an increase in the scaling of home range size with body mass, resulting in extreme home range sizes with large body mass. This would be the case, especially with the inclusion of the various whale migrations, which cover a large area (e.g., the length of a migration (i.e. one direction, single track) can be greater than 5000 km, without accounting for the “width” of the home range (Alerstam et al., 2003). At present, there is a limited amount of tracking data on whales available, especially long term data that also includes their migration.
Like mammals, birds provide an interesting comparison to the home range size of marine mammals. Birds also live within a three dimensional environment (excluding the flightless species) and home range sizes in non-migratory birds tend to be larger than mammals for their size (Haskell et al., 2002). The literature suggests that body mass and food resources are the main drivers of bird home range size, similar to mammals.
Body mass was attributed to energy requirements, where large birds “require more 37
Chapter 2 – Mammalian Home Range
food per unit area than smaller birds” (Schoener, 1968). Also, birds with an increasing amount of vertebrate prey in their diet will have larger home range sizes due to lower densities of their prey compared to that of herbivores and omnivores (Schoener, 1968).
The effects of diet on the relationship between home range size and body mass in this study is likely to only detect large scale effects of resource use and distribution constraints, across the broad diet categories of carnivores, omnivores and herbivores.
This is due to resource use and resource distribution constraints having varied effects on home range size. Changes in the type of resources used and their abundance can vary on different temporal scales. For example, resource distribution and availability in the Arctic are highly seasonal, with a distinct set of resources available during winter versus summer. This would have a strong effect on home range size of individuals living in this region (e.g. polar bears; Ferguson et al., 1999). However, an individual may also change which resources they use on a much smaller temporal scale, such as on a day to day. Shifts in resource use or distribution on this small scale are unlikely to be detected in home range analyses due to home range size being calculated over longer periods (i.e. generallyseasonally or yearly). Small scale studies with a focus on a single species and a more direct approach, such as state-space models (Bestley et al., 2013), would be ideal to investigate dietary effects on these shorter periods.
The sample sizes were biased towards terrestrial mammals despite the data including all available information on home range size for marine species (Fig. 2.1). This partly reflects the difference in the number of mammalian species on land versus in the water that were included in the analyses. Calculating home range for marine species is difficult because of issues associated with tracking marine species (often requiring satellite tracking). For example, home ranges are often calculated over shorter tracking periods in marine species compared to those on land. As tracking technology improves, and methodologies become more sophisticated for estimating home ranges 38
Chapter 2 – Mammalian Home Range
in marine species, the number of species for which home range information is available should increase. Nevertheless, mammalian species diversity in marine environments is much lower than on land, so this bias in sampling partly reflects biological reality and this will not change with improved methods of home range estimation.
It should also be noted that the home range values of marine species used in this study may be conservative, as they were measured in two dimensions, but marine mammals use a three dimensional environment (Pawar et al., 2012). However, Carbone et al.
(2007b) investigated abundance scaling in mammals in three dimensional environments, and their models predict -2/3 scaling similar to abundance scaling within two dimensional environments. As there is a relationship between animal abundance scaling and home range size (Jetz et al., 2004), we may expect to see a similar pattern in the scaling of home range size in mammals. The effect of dimensions of environments would be an interesting concept to examine in a future study, using similar mathematical methods to those used in Carbone et al. (2007b).
It is unlikely that differences in home range size across the marine and terrestrial environments are driven by how species are related (i.e. collinearity between environment and relatedness). Marine mammals are interspersed across the mammalian clade (see Fig. S2.1). For example, within carnivora sit both marine (e.g. pinnipeds, Ursus maritimus and Enhyrda lutris) and terrestrial (e.g. canidae, mephitidae, procyonidae) representatives.
2.6 CONCLUSION
Home range is a complex behaviour influenced by a range of variables, including body mass, diet and environment. My aim was to clarify the role and extent to which these variables impact home range size in mammals. I highlight that across the mammalian
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Chapter 2 – Mammalian Home Range
radiation the evolution of home range has been driven by a hierarchy of variables, but some variables have clearly been more influential than others. The key explanatory variable of home range size was body mass, followed by the secondary variables of diet and then environment. To better understand the evolution of mammalian home range size we need to investigate the proximate mechanisms (here, proximate mechanisms are the physiological and morphological drivers) of its relationship to body size. Furthermore, because the effects of diet and environment on home range use were small, it would be prudent to reconsider past assumptions regarding the influence of differing resource bases (meat versus plant), modes of transport (swimming versus walking and running) and altered physical properties (water versus air) as underlying mechanisms of home range use.
Broad models developed using information from many species, such as the allometric model of home range size (Jetz et al., 2004; this study), are often used to guide conservation and management strategies. It is critical then that the underlying assumptions of these models are biologically appropriate. With previous models focusing exclusively on select groups of species (e.g. terrestrial mammals), I have developed an important amendment to these models to show that home range drivers once thought as highly influential are not so. I have demonstrated that by using an integrative model that incorporates an inclusive list of predictor variables, species and phylogenetic information, our knowledge of home range patterns across mammals can be significantly enhanced.
40
Chapter 3 Examining the prey mass of terrestrial
and aquatic carnivorous mammals:
minimum, maximum and range.
This chapter has been published in PLoS ONE (Appendix 3): Tucker, M.A. and Rogers, T.L. (2014) Examining the prey mass of terrestrial and aquatic carnivorous mammals: minimum, maximum and range. PLoS ONE 9(8): e106402.
3.1 SUMMARY
Predator-prey body mass relationships are a vital part of food webs across ecosystems and provide key information for predicting the susceptibility of populations of carnivores to extinction. Despite this, there has been limited research on the minimum and maximum prey size of mammalian carnivores. Without information on large-scale patterns of prey mass, we limit our understanding of predation pressure, trophic cascades and susceptibility of carnivores to decreasing prey populations. The majority of studies that examine predator-prey body mass relationships focus on either a single or a subset of mammalian species, which limits the strength of our models as well as their broader application. I examine the relationship between predator body mass and the minimum, maximum and range of their prey’s body mass across 108 mammalian carnivores, from weasels to baleen whales (Carnivora and Cetacea). I test whether mammals show a positive relationship between prey and predator body mass, as in reptiles and birds, as well as examine how environment (aquatic and terrestrial) and
41
Chapter 3 – Examining the Prey Mass of Carnivorous Mammals
phylogenetic relatedness play a role in this relationship. I found that phylogenetic relatedness is a strong driver of predator-prey mass patterns in carnivorous mammals and accounts for a higher proportion of variance compared with the biological drivers of body mass and environment. The results show a positive predator-prey body mass pattern for terrestrial mammals as found in reptiles and birds, but no relationship for aquatic mammals. The results will benefit our understanding of trophic interactions, the susceptibility of carnivores to population declines and the role of carnivores within ecosystems.
3.2 INTRODUCTION
Examining patterns in predator-prey relationships provides information on predation pressure (e.g. on specific size guilds; Hayward & Kerley, 2005; Hayward, 2006), the impact of decreasing prey species on predators (Novaro et al., 2000) and the potential for trophic cascades and the collapse of prey populations (Fortin et al., 2005; Daskalov et al., 2007; Johnson et al., 2007). However, previous research on predator-prey body mass relationships in mammalian carnivores has focused upon the mean mass of prey, largely ignoring the minimum and maximum body mass of prey consumed by predators. It is important to include the minimum, maximum and range of prey mass consumed as it allows the examination of the upper and lower limits of carnivore prey selection. In addition, prey selection provides information such as energetic requirements (e.g. intake rates), which is often used for predicting the susceptibility of carnivores to population declines, the role of carnivores within ecosystems and community structure (Carbone et al., 2007a).
Larger-sized predators can utilise a wide variety of prey types because they have large home ranges (Tucker et al., 2014) that provide access to a diversity between prey species (Ottaviani et al., 2006), as well as a wide gape size that allows them to feed on
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Chapter 3 – Examining the Prey Mass of Carnivorous Mammals
prey of a variety of sizes. Despite this, large predators tend to eat larger-sized prey
(Carbone et al., 2007a). It is not always profitable for large species to feed on small- sized prey due to capture inefficiency as it is costly to pursue small-sized prey in relation to the small energetic benefit gained (Brose, 2010). The minimum and maximum size of prey should scale positively with predator body mass, resulting in there being no relationship between predator body mass and diversity of prey size (i.e. dietary niche breadth - DNB) (Brandl et al., 1994; Costa et al., 2008). However, if maximum prey size scales positively with predator mass and minimum prey size does not this will result in a larger diversity of prey size for larger predators (i.e. wider DNB).
Our knowledge of mammalian broad-scale patterns of prey-size range is limited. There has been limited work investigating the prey mass of African predators and its effect on the system (Sinclair et al., 2003). However, this work largely focuses upon predation pressure on prey species, particularly herbivorous mammals. The remaining predator- prey body mass research is based on the mean prey mass of predators (Carbone et al., 2007a; Riede et al., 2011). Investigations into other animal groups include predatory fish (Scharf et al., 2000; Costa, 2009), reptiles (King, 2002; Costa et al.,
2008) and birds (Brandl et al., 1994), where there is a general consensus that there is a positive relationship between predator body mass and prey minimum, maximum and range in mass, except for fish where the evidence is conflicting (positive or no relationship between predator mass and minimum prey mass).
Using minimum, maximum and range of prey mass for 108 carnivorous mammals from the orders Carnivora and Cetacea, I investigated the nature of the relationship between carnivore body mass and prey body mass and how living in either the marine or terrestrial environment has impacted this relationship. This study has two objectives: first to examine the influence of physical environment on minimum, maximum and range of prey mass; and second to investigate the influence physical environment has
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Chapter 3 – Examining the Prey Mass of Carnivorous Mammals
had on the distribution of minimum, maximum and range of prey mass. Based on previous research (Carbone et al., 2007a; Costa et al., 2008), I predict that prey mass
(minimum, maximum and range) will be positively correlated with predator body mass for terrestrial carnivores. However, for marine carnivores there could be two possible outcomes: first, prey mass (minimum, maximum and range) could be positively correlated with body mass similar to terrestrial carnivores and other marine non- mammalian predators (Costa, 2009); or second, there could be no relationship between prey mass (minimum, maximum and range) and predator body mass. No relationship between predator mass and prey mass is a possibility due to the high abundance of small species that form dense aggregations in aquatic environments
(e.g. krill or fish) which lead to an increase in the encounter rates between aquatic predators and these small prey species. With both small and large predators exposed to these abundant food resources, this would result in both small and large predators feeding upon small prey species and therefore suggest no relationship between predator mass and prey mass in aquatic systems.
By examining the moments (e.g. mean, mode, skewness etc.) of the prey mass distributions, we can gather information on how the mass of the prey consumed by carnivorous mammals differs or is similar across different environments. This information is important for building our knowledge of predator-prey relationships and the drivers behind these relationships.
3.3 MATERIALS AND METHODS
3.3.1 Database
Data were collated on the minimum and maximum prey mass (kg) consumed by 108 carnivorous mammal species (Appendix 4). Table 3.1 provides a summary of the orders and families sampled. Prey mass range was calculated by subtracting the
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Chapter 3 – Examining the Prey Mass of Carnivorous Mammals
minimum prey mass from the maximum prey mass. Mean body mass (kg) was also collected for these 108 predator species using the database PanTHERIA (Jones et al.,
2009). All carnivores were classified as terrestrial or aquatic, where aquatic species forage in water to survive (e.g. foraging) and terrestrial species forage on land to survive. All values including carnivore mass and prey mass were log10 transformed prior to all analyses.
Table 3.1 Summary of the orders and families included in the study sample.
Order Family Carnivora Canidae Felidae Herpestidae Hyaenidae Mephitidae Mustelidae Otariidae Phocidae Procyonidae Ursidae Viverridae Cetacea Balaenidae Balaenopteridae Cetotheriidae Delphinidae Eschrichtiidae Kogiidae Monodontidae Phocoenidae Physeteridae Pontoporiidae Ziphiidae
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Chapter 3 – Examining the Prey Mass of Carnivorous Mammals
3.3.2 Phylogenetic Information
I required a single phylogenetic tree to examine minimum prey mass, maximum prey mass and prey mass range in carnivorous mammals. Phylogenetic information was obtained from the Fritz et al. (2009) mammal supertree containing 5,020 species and branch lengths proportional to time since divergence. This tree was pruned using
Mesquite ver 2.74 (Maddison & Maddison, 2010) to create the tree (n=108) based on the data in the database. Sotalia guianensis (Guiana dolphin) was positioned within the pruned tree based on the topologies of Caballero et al. (2008). Due to insufficient phylogenetic information, the Fritz et al. (2009) tree included soft polytomies where more than two species diverge at a single point in time. To resolve the polytomies, I used a semi-automated polytomy resolver for dated phylogenies (Kuhn et al., 2011).
The polytomy resolution involved two steps; 1) R 3.0.2 (R Core Team, 2013) was used to create an XML input file containing topology constraints and input commands for
BEAST, and 2) the XML input file was run through the program BEAST 1.8 (Drummond et al., 2012) which uses a Bayesian Markov chain Monte Carlo (MCMC) algorithm to permute the unresolved relationships within the tree based on the birth-death model.
This produced 1,000 alternative phylogenetic trees to be used for the phylogenetic comparative analyses and the ancestral state reconstructions.
3.3.3 Analyses
Model selection using second-order Akaike’s information criterion with a correction for sample size (AICc) and phylogenetic generalised least squares (PGLS) regression
(see Analysis section in Chapter 2) were used to examine alternative models of prey mass. I performed three separate PGLS analyses for minimum prey mass, maximum prey mass and range of prey mass respectively. For each I examined the level of support of the relationship between prey mass (minimum, maximum or range), carnivore body mass and environment across 108 species. The models were
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Chapter 3 – Examining the Prey Mass of Carnivorous Mammals
formulated as; (a) β0+βmass*βenvironment, where environment was coded as “terrestrial” or
“aquatic” and included an interaction term between carnivore mass and environment;
(b) β0+βmass, which assumed body mass was the only variable predicting prey mass; (c)
β0, the evolutionary null model in which no predictor variable was included and subsequently modelled variance in species prey mass as the outcome of Brownian evolution (i.e. under Brownian motion, trait evolution proceeds as a random walk through trait space and Brownian motion has been proposed as a null model of evolution for testing hypotheses of trait evolution (Felsenstein, 1985). The PGLS analyses were conducted using the CAPER package in R (Orme et al., 2012)
To examine the effect of phylogeny and ecology on the minimum and maximum prey mass of carnivores, I ran variance component analyses (Pinheiro & Bates, 2000).
Variance was examined among species, focusing on the contribution of order, family, genus, mass and environment (aquatic or terrestrial). Variance components analysis was performed using the lme4 package (Bates et al., 2013) in R version 2.13.2.
To gain an understanding on the shape of the prey mass distributions across species and environments, I extracted the descriptive statistics including the mean, median, mode, range, minimum, maximum, standard deviation (S.D.), skewness and kurtosis.
Skewness measures the degree of asymmetry of a distribution. If the skewness value is positive the data have a right skewed distribution and a negative value suggests left skewed data. Kurtosis measures height of the curve relative to its standard deviations.
Data with a peaked distribution with values around zero (i.e. normal distribution) have a positive kurtosis value, whereas negative values between 0 and -1 implies that the data have a flat distribution and values lower than -1.5 suggest a bimodal distribution.
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Chapter 3 – Examining the Prey Mass of Carnivorous Mammals
3.4 RESULTS
3.4.1 Phylogenetic Generalized Least Squares Regression
The model including an interaction between body mass and environment (mass- environment) was the best supported model for minimum prey mass, maximum prey mass and prey mass range (Table 3.2). However, for the maximum prey mass and prey mass range there was less than 2 ∆AIC units between the mass model and the mass-environment model, suggesting that these models are equally supported. In both cases, the addition of environment explained a limited amount of additional variance
(3% for both maximum prey and prey range) however for minimum prey mass, environment explained an additional 7% of variance. The phylogenetic signal (λ) was consistently high for the mass model for minimum, maximum and prey size range
(>0.7). Lambda however, was mixed for the mass-environment models, where it was low (<0.5) for the maximum prey and prey range size, it was higher (0.62) for the minimum prey mass.
Table 3.2 Level of support for explanatory models of prey mass evolution in carnivorous mammals. Results are from phylogenetic least squares (PGLS) regression analyses computed for 1000 alternative resolutions of the mammalian phylogeny.
Model terms include carnivore body mass (βmass), environment either aquatic or terrestrial (βenvironment) and the intercept (β0).
Prey mass Model ∆AICc ∆AICc 95% CI Lambda Effect (upper, lower) size (r) Minimum β0+βmass* βenvironment 0.0 NA 0.62 0.28 β0+βmass 5.8 4.99, 6.58 0.71 0.10 β0 5.5 4.78, 6.28 0.64 NA Maximum β0+βmass* βenvironment 0.0 NA 0.48 0.28 β0+βmass 0.9 0.04, 2.07 0.74 0.23 β0 4.8 4.23, 5.29 0.57 NA Range β0+βmass* βenvironment 0.0 NA 0.30 0.28 β0+βmass 1.6 0.23, 3.1 0.73 0.23 β0 5.3 4.54, 5.84 0.57 NA
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Chapter 3 – Examining the Prey Mass of Carnivorous Mammals
I found there was no significant difference (confidence intervals overlap 0) in intercept between terrestrial and aquatic carnivores for minimum (CI -2.22, 1.54; Fig. 3.1A), maximum (CI -2.48, 1.47; Fig. 3.1B) and range of prey mass (CI -2.70, 1.00; Fig. 3.1C).
There was a significant difference (confidence intervals do not overlap 0) in slope between terrestrial and aquatic carnivores for minimum (CI 0.37, 1.93), maximum (CI
0.24, 1.94) and range of prey mass (CI 0.49, 2.16). Despite the negative slopes of the aquatic regression lines, these values were not significantly different from 0 for minimum, maximum or prey mass range. The terrestrial regression slopes were positive and significantly different from 0 for minimum, maximum or prey mass range
(Fig. 3.1A, B and C).
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Chapter 3 – Examining the Prey Mass of Carnivorous Mammals
Figure 3.1 Minimum prey mass (A), maximum prey mass (B) and prey mass range (C) as a function of carnivore body mass compared for terrestrial (green circles) and aquatic (blue circles) species. Each datum represents a species mean value. The solid green line is the phylogenetic regression of terrestrial mammals: (A) log(Y)=1.13log(X)- 3.3, (B) logY=1.12(logX)-1.01 and (C) logY=1.26(logX)-0.87. The solid blue line is the phylogenetic regression of aquatic mammals: (A) logY=-0.03(logX)-2.96, (B) logY=0.11(logX)+-0.50 and (C) logY=-0.07(logX)-0.02. Insert: intercept values and confidence intervals (CI) for aquatic (A) and terrestrial (T) species. Values were calculated from phylogenetic least squares (PGLS) regression analyses applied to 1000 alternative resolutions of the mammalian phylogeny. Error bars represent CI’s for the intercept values and are calculated using the standard error (SE) multiplied by 1.96.
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Chapter 3 – Examining the Prey Mass of Carnivorous Mammals
3.4.2 Variance Components Analysis
Order, family and genus explained the maximum proportion of variance in prey mass of carnivores (58-73%; Table 3.3), providing additional support for the strong influence of phylogenetic relatedness on the prey mass consumed by carnivorous mammals. Body mass of the carnivore explained a relatively large degree of variance (32-39%), where environment had little influence over the mass of prey consumed (<0.01-3%).
Table 3.3 Variance components analysis of prey mass across 108 carnivorous mammal species. Categories include minimum prey mass (smallest prey size consumed), maximum prey size (largest prey size consumed) and range of prey mass
(maximum minus minimum prey mass).
Prey Mass Variance Variance Total Variance Source Component Explained (%) Minimum Total 3.17 100 Order 0.18 5.65 Family 1.13 35.65 Genus 0.52 16.65 Mass 1.23 38.83 Environment 0.11 3.43 Maximum Total 3.31 100 Order 0.43 13.79 Family 0.19 6.26 Genus 1.64 52.60 Mass 1.05 33.70 Environment <0.01 <0.01 Range Total 3.50 100 Order 0.40 11.33 Family 0.17 4.88 Genus 1.81 51.69 Mass 1.12 31.97 Environment <0.01 <0.01
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3.4.3 Descriptive Statistics
Examining the descriptive statistics, the minimum prey mass distribution across all mammals is positively skewed (skew = 0.11), while maximum and range of prey mass is negatively skewed (-0.40 to -0.37; Table 3.4). The prey mass data have a normal distribution for minimum, maximum and range of prey mass with kurtosis values between 0.62 and 1.18 (Table 3.4).
Table 3.4 Descriptive statistics for the prey mass distributions across 108 carnivorous mammals. Minimum is the minimum prey mass consumed, maximum is the maximum prey mass consumed and range is the total range of prey mass consumed (maximum minus minimum).
Prey Skew Kurtosis Median Mean Mode S.D. Min Max Range Mass Minimum 0.11 0.62 -2.92 -2.71 -3.22 1.64 -7.52 1.65 9.18 Maximum -0.37 1.18 0.13 0.16 0.64 1.73 -6.10 4.11 10.21 Range -0.40 1.18 0.08 0.10 -1.30 1.78 -6.11 4.11 10.23
When examining the aquatic and terrestrial prey mass distributions, I found that aquatic carnivores tend to feed on smaller-sized prey, with mean prey mass for minimum, maximum and the range being lower than terrestrial carnivores (Fig. 3.2, Table 3.5 and
3.6). Aquatic carnivore prey mass distributions are all negatively skewed (-0.39 to -
0.63), but in terrestrial carnivores negatively-skewed distribution are only seen for maximum and range prey mass distributions (-0.25 and -0.35). The prey mass distribution for terrestrial carnivores is relatively flat as suggested by the negative kurtosis values (-0.25 to -0.75). For aquatic species, the prey mass distributions are normally distributed with kurtosis value between 0.88 and 3.17. Additionally, aquatic carnivores feed on prey spanning 12 900 kg, compared with 2 700 kg for terrestrial carnivores. 52
Chapter 3 – Examining the Prey Mass of Carnivorous Mammals
Figure 3.2 Distributions of the minimum prey mass for (A) terrestrial carnivorous mammals (white bars) and (B) aquatic carnivorous mammals (grey bars), and the maximum prey mass for (C) for terrestrial carnivorous mammals (white bars) and (D) for aquatic carnivorous mammals (grey bars). Silhouettes by uncredited and Chris Huh, available for reuse under the Public Domain Mark 1.0 license (Panthera) and the
Creative Commons Attribution-ShareAlike 3.0 Unported license (Eubalaena).
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Chapter 3 – Examining the Prey Mass of Carnivorous Mammals
Table 3.5 Descriptive statistics for the prey mass distributions across 51 carnivorous terrestrial mammals. Minimum is the minimum prey mass consumed, maximum is the maximum prey mass consumed and range is the total range of prey mass consumed
(maximum minus minimum).
Prey Skew Kurtosis Median Mean Mode S.D. Min Max Range Mass Minimum 0.46 -0.25 -2.64 -2.23 -3.22 1.66 -5.61 1.65 7.27 Maximum -0.25 -0.75 0.54 0.70 2.74 1.66 -3.12 3.43 6.55 Range -0.35 -0.43 0.51 0.64 2.79 1.71 -3.78 3.43 7.22
Table 3.6 Descriptive statistics for the prey mass distributions across 57 carnivorous aquatic mammals. Minimum is the minimum prey mass consumed, maximum is the maximum prey mass consumed and range is the total range of prey mass consumed
(maximum minus minimum).
Prey Skew Kurtosis Median Mean Mode S.D. Min Max Range Mass Minimum -0.39 0.88 -3.22 -3.12 -3.30 1.52 -7.52 0.53 8.05 Maximum -0.59 3.17 -0.11 -0.33 0.64 1.65 -6.10 4.11 10.21 Range -0.63 3.10 -0.11 -0.36 -1.30 1.68 -6.11 4.11 10.22
3.5 DISCUSSION
The best model of prey mass evolution includes both carnivore mass and environment, although environment explains a small percentage (~8%) of variance in prey size. In spite of this, aquatic and terrestrial mammalian carnivores have different relationships suggesting different optimal foraging strategies. Aquatic mammalian carnivores have no relationship between prey (neither minimum nor maximum) and predator body mass, unlike terrestrial mammalian carnivores where there is a positive prey-predator
(both minimum and maximum) body mass relationship. In contrast to terrestrial predators, larger marine carnivores do not have to actively pursue prey with large body 54
Chapter 3 – Examining the Prey Mass of Carnivorous Mammals
mass to meet their energetic requirements (Carbone et al., 2007a). The abundance of small-sized prey in aquatic and marine environments (Fig. 3.2) is likely to have driven these patterns in marine carnivores. As well as prey availability, it is also important to note the effect of dimensionality on predator-prey relationships and consumption rates.
In 3D environments, it has been demonstrated that consumption rates are higher, not only the baseline rates but also the scaling exponent (Pawar et al., 2012). This not only has an impact on predator-prey relationships (e.g. larger consumer-resource body mass ratios) but also the strength of interactions between trophic levels and the stability of the community.
In addition to the effect of differences in prey availability and dimensionality, there are differences in body size patterns across aquatic and terrestrial carnivores. Marine mammals tend to have larger body sizes compared to terrestrial mammals because of the relaxation of biomechanical constraints and increased thermoregulatory constraints
(Smith & Lyons, 2011). This has an effect on the predator-prey relationships, which tend to be more accentuated in the marine environment due to this disparity in body size between predators and their prey. This has been illustrated by the presence of larger predator-prey mass ratios in aquatic environments (Brose et al., 2006b; Riede et al., 2011).
The lack of relationship between prey mass and predator mass could be because predator morphology is a large driver behind the prey choice of aquatic mammalian carnivores. Morphology is a limiting factor for aquatic carnivores physically unable to capture larger-sized prey (e.g. altered morphology of appendages to aid with swimming rather than grasping). Also, the combination of gape size and bite force in aquatic systems is believed to impact the number of trophic levels that predators can feed from
(Hairston & Hairston, 1993), where larger species often have a high trophic position
(Andersen et al., 2009b). When mammals feed on large prey, they tend to have a
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larger gape and a stronger bite force (Santana et al., 2012). For example, leopard seals have large muscles for mastication (e.g. masseter mass) as they feed on a mixture of prey including large and small species, compared to a crabeater seals that have a similar gape, yet smaller muscles of mastication as they predominantly feed on small prey species (Jones et al., 2013). Dentition is also likely to be important as carnivores with highly overlapping ranges often have different tooth morphology driven by competition for resources (Jonathan Davies et al., 2007). In the aquatic system mammals have specialised feeding morphology including keratinized baleen plates for filter feeding (mysticete whales), multi-cuspidate interlocking teeth for krill sieving (e.g. crabeater and leopard seals), simple teeth with reduced serration for catching fish
(piscivory e.g. dolphins), reduced teeth (e.g. Ross seal), rounded teeth (e.g. walrus) for eating hard-shelled molluscs or even the loss of teeth (e.g. sperm whale and beaked whales) for eating soft-bodied molluscs. Having specialised dentition can minimise resource competition; however it can leave these specialist carnivores vulnerable to higher extinction pressure if their prey populations were to collapse or become extinct
(Renaud et al., 2005; Dell'Arte et al., 2007).
The addition of environment into the PGLS models explains greater variance and has the highest phylogenetic signal only for minimum prey mass and not for models of maximum or range in prey mass. This suggests there are differences between aquatic and terrestrial mammalian carnivores in the patterns of minimum prey body mass only.
There is a great number of large aquatic mammalian carnivores feeding on small-sized prey whereas all large terrestrial mammalian carnivores are tied to feeding upon large- sized prey to maximise their energetic intake while minimising their expenditure
(Carbone et al., 2007a). In aquatic environments, particularly the marine system, the combination of the high abundance of prey below 500g, and the schooling nature of these prey, makes it efficient for large carnivores to switch to feeding on smaller prey.
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The combined results from the PGLS (phylogenetic signal; λ) and the variance components analysis suggest that phylogenetic relatedness is a major influence of prey mass distribution patterns across carnivorous mammals. The driving factor behind this result are the baleen whales, as they represent closely related species that share a common feeding strategy. This group represents some of the largest species today (up to 200 tonnes) and they feed on some of the smallest prey species (e.g. zooplankton).
Baleen whales consist of species from Balaenopteridae and Balaenidae, and all use filter feeding to capture their prey. There are also other feeding strategies, such as pack hunting, that are generally shared across taxonomic levels (i.e. at the family and genus level).
The most likely reason behind the scatter present in the relationship between body mass and prey mass of terrestrial carnivores (Fig. 3.1A-C), is related to carnivore feeding strategy. Terrestrial carnivores follows two feeding strategies: large prey consumers or small prey consumers (Carbone et al., 1999; Carbone et al., 2007a).
Terrestrial carnivore species weighing 21.5 kg or less feed on invertebrates and small vertebrate prey species (<10 kg) (Carbone et al., 1999). Above the 21.5 kg threshold, carnivores must shift to feeding on large vertebrate prey to meet their energetic requirements (Carbone et al., 1999). Several carnivore species that feed upon large vertebrate prey have evolved cooperative or pack hunting strategies, which confer several benefits. One benefit of hunting in a pack is the minimisation of the energy expended whilst hunting, but also maximising the size of the prey captured and prey capture efficiency (Creel, 1997; Rasmussen et al., 2008). An increase in the size of the prey captured, energetic intake and hunting success also follows an increase in the number of individuals within the group (Rasmussen et al., 2008). Another advantage of hunting cooperatively is that individuals may gain other benefits including increased body size or reproductive success. For example, individual male fossa (Cryptoprocta
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ferox) that forage in groups tend to have larger body size, which also enables increased competition and mating success (Lührs et al., 2013).
There are various drivers influencing the patterns of prey mass consumed by carnivorous mammals. The size of prey chosen by carnivores is driven by the trade-off between energy acquisition and expenditure, the available ecological niches and the dimensions of the environment (Pawar et al., 2012). Foraging animals minimise their energetic costs while maximising energetic gains by moving towards an optimal foraging strategy. As different species evolved different foraging strategies, driven by their evolutionary history and environmental influences, this shapes the patterns of prey mass that are consumed by carnivores. Additionally, the mass of prey utilised by carnivores is influenced by the ecological niches available to them and the resource encounter rate, both of which have an effect on the foraging strategy and the prey availability (Moritz et al., 2008; Bromham et al., 2012; McCain & King, 2014).
Carnivore energetic costs and prey density both influence the minimum prey mass consumed. Carnivores tend to feed on prey above a certain mass due to the increasing inefficiency of feeding on small prey, because a low capture rate will arise when carnivores forage on prey much smaller than themselves (Brose, 2010). However, this can be overcome in instances where prey species are in high densities, as illustrated by marine carnivores (e.g. baleen whales) who can survive feeding upon prey less than
1 g (e.g. krill and other invertebrates). This is further highlighted by the lower minimum prey mass of aquatic carnivores compared to that of terrestrial carnivores (Fig. 3.2).
At the other end of the scale, maximum prey mass is driven by morphological constraints (i.e. gape and locomotion) and energetic costs. A carnivore feeding on prey considerably larger than their own mass will result in a mismatch of reaction time, where the carnivore will respond at a slower rate than that of the prey and will end with
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the prey escaping and the carnivore in an energetic deficit (Brose, 2010). Additionally, while it would be ideal for all carnivores to feed on large-sized prey species (provided that all carnivores could successfully capture large prey), it would be considerably costly from an energetic perspective, not to mention the increased amount of time spent processing and ingesting the prey (Carbone et al., 2007a; McCain & Colwell,
2011).
Modal prey mass is influenced by environmental drivers. Based on the data used in the study, the minimum prey mass range (0.0001 to 0.01 kg) is the most commonly utilised by carnivorous species from the aquatic and terrestrial environments. The type of prey included within this weight range are invertebrates (aquatic and terrestrial), small mammals, fish and squid. The most common maximum prey range differs between environments, with terrestrial carnivores predominantly feeding on prey between 1 to
100 kg (i.e. small and large mammal prey), compared with 0.01 to 1 kg for aquatic carnivores (i.e. invertebrate, squid and fish prey). With the prey-weight categories of
0.0001 - 0.01kg, 1 - 100 kg and 0.01 - 1 kg being the most abundant, this suggests that feeding within these ranges is a common foraging strategy across carnivores.
Additionally, modal prey mass will also be driven by the characteristics of the environment, where primary productivity and trophic interactions will shape the size of prey available and the abundance of these prey species. For example, productivity within the marine environment is driven by small, single-celled organisms, allowing higher availability of productivity to consumers and higher predator-prey body mass ratios (Riede et al., 2011).
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3.6 CONCLUSION
In summary, carnivorous mammals within my sample differ in the size of prey they consume and this is influenced by a suite of factors including phylogenetic relatedness, carnivore body mass, the characteristics of the environment in which the carnivore resides, and has evolved within, as well as carnivore energetics. Whilst phylogenetic relatedness and carnivore body mass are the dominant drivers of the prey mass consumed by mammals, the physical environment has a role in the minimum-size prey that can be consumed. Previous research has shown that there is a positive relationship between carnivore mass and the mass of their prey. However, I have demonstrated that this is not the case for aquatic mammalian carnivores. Differences in environmental characteristics including primary productivity and food-web structure are driving the differences in prey mass consumed across aquatic and terrestrial carnivores.
Optimal foraging strategies in mammalian carnivores differ not only across species but also physical environments, which needs to be accounted for when thinking about carnivore behaviour. Gaining a better understanding of the relationship between mammalian carnivores and their prey, predator strategies and the factors driving these patterns, will aid with predictions of carnivore susceptibility to population declines and the role of carnivores within ecosystems.
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4.1 SUMMARY
Predator-prey relationships play a key role in the evolution and ecology of carnivores, as well as the structure of ecosystems. An understanding of the relationship between predators and their prey and how this differs across species and environments provides information on how carnivorous strategies have evolved and how they may change into the future with environmental changes. Prey consumed by mammals is size-dependent, with terrestrial carnivores above 21kg feeding on larger-sized prey to meet increasing absolute energetic requirements. However, previous studies did not consider marine carnivores. This is an important omission because it is likely that an aquatic lifestyle has altered the predator-prey body-size relationship due to larger body sizes (up to 200 tonne), higher thermoregulation costs and differences in prey distributions. I reassess the predator-prey body-size relationship across mammalian carnivores, with the inclusion of marine mammals, to determine how the predator-prey body-size relationship relates to the energetic requirements in different environments and how it shapes the feeding strategies adopted by different predatory mammals. I compiled data on prey mass, daily energetic intake and daily energetic expenditure from the literature. Using a phylogenetic framework and piecewise regression, I investigated the relationship between predator-prey size, and energetic requirements across 107 carnivorous mammals, including 51 terrestrial and 56 marine mammals. I found that marine and terrestrial carnivores have evolved opposing predatory
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behaviours likely to minimise energy expenditure while maximising energy intake.
Large marine carnivores (>11 000 kg) feed on prey equal to 0.01% of the carnivore’s body size on average, compared to 45% or greater in large terrestrial carnivores (>21 kg). Differences in primary productivity and ecosystem structure across the marine and terrestrial environments seem to have altered the type of prey available to mammals, which has subsequently led to the evolution of novel foraging strategies. The results provide important insights into the selection pressures early marine mammals may have faced that ultimately led to the evolution of a range of feeding strategies (e.g. bulk feeding) and other behaviour (e.g. extreme diving capabilities), and may also explain the massive body sizes many marine mammals have obtained.
4.2 INTRODUCTION
There is a strong link between physiology and behaviour in carnivorous mammals. For example, much of the variation in ranging behaviour of carnivorous mammals can be attributed to the energetic requirements of being a carnivore and the distribution of preferred prey (Kelt & van Vuren, 2001; Carbone et al., 2005). Carnivore body mass is a strong predictor of average prey size in terrestrial environments, where small carnivores less than 14.5-21 kg feed on small prey and carnivores above this weight range feed on large prey (>45% of their own body weight; Carbone et al., 1999). The population dynamics of predators is impacted by prey choice and the population fluctuations of those prey species. This is because a drop in prey density will result in a drop in carnivore density, especially in large-sized predator species who require large quantities of prey to survive (Carbone & Gittleman, 2002; Carbone et al., 2011).
Carnivorous mammals generally have low population densities and slow growth rates, which make them highly susceptible to population declines whenever changing environmental conditions start to impact the distribution of their prey (Cardillo et al.,
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2005; Davidson et al., 2009; Carbone et al., 2011; Angerbjörn et al., 2013). The trophic importance and key role of carnivores within their ecosystems (e.g. indirect influence on carbon storage and disease regulation; Miller, 1996), renders them an important group to investigate predator-prey interactions on a global scale.
Information on prey choice in mammals and the evolutionary processes that have led to these patterns is important for two reasons. First, building our knowledge of carnivore behaviour is essential for linking patterns and processes of ecosystem structure and function, foraging patterns and predator-prey interactions (Gaston &
Blackburn, 1996; Carbone et al., 2011). For example, examining the behaviour of wolves within Yellowstone National Park has illustrated the direct and indirect impacts of their behaviour on this ecosystem, including the population dynamics of herbivorous mammals, plants and scavenger species (Brown et al., 2002; Warton et al., 2012;
Banbury & O'Meara, 2014). Second, with improved information on carnivore behaviour we can develop broad-scale models of predator-prey relationships that feed back into our understanding of species diversity, in terms of the number of species present in an ecosystem, and the function of carnivore species in an ecosystem (e.g. Yellowstone wolves). Despite previous investigations into mammalian predator-prey relationships
(Carbone et al., 2007a; Barnes et al., 2010), we still lack a global understanding of the nature of mammalian predator-prey relationships because of the bias toward terrestrial carnivorous mammals.
Marine carnivorous mammals provide an interesting comparison to terrestrial carnivores for several reasons. Marine mammals can reach sizes several orders of magnitude larger than the largest terrestrial carnivore (Smith et al., 2010). Marine mammals have achieved impressive sizes in part because there are fewer mechanical constraints in an aquatic environment and the associated advantages of large body size in a marine environment (e.g. thermoregulation; Clauset, 2013). Despite the 63
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relaxation of mechanical constraints in water, marine mammals still demonstrate a positive allometric relationship in energy requirements with body size (Nagy, 2005).
Any increase in energetic expenditure will therefore lead to an increase in energy intake and directly impact the feeding strategies adopted by marine mammals.
Physiological adaptations could offset some of these increased absolute energy requirements by allowing more efficient assimilation of food. Marine carnivores have longer small intestines than their terrestrial relatives (Williams et al., 2001) to enhance the digestion and assimilation of food (Slijper, 1976; Stevens & Hume, 1995). Marine mammals also have behaviours that enable them to deal with changes in energy expenditure and intake that include adjusting their reproductive output and foraging effort (Boyd & Murray, 2001; Costa, 2007). Furthermore, I predict that strategies that are suitable for a given sized predator on land might not be viable in marine environments because prey are distributed differently on land compared to at sea
(Brose et al., 2006b). I reassess the predator-prey body-mass relationship across mammalian carnivores, with the inclusion of marine species, to determine how the predator-prey body-mass relationship relates to the energetic requirements in different environments and how it shapes the feeding strategies adopted by different predatory mammals.
So far two feeding strategies have been formally identified and modelled for terrestrial carnivores, and these reflect the different energetic requirements of different sized predators (Carbone et al., 1999). Small carnivores are able to meet their energetic requirements while minimising the energetic costs of feeding by eating invertebrates.
As carnivores increase in body size, their absolute energy requirements also increase and a feeding strategy relying exclusively on invertebrates becomes inefficient
(Carbone et al., 2007a). As body size converges on 15-21 kg, there is a sudden two- fold increase in both energy intake and energy expenditure and this in turn corresponds with a shift to feeding on larger prey (Carbone et al., 2007a). 64
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Previous investigations, including terrestrial and some marine mammals, have identified an increase in energetic expenditure with increasing body size across mammals (Nagy, 2005). Despite the similarities in the patterns of energetics and body mass across marine and terrestrial mammals, we might expect the nature of the predator-prey relationships in the marine environment to be potentially very different to those seen in terrestrial carnivores. This is because of the differences in primary productivity and food web structure across the marine and terrestrial environments
(Shurin et al., 2006; Brose, 2010), which has driven the abundance of small species that form dense aggregations (e.g. invertebrates and vertebrates). The abundance of small prey has resulted in an increase in the encounter rates between marine carnivores and small prey species, as well as providing a resource with sufficient energy to support populations of marine carnivores (Scharf et al., 2000; Goldbogen et al., 2011). This has enabled both smaller carnivores (e.g. crabeater seals) and large carnivores (e.g. blue whales) to consume small prey species (<50 g) (Dalla Rosa et al.,
2008; Brierley & Cox, 2010; Hückstädt et al., 2012). With the exposure of marine carnivores of various body sizes to both small (<10 kg) and large (>10 kg) prey species, it is possible there is no relationship between marine carnivore mass and prey mass. Previous work by Tucker and Rogers (2014) examined the minimum, maximum and range of prey masses consumed by mammalian carnivores, and found that there was no relationship between prey mass and carnivore mass for marine mammals (see also Chapter 3). If there is also no relationship for mean prey mass, then it is likely that the quantity of prey consumed by marine carnivores will become more important than the size of the prey in order to meet the increase in the energy required by larger marine carnivores.
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4.3 MATERIALS AND METHODS
To investigate the relationship between mammalian carnivore body mass, prey body mass and the energetic expenditure and gain, I compiled data on predator and prey mass, daily energy intake and expenditure for 107 mammal species across the marine and terrestrial environments. I began by first establishing the energetic requirements of mammals on land and in water by examining the relationships between daily energy intake (DEI) and body mass, and daily energetic expenditure (DEE) and body mass.
Based on the two-fold increase in energy intake and expenditure above a mass of 21kg in terrestrial carnivores, my first objective was to identify what this threshold, or
“breakpoint”, might be for marine carnivores. I applied a piecewise or segmented regression (McGee & Carleton, 1970) within a phylogenetic framework to test whether species above a certain mass had a corresponding jump in DEI or DEE. Once these energetic relationships were established, I used the same phylogenetic piecewise regression approach for my second objective, which was to determine whether changes in energy intake and expenditure were associated with corresponding changes in prey mass. I expected that for at least terrestrial mammals, predators above
21kg would exhibit the previously identified shift to consuming larger-sized prey
(Carbone et al., 1999). In the case of marine mammals, however, the specific relationship between predator mass and prey mass, and how this relationship relates to the energetics of marine mammals, has not been examined and it was subsequently unclear what the impacts of large size might be for prey choice in marine carnivores.
4.3.1 Data
I analysed prey mass and predator mass for 107 carnivorous mammal species across the marine and terrestrial environments (Appendix 5, Table S5.1). Carnivores were defined as those species with diets compromising of at least 90% meat. This classification included insectivores as carnivores (Kelt & van Vuren, 2001). Insectivores
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were also included as they represent a carnivorous strategy for species below ~10 kg and contribute towards the breakpoint in terrestrial predators (Carbone et al., 2007a).
Mean prey mass data was obtained in two ways; (1) from published prey mass values
(n=53), and (2) using data from the literature to calculate mean prey mass values based on the proportion of prey species consumed by that carnivore (n=54). When prey preference information was not available, the mean prey mass was calculated from the listed prey species (n=2). Mean prey mass values were calculated using information on both sexes and dietary information across populations. Published information on adult daily energy intake (DEI) and expenditure (DEE) in kJ day-1 were also collected for species where this data was available (Appendix 5, Table S5.1). The values of DEI and DEE consisted of a mixture of directly measured values (e.g. accelerometry) and estimated values using allometric equations (e.g. Sigurjónsson &
Vikingsson, 1997). I have had to include estimated energetic values because of the difficulties associated with measuring energetic intake and expenditure in large marine carnivores (e.g. cetaceans), resulting in little or no published data available for these species. In this study, the main purpose of the energetic data is to examine whether patterns in mean prey mass are similar to those of DEI/DEE, not whether there is a relationship between DEI/DEE and body mass. Additionally, I am aware that there are different methodologies utilised to directly measure energetics in mammals including accelerometry, doubly labelled water and calorimeter/respirometry chambers, and there is variability across these methodologies (e.g. Dalton et al., 2014). However, at the scale of this study and with all of the data undergoing log10 transformation prior to analysis, these effects are likely to have little effect on the results.
4.3.2 Phylogenetic Information
Phylogenetic information was based on a pruned version of the mammalian supertree of Fritz et al. (2009) in which branch lengths were proportional to time since divergence. Divergence times were calculated using molecular clock analysis and the 67
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tree included fossil data for calibration (Bininda-Emonds et al., 2007). Sotalia guianensis was positioned onto this phylogeny based on the typology from Caballero et al. (2008) and the branch length was time-scaled based on the cetacean phylogeny by
Slater et al. (2010). Carnivora and cetacean positioning was updated using the recently published trees by Slater et al. (2010) and Nyakatura & Bininda-Emonds (2012), respectively. All tree manipulations were performed using Mesquite ver 2.74 (Maddison
& Maddison, 2010).
4.3.3 Analysis
Model selection using second-order Akaike’s information criterion with a correction for sample size (AICc) and phylogenetic generalised least squares (PGLS) regression
(see Analysis section in Chapter 2) were used to examine alternative models of DEE,
DEI and mean prey mass. The PGLS analyses were conducted using COMPARE ver
4.6b (Martins, 2004). Daily energetic expenditure and intake have been demonstrated to drive predator behaviour (Carbone et al., 2007a). To establish the energetic requirements of mammals with the addition of marine mammals, I investigated DEE and DEI with body mass using Piecewise regression. Piecewise regression tests whether the (McGee & Carleton, 1970). The value where one interval transitions to the next interval is the breakpoint. Piecewise regression can be described by;
푏1 ln(푥) + 푐, ln(푥) ≤ 퐵푃 ln(푦) = { (1) 푏2 ln(푥) + 푑, ln(푥) > 퐵푃
where, b1 is the slope when x is equal to or below the breakpoint value of BP , b2 is the slope when x sits above the breakpoint value of BP , c is the intercept when x is equal to or below the breakpoint (BP) and d is the intercept when x sits above the
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breakpoint (BP). The breakpoint analyses for DEE and DEI were performed using
βintercept+βmass+βbreak_x+βmass*βbreakpt_x, a model to examine the DEE or DEI of predators, including predator mass (βmass) and the potential breakpoint (βbreak_x), where x represented a range of percentages between 0 to 0.95 at 0.05 increments. An interaction term was included (βmass*βbreakpt_x) to test for the slope of the relationship (i.e.
DEE or DEI vs. predator body mass) above the breakpoint. The upper and lower credible support limits associated with the best-supported breakpoint were determined by the minimum and maximum breakpoint values within two AICc units of the best- supported model.
I then looked at the relationship between predator body mass and prey body mass, specifically looking for a change in intercept to identify whether there has been a major shift in predatory behaviour across mammals with the inclusion of marine species. To begin with, I used three sets of piecewise analyses using data on all species (marine and terrestrial), only marine species and only terrestrial species. Using a similar model to the energetic models, mean prey mass consumed by predators was examined using
βintercept+βmass+βbreak_x+βmass*βbreakpt_x, a model to examine the average prey size consumed by predators, including predator mass (βmass) and the potential breakpoint
(βbreakpt_x), where x represented a range of percentages between 0 to 0.95 at 0.05 increments. An interaction term was included (βmass*βbreakpt_x) to test for the slope of the relationship (i.e. predator mass vs. predator body mass) above the breakpoint.
To clarify the presence of 3 separate trends of predator and prey body mass, I assessed the fit of four additional models: (1) βintercept+βmass+βenvironment+βmass*βenvironment, a model where both predator body mass and whether species occupied a terrestrial or marine environment (coded as 0 or 1 respectively) explained differences in prey mass;
(2) β0, a null model with no predictor variables that assumed variance in prey body mass consumed by predators simply reflected the process of Brownian motion and 69
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stochastic factors associated with evolutionary differentiation; (3)
βintercept+βmass+βterrestrial_large+βmarine_small+βmarine_large, a model which includes predator body mass and four dummy variables (terrestrial and marine below breakpoint, terrestrial and marine above breakpoint); and (4) βintercept+βmass+βterrestrial_large+βmarine_large, a model which includes predator body mass and 3 dummy variables (terrestrial and marine above breakpoint and the remaining species). All dummy variables were coded as either 0 or 1, where 0 represents a species below the associated body mass breakpoint
(i.e. marine or terrestrial breakpoint) and 1 represents a species above the body mass breakpoint. Models 3 and 4 also included all possible combinations of interaction terms
(i.e., βintercept+ βmass+βx+βmass*βx) to test for differences in the scaling of predator-prey mass for each group (e.g. marine above breakpoint versus terrestrial above breakpoint).
4.4 RESULTS
4.4.1 Energetics
The DEI model with the lowest AIC value revealed a single breakpoint at 18kg (45th percentile, with a two unit credible range of 35th to 50th percentile or 11 to 37 kg; Fig.
4.1A and S5.1A) and the estimated parameter values of this model showed an approximately 3-fold jump in energy intake above the breakpoint (Table 4.1). The DEE model with the lowest AIC inferred a single breakpoint at 49kg (55th percentile, with a two unit credible range of 50th to 60th percentile or 40 to 79 kg; Fig. 4.1B and S5.2A) and an approximately 3-fold jump in energy expenditure above the breakpoint (Table
4.1). I did not find any support for a second breakpoint for large marine carnivores (>
10 000 kg) for either DEI or DEE.
70
Chapter 4 – The Cost of Carnivory Revisited
Fig. 4.1 Estimates of (A) Daily energy intake (DEI) against carnivore body mass (n=48) and (B) daily energy expenditure (DEE) against carnivore body mass (n=27) in marine and terrestrial mammals combined. The solid lines represent the breakpoint regression fit and the dotted lines represent the breakpoint at 18.73kg and 49.71kg for DEI and
DEE respectively. Eubalaena silhouette by Chris Huh and available for reuse under the
Creative Commons Attribution-ShareAlike 3.0 Unported license. Panthera silhouette is uncredited and is available for reuse under the Public Domain Mark 1.0 license.
71
Chapter 4 – The Cost of Carnivory Revisited
Table 4.1 Best supported breakpoint models and associated coefficients for daily energetic intake (DEI) and daily energetic expenditure (DEE) in relation to predator mass (M). The breakpoint (BP) represents the percentile threshold of the log10- transformed body mass above which expenditure or intake shifts to the higher intercept
(βintercept, >BP) or differing slope (βmass, >BP), compared to the intercept (βintercept, Parameter Parameter Coefficients (95% CI) βmass, DEI βmass, >BP 0.53 (0.33,0.73) βintercept, βintercept, >BP 3.62 (3.34,3.90) BP 1.27 βmass, βmass, >BP 0.52 (0.259,0.781) DEE βintercept, βintercept, >BP 3.67 (3.23,4.11) BP 1.70 4.4.2 Prey Size Across all species (terrestrial and marine species combined), the PGLS model with the lowest AIC value included a breakpoint at ~11.1 kg (35th percentile, with a two unit credible range of 30th to 45th percentile or 11 to 36 kg; Table 4.2 and Fig. S5.3C) and a shift to feeding on prey 58 times larger (0.03 kg to 1.56 kg). By design this analysis only identified a single breakpoint and I had predicted that there were likely unique breakpoints (or no breakpoints) for terrestrial and marine mammals. I therefore looked for breakpoints using a second analysis that treated terrestrial and marine species separately. For terrestrial mammals, a similar breakpoint to the initial inclusive analysis was highlighted at ~11 kg (70th percentile, with a two unit credible range of 60th to 80th 72 Chapter 4 – The Cost of Carnivory Revisited percentile or 10 to 21 kg; Table 4.2 and Fig. S5.3A) that was associated with a shift to feeding on prey 37 times larger (from 0.09 kg to 3.23 kg). However, for marine mammals there was a unique breakpoint at ~11 000 kg (80th percentile, with a two unit credible range of 60th to 85th percentile or 1412 to 19498 kg; Table 4.2, Fig. S5.3B) that was associated with a dramatic drop in prey size (~1300 times smaller, from 0.22 kg to 0.0002 kg). The phylogenetic effect size (r) of the piecewise analyses also increased when terrestrial and marine species were examined separately (all species = 0.34, marine = 0.50 and land = 0.78), suggesting these separate analyses had a greater explanatory power. Table 4.2 Best supported breakpoint models and associated coefficients for prey mass (P) against predator mass (M). The breakpoint (BP) represents the percentile threshold of the log10-transformed body mass above which prey mass shifts to the new intercept (βintercept, >BP) or differing slope (βmass, >BP), compared to the intercept (βintercept, Parameter Parameter Coefficients (95% CI) βmass, βmass, >BP -0.56 (-1.76,0.64) All Species βintercept, βintercept, >BP 0.78 (-0.52,2.08) BP 1.05 βmass, βmass, >BP -0.19 (-2.70,2.32) Marine βintercept, βintercept, >BP -3.01 (-14.33,8.31) BP 4.06 βmass, βmass, >BP 1.74 (0.69, 2.79) Terrestrial βintercept, βintercept, >BP -1.30 (-2.57, -0.02) BP 1.04 73 Chapter 4 – The Cost of Carnivory Revisited These results confirmed the existence of contrasting feeding strategies in mammals that were associated with differing predator mass thresholds depending on the type of environment in which predators lived (Fig. 4.2). Small terrestrial mammals (<11 kg) feed on small prey, while large terrestrial mammals (>11 kg) make an abrupt transition to feeding on large prey (see also Carbone et al., 1999). However, within the same size range of these large terrestrial mammals, marine mammals have continued to feed predominantly on smaller-sized prey, up to a point, after which the largest marine mammals make a major shift to feeding on very small prey (< 0.0001 kg). Looking at the distribution of data in Figure 4.2, smaller marine species seem to exploit similar sized prey to the smaller class of terrestrial species (0.01-1 kg). 74 Chapter 4 – The Cost of Carnivory Revisited Figure 4.2 Mean prey body mass as a function of carnivore body mass for 107 species across the marine and terrestrial environments. The blue and green lines are the breakpoint regression fit for marine and terrestrial species respectively. The dotted vertical lines represents the 11 kg threshold where terrestrial carnivores shift from feeding on small prey to large prey, and the 11 380 kg threshold where marine carnivores shift from feeding large prey to feeding on smaller prey. Letters a-e represent outlying species; (a) Zalophus californianus, (b) Hydrurga leptonyx, (c) Ursus maritimus, (d) Orcinus orca and (e) odontocete whales including Physeter macrocephalus and Berardius_bairdii. 75 Chapter 4 – The Cost of Carnivory Revisited To determine whether small terrestrial mammals and small marine mammals were in fact selecting similar sized prey, I formulated a series of models to detect similarities or differences in slope and intercept of the relationship between predator mass and prey mass among four subgroups: small terrestrial mammals (< 11 kg), large terrestrial mammals (>11 kg), small marine mammals (10-10 999 kg) and large marine mammals (> 11 000 kg). The results were mixed, with various models obtaining equivalent support (models at or near a ∆AIC value of 2; Table 4.3 and Fig. 4.2). In general, the supported models were those that assumed some combination of difference in intercept and slope among the four subgroups (Table 4.3). Despite impressions from Figure 4.2 that assumed similarities in prey preference between small terrestrial mammals and small marine mammals, and also that breakpoints were specifically associated with the transition to the marine environment and not body mass per se, the models which tested these impressions received little support (Table 4.3). 76 Chapter 4 – The Cost of Carnivory Revisited Table 4.3 Level of support for explanatory models of prey mass of predatory mammals. Results are from phylogenetic regression analyses. Models with the strongest support have small AIC values. Model * Rank ∆AIC Linear βintercept+βmass+βenvironment+βmass*βenvironment 9 23.01 Null βintercept 14 42.58 βintercept + βmass + βterrestrial_large + βterrestrial_large * βmass + βmarine_small + βmarine_large 1 0 βintercept + βmass + βterrestrial_large + βmarine_small + βmarine_small * βmass + βmarine_large 2 0.60 βintercept + βmass + βterrestrial_large + βterrestrial_large * βmass + βmarine_small Piecewise + βmarine_small * βmass + βmarine_large 3 1.01 4 groups βintercept + βmass + βterrestrial_large + βmarine_small + βmarine_large 4 1.01 βintercept + βmass + βterrestrial_large + βterrestrial_large * βmass + βmarine_small + βmarine_large + βmarine_large * βmass 5 2.03 βintercept + βmass + βterrestrial_large + βterrestrial_large * βmass + βmarine_small + βmarine_large + βmarine_large * βmass 6 2.33 βintercept + βmass + βterrestrial_large + βterrestrial_large * βmass + βmarine_small + βmarine_small * βmass + βmarine_large + βmarine_large * βmass 7 2.89 βintercept + βmass + βterrestrial_large + βmarine_small + βmarine_large + βmarine_large * βmass 8 2.99 βintercept + βmass + βterrestrial_large + βterrestrial_large * βmass + βmarine_large 10 23.28 βintercept + βmass + βterrestrial_large + βterrestrial_large * βmass + βmarine_large Piecewise + βmarine_large * βmass 11 25.27 3 groups βintercept + βmass + βterrestrial_large + βmarine_large 12 28.11 βintercept + βmass + βterrestrial_large + βmarine_large + βmarine_large * βmass 13 30.05 * terrestrial/marine_large = species above 11kg/11000kg breakpoints, terrestrial/marine_small = species below the 11kg/11000kg breakpoints 77 Chapter 4 – The Cost of Carnivory Revisited 4.5 DISCUSSION I show that four distinct predator feeding strategies have evolved in mammals (not two, as previously thought; Carbone 1999): small terrestrial carnivores (less than 11kg) feed on small terrestrial prey less than 1 kg, large terrestrial carnivores (above 11 kg) feed on large terrestrial prey above 3 kg, small marine mammals (below 11 000 kg) feed on small marine prey less than 2 kg, and larger marine carnivores (above 11 000 kg) feed on very small marine prey less than 0.0005 kg (or 0.5 g). Following the colonisation of the marine environment, mammals below 11 000 kg in general seem to behave in a manner broadly similar to terrestrial carnivores below 11kg as they feed predominantly on small sized prey (for marine species this includes squid and fish, but may also include zooplankton and some large vertebrates such as seals). However, marine mammals larger than 11 000 kg have switched to a strategy of consuming tiny prey items, and in huge quantities to meet their massive energy requirements. Based on my data, I did not find a second DEI or DEE breakpoint for marine carnivores, suggesting that there may not be a shift up or down in energetics for large marine carnivores. This finding may be an actual trend, but this could also be an artefact of my data. Due to the small sample sizes across marine and terrestrial species I could not split the species by their environment and examine the energetic thresholds independently. The results did suggest that there might be a difference between the DEI and DEE breakpoints across marine and terrestrial carnivores (18 kg vs. 49 kg). The DEI breakpoint overlaps with the previously identified threshold for terrestrial mammals of 15-21 kg (Carbone et al., 1999), but the DEE breakpoint is nearly 3 times larger. However, a possible reason for this disparity between the breakpoints again relates to the potential limitations of data on energetic intake and expenditure of marine mammals resulting from the difficulties associated with collecting energetic information on animals living permanently in water. Probably as a result of 78 Chapter 4 – The Cost of Carnivory Revisited this, the species included in these two analyses did not overlap exactly (n = 48 for DEI, n = 27 for DEE). Improving tagging technologies will hopefully allow more energetic information to become available in the near future and clarify the nature of this disparity between DEI and DEE, as well as improving our ability to examine the energetic thresholds across marine and terrestrial carnivores. Nevertheless, the results are clear in showing that terrestrial mammals manage the jump in energy demand associated with their large size by making an abrupt transition to consuming much larger prey (prey> 45% of predator body mass; Carbone et al., 1999), for example lions (Panthera leo) on average can consume about 6kg of prey, which is equivalent to ~ 0.07 wildebeest per day (Fryxell et al., 2007). However, this same transition to consuming larger prey has not occurred in marine mammals. Once marine carnivores reach 11 000 kg there is a major shift in feeding ecology, but to the transition of feeding on massive quantities of very small prey (~0.01% of the predator’s body mass; this study), including invertebrates such as zooplankton. For example, minke whales (Balaenoptera bonaerensis) consume up to 300kg of prey per day, which is equal to enormous quantities of individual krill (i.e. thousands of individuals; Reilly et al., 2004). There are several drivers behind the different strategies identified across the marine and terrestrial carnivores. There are differences in the availability of protein to predators between the two environments. In the ocean, protein is available as dense aggregations of small species (Tarling & Thorpe, 2014). Around 34 million years ago changes in the climate and the ocean altered marine productivity and saw the emergence of large quantities of small marine invertebrates. For these marine invertebrates, refuge from predators was available in coastal waters (among sea-grass, coral and kelp forests or in the sediment) and in polar regions (under-ice habitats), however in the pelagic deep oceans, which are dominant habitats within the earth’s 79 Chapter 4 – The Cost of Carnivory Revisited landscape, there are few refugia. Around this time one of the earliest mysticete-like whales, Llanocetus, was presumed to be filter-feeding as mysticetes do today (Clementz et al., 2014). Marine invertebrates living within a deep-sea habitat (e.g. krill) avoid predation by aggregating in swarms (Brierley & Cox, 2010) and vertical migration (Cox et al., 2009). Marine mammals evolved strategies to exploit this swarming behaviour. Archaeocetes (a group of primitive cetaceans in the early Eocene), crabeater seals and leopard seals have specialised molar teeth for krill-sieving and oral cavity adaptations for suction feeding (Kissling et al., 2014). Mysticete whales saw further anatomical adaptations. This included the loss of teeth completely and the development of baleen (keratinized plates that hang from the rostrum and are used for filter-feeding; Goldbogen et al., 2013) and a specialised joint between the frontal bone and the mandible (the frontomandibular stay; Lambertsen et al., 1995), which allows the oral cavity to open wider (~ 75 degrees compared with ~55 degrees in terrestrial carnivores; Falkowski & Raven, 1997; Andersson et al., 2011) to allow the rapid influx of prey-laden water. Pleating of the buccal region allowed for further expansion, the buccal cavity (Courchamp & Macdonald, 2001; Van Valkenburgh, 2007; Burnham et al., 2011), providing additional capacity for rapid bulk feeding as animals swam through swarming prey. The structure of the hyolingual apparatus in mysticete whales differs depending on their feeding method. In the balaenopterids, for example, the tongue is less muscular and facilitates the expansion of the buccal cavity (Werth, 2007). In the three-dimensional pelagic waters (where nutrients are available) the presence of phytoplankton communities, and the zooplankton communities (e.g. protozoans) that feed on the phytoplankton, supports enormous densities of predatory marine invertebrates (e.g. krill, copepods and amphipods). For example, in the Southern Ocean the density of krill has been measured up to 2559 individuals m-3, with the 80 Chapter 4 – The Cost of Carnivory Revisited swarm measuring up to 18 km long and spanning an area of 132,798 m2 (Tarling & Thorpe, 2014). The ability to harvest greater resources (swarming invertebrates) may have led to greater body size, which in turn allowed these mammals to dive to greater depths. At these depths whales had the ability to overcome the vertical-migration anti-predator strategy of the swarming marine invertebrates and exploit a new niche. Marine carnivores evolved physiological and behavioural adaptations to enhance deep diving. These include apnoea (breath holding), bradycardia (slowed heart rate), redistribution of blood to vital organs, hypometabolism, cooperative feeding and gliding for deeper diving (Boyd, 1997). In the terrestrial system there is no similar invertebrate schooling biomass. This same schooling behaviour is not seen in protein-rich terrestrial systems perhaps due to the heterogeneity of the terrestrial landscapes, which provides adequate refugia for invertebrates. There are aggregations of terrestrial invertebrates in mounds (e.g. termites, densities of 2139 individuals m2; Bodine & Ueckert, 1975) that are exploited by a range of mammal species (e.g. aardwolf, anteater and pangolin) and insects in the air that are exploited by bats (e.g. microbats). However, invertebrates can only support terrestrial carnivores up to 11-21kg (this study; (Carbone et al., 1999). This is due to the lower abundance of these aggregations and the associated increase in energy expenditure when capturing these small prey items and the decrease in energy assimilated (Carbone et al., 2007a). Another factor behind the different strategies across carnivorous mammals is related to the differences in energy allocation across species from the marine and terrestrial environments. Terrestrial mammals allocate a higher proportion of their energy to locomotion (~90%), compared with marine mammals which allocate more of their 81 Chapter 4 – The Cost of Carnivory Revisited energy to maintenance (~40%; Williams, 1999). Additionally, it has been illustrated that marine carnivores have a higher hunting efficiency than terrestrial carnivores (energy ingested > energy expended; Williams & Yeates, 2004). Despite these differences, terrestrial and marine carnivores have adopted strategies that minimise energy expenditure whilst hunting, whether it is consuming prey of increasing body mass on land or feeding on large quantities of small prey in the ocean. Carnivores towards the maximum body size in both environments have additional strategies to cope with their high absolute energy requirements and the elevated costs associated with prey capture. On land, lions spend the majority of their time resting in addition to cost- minimising strategies during the hunt (Schaller, 1972; Carbone et al., 2007a). In the ocean, there are high costs associated with lunge feeding including bursts of high energy muscle activity and elevated metabolic demands (Potvin et al., 2012). However, these costs are mitigated by decreasing the number of lunges per dive, passive feeding (e.g. cooperative feeding at the surface) and an increased recovery period post diving (Potvin et al., 2012). There are a couple of exceptions to the feeding strategies identified in this study. I have discussed at length the feeding adaptations in the mysticete whales, but there is an alternate feeding method for large-bodied marine carnivores demonstrated by odentocete whales. Most odontocetes have retained their teeth and generally utilise swarms of larger-sized prey species including fish (e.g. Genypterus blacodes (Gaskin & Cawthorn, 1967) and Merluccius merluccius (Agosta & Bernardo, 2013)) and squid (e.g. Nototodarus sloanei (Gaskin & Cawthorn, 1967) and Gonatus steenstrupi (Hanna & Cardillo, 2014)). In the extreme case, some odontocetes can consume prey over 30 kg (Dalerum, 2013; Clarke & O'Connor, 2014), such as sperm whales (Physeter macrocephalus). Killer whales (Orcinus orca) that specialise on feeding on whales and seals are an example of a large marine predator that feeds on large prey and in some cases prey that are larger than the killer whales themselves (e.g. minke whales). Killer 82 Chapter 4 – The Cost of Carnivory Revisited whales are similar to the terrestrial carnivores such a lion that employs cooperative hunting behaviour to capture large prey (Pitman & Durban, 2012). I should also point out that there are also other species within the marine environment which utilise cooperative hunting to maximise capture efficiency including dolphins and baleen whales (Gazda et al., 2005; Wiley et al., 2011). However, these species tend to capture smaller prey that form schools or swarms (e.g. plankton or fish). The polar bear (Ursus maritimus) is another unusual large marine predator that feeds on large prey (e.g., seals; Derocher et al., 2002). However, the polar bear is a comparably recent convert to a marine lifestyle (~1.1 Myr; Nyakatura & Bininda-Emonds, 2012), so it is perhaps not too surprising that they retain a terrestrial-like feeding ecology. The remaining two exceptions that sit within the lower limits of large land predators are the leopard seal (Hydrurga leptonyx) which feeds on a mixture of vertebrates, fish and zooplankton but predominantly vertebrate prey (Kleiber, 1961), and the Californian sea lion (Zalophus californianus) which feeds on fish and squid (Pauly et al., 1998) act as top predators within their ecosystems (Rogers et al., 2005; Block et al., 2011). While I have examined patterns in mean prey mass, there are additional questions on predator-prey relationships that are still to be answered. One avenue that is yet to be explored is the variability in prey size consumed by the same carnivore, and the extent to which and why this variability differs among carnivore species. For example, leopard seals can consume a range of prey species from krill through to 100 kg seal pups (Hall- Aspland & Rogers, 2004). Examining whether there are patterns in dietary niche breadth can provide insights into prey choice and optimal foraging strategies (Costa et al., 2008). In addition, this previous work on dietary niche breadth has been largely based on non-mammalian predators such as reptiles and birds (Braendle et al., 2002; Costa, 2009), providing an opportunity to examine these patterns in mammals in comparison with other predatory taxa. 83 Chapter 4 – The Cost of Carnivory Revisited 4.6 CONCLUSION This study has added an extra dimension to our understanding of predator energetics and prey requirements to include both marine and terrestrial carnivorous mammals. The colonisation of the marine environment by mammals has had a profound effect on carnivore diets, resulting in the evolution of feeding and behavioural strategies that differ to those demonstrated by terrestrial carnivores. Understanding mammalian diets is important for three reasons. First, it provides a clearer understanding of the selective forces that have shaped predator-prey relationships and the associated behavioural/foraging strategies adopted by extant carnivorous mammals. Second, it provides critical information on how species interact (i.e. consumers and their resources), how energy is transferred through an ecosystem (i.e. from small species to large species) and how trophic structures are shaped across different environments (i.e. food chain length). Third, information on the prey consumed by carnivores and the physiological underpinnings of carnivore behavioural strategies that I have identified have potentially important conservation implications, such as the identification of scenarios where conflict may arise between human activities and mammals. For large marine carnivores, the combination of elevated energetic requirements, the reliance upon dense aggregations of small prey species and the fact that these same prey species are also being commercially harvested, highlights one of the many threatening processes currently faced by marine mammals. More generally, given that both marine and terrestrial carnivorous mammals are under threat from climate change and increasing human activities at a global scale (Ripple et al., 2014), understanding the dynamics behind carnivore diets could provide the information needed to help minimise some of these negative impacts faced by carnivorous mammals. 84 Chapter 5 Examining predator-prey body size, trophic level and body mass across marine and terrestrial mammals 5.1 SUMMARY Predator-prey relationships and trophic levels are indicators of community structure and are important for monitoring ecosystem changes. Mammals colonised the marine environment on seven separate occasions (beginning in the early Eocene ~55 million years ago), which resulted in differences in species’ physiology, morphology and behaviour. It is likely that these changes have had a major effect upon predator-prey relationships and trophic position; however the effect of environment is yet to be clarified. I compiled a dataset, based on the literature, to explore the relationship between body mass, trophic level and predator-prey ratio across terrestrial (n=51) and marine (n=56) mammals. I did not find the expected positive relationship between trophic level and body mass, but I did find that marine carnivores sit 1.3 trophic levels higher than terrestrial carnivores. Also, marine mammals are largely carnivorous and have significantly larger predator-prey ratios compared to their terrestrial counterparts. I propose that primary productivity, and its availability, is important for mammalian trophic structure and body size. Also, energy flow and community structure in the marine environment is influenced by differences in energy efficiency and increased food web stability. Enhancing our knowledge of feeding ecology in mammals has the 85 Chapter 5 – Predator-Prey Relationships and Trophic Level potential to provide insights into the structure and functioning of marine and terrestrial communities. 5.2 INTRODUCTION Mammals are a diverse group of organisms spanning eight orders of magnitude in body mass, exploiting a variety of habitats and niches, and encompass a range of feeding ecologies (Smith & Lyons, 2011; Price et al., 2012). These characteristics make mammals ideal to investigate patterns in trophic level. Mammals have re-entered the marine environment on seven separate occasions, and there are five extant clades: Cetacea, Sirenia, Pinnipedia, Ursus maritimus and Enhydra lutris (Uhen, 2007). Cetacea and Sirenia re-entered the water during the early Eocene (~55 million years ago) and Pinnipedia returned to the water during the Oligocene (~30 million years ago) (Uhen, 2007). This provides a unique opportunity to explore the possible changes that have occurred as mammals moved into an environment where not only physiological and morphological modifications have taken place, but additional behavioural changes were associated with foraging ecology. Two relationships used to investigate the feeding ecology of carnivorous species include the association between trophic level and body mass, as well as the relationship between trophic level and the predator-prey body-mass ratios. Depending on the complexity of the ecosystem, carnivores are not always secondary consumers. For example, a carnivore from a complex food web with more than five trophic levels, will sit higher in the food chain than a carnivore in a simple food web with just three trophic levels (Pauly & Christensen, 1995). Also, as large mammalian carnivores tend to feed on larger-sized prey, a requirement of their high energetic requirements (Carbone et al., 2007a), larger carnivores also tend to have higher trophic positions. 86 Chapter 5 – Predator-Prey Relationships and Trophic Level This is linked with the idea that food webs are size structured, for example a large carnivore targeting larger-sized prey (e.g. fish) will have a higher trophic level than a carnivore feeding upon smaller-sized prey (e.g. zooplankton). Productivity differs between the marine and terrestrial environments. In the ocean, primary producers represent around 0.2% of the global primary-producer biomass however turnover rate (i.e. carbon productivity) is greater in the marine environment (up to 1000 times higher; Field et al., 1998; Shurin et al., 2006). With the combination of the dominance of single-celled plants such as phytoplankton, energy flow is faster and more easily accessible to consumers within the marine environment. Where terrestrial primary producers represent a higher proportion of producers (~99.8%) the net turnover rate is much slower on land than within the oceans (e.g. carbon turnover 19 years (terrestrial) vs. 2-6 days (marine); Falkowski & Raven, 1997; Thompson & Randerson, 1999) . Multicellular plants are dominant on land and are more difficult for consumers to process and extract energy from compared with single-celled species. As the majority of primary production is driven by small, single-celled organisms in the marine environment, aquatic systems tend to be heavily size structured so that trophic interactions are driven by large consumers feeding on small species (Andersen et al., 2009b). The relationship between trophic level and body mass across mammals has three possible patterns that I aim to test. (1) Differences in the environmental characteristics are driving trophic-level patterns across mammals, with a positive relationship expected between trophic level and body mass in both marine and terrestrial species, as demonstrated by Riede et al. (2011). This would mean that differences in the food-web structure and the number of trophic levels (see Brose, 2010) would result in marine mammals having a higher intercept for trophic level than terrestrial mammals. (2) Body mass, regardless of environment, is driving trophic-level patterns. If body mass is the 87 Chapter 5 – Predator-Prey Relationships and Trophic Level key driver for trophic-level patterns, then the relationship should remain the same with the addition of marine species. (3) The trophic level-body mass relationship would be quadratic (i.e. hump-shaped) because the addition of the marine species complicates the relationship. The positive relationship between trophic level and body mass holds up to a maximum threshold, where the relationship then shifts and becomes negative due to the largest mammals, the mysticete whales, feeding largely upon small invertebrates situated at low trophic levels (Pauly et al., 1998). In this scenario, the terrestrial carnivores would contribute to the initial positive relationship between trophic level and body size (Riede et al., 2011). Predator-prey body-mass ratios (PP ratios) provide information on food web complexity, ecosystem stability and community structure (Weitz & Levin, 2006; Petchey et al., 2008). Food webs are usually more stable when predators are larger than their prey (Jennings & Mackinson, 2003; Brose et al., 2006b), as this minimises the chance that new predators invade and outcompete current predatory species (Weitz & Levin, 2006; Kartascheff et al., 2010). There are however exceptions, such as pack-hunting mammalian carnivores (e.g. wolves) and large cats (e.g. tigers). It has been demonstrated across whole food webs that PP ratios vary with the trophic position of the predator, where the PP ratio approaches one with increasing trophic level (Riede et al., 2011) (i.e. the predators with high trophic positions consume prey more similar to their own body size). Using diet information and trophic level data for terrestrial and marine mammals I investigate how living within the marine or the terrestrial environment has impacted the relationship between body size, trophic level and PP ratio across mammals. To achieve this I (1) examine how the differences between consumers within terrestrial and marine environments influence the trophic and food-web structure of mammals; and (2) I test if 88 Chapter 5 – Predator-Prey Relationships and Trophic Level the negative relationship between PP ratio and predator trophic level is a general rule across mammals by examining this relationship with the addition of marine mammals. 5.3 MATERIALS AND METHODS 5.3.1 Database I analysed trophic level and species’ body masses from 107 carnivorous mammal species across marine (n=56) and terrestrial (n=51) environments. I chose these 107 species based upon the availability of detailed dietary information within the literature, which also means that the data is skewed towards species that have been well studied. Carnivores were defined as those species with diets compromising at least 90% meat, with insectivores also classified as carnivores (Kelt & van Vuren, 2001). Trophic level positions for marine mammals is readily available in the literature (Pauly et al., 1998) however, this information is more difficult to obtain for terrestrial mammals and had to be calculated. To achieve this, terrestrial prey-preference data were collected from the literature (i.e. the proportion of prey species consumed by that carnivore), and this data included all species preyed upon by the carnivore species. Each prey species was assigned a trophic position, where herbivorous prey species were assigned a trophic level of 2, omnivorous prey species were assigned 2.5 and carnivorous prey species were assigned 3. Combining the information on carnivore prey preference and the trophic level of the prey, the carnivore trophic level was then calculated using the equation from Pauly et al. (1998): 푛 푛 TLi = 1 + (∑ DCij∙TLj / ∑ DCij) (ퟏ) 푗=1 푗=1 where DCij , is the diet composition with the proportion of prey (j) in the diet of species (i), TLj is the trophic level of prey (j), and n is the number of groups in the system. Body mass data were log10 transformed prior to analysis. 89 Chapter 5 – Predator-Prey Relationships and Trophic Level Predator and prey body masses were extracted from the literature (n=107). Where predators consume more than one prey item, I calculated mean prey size that represented the common prey items consumed by that species. Predator-prey body mass ratio (PP ratio) was calculated for the carnivorous species, by dividing the average mass of each predator species by their average prey mass. 5.3.2 Phylogenetic Information Due to the absence of a single phylogeny with all species of interest, a composite tree was created by combining information from several sources (see Figure S6.1). The majority of the phylogenetic information was based on the mammalian supertree of Fritz et al. (2009) in which branch lengths were proportional to time since divergence. Divergence times were based on molecular clock analysis and the tree included fossil data for calibration (Bininda-Emonds et al., 2007). Two species were positioned within the pruned trees based on the topologies of the following sources: Sciurus aberti (Grill et al., 2009); and Sotalia guianensis (Caballero et al., 2008). Carnivora and cetacea positioning were updated using the recently published trees by Slater et al. (2010) and Nyakatura & Bininda-Emonds (2012) respectively. All tree manipulations were performed using Mesquite ver 2.74 (Maddison & Maddison, 2010). 5.3.3 Analysis A model selection approach was applied to test the level of support for alternative models of trophic level patterns in carnivorous mammals: (a) Body mass and environment model (β0+βmass+βenvironment) where both body mass and environment (i.e. whether species occupied a terrestrial or marine environment) explained differences in trophic level position (environment was coded in a binary fashion as living in either the terrestrial (0) or marine (1) environment), (b) Body mass and environment model with an interaction term (β0+βmass+βenvironment+βmass*βenvironment) which is the same as the previous model but with an interaction term (i.e., βmass*βenvironment) to test for differences 90 Chapter 5 – Predator-Prey Relationships and Trophic Level in allometry in relation to the physical environment; (c) Quadratic model (β0+βmass+ 2 2 βmass ) where a quadratic term was added (βmass ) to explained differences in trophic level position and body mass across all species as a quadratic relationship; (d) Body mass model (β0+βmass) which predicted differences in trophic level among species was exclusively explained by body size; and (5) Null model (β0) where no predictor variable was included and I subsequently modelled the variance in species trophic level as the outcome of both Brownian evolution and stochastic factors associated with evolutionary differentiation. The model selection and phylogenetic least squares (PGLS) regression analyses were run as per Chapter 2 (see Analysis section), using COMPARE ver 4.6b (Martins, 2004). The relationship between trophic level and PP ratio was investigated using PGLS regression. For all PGLS regression results, significance was deemed when the confidence intervals (CI’s) did not overlap 0. Differences in body mass associated with diet across the two environments were examined using ANOVA respectively, using R 2.13.2 (R Development Core Team, 2011). Sample sizes for the diet categories in each environment were as follows: marine carnivores (n=56), marine herbivores (n=5), terrestrial carnivores (n=51) and terrestrial herbivores (n=99). 5.4 RESULTS 5.4.1 Trophic Level Patterns A model including body mass and physical environment (marine vs. terrestrial) was the best supported model for predicting the evolution of trophic level in carnivorous mammals, explaining 46% of the variance in trophic level among species (Table 5.1). The second most supported model which included the interaction term of βmass*βenvironment, was within 2 units of the best model, and was therefore considered to 91 Chapter 5 – Predator-Prey Relationships and Trophic Level be equally supported (Table 5.1). The remaining models had virtually no support with ∆AICc being greater than 2. Examining the parameters of the β0+βmass+βenvironment+βmass*βenvironment model, the interaction term was not significant (CI’s -0.24, 0.14), indicating that the slope of the relationship between trophic level and body mass is the same across the two environments. This means that the results of the two best supported models (β0+βmass+βenvironment and β0+βmass+βenvironment+βmass*βenvironment) are essentially identical. Table 5.1 Level of support for explanatory models of trophic level evolution in mammals. Results are from phylogenetic least square (PGLS) regressions computed for the mammalian phylogeny. Model ∆AICc PGLS Effect α size (r) β0+βmass+βenvironment 0.00 8.55 0.69 β0+βmass+βenvironment+βmass*βenvironment 1.68 8.71 0.69 β0+βmass 27.30 2.65 0.11 2 β0+βmass+ βmass 32.07 2.00 0.08 β0 44.36 0.78 - When investigating the parameters of the environment model, there is a significant difference in intercept of trophic level between marine and terrestrial species (CI’s 0.71, 1.39; Fig. 5.1A), with a mean trophic level for terrestrial carnivores of 2.7 and marine carnivores of 3.9. The relationship between mass and trophic level was not significant (CI’s -0.08, 0.06), indicating that there is no relationship between mass and trophic level in either environment. 92 Chapter 5 – Predator-Prey Relationships and Trophic Level Figure 5.1 (A) Trophic level as a function of species body mass compared for species occupying terrestrial (grey circles) and marine (coloured circles) environments. Each datum represents a species mean value (n = 107 species). The solid black lines are the PGLS regression lines for terrestrial mammals: log Y = 0.01(log X) +2.98 and for marine mammals: log Y = 20.02(log X) + 4.03. River otter (9 kg) and blue whale (155 000 kg) are the smallest and largest marine mammal, respectively, whereas the collared pika (120 g) and brown bear (217 kg) are the smallest and largest terrestrial mammals, respectively. Note that body mass is on a log10 scale. (B) Schematic of general trophic-level patterns for terrestrial mammals (grey), odontocetes (red) and mysticetes (blue). Images: Chris Huh (marine mammals), Hans Hillewaert (Amphipoda) and Lukasiniho (Alcelaphus) and uncreditied (Panthera) were downloaded from http://phylopic.org. Fish and grass silhouettes by Marlee Tucker. 93 Chapter 5 – Predator-Prey Relationships and Trophic Level 5.4.2 Predator-Prey Ratios The PP ratio decreases with increasing trophic level in both marine and terrestrial environments (Fig. 5.2A). There was no significant interaction between trophic level and environment (CI’s -34.13, 0.61), suggesting that the scaling of the relationship between predator-prey ratio and trophic level is the same in both environments. However, the intercept values for marine and terrestrial mammals were significantly different (CI’s 5.16, 23.06), with marine species having larger PP ratios than terrestrial species of a similar mass. 94 Chapter 5 – Predator-Prey Relationships and Trophic Level Figure 5.2 (A) The relationship between log10 predator–prey ratio as a function of predator trophic level, across marine (coloured circles) and terrestrial mammals (grey circles), n = 107. The solid black lines are the PGLS regression line for terrestrial mammals: log Y = - 13.08(log X) + 7.83 and for marine mammals: log Y = -26.83(log X) + 20.54. (B) Examples of feeding strategies used by marine (blue) and terrestrial (green) carnivorous mammals. Marine (left to right): bulk feeding (mysticetes), small vertebrate feeders (odontocetes) and large vertebrate feeders (orcas and polar bears). Terrestrial (left to right): small insectivores (echidnas), small vertebrate feeders (mustelids) and large vertebrate feeders (lions). Images: Chris Huh (marine mammals), Hans Hillewaert (Amphipoda), Lukasiniho (Alcelaphus), Tracy Heath (Phocid and U. maritimus), Nobu Tamura/T. Michael Keesey (Tachyglossus) and uncredited (Mustelid and Panthera) were downloaded from http://phylopic.org. Fish and bird silhouettes by Marlee Tucker. 95 Chapter 5 – Predator-Prey Relationships and Trophic Level 5.4.3 Diet and body size There was a significant difference between the average mass of herbivores (F1,102=10.66, p<0.01) and carnivores (F1,105=134.12, p<<0.01) between the marine and terrestrial environments (Fig.S6.2), with marine mammals having larger body masses in both diet categories. A caveat of this analysis across terrestrial and marine mammals is the presence of a dietary bias. In the marine environment, mammals are predominantly carnivorous and there are fewer than five herbivorous mammals. This limits the number of species that can be compared across diet categories, specifically for marine mammals. When investigating the relationship between diet niche and body mass, there is a broader range of mass values across terrestrial herbivores (0.03 – 3981 kg), compared with terrestrial carnivores (0.09 – 177 kg; Fig. S6.2). Conversely, the opposite is found in the marine system with marine carnivores ranging from 9 to 155 000 kg, and marine herbivores ranging from 195 to 19 200 kg (Fig. S6.2). 5.5 DISCUSSION 5.5.1 The effects of body mass on trophic position The evolution of trophic position in mammalian carnivores appears to be driven by the environment in which they live. Marine carnivores sit on average 1.3 trophic levels higher than mammals that live on land. This trophic shift is driven by the more complex nature of marine food webs where there are higher numbers of trophic levels (Fig. 5.1A and B) as well as interactions between these trophic levels (Brose, 2010; Riede et al., 2011). The absence of a relationship between changes in body mass and trophic level was present for both terrestrial and marine mammals. Our results contradict previous studies which combined data from endothermic vertebrates (i.e. mammals and birds) and showed a strong positive relationship between body mass and trophic level in 96 Chapter 5 – Predator-Prey Relationships and Trophic Level vertebrates (Riede et al., 2011). This study examined the relationship between body mass and trophic level within mammals only and I used different methodologies (e.g. data normalisation; see Riede et al., 2011). Ideally I would like to examine trophic-level patterns in mammals across food webs more broadly however at present data using complete food webs is limited. It was surprising that there was no positive relationship between body mass and trophic level for terrestrial mammals. The strong negative body mass and trophic level relationship described previously appears to be seen only when using data from whole food webs and a smaller sample size of mammals (Riede et al., 2011). Similar to this study, a weak relationship between body mass and trophic level is also seen in fish (Jennings et al., 2001). By including the largest species, the marine mammals, I demonstrate that the trophic-level body-mass relationship may not be uniform across animals. The mysticete whales cluster towards the bottom right of the trophic-level body-mass relationship (having large body mass and yet feed at low trophic levels; Fig. 5.1B). As previous studies did not include the largest mammals (e.g. mysticete whales), the species that feed on prey within the lower trophic levels (~ 3 to 3.5), important information on trophic level patterns and the drivers behind these patterns have been missed. 5.5.2 Environmental Effects on Herbivory Productivity appears to drive the differences in trophic-level patterns and food-web structures across the two environments. Marine productivity is driven by high quantities of small, single-celled primary producers, which is the reverse of the trophic-level patterns and food-web structures found on land. Vegetation on land (typically composed of complex long-chain chemical structures e.g. lignin), is generally multi- cellular, with a high proportion of structural tissues and chemical defences to protect themselves against herbivores (Shurin et al., 2006; Cebrian et al., 2009). Terrestrial 97 Chapter 5 – Predator-Prey Relationships and Trophic Level vegetation has to compete for sunlight, nutrients and against the effects of gravity and a diverse array of vegetation types; fast (i.e. grasses) to slow (i.e. woody plants) growth rate (Polis & Strong, 1996) plant types have arisen. This provides terrestrial herbivores with a number of niches form browsers (woody-plant foliage specialists), granivores (grain specialists) and frugivores (fruit specialists). The presence of numerous herbivorous niches has also driven the diversification and abundance of herbivorous mammals on land. Although the primary productivity in the ocean supports complex food-webs and a greater range of trophic levels (Polis & Strong, 1996; Takimoto et al., 2012), herbivory is rare in marine mammals. Only one group of mammals, the sirenians (including dugongs, manatees and sea cows) are truly herbivorous. Marine mammal herbivores have restricted food resources on which they can feed: seagrass, multi-cellular algae or phytoplankton. The sirenians feed mostly on seagrasses but use multi-cellular algae (of marine origin) and mangrove leaves (of terrestrial origin) as well. Seagrasses are marine flowering plants that grow in meadows under restricted conditions, as they require shallow and sheltered coastal waters with a sandy or soft-mud substrate (restricted to temperate and tropical coastlines across the globe) (Short et al., 2007). The limited availability of seagrass habitat, and consequently seagrass, may have restricted herbivory in marine mammals. In comparison, the typically single-celled phytoplankton lack well-developed chemical defences, have fast growth rates and a high proportion of photosynthetic tissues which are high in phosphorous and nitrogen (Shurin et al., 2006). The differences in structure and chemical stoichiometry of terrestrial and marine primary production means that marine herbivores feed on an abundant, nutrient-rich (high in phosphorous and nitrogen) and easily digested resource compared with terrestrial herbivores. Mammals have not specialised to use phytoplankton or multi-cellular algae as a primary food resource although phytoplankton may be ingested incidentally while filter feeding. 98 Chapter 5 – Predator-Prey Relationships and Trophic Level 5.5.3 Environmental Effects on Carnivory The abundance of protein-rich resources (composed of amino acids) in the ocean supports a greater number of carnivorous marine mammals. The great quantities of phytoplankton in the ocean and aquatic bodies, support large communities of small zooplankton (passively moving aquatic organisms e.g. protozoans including foraminiferans, radiolarians and dinoflagellates). These tiny primary consumers eat the phytoplankton, along with bacterioplankton (the bacterial component of the plankton), detritus and other zooplankton. The zooplankton themselves become a source of energy for larger metazoan zooplankton (e.g. cnidarians such as jellyfish; crustaceans such as copepods and larval krill; molluscs such as pteropods; and chordates such as salps and juvenile fish). The metazoan zooplankton are in turn eaten by larger-sized metazoan zooplankton and/or nektonic species (actively swimming aquatic organisms e.g. molluscs such as squid and octopus; crustaceans such as krill and amphipods; and vertebrates such as fish, turtles, seals and whales). The small size and fast generation times of zooplanktonic species means that their communities can reproduce and grow rapidly to exploit increases in phytoplankton abundance, harnessing rapid spikes in primary productivity typical of phytoplanktonic blooms. This high abundance of small-sized primary producers and primary consumers supports a high diversity of small carnivorous species within the metazoan zooplanktonic, and in turn in the nektonic communities. The high abundance of small-sized organisms forming the base of marine food webs facilitates the presence of numerous steps within marine food chains, as larger species feed upon smaller species (Polis & Strong, 1996; Takimoto et al., 2012). The abundance of protein-rich resources spanning a range of body sizes from extremely small (30 µm) to large (13 000 kg) results in a wide range of available niches for carnivorous marine mammals, from invertebrate feeders (krill, amphipods, squid, shellfish etc.) to vertebrate consumers (fish, birds, mammals). 99 Chapter 5 – Predator-Prey Relationships and Trophic Level 5.5.4 Body Size, Diet and Environment For mammals, changes in body mass have followed reverse patterns of diet dominance in the marine and terrestrial environments. Theory predicts that for mammals with increasing body mass the number of prey items they consume should decrease [11]. This is based on the imbalance between the increase in resources that larger carnivorous mammals require against the finite resources that are available to meet their requirements (Riede et al., 2011). This is the case for mammals living on land, where the majority of large mammals are herbivorous (Fig. S6.2). In the terrestrial environment, where vegetation is an abundant resource, most of the net primary productivity is lignocellulose, which is difficult for mammals to digest, and there is relatively little easily digestible material (Polis & Strong, 1996). Herbivorous land mammals have long, complex digestive systems to digest and assimilate nutrients from large quantities of poor-quality vegetation. They have symbiotic relationships with microbes and protozoa in their gut which assists in the further extraction of nutrients from their poor-quality diet (Polis & Strong, 1996; Smith et al., 2010) (Demment & Soest, 1985). Herbivores retain vegetation within their digestive systems for long periods (up to 92 hours; Clauss et al., 2009) to allow enzymatic and microbial action to maximise the breakdown and then assimilation of nutrients (Demment & Soest, 1985). In some instances, large body size has evolved to accommodate these long and complex digestive systems as well as the large quantities of poor-quality vegetation that need to be processed over long periods of time. This has resulted in the trend towards large body mass in terrestrial herbivorous mammals. By contrast, there has been an increase in carnivore body size in the marine environment (Fig. S6.2). For marine carnivorous mammals, the combination of the thermal advantages, prey availability and hunting efficiency have resulted in large body size. Utilising dense aggregations of prey (up to 770 000 m-3; Nicol, 1986) has aided the evolution and maintenance of extreme body size in mysticete (~ 0.9 to 5 cm 100 Chapter 5 – Predator-Prey Relationships and Trophic Level swarming prey) and odontocete (~ 1 to > 37 cm cephalopod prey) whales (Goldbogen et al., 2011). Large marine carnivores are more efficient at hunting than their terrestrial counterparts. Terrestrial carnivores spend long periods of time foraging (up to several hours) and expend large amounts of energy hunting (including capture and prey consumption; Williams & Yeates, 2004). Marine carnivores, particularly those above 100kg, have a higher hunting efficiency (Williams & Yeates, 2004). They have evolved physiological (e.g. increased levels of globins for more efficient oxygen transfer; Williams et al., 2008), morphological (e.g. feeding apparatus such as baleen) and behavioural traits (e.g. alternate forms of locomotion during diving; Williams, 1999) to become more energy efficient hunters. Marine vegetation contains small amounts of lignin and cellulose so that higher amounts of nutrients are available to marine consumers (including zooplankton, fish and sirenians) which passes up through the food web (Polis & Strong, 1996; Shurin et al., 2006). This greater productivity provides support for large populations of consumers, resulting in the reverse patterns to that seen on land (Riede et al., 2011). Where marine clades (cetaceans, pinnipeds and sirenians) tend to stick to a single diet type (i.e. either carnivory or herbivory), some terrestrial carnivorous mammals switch between diets depending on food availability (e.g. bears shift between omnivory and carnivory; Price et al., 2012). Not only have there been changes in body mass across different diets, we also see changes in minimum and maximum body size trends across marine and terrestrial mammals. This is driven by the combined effects of environmental characteristics, physiology and vegetation/prey availability. Terrestrial mammals can reach smaller body sizes compared to marine mammals (~0.001 kg vs. ~10 kg; Smith & Lyons, 2011). Mammals living in the water experience high thermoregulation costs and this constrains how small a marine mammal can be. This is accentuated at birth when the surface area to body volume is high, resulting in an increased rate of heat loss and energy spent on maintaining body temperature (Downhower & Blumer, 1988; Smith & 101 Chapter 5 – Predator-Prey Relationships and Trophic Level Lyons, 2011). Four of the six marine mammal lineages have retained giving birth and raising their young out of the water, either on land or ice (mustelids, otariids, phocids, and ursids). For both young and adults, it is a thermal advantage to have larger body size in the marine environment. Marine mammals reach much larger body sizes than terrestrial mammals (~ 4 tonne vs. ~ 200 tonne; Smith & Lyons, 2011). On land, resource availability constrains how large mammals can become because having a large body size has high energetic costs and requires abundant and reliable resources. In particular, the interaction between resource availability, land mass area, and the cost of gathering sufficient resources limits how large a terrestrial mammal can become (Burness et al., 2001). In the ocean, similar constraints are present, but take effect at a much larger body size. For example, the size of the blue whale is likely to be constrained by biomechanical limitations (e.g. gape size and lunge feeding costs) and prey availability (e.g. prey density; Goldbogen et al., 2011). 5.5.5 Trophic level and predator-prey ratio relationships A general rule for the relationship between PP ratio and the trophic level of carnivorous mammals appears to apply to both the marine and terrestrial environments. With increasing trophic level, carnivores shift to feeding on prey that have a body mass more similar to that of the carnivore’s own body mass (i.e. PP ratio approaching ≥ 1). The underlying drivers behind this negative relationship are believed to be the combined effects of increasing body mass with trophic level for endotherms, and increasing prey mass with increasing carnivore body mass (Riede et al., 2011). However, this study suggests that there are issues with this reasoning as: (1) I did not find a relationship between trophic level and carnivore body mass; and (2) whilst terrestrial carnivores demonstrate a positive relationship between carnivore body size and prey body size (Carbone et al., 1999), this is not the case for many marine carnivores (e.g. mysticete whales feeding on krill). 102 Chapter 5 – Predator-Prey Relationships and Trophic Level The large predator-prey body-mass ratios found in the marine system are not plausible on land, as small prey (excluding invertebrates) do not form large swarms or groups that are easily accessible as they do in the ocean. In the marine system, small prey such as plankton or fish form large aggregations (schools or swarms) as protection from predation. Large marine mammals, such as the mysticetes and smaller marine mammals such as seals, have morphological adaptations for bulk feeding (e.g. baleen instead of teeth in mysticete whales and specialised multi-cuspidate teeth in pinnipeds) and behavioural (bubble netting, group feeding, lunge diving) specialisations to capture large quantities of small prey in a single feeding event. Harvesting small-sized swarming prey requires minimal capture (individual pursuit and capture) and processing (e.g. butchering) time. There are invertebrate-feeding specialists on land, yet this type of diet can support animals only up to the restricted weight range of under 20kg due to the increasing costs associated with larger body mass (Carbone et al., 2007a). For terrestrial mammalian carnivores the abundance, distribution and energy content of terrestrial invertebrates are not sufficient to support body masses above 20kg (Carbone et al., 2007a). An implication, arising from the combination of a mean trophic level position of 3.9 for marine carnivores and the abundance of higher PP ratios in the marine environment, is its effect on trophic efficiency. Trophic efficiency includes the exchange of energy between trophic levels based on predator-prey interactions, but excludes growth (i.e. somatic) (Andersen et al., 2009a). When PP ratios are large, trophic efficiency decreases (Andersen et al., 2009a). For example, a marine organism with a PP ratio of 1000 has an efficiency of ~13%, compared with a marine organism with a PP ratio of 10 that has an efficiency of 50% (irrespective of size or trophic position; Andersen et al., 2009b). This has follow-on effects for the energy flow through an ecosystem, as well as community structure and dynamics. However, this is less of an issue in the marine environment, where large PP ratios (i.e. predators are larger than their prey) 103 Chapter 5 – Predator-Prey Relationships and Trophic Level increase the stability of marine food webs (Brose et al., 2006a; Kartascheff et al., 2010; Heckmann et al., 2012). Large PP ratios cause a reduction in the interaction strengths between predators and their prey (per unit biomass) (Yodzis & Innes, 1992; Brose et al., 2005). In addition, there are benefits for carnivores that feed from lower trophic levels. The similarity between the tissue composition of carnivores and their prey (amino acids) has been shown to result in higher energy transfer efficiencies (Sterner & Elser, 2002; Dickman et al., 2008). When herbivores are included in a food chain, this can limit the energy efficiency between trophic levels. This is because of the decreased assimilation efficiency of herbivores who have greater difficulty extracting energy from plants with high carbon-nitrogen ratios (Frost et al., 2006). This study provides insights into the drivers behind mammalian predator-prey body- mass ratios, trophic-level positions and body mass. I caution that my approach is simplistic, yet ecosystems are often complex. Collecting prey-preference and trophic level information from the literature has limitations. Historical studies may have over simplified food webs (Polis, 1991). While I attempted to select studies that did not oversimplify food-web data, as I examined patterns across mammals and from a wide range of food webs with different structures, this may not have always been the case. Into the future I propose using equations that incorporate complete food web data to calculate trophic levels (Williams & Martinez, 2004). At present we are restricted by the limited amount of detailed food web data available. To gather information across 107 species I was reliant upon published dietary studies and this biased data toward well-studied species. Unfortunately this cannot be avoided at present and can only be overcome by further research into lesser known species, which are often difficult to study (e.g. beaked whales). This study provides a framework for exploring how environment impacts upon the broad patterns in ecology across the marine and terrestrial systems. 104 Chapter 5 – Predator-Prey Relationships and Trophic Level 5.6 CONCLUSION These results demonstrate that primary productivity, and its availability, is important for the mammalian trophic structure of food webs, body size and prevalence of carnivory and herbivory. Marine and terrestrial mammals share the same relationship between trophic level and mass, with the trophic level of marine species shifting 1.3 levels higher. Interestingly, carnivorous mammals do not follow strictly the expected patterns for the relationship between trophic level and body mass (i.e. positive or quadratic). While there is a distinct shift in trophic position between marine and terrestrial carnivores (Fig. 1A), I did not find a positive relationship or a quadratic relationship. The marine environment has a higher abundance of carnivorous mammals and a shift towards larger minimal and maximal body size. The terrestrial system has greater diversification of herbivores and a general trend towards a smaller minimal and maximal body size. The relationship between body mass and diet on land has been reversed in the marine system, where carnivores tend to be larger and herbivores smaller, the opposite to terrestrial mammals. The patterns in trophic level and PP ratio are stronger within each environment than across mammals in general, further suggesting the importance of environment. When mammals colonised the marine environment, the shift from a plant-dominated landscape to a habitat rich in protein-rich resources, with little competition, resulted in changes to the trophic-level relationships, dietary niches and foraging ecology. Large body mass, the shift in available resources and altered physiology have driven marine mammals to be largely carnivorous. Marine carnivores consume highly mobile prey that sit within a wide range of trophic levels and have smaller body masses compared with terrestrial carnivores which in the main consume larger prey, to meet their metabolic requirements. This study illustrates the influence this shift in environment has had on 105 Chapter 5 – Predator-Prey Relationships and Trophic Level mammalian ecology and the importance of utilising this information to examine the structure and function of marine and terrestrial communities. 106 Chapter 6 General Conclusion Body size is a fundamental trait of animals which has driven the macroecological patterns of mammalian spatial behaviour, carnivorous strategies and trophic level, providing the basis for many ecological theories. It was necessary to re-examine these macroecological patterns because previous research had been performed on a restricted group of mammalian representatives, largely excluding both aquatic and aerial species. This causes issues for the broad application of the ecological theories due to the effect that environment can have on macroecological patterns. With extinction rates across mammals increasing due to the conflict between human activities and mammals (González-Suárez & Revilla, 2014), it is crucial that we are confident about our broad-scale ecological theories, where information is extracted by conservation managers in order to construct management plans. I have demonstrated that whilst body mass is a key factor driving home range size, carnivore feeding strategies and trophic structure are also influenced by diet and the environment in which a species resides. As information on spatial behaviour, predator- prey relationships and trophic structure is often incorporated into conservation plans or managements strategies, we need to be confident that the ecological theories are providing accurate information (Margules & Pressey, 2000). 107 Chapter 6 - Discussion 6.1 HOME RANGE SIZE There have been numerous studies examining home range patterns in mammals at a macroecological level (Burt, 1943; McNab, 1963; Lindstedt et al., 1986; Swihart et al., 1988; Kelt & Van Vuren, 1999), however, the most recent of these was by Jetz et al. (2004). Most home range investigations that have been carried out over the past 9 years have been focused on a single species (Andres et al., 2013; Newsome et al., 2013; Niemi et al., 2013; Pearce et al., 2013). With the combination of phylogenetic information, over 600 species spanning various diets and environments I revisited home range patterns in mammals (Chapter 2). The objectives of Chapter 2 were achieved: (1) the level of support for the relationship between diet and home range among 279 species of terrestrial mammals was re-examined; and (2) the dataset was expanded to cover both marine and terrestrial species, to examine the effects of living within fundamentally different environments including physiology, morphology and ecology. The results demonstrated that home range is a complex behaviour influenced by a range of factors including body size and its influence on energetic costs and intake, diet and its influence on resource distribution and lastly environment and its overarching influence on body size and food resources. Despite diet being suggested as one of the main driving forces behind home range size (Kelt & van Vuren, 2001), I found that its influence is limited compared to the effect of body size. If we are to delve into how home range has evolved, we need to examine physiological drivers and how this influences animal movements (e.g. cost of transport vs. home range size). The macroecological approach I have taken to investigate home range patterns is only one way of exploring the driving factors of animal space use. There is also an active field of research using smaller scale approaches including the combination of spatial learning or cognitive maps and state-space modelling. For example, use of the mechanistic optimality models of Bayesian foraging and correlated random-walk 108 Chapter 6 - Discussion models has led to insights into why home range exists as well as into home range structure and stability, home range overlap and territoriality and the cognitive mechanisms behind these patterns (Spencer, 2012; Bestley et al., 2013). The majority of the approach utilises data from either a couple of species or computer simulations to predict and build the underlying theories of space use in animals. I think there is benefit from using both methodology types, macroecology and mechanistic models, as approaching the task from different angles allows us to better understand what is driving animal movement patterns at varying spatial scales. 6.2 MINIMUM, MAXIMUM AND RANGE OF PREY MASS Carnivorous mammals are a diverse group of species which have evolved to consume a wide range of resources from invertebrates through to large mammals. A large quantity of research has been performed on carnivores and their vulnerability to changes within their environment (Purvis et al., 2000; Gittleman & Gompper, 2005; Cardillo et al., 2008; Lau et al., 2010; Carbone et al., 2011; Angerbjörn et al., 2013). Carnivores across the globe are having to adapt to change, whether it be habitat loss and harvesting on land (Schipper, 2008) or fisheries and ocean acidification within the ocean (Hilborn et al., 2003; Hoegh-Guldberg & Bruno, 2010; Schiermeier, 2010). As our knowledge on the broad scale relationship between carnivore mass and the minimum, maximum and range of prey mass is limited, the aim of Chapter 3 was to investigate how environment and phylogenetic relatedness influences predator-prey relationships across over 100 carnivorous mammal species. I demonstrate that in the terrestrial environment carnivores have a positive relationship between prey mass (minimum, maximum and range) and carnivore mass, as previously demonstrated in birds and lizards. In contrast, there is no relationship between prey mass and carnivore mass in aquatic carnivores. Differences in the environmental characteristics (e.g. 109 Chapter 6 - Discussion trophic structure and dimensionality) across the terrestrial and aquatic environments are likely to be driving these differences. My findings are important for understanding the relationship between mammalian carnivore foraging strategies and body size, and the role of environment and evolutionary history has had on these patterns. This information will aid with predictions of carnivore susceptibility to population declines and the role of carnivores across different ecosystems. To my knowledge, my work in Chapter 3 is the first attempt to examine the upper/lower limits and range of prey mass consumed by mammalian carnivores. In Chapter 3, I utilised data extracted from the vast literature investigating mammalian diets. Despite the abundant publications, information on diet across mammals are incomplete with data lacking for species that a difficult to study (e.g. rare or pelagic species). There costs (both monetary and time) associated with collecting this type of data, which also limits the information available. With improving technologies, such as the increasing use of stable isotopes (Marques et al., 2014; Middelburg, 2014; Teunissen van Manen et al., 2014), data collection issues will be minimised and a more complete picture of diet information will be obtained. 6.3 CARNIVOROUS STRATEGIES The objective of Chapter 4 was to examine how marine mammals might have adapted their feeding strategies to compensate for living within a three-dimensional aquatic environment. Chapter 4 expands our current knowledge on the relationship between carnivores and their prey by demonstrating that differences in food web structure between the marine and terrestrial environment has driven the evolution of quite different feeding strategies. Due to the evolution of varying carnivorous strategies, where marine and terrestrial carnivores are exploiting prey of different body sizes and trophic positions, it is probable that carnivores will respond to changes differently 110 Chapter 6 - Discussion depending on their environment and its food web structure. For example, Antarctic whales are impacted directly by changes within the lower trophic levels such as the drastic drop in krill over the past 40 years which is driven by increasing ocean temperatures and decreasing sea ice cover (Reid & Croxall, 2001; Atkinson et al., 2004). This is particularly pertinent as the majority of Antarctic whales migrate to reproduce and mate, relying on the Antarctic summer to feed and store reserves for the migration. Additionally, carnivores have varying top-down effects on food webs within their respective systems depending on their trophic position. Apex predators, carnivores that are at the top of the food chain and have no or few predators of their own, can have wide scale impacts by influencing mesoconsumers and their associated resources (Heithaus et al., 2008). This includes the mediation of mortality rates (including density), prey behaviour and habitat structure (Heithaus et al., 2008), which can have severe effects on the ecosystem such as a trophic cascade if the apex predator is removed. Examples of this effect can be found in both marine and terrestrial environments. For example, morwong (a temperate reef fish, Chelilodactulus nigripes) decrease their foraging effort leading to the reduced grazing of turf algae in the presence of New Zealand fur seals (Arctocephalus forsteri) (Connell, 2002). In the terrestrial system, the reintroduction of wolves (Canis lupis) into Yellowstone National Park has resulted in the population control of elk (Cervus elaphus), decreasing the herbivory effect of the elk on the aspen population (Populus tremuloides) (Ripple & Beschta, 2007). Carnivores can also be classified as mesopredators and include species that feed on small birds and mammals. Mesopredator populations are controlled by apex predators, but problems can arise when apex predators are removed, allowing mesopredator populations to increase resulting in prey declines and ecosystem destabilisation (Prugh 111 Chapter 6 - Discussion et al., 2009). For example, the use of dingoes to control fox populations to enable to success of small native Australian mammals (Letnic et al., 2011). Lastly, mammalian insectivores play a large role in terrestrial plant-arthropod communities, where is has been demonstrated that insectivores can reduce herbivory by 40% (Mooney et al., 2010). In the marine system, whales have been identified as major forces impacting the trophic structure of the Southern Ocean (Ainley et al., 2010). This was based on whales feeding upon krill and fish and therefore competing with penguin populations for a potentially limited resource (Ainley et al., 2010). 6.4 TROPHIC LEVEL Improving our knowledge of the trophic level concept is important for informing our understanding of energy flow as well as top-down and bottom-up control of food webs. This information then feeds into real world applications including predicting human impacts of food webs and constructing and producing ecosystem models. The objective of Chapter 5 was to investigate how the colonisation of the marine and terrestrial environments has impacted upon the relationship between body size, trophic level and predator-prey ratio (PP ratio) across mammals. This was accomplished using diet information (including predator mass, prey mass and diet niche) and trophic level data for terrestrial and marine mammals. Difference in primary productivity between the marine and terrestrial environments are driving differences in the trophic position, PP ratios and body size of mammals and the resources utilised by them. Whilst incorporating the prevalence of herbivory and carnivory within this thesis, the analysis of trophic structure is simplified, focusing largely upon carnivorous species and excluding omnivorous species. Omnivory has been proven to be important in food web structure particularly in long food chain (Thompson et al., 2007). The next step of this research would be increase the complexity of the analysis and alter the 112 Chapter 6 - Discussion classification of diet to include omnivores to refine the analysis and patterns found in Chapter 5. Trophic level patterns and information are useful for predicting the movement of compounds such as iron, copper and zinc, which are useful dietary tracers, and other substances such as toxins, which are transferred through foodwebs (Jaouen et al., 2013). Gathering further information on trophic interactions is important for improving our understanding of top-down and bottom-up drivers of trophic levels, as well as their role in structuring ecosystems (past, present and future) (Sandom et al., 2013). 6.5 GENERAL FINDINGS With the incorporation of phylogenetic information into the analyses, I was able to identify the importance and influence of phylogenetic signal (as seen in null and mass models in Chapters 2, 3 and 5). This adds additional weight to the argument that phylogenetic information should be included when comparing a wide range of species (Harvey, 1996; Chamberlain et al., 2012). The effect of phylogenetic information was highlighted in Chapter 2, where the scaling of home range size with body mass was equal across diet categories of terrestrial mammals, contrary to previous studies using the same data. Currently the mammalian phylogeny includes unresolved relationships between species resulting in uncertainties across the tree. Within this thesis, I have attempted to incorporate this uncertainty into my analyses however, with future research the uncertainty within the mammalian phylogeny may be resolved, further clarifying any patterns found. Dimension is likely to play a large role in the patterns found within this thesis (Chapter 2 to 5). Recently some theoretical work has demonstrated that within a 3-dimensional environment there are increased encounter rates with resources when compared with a 113 Chapter 6 - Discussion 2-dimenstional environment (Pawar et al., 2012). Additionally, there are further implications of dimension for food-web dynamics and consumer-resource dynamics (Pawar et al., 2012; Dell et al., 2013). A closer examination of the effect of dimension would be a next step to the work carried out in this thesis, to determine whether there are dimensionality influences on scaling or other ecological traits. This would be accomplished using a theoretical approach and mechanistic models (as seen in Carbone et al., 2007b). A suite of studies have been carried out looking at changes in body size over time (Smith et al., 2010; Evans et al., 2012; Smith & Lyons, 2013), however it would be of interest to examine changes in space use, carnivorous strategies and trophic level not only across space, but also time. How have these patterns change historically? This would provide useful information not only on human impacts but also the effect of other processes such glacial periods and changes in atmospheric oxygen. Lastly, in Chapters 2 and 5 there is still some residual variance for home range size and trophic level that was not explained by body size or environment. As a next step, it would be worth exploring what is behind this variance, as it accounts for between 32 and 52% to the total variance. Potential factors may include resource density (e.g. units per km2), available area (or geographic range) and population abundance. The incorporation of more information would involve shifting from phylogenetic regression models towards linear mixed models. 114 Chapter 6 - Discussion 6.6 CONCLUSION This thesis demonstrated the value in harnessing the plethora of published data to re- examine ecological theories and identify the driving influences of macroecological patterns. I show that living in different environments impacts upon spatial behaviour, foraging, food web structure and energetics. 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Ord and Tracey L. Rogers Evolution and Ecology Research Centre, School ABSTRACT of Biological, Earth and Environmental Aim Mammalian home range patterns provide information on spatial behaviour Sciences, University of New South Wales, Sydney, NSW, 2052, Australia and ecological patterns, such as resource use, that is often used by conservation managers in a variety of contexts. However, there has been little research on home range patterns outside of the terrestrial environment, potentially limiting the rel- evance of current home range models for marine mammals, a group of particular conservation concern. To address this gap, we investigated how variation in mam- malian home range size among marine and terrestrial species was related to diet, environment and body mass. Location Global. Methods We compiled data on home range size, environment (marine and ter- restrial), diet and body mass from the literature and empirical studies to obtain a dataset covering 462 mammalian species. We then used phylogenetic regression analyses (to address non-independence between species) to examine the relative contribution of these factors to variation of home range size among species. Results Body size explained the majority of the difference in home range size among species (53–85%), with larger species occupying larger home ranges. The type of food exploited by species was also an important predictor of home range size (an additional 15% of variation), as was the environment, but to a much lesser degree (1.7%). Main conclusions The factors contributing to the evolution of home ranges are more complex than has been assumed. We demonstrate that diet and body size both influence home range patterns but differ in their relative contribution, and show that colonization of the marine environment has resulted in the expansion of home range size. Broad-scale models are often used to inform conservation strategies. We propose that future integrative models should incorporate the possibility of phylogenetic effects and a range of ecological variables, and that they should *Correspondence: Marlee Tucker, School of include species representative of the diversity within a group. Biological, Earth and Environmental Sciences, Keywords University of New South Wales, Sydney, NSW, 2052, Australia. evolutionary allometry, marine, phylogenetic comparative analysis, spatial E-mail [email protected] behaviour, terrestrial. consequences of allometry, the size of an animal’s home range INTRODUCTION provides valuable information on a variety of ecological vari- In animals, a broad range of physiological, ecological and behav- ables, including resource use, social behaviour and other activ- ioural factors scale with body size (Peters, 1983). Body mass, a ities (Knight et al., 2009). The strong positive relationship measure of body size, accounts for a large proportion of the between home range size and body mass reflects the balance variation in home range size among terrestrial mammals (Kelt & between the cost of locomotion and metabolic requirements van Vuren, 2001; Jetz et al., 2004). Among the various potential with increasing body mass (McNab, 1963). Larger individuals © 2014 John Wiley & Sons Ltd DOI: 10.1111/geb.12194 http://wileyonlinelibrary.com/journal/geb 1 M. A. Tucker et al. can travel further than smaller individuals, but larger individ- In this study, we set out to clarify these issues by conducting uals have higher absolute energetic demands and need to travel inclusive analyses across both terrestrial and marine mammals further to gain the resources to meet those demands (McNab, to test the diet and the body mass hypotheses alongside each 1963). other (i.e. that home ranges will increase with increasing pro- In addition to an animal’s size, diet is another important portion of meat in the diet in addition to, and independently of, factor that is believed to dictate home range patterns. Carni- increasing body mass) and against an evolutionary null model vores, omnivores and herbivores have differences in their forag- (stochastic variation). As part of these analyses, we examined if ing costs (i.e. food acquisition and processing costs) due to their when the relative contribution of these factors is the same it has reliance on different food resources, which also have temporally affected the evolution of home range in the same way in terres- and spatially different distributions. Carnivores feed on trial and marine mammals. resources that are sparsely distributed, mobile and unpredict- Colonization of the marine environment has been accompa- able across the landscape, and so they require a large home range nied by fundamental shifts in physiology and ecology that may (Kelt & van Vuren, 2001; Carbone et al., 2007a). There are also have changed the way in which body mass and diet affect home additional costs for carnivores such as the time and energy range size in marine species. One example of this is the ability of required to hunt for food (Carbone et al., 1999). In contrast, marine mammals to utilize buoyancy. Marine mammals have herbivores tend to have the smallest home ranges because they evolved various mechanisms to achieve neutral buoyancy, such feed on vegetation which is fixed in time and space and is gen- as increases in bone density and large blubber stores (Wall, erally abundant. However, there are additional energetic costs 1983). Buoyancy is a key strategy for marine mammals to mini- associated with processing plant material (e.g. Clauss et al., mize the costs associated with diving. An example of this is the 2003), which limit the ability of herbivores to forage widely. North Atlantic right whale (Eubalaena glacialis) which utilizes Omnivores have an intermediate-sized home range that reflects positive buoyancy when ascending (Nowacek et al., 2001). their mixed diet (meat and vegetation) (Kelt & van Vuren, 2001) Marine mammals have also evolved other adaptations that allow and the intermediate costs associated with processing these them to survive in the ocean and decrease their cost of transport foods (McNab, 1986). (COT) per unit weight (Williams, 1999). These include a Despite the large body of work on the physiological and eco- mixture of adaptations that are physiological (e.g. increased logical variables that might affect the size of an animal’s home globin levels for more efficient oxygen transfer; Williams et al., range (e.g. body mass and diet), gaps remain in our understand- 2008) and behavioural (e.g. alternative forms of locomotion ing of which factors (or combination of factors) actually drive during diving; Williams, 1999). The subsequent decrease in mammalian home range patterns. While it is clear that diet and COT per unit weight, combined with passive movement via body mass are important, past studies have examined these oceanic currents (Tremblay et al., 2006), results in the relaxation factors separately (e.g. Kelt & van Vuren, 2001; Jetz et al., 2004) of energetic costs in marine environments compared with the and we have little idea of the relative contribution each makes to terrestrial environment. Given that marine COT is approxi- mammalian home range size. Furthermore, home range data mately half that of land COT, e.g. COT for a Californian sea lion have been historically biased towards terrestrial mammals, is 2.5 J kg−1 m−1 (Williams, 1999) versus COT for a grey wolf of resulting in the exclusion of the larger mammals (> 4000 kg). 4.6 J kg−1 m−1 (Pontzer, 2007), marine mammals on average Marine mammals represent a prominent group of large carni- should have home ranges at least twice as large as terrestrial vores. It is also unclear whether the factors driving home range mammals for any given body mass. Moreover, as the marine size in mammals are the same in terrestrial and marine environ- system is fluid with few boundaries to limit movement, food ments. Furthermore, previous studies have failed to consider the resources tend to be highly mobile across the ecosystem (Sims phylogeny of the species being studied. On methodological et al., 2008). In response, marine mammals are highly mobile, grounds, not incorporating information on the phylogenetic and this should result in further increases in home range size. relatedness among species violates the statistical assumption Therefore, we anticipated that a regression of home range size that data points are independent of one another. This results in on body mass should give a higher intercept for marine inflated Type I error rates and correlations between variables mammals (larger home ranges) than for terrestrial mammals. that may not actually exist (Stone et al., 2011). On biological However, as the COT per unit weight decreases with body mass grounds, while closely related species are more likely to share at a similar rate in both marine and terrestrial mammals characteristics through common ancestry (and are therefore not (Hildebrand & Goslow, 1995; Pontzer, 2007), the scaling rela- independent of one another), variation among species can also tionship of home range size and body mass should remain the be generated through the inherently stochastic process of evo- same across both environments. lutionary differentiation (e.g. drift) or phenotypic correlations Our study was conducted in two parts. First, we revisited the that track the phylogeny and indirectly affect home range rather relationship between diet, body mass and home range size in than through adaptation in the home range specifically. That is, terrestrial mammals within an explicit phylogenetic framework variation in home range size among mammals may have little and assessed the relative contribution of each factor to shaping adaptive significance and might simply reflect a history of home range size. Second, we combined data on marine and stochastic differentiation or other factors associated with terrestrial species to examine the effect of diet and body mass on phylogeny. the evolution of home range size across all mammals, while also 2 Global Ecology and Biogeography, © 2014 John Wiley & Sons Ltd Home range-body mass patterns: are all mammals equal? evaluating the role of the environment (marine versus terres- from satellite tracking data. These species were Hydrurga trial). Each of the factors – diet, environment and body mass – leptonyx, Leptonychotes weddellii, Lobodon carcinophaga, was formulated into mathematical functions and tested against Mirounga leonina, Arctocephalus tropicalis and Arctocephalus an evolutionary null model. This null model provides a biologi- gazella. For information on sample size, data collection and cal benchmark to establish the extent to which ‘neutral’ evolu- sampling protocols see Appendix S2. The satellite tracking data tionary differentiation in home range evolution can be were filtered using a speed–distance–angle filter (Freitas & excluded. In this second part of our study we tested two main Lydersen, 2008), resulting in the use of location classes A, B, 1, 2, hypotheses: (1) diet type underpins home range patterns in 3. These classes represent the accuracy of the positional data mammals because of differences in the distribution and assimi- where 3 has an accuracy of 0.49 km, 2 of 1.01 km, 1 of 4.18 km, lation of food types; and (2) the home range–body mass rela- A of 6.19 km and B of 10.28 km (Costa et al., 2010). The average tionship differs between marine and terrestrial mammals daily position was calculated for each individual based upon all because of differences in the physiology of species and the physi- location data for a given day and only adult individuals were cal properties of the two environments. However, we predicted used. Home range was calculated via the fixed kernel density that body mass would be the primary variable determining the estimation (KDE) method (Seaman & Powell, 1996) using the evolution of home range size across all species. This is due to the ArcGIS extension Hawth’s Tools (Beyer, 2004). We chose KDE metabolic and energetic costs associated with body mass driving to calculate home range size, as reviews into the benefits and the food requirements of individuals, which are a key determi- biases of home range methods, including kernels and minimum nant of spatial movements in mammals (Kelt & van Vuren, convex polygons (Laver & Kelly, 2008), suggest that kernels are 2001). Given this overarching effect of body mass, we then pre- preferable to polygons which are biased by outliers and low dicted that the environment would have an important second- numbers of location fixes (Börger et al., 2006). ary effect on home range size because it influences both the We made an attempt to minimize any effects from different physiology of animals and the distribution of resources. Finally, tracking methods (e.g. GPS, satellite and radiotelemetry), analy- within a given environment (e.g. terrestrial), we predicted that sis methodologies (kernels and polygons) and environments diet type would generate additional variation in home range size (terrestrial and marine) (Börger et al., 2006; Frair et al., 2010), among species, reflecting the interaction of diet with the meta- yet published studies differ in the methods used, meaning that bolic and energetic costs associated with a given body mass. our final database included mixed home range values by neces- sity. However, these types of methodological effects are minimal at the scale of our study (Appendix S3), which aims to investi- MATERIALS AND METHODS gate large-scale home range patterns across 462 species from across the globe. Database A database of 462 mammalian species, representing 293 genera, Phylogeny construction 89 families and 24 orders, was collated. We collected information on body mass and home range values, physical environment Due to the absence of a single phylogeny including all species of (marine versus terrestrial) and diet (carnivore, omnivore or her- interest, a composite tree was created by combining information bivore). The home range values for individual species were cal- from several sources (see Fig. S1). The majority of the phylogeny culated as weighted averages which included both sexes, but did was based on the mammalian supertree from Fritz et al. (2009) not incorporate sex ratios or averaged population densities. All in which branch lengths were proportional to time since diver- body mass and home range data for terrestrial mammals was gence. The following species were added to the Fritz et al. (2009) obtained from Kelt & van Vuren (2001) and the PanTHERIA supertree using Mesquite version 2.74 (Maddison & Maddison, database (Jones et al., 2009). Body mass and home range data for 2010) and species were positioned based on the topologies of the marine species were collected from published literature and following sources: Callosciurus erythraeus (Steppan et al., 2004), unpublished empirical data (Appendix S1 in Supporting Infor- Canis familiaris (Agnarsson et al., 2010), Eremitalpa granti mation). Home range was defined as the area covered by an (Kuntner et al., 2011), Orcaella heinsohni (McGowen, 2011), animal during its daily activities such as mating and foraging Sciurus aberti (Grill et al., 2009) and Sotalia guianensis (Burt, 1943), and was used across the marine and terrestrial (Caballero et al., 2008). The Fritz et al. (2009) supertree environments. Marine mammals were defined as species that included polytomies, which are defined as a node where rely upon the ocean to survive (e.g. foraging etc.). Carnivores more than two species diverge at a single point in time were defined as those species with diets comprising at least 90% (multifurcations). In this instance, these are soft polytomies due meat, herbivores at least 90% vegetation and omnivores between to insufficient phylogenetic information. To resolve the branch 10 and 90% vegetation (Kelt & van Vuren, 2001). Insectivores lengths and the polytomies present, we randomly generated were classified as ‘carnivores’,while frugivores and folivores were 1000 alternative branch lengths using the ‘randomly resolve classified as ‘herbivores’. Home range and body mass data were polytomies’ function in Mesquite version 2.74 (Maddison & log10-transformed prior to analysis. Maddison, 2010). This produced 1000 alternative phylogenies To supplement data for six species that were not well repre- and provided the basis for all of the phylogenetic comparative sented in the published literature, we calculated home range size analyses. Global Ecology and Biogeography, © 2014 John Wiley & Sons Ltd 3 M. A. Tucker et al. Table 1 Level of support for explanatory models of evolution of Analysis home range size in land mammals. Results are from phylogenetic We applied a model selection approach to test the level of generalized least squares (PGLS) regression computed for 1000 support for alternative models of home range evolution. The alternative resolutions of the mammalian phylogeny. Model terms best model was selected using the second-order Akaike informa- include herbivores (diet_H), omnivores (diet_O), body mass (mass) and intercept (0). tion criterion with a correction for sample size (AICc; Johnson & Omland, 2004). The model with the lowest AICc value reflects ΔAICc 95% the model with the highest support, although any other model CI (upper, PGLS Effect within two units of the lowest AICc value was also considered to Model ΔAICc lower) α size (r) be a likely candidate (i.e. ΔAIC < 2.0; Burnham & Anderson, 2002). To compute AICc values, we applied each model as a β0 +βmass +βdiet_H +βdiet_O 0.0 n.a. 14.8 0.82 β +β phylogenetic generalized least squares (PGLS) regression, using 0 mass 40.6 34.8, 51.0 8.4 0.72 β compare version 4.6b (Martins, 2004), to each of the 1000 trees 0 281.5 268.5, 298.4 2.9 – (see Phylogeny construction). Computed log-likelihood esti- mates from these analyses were converted into AICc values using AICc, Akaike information criterion with a correction for sample size; n.a., not applicable. equations presented in Burnham & Anderson (2002). PGLS regression also computes an α parameter using maximum like- lihood that estimates the extent to which phenotypic variation RESULTS among species (e.g. mean body mass and associated home range size) is correlated to phylogeny. When α is close to 0, phenotypic We found that diet and body mass together accounted for a differentiation among present-day taxa reflects the phylogenetic portion of the variation in home range size observed among relationships among those species and is the product of Brown- terrestrial mammals (Table 1, Fig. 1). Carnivores, omnivores ian evolution. When α is large (e.g. 15.50) phenotypic differen- and herbivores demonstrated the predicted difference in inter- tiation is unrelated to phylogeny and might be the outcome of cept values. Carnivores showed the predicted large home ranges adaptive evolution (Martins & Hansen, 1997; but also see Revell with an intercept that was significantly higher than omnivores et al., 2008). and herbivores. Omnivores had intermediate home range sizes First, we assessed the level of support for the relationship that were significantly larger than those of herbivores, and her- between diet and home range among 429 species of terrestrial bivores had the smallest home ranges across the three dietary mammals relative to the level of variation in home range size categories (Fig. 1). However, whereas body mass accounted for generated solely by body mass or the evolutionary null model. 52% of the variance in home range size among terrestrial species These models were formulated as: (1) β0 +βmass+βdiet_H +βdiet_O, (r = 0.72), the inclusion of diet improved the explanatory power where diet was scored as binary dummy variables with the of the model by 15% (r = 0.82). There was also a substantial resulting parameters β0, βdiet_H and βdiet_O corresponding to car- improvement in the computed AICc value between the diet nivores, herbivores and omnivores, respectively (this was effec- model and the body mass only model (ΔAICc = 40.6). The tively a phylogenetic ANCOVA); (2) β0 +βmass, which predicted inclusion of phylogeny was important for these analyses as the that differences in home range size among species were exclu- estimated phylogenetic signal in home range size among species sively explained by body mass; and (3) β0, the evolutionary null was high (the null model, α=2.9; note that values approaching model in which no predictor variable was included, and which 0 indicate a high phylogenetic signal in species data). That is, therefore modelled variance in species home range size as the closely related species tended to share similar home range sizes outcome of Brownian evolution and stochastic factors associ- and this could not be explained by phylogenetic inertia in body ated with evolutionary differentiation. mass (i.e. α is a combined estimate of phylogenetic signal across Second, we expanded our analyses to cover both marine and all the variables entered into the model, and when body mass terrestrial species in order to examine the relationship between was included α was 8.36, suggesting that the level of environment and home range, and the extent to which environ- phylogenetic signal exhibited by body mass was potentially ment overrides the influence of diet. This analysis included new lower than for home range size, otherwise the estimate would be empirical data on several marine species (see Database) and similar to or even lower than that estimated by the null model). covered 462 species. Models were formulated as: (1) β0 +βmass When the analysis was expanded to all mammals in both +βenvironment, where environment was entered as a binary variable terrestrial and marine environments, the model that included in which species were coded as living in either a terrestrial (0) or environment, diet and body mass was by far the best-supported marine (1) environment; (2) β0 +βmass+βdiet_H +βdiet_O, the diet model and explained 74% of the variance in home range size model which is described above for the terrestrial mammal analy- among species (r = 0.86; Table 2). There was virtually no sis; (3) β0 +βmass +βdiet_H +βdiet_O +βenvironment, where both diet support for any of the alternative models (ΔAICc > 10), and environment were included together in the same model; (4) although it was noteworthy that the second best model of diet β0 +βmass, which assumed body mass was the only variable pre- and body mass provided a similarly high level of explanatory dicting home range size; and (5) β0, the evolutionary null model power (72% variance explained; r = 0.85; Table 2). The majority described above for the terrestrial mammal analysis. of marine species are large and carnivorous (c. 95% carnivorous 4 Global Ecology and Biogeography, © 2014 John Wiley & Sons Ltd Home range-body mass patterns: are all mammals equal? Figure 1 Home range size as a function of species body mass compared for terrestrial carnivorous (black circles), herbivorous (white circles) and omnivorous (grey circles) species. Each datum represents a species mean value (n = 429 species). The solid black line is the phylogenetic regression of carnivorous mammals: logY = 1.12logX – 0.48. The dashed black line is the phylogenetic regression of omnivorous mammals: logY = 1.12logX – 0.94. The solid grey line is the phylogenetic regression of herbivorous mammals: logY = 1.12logX – 1.45. Bottom right insert: intercept values and confidence intervals for terrestrial herbivores (H), omnivores (O) and carnivores (C). Values were calculated from phylogenetic least squares regression analyses applied to 1000 alternative resolutions of the mammalian phylogeny. Table 2 Level of support for explanatory models of home range another: carnivores had the largest home ranges, omnivores had size evolution in mammals. Results are from phylogenetic intermediate home ranges and herbivores had the smallest generalized least squares (PGLS) regression computed for 1000 home ranges (Fig. 2). That is, with the inclusion of the marine alternative resolutions of the mammalian phylogeny. Model terms mammals, the primary effect seems to have been a divergence in include herbivores (diet_H), omnivores (diet_O), environment intercept values between the carnivores and omnivores (marine or terrestrial), body mass (mass) and intercept (0). (compare Figs 1 & 2). To examine whether the environment has had any impact on ΔAICc 95% CI (upper, PGLS Effect home range size, we restricted our analyses to only carnivorous Model ΔAICc lower) α size (r) marine and terrestrial mammals and refitted the environment and body mass model (β0 +βmass +βenvironment), the body mass β0 +βmass +βdiet_H +βdiet_O + 0.0 n.a. 14.6 0.86 only model (β0 +βmass) and the evolutionary null model (β0). β environment The environment model was the best-supported model of the β +β +β +β 0 mass diet_H diet_O 21.3 7.0, 44.3 14.1 0.85 three, but only explained an additional 1.7% of the variance in β +β +β 0 mass environment 43.9 24.2, 61.8 8.9 0.79 home range size above the 72% explained by body mass only β +β 0 mass 77.9 58.8, 100.8 7.2 0.73 (Table 3). In general, however, marine carnivores have home β 0 322.9 302.3, 354.2 2.4 – ranges that are 1.2 times larger than those of terrestrial species of a similar mass (Fig. 3). AICc, Akaike information criterion with a correction for sample size; n.a., not applicable. Overall, our results confirmed the overarching effect of body mass on mammalian home range size. In addition to body mass, diet and the physical environment, both explained additional variance in home range size among species, but their influence species) and this led us to question whether the environment was less than that of body mass. There was evidence to suggest specifically influenced the best-supported model or whether it that diet might have had a greater impact on home range size was due to the inclusion of larger carnivores in the data set. To than the physical environment (19% additional variance explore this, we examined the parameter estimates for the explained for diet compared with 9% for the environment). In second best-supported model which included only diet and no instance was the evolutionary null model a compelling alter- body mass. These estimates confirmed the expected positive native explanation for differences in home range size among relationship between home range and body mass and showed species, but home range size was found to exhibit a strong that all the diet categories were significantly different from one phylogenetic signal in all analyses (α=1.50–2.90; Tables 1–3). Global Ecology and Biogeography, © 2014 John Wiley & Sons Ltd 5 M. A. Tucker et al. Figure 2 Home range size as a function of species body mass compared for carnivorous (black circles), herbivorous (white circles) and omnivorous (grey circles) species. Each datum represents a species mean value (n = 462 species). The solid black line is the phylogenetic regression of carnivorous mammals: logY = 1.19logX – 0.29. The dashed black line is the phylogenetic regression of omnivorous mammals: logY = 1.19logX – 0.91. The solid grey line is the phylogenetic regression of herbivorous mammals: logY = 1.19logX – 1.47. Bottom right insert: intercept values and confidence intervals for carnivores (C), omnivores (O) and herbivores (H). Values were calculated from phylogenetic least squares regression analyses applied to 1000 alternative resolutions of the mammalian phylogeny. Table 3 Level of support for explanatory models of home range trast, the energetic costs associated with movement are greater in size evolution in carnivorous mammals. Results are from smaller species (Pontzer, 2007), which tends to constrain their phylogenetic generalized least squares (PGLS) regression movements and results in smaller home range sizes. In addition computed for 1000 alternative resolutions of the mammalian to the effects of body mass, we found that the amount of meat phylogeny. Model terms include environment (marine or included in diets was a second-order predictor of home range, terrestrial), body mass (mass) and intercept (0). followed closely by the physical environment (terrestrial versus marine). ΔAICc 95% CI (upper, PGLS Effect However, while providing significant improvements in the Model ΔAICc lower) α size (r) level of support for models, there were varying effects of diet and physical environment on home range size. Both could only β0 +βmass +βenvironment 0.0 n.a. 11.6 0.86 explain a further 1–19% of the variation in home range size β +β 0 mass 4.0 3.6, 4.6 11.0 0.85 among species beyond the effect of body mass. Such a small β 0 93.7 90.3, 101.5 1.5 – effect was surprising for diet because several past studies have concluded diet to be the key determinant of the home range– AICc, Akaike information criterion with a correction for sample size; body mass relationship in terrestrial mammals (Swihart et al., n.a., not applicable. 1988; Kelt & van Vuren, 2001). This seems reasonable consider- ing that what species eat has a direct impact on both their energetic requirements and the types of costs incurred in DISCUSSION obtaining and processing food resources. However, while our Body mass was the principal predictor of home range size in results confirm that diet has been a factor in shaping mamma- mammals, accounting for 53–85% of the observed variation in lian home ranges (support was high for models that included a home range size among species. The evolution of home range parameter for diet) it has nevertheless been far less influential size appears to have been driven, for the most part, by the than body mass. Previous studies of diet and home range use energetic requirements and costs or benefits associated with a were based on datasets with limited species coverage across given body mass. Energetic requirements, such as metabolic rate physical environments (i.e. marine and terrestrial), which can (kJ day−1), are positively correlated with body mass (Nagy, 2005). result in model bias and cause issues when these models are As large species have higher absolute energy needs, they must extrapolated over a broader range of species (Sibly et al., 2012). consume more resources and cover larger areas in order to be Furthermore, phylogenetic information was not incorporated able to meet their energetic demands (McNab, 1963). By con- into previous analyses and our results showed that home range 6 Global Ecology and Biogeography, © 2014 John Wiley & Sons Ltd Home range-body mass patterns: are all mammals equal? Figure 3 Carnivore home range size as a function of species body mass compared for species occupying terrestrial (white circles) and marine (black circles) environments. Each datum represents a species mean value (n = 134 species). The solid black line is the phylogenetic regression of terrestrial mammals: logY = 1.2logX + 0.39. The dashed black line is the phylogenetic least squares (PGLS) regression line of marine mammals: logY = 1.2logX – 0.44. The river otter (9 kg) and southern humpback whale (32,000 kg) are the smallest and largest marine mammals, while the masked shrew (4.2 g) and lion (204 kg) are the smallest and largest terrestrial mammals. Bottom right insert: intercept values and confidence intervals for terrestrial (T) and marine (M) mammals. Values were calculated from PGLS regression analyses applied to 1000 alternative resolutions of the mammalian phylogeny. size does exhibit a large amount of phylogenetic signal (and this mizing energy expended during the hunt. There is the potential was not likely to be the by-product of phylogenetic inertia in that pack hunting may alter home range size due to the body mass). increased density of individuals within an area. Our data did not When our analyses were applied to all species,an apparent dual suggest any difference in home range size between carnivores role of both diet and the environment seemed to be supported that utilize pack hunting and those that do not (Appendix S3). It (Table 2). However, the precise relationship with the physical would be ideal to have more complete home range information environment was unclear because the majority of marine on whales. With the addition of more whale species, we would mammals were large carnivores with very large home ranges. The expect to see a different home range relationship with body specific relevance of the marine environment to home range mass, such as an increase in the scaling of home range size with evolution was therefore unclear. When the effect of diet was body mass, resulting in extreme home range sizes with large controlled for by focusing on carnivorous mammals across ter- body mass. This would especially be the case with the inclusion restrial and marine environments, we found that home ranges of the various whale migrations, which cover a large area, for were significantly larger in marine environments for a given body example the length of a migration (i.e. one direction, single mass than they were on land (Table 3),but the effect was arguably track) can be greater than 5000 km, without accounting for the smaller than that of diet (environment only accounted for an ‘width’ of the home range (Alerstam et al., 2003). At present, additional 1.7% of the variation in home range size among there are a limited number of tracking data available for whales, species over body mass). The combination of living in an open especially long-term data that also include their migration. environment, feeding on mobile resources and lower transport Like mammals, birds provide an interesting comparison with costs has resulted in the evolution of large home range sizes in the home range size of marine mammals. Birds also live within marine carnivorous mammals (roughly 1.2 times larger than a three-dimensional environment (excluding the flightless those of terrestrial carnivorous mammals), but the impact of species) and home range sizes in non-migratory birds tend to be these factors has been minimal compared with the energetic larger than those of mammals for their size (Haskell et al., 2002). requirements/costs driven by body mass. Unfortunately we were The literature suggests that body mass and food resources are unable to examine the relationship between home range,diet and the main drivers of home range size in birds, similar to environment more closely for herbivores and omnivores due to mammals. Body mass was attributed to energy requirements, as the predominance of carnivory within the marine environment. large birds ‘require more food per unit area than smaller birds’ Large carnivorous mammals have high daily energy require- (Schoener, 1968). Also, birds with an increasing amount of ver- ments, and one strategy for meeting these requirements is to tebrate prey in their diet will have larger home range sizes due to utilize pack hunting (Carbone et al., 2007a). Pack hunting lower densities of their prey compared with that of herbivores enables prey with a large body mass to be hunted whilst mini- and omnivores (Schoener, 1968). Global Ecology and Biogeography, © 2014 John Wiley & Sons Ltd 7 M. A. Tucker et al. The effects of diet on the relationship between home range size clade (see Fig. S1). For example, within Carnivora there are and body mass found by this study are likely to only be large-scale both marine (e.g. pinnipeds, Ursus maritimus and Enhyrda effects of resource use and distribution constraints across the lutris) and terrestrial (e.g. Canidae, Mephitidae, Procyonidae) broad diet categories of carnivores, omnivores and herbivores. representatives. This is because resource use and resource distribution constraints have varied effects on home range size. Changes in the type of Conclusion resources used and their abundance can vary on different tem- poral scales. For example, resource distribution and availability Home range is a complex factor influenced by a range of vari- in the Arctic are highly seasonal, with a distinct set of resources ables, including body mass, diet and environment. Our aim was available during winter compared with summer.This would have to clarify the role of these variables and extent to which they a strong effect on the home range size of individuals living in this affect home range size in mammals. We highlight that across the region (e.g. polar bears; Ferguson et al., 1999). However, an mammalian radiation the evolution of home range has been individual may also change which resources they use on a much driven by a hierarchy of variables, but some variables have shorter temporal scale, such as on a day to day basis. Shifts in clearly been more influential than others. The key explanatory resource use or distribution on this small scale are unlikely to be variable for home range size was body mass, followed by the detected in home range analyses due to home range size being secondary variables of diet and then environment. To better calculated over longer periods (i.e. generally on a seasonal or understand the evolution of mammalian home range size we yearly scale). Small-scale studies with a focus on a single species need to investigate the proximate mechanisms (here, proximate and a more direct approach, such as state-space models (Bestley mechanisms are the physiological and morphological drivers) of et al., 2013), would be ideal for investigating dietary effects over its relationship to body size. Furthermore, because the effects of these shorter periods. diet and environment on home range use were small, it would be Our sample sizes were biased towards terrestrial mammals prudent to reconsider past assumptions regarding the influence despite our data including all available information on home of differing resource bases (meat versus plant), modes of trans- range size for marine species (Fig. 1). This partly reflects the port (swimming versus walking and running) and altered physi- difference in the number of mammal species on land versus cal properties (water versus air) as underlying mechanisms of those in the water that were included in our analyses. Calculat- home range use. ing home range for marine species is difficult because of issues Broad models developed using information from many associated with tracking marine species (satellite tracking often species, such as the allometric model of home range size (Jetz being required). For example, home ranges are often calculated et al., 2004; this study), are often used to guide conservation and over shorter tracking periods in marine species compared with management strategies. It is critical then that the underlying those on land. As tracking technology improves, and methodol- assumptions of these models are biologically appropriate. Pre- ogies for estimating home ranges in marine species become vious models have focused exclusively on select groups of more sophisticated, the number of species for which home species (e.g. terrestrial mammals), and we have developed an range information is available should increase. Nevertheless, important amendment to these models to show that home range mammalian species diversity in marine environments is much drivers once thought to be highly influential are not so. We have lower than on land, so this bias in sampling partly reflects bio- demonstrated that by using an integrative model which incor- logical reality and this will not change with improved methods porates an inclusive list of predictor variables, species and of home range estimation. phylogenetic information, our knowledge of home range pat- It should also be noted that the home range values of marine terns across mammals can be significantly enhanced. species used in this study may be conservative because they were measured in two dimensions while marine mammals use a ACKNOWLEDGEMENTS three-dimensional environment (Pawar et al., 2012). However, Carbone et al. (2007b) investigated abundance scaling in We wish to thank two anonymous referees for their constructive mammals in three-dimensional environments and their models suggestions that have strengthened the manuscript.We acknowl- predict a −2/3 scaling similar to abundance scaling within two- edge and sincerely thank Horst Bornemann (Alfred Wegener dimensional environments. As there is a relationship between Institute), Joachim Plötz (Alfred Wegener Institute), Nick Gales animal abundance scaling and home range size (Jetz et al., (Australian Antarctic Division), P.J. Nico deBruyn (University of 2004), we may expect to see a similar pattern in the scaling of Pretoria), Cheryl Tosh (University of Pretoria), Colin Southwell home range size in mammals. The effect of the dimensionality (Australian Antarctic Division), Iain Staniland (British Antarctic of environments would be an interesting concept to examine in Survey), Douglas Kelt (UC Davis) and Dirk van Vuren (UC a future study, using similar mathematical methods to those Davis) for their data contributions. Some of the data used within used in Carbone et al. (2007b). this paper were obtained from the Australian Antarctic Data It is unlikely that differences in home range size across the Centre (IDN Node AMD/AU), part of the Australian Antarctic marine and terrestrial environments are driven by how species Division (Commonwealth of Australia). The data are described are related (i.e. collinearity between environment and related- in the ARGOS satellite tracking record ‘1994 to 2000 – Antarctic ness). Marine mammals are interspersed across the mammalian Pack Ice Seals (APIS) Survey’(Southwell,2007).Wewish to thank 8 Global Ecology and Biogeography, © 2014 John Wiley & Sons Ltd Home range-body mass patterns: are all mammals equal? the personnel from the Instituto Antártico Argentino at Ferguson, S.H., Taylor, M.K., Born, E.W., Rosing-Asvid, A. & Primavera Station in the years 2007–11 for field work support. Messier, F. (1999) Determinants of home range size for polar Logistics support provided by the grant from Instituto Antártico bears (Ursus maritimus). Ecology Letters, 2, 311–318. Argentino (IAA) to Alejandro Carlini, and the Australian Frair, J.L., Fieberg, J., Hebblewhite, M., Cagnacci, F., DeCesare, Research Council (ARC) grant # LP0989933 to T.L.R. N.J. & Pedrotti, L. (2010) Resolving issues of imprecise and habitat-biased locations in ecological analyses using GPS telemetry data. 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Ecology, 49, 123–141. Appendix S1 Database of home range and body mass values for Seaman, D.E. & Powell, R.A. (1996) An evaluation of the accu- 462 species of mammal, including sources. racy of kernel density estimators for home range analysis. Appendix S2 Additional information on sample size, data col- Ecology, 77, 2075–2085. lection and sampling protocols for data used in home range Sibly, R.M., Zuo, W., Kodric-Brown, A. & Brown, J.H. (2012) calculation. Rensch’s rule in large herbivorous mammals derived Appendix S3 Additional analyses and results. from metabolic scaling. The American Naturalist, 179, 169– Figure S1 The phylogeny of 462 extant species of mammal and 177. their home range size. Sims, D.W., Southall, E.J., Humphries, N.E., Hays, G.C., Bradshaw, C.J.A., Pitchford, J.W., James, A., Ahmed, M.Z., BIOSKETCHES Brierley, A.S., Hindell, M.A., Morritt, D., Musyl, M.K., Righton, D., Shepard, E.L.C., Wearmouth, V.J., Wilson, R.P., Marlee Tucker is a PhD candidate under the Witt, M.J. & Metcalfe, J.D. (2008) Scaling laws of marine supervision of Tracey Rogers. Marlee’s research predator search behaviour. Nature, 451, 1098–1102. encompasses macroecological patterns in mammals, Southwell, C. (2007) 1994 to 2000 - Antarctic Pack Ice Seals specifically changes in behaviours and patterns that (APIS) Survey, Australian Antarctic Data Centre - ARGOS sat- have occurred with the colonization of the marine ellite tracking record. Available at http://data.aad.gov.au/aadc/ environment. argos/profile_list.cfm?taxon_id=25 (accessed 6 May 2014). Steppan, S.J., Storz, B.L. & Hoffmann, R.S. (2004) Nuclear DNA Terry Ord is an evolutionary ecologist with broad phylogeny of the squirrels (Mammalia: Rodentia) and the interests in animal behaviour, adaptation and evolution of arboreality from c-myc and RAG1. Molecular macroevolution. Phylogenetics and Evolution, 30, 703–719. Tracey Rogers is an ecologist interested in how Stone, G.N., Nee, S. & Felsenstein, J. (2011) Controlling for mammals respond to environmental change including non-independence in comparative analysis of patterns across broad-scale patterns in ecology related to body size, diet populations within species. Philosophical Transactions of the and trophic level. Royal Society B: Biological Sciences, 366, 1410–1424. Swihart, R.K., Slade, N.A. & Bergstrom, B.J. (1988) Relating Author contributions: M.A.T., T.L.R. and T.J.O. body size to the rate of home range use in mammals. Ecology, conceived the study. M.A.T. and T.L.R. collected and 69, 393–399. compiled the data. M.A.T. conducted the analyses. Tremblay, Y., Shaffer, S.A., Fowler, S.L., Kuhn, C.E., McDonald, M.A.T., T.J.O. and T.L.R. wrote the paper. B.I., Weise, M.J., Bost, C.A., Weimerskirch, H., Crocker, D.E., Goebel, M.E. & Costa, D.P. (2006) Interpolation of animal Editor: Marcel Cardillo 10 Global Ecology and Biogeography, © 2014 John Wiley & Sons Ltd Appendix 2 Supplementary Information for Chapter 2 144 Table 2.1 Database of home range and body mass values for 462 mammal species, including sources. log10 log10 Home Taxon Mass Diet Environment References range (kg) (km2) Abrothrix_olivaceus -3.33 -1.61 Omnivore Terrestrial Jones et al. 2009 Acinonyx_jubatus 2.91 1.70 Carnivore Terrestrial Caro 1994 Aepyceros_melampus 0.51 1.80 Herbivore Terrestrial duToit 1990, Murray 1982 Ailuropoda_melanoleuca 0.62 1.94 Herbivore Terrestrial Schaller et al. 1985 Ailurus_fulgens 0.01 0.73 Herbivore Terrestrial Reid et al. 1991 Alcelaphus_buselaphus 0.34 2.13 Herbivore Terrestrial Ables and Ables 1971 Addison et al. 1980, Ballard et al. 1991, Bangs and Bailey 1980b, Bangs et al. 1984, Cederlund and Okarma 1988, Cederlund and Sand 1994, Doerr 1983, Grauvogel 1984, Hauge and Keith Alces_alces 1.97 2.49 Herbivore Terrestrial 1981, Leptich and Gilbert 1989, MacCracken et al. 1997, Stenhouse et al. 1994, Van Dyke et al. 1995 Alouatta_seniculus -0.80 0.81 Omnivore Terrestrial Jones et al. 2009 Amblysomus_hottentotus -3.33 -1.20 Omnivore Terrestrial Jones et al. 2009 Ammospermophilus_leucurus -1.30 -0.98 Omnivore Terrestrial Jones et al. 2009 Ammospermophilus_nelsoni -1.40 -0.79 Omnivore Terrestrial Jones et al. 2009 Ammotragus_lervia 0.96 2.22 Herbivore Terrestrial Hampy 1978 Antechinus_stuartii -1.46 -1.56 Carnivore Terrestrial Lazenby-Cohen and Cockburn 1991 Antilocapra_americana 1.01 1.66 Herbivore Terrestrial Bayless 1969, Reynolds 1984 Aonyx_capensis 2.08 1.29 Omnivore Terrestrial Jones et al. 2009 Aotus_trivirgatus -1.30 -0.04 Omnivore Terrestrial Jones et al. 2009 Aplodontia_rufa -2.98 0.05 Herbivore Terrestrial Martin 1971 Apodemus_flavicollis -2.12 -1.50 Herbivore Terrestrial Scharzenberger and Klingel 1995 Apodemus_sylvaticus -1.88 -1.67 Herbivore Terrestrial Attuquayefio et al. 1986, Corp et al. 1997, Wolton 1985 Apomys_musculus -2.63 -1.67 Omnivore Terrestrial Jones et al. 2009 Arctocephalus_gazella 3.75 1.53 Carnivore Marine Personal communication; Staniland et al., 2010 Arctocephalus_tropicalis 5.34 1.52 Carnivore Marine This study 145 Atherurus_africanus -0.82 0.44 Herbivore Terrestrial Emmons 1983 Atilax_paludinosus 0.35 0.56 Carnivore Terrestrial Ray 1997 Axis_axis 0.56 1.80 Herbivore Terrestrial Ables et al. 1977, Moe and Wegge 1994 Balaena_mysticetus 4.39 4.49 Carnivore Marine Heide-Jorgensen et al., 2007 Bassariscus_astutus -0.08 0.01 Omnivore Terrestrial Toweill and Teer 1981, Trapp 1978 Bathyergus_suillus -2.57 -0.20 Herbivore Terrestrial Davies and Jarvis 1986 Bettongia_gaimardi -0.34 0.22 Herbivore Terrestrial Taylor 1993 Bison_bison 2.42 2.80 Herbivore Terrestrial Larter and Gates 1994, Lott and Minta 1983, Van Vuren 1983 Bison_bonasus 1.01 2.80 Herbivore Terrestrial Krasinska and Krasinski 1995 Brachylagus_idahoensis -2.31 -0.47 Herbivore Terrestrial Katzner and Parker 1997 Brachyteles_arachnoides 0.33 1.02 Omnivore Terrestrial Jones et al. 2009 Bradypus_torquatus -1.35 0.59 Herbivore Terrestrial Chiarello 1998 Bunopithecus_hoolock -0.64 0.83 Omnivore Terrestrial Jones et al. 2009 Callicebus_moloch -1.52 -0.02 Omnivore Terrestrial Jones et al. 2009 Callimico_goeldii -0.35 -0.25 Omnivore Terrestrial Jones et al. 2009 Callithrix_humeralifera -0.89 -0.43 Omnivore Terrestrial Jones et al. 2009 Callithrix_pygmaea -2.51 -0.91 Omnivore Terrestrial Jones et al. 2009 Callosciurus_erythraeus -1.85 -0.44 Omnivore Terrestrial Tamura et al. 1989 Caluromys_philander -1.50 -0.58 Omnivore Terrestrial Julien-Laferriere 1995 Canis_adustus 0.04 0.98 Omnivore Terrestrial Fuller et al. 1989 Canis_aureus 0.17 0.96 Omnivore Terrestrial Fuller et al. 1989, Poche et al. 1987 Daniels and Bekoff 1989, Gipson 1983, Harden 1985, Nakada et al. 1996, Scott and Causey Canis_familiaris 1.46 1.15 Omnivore Terrestrial 1973, Thomson 1992 Althoff 1978, Andelt 1985, Andelt and Gipson 1979, Babb and Kennedy 1988, Berg and Chesness 1978, Bowen 1982, Bradley and Fagre 1988, Danner and Smith 1980, Fuller and Keith 1981, Gese et al. 1988, Harrison et al. 1989, Hibler 1977, Holzman et al. 1992, Laundre Canis_latrans 1.46 1.20 Omnivore Terrestrial and Keller 1983, Litvaitis and Shaw 1980, Major and Sherburne 1987, Mills and Knowlton 1991, Person and Hirth 1991, Pyrah 1984, Roy and Dorrance 1985, Sargeant et al. 1987, Servin and Huxley 1995, Springer 1982, Sumner et al. 1984, White et al. 1994, Windberg and Knowlton 146 1988, Windberg et al. 1997, Witmer and de Calesta 1986, Woodruff and Keller 1982 Ballard et al. 1997, Bjorge and Gunson 1989, Carbyn 1983, Ciucci et al. 1997, Fritts and Mech Canis_lupus 2.67 1.63 Carnivore Terrestrial 1981, Fuller 1989, Messier 1985, Okarma et al. 1998, Peterson et al. 1984, Potvin 1987, VanBallenberghe et al. 1975 Canis_mesomelas 1.20 1.00 Omnivore Terrestrial Ferguson et al. 1983, Fuller et al. 1989 Canis_simensis 0.73 1.44 Carnivore Terrestrial Sillero Zubiri and Gottelli 1995 Capra_hircus 1.81 1.71 Herbivore Terrestrial King 1992, OBrien 1984 Capra_pyrenaica -0.15 1.84 Herbivore Terrestrial Escos and Alados 1992 Capreolus_capreolus -0.17 1.38 Herbivore Terrestrial Bideau et al. 1993, Cederlund 1983, Chapman et al. 1993, Guillet et al. 1996 Avenant and Nel 1998, Bothma and ldRiche 1994, Norton and Lawson 1985, vanHeezik and Caracal_caracal 2.58 1.11 Carnivore Terrestrial Seddon 1998 Castor_canadensis -1.11 1.31 Herbivore Terrestrial Davis and Guynn 1993, Wheatley 1997 Catagonus_wagneri 1.04 1.54 Herbivore Terrestrial Taber et al. 1994 Cebus_capucinus -0.20 0.48 Omnivore Terrestrial Jones et al. 2009 Cephalophus_callipygus -0.38 1.26 Herbivore Terrestrial Feer 1989 Cephalophus_dorsalis -0.45 1.31 Herbivore Terrestrial Feer 1989 Cephalorhynchus_heavisidii 2.78 1.88 Carnivore Marine Elwin et al., 2006 Ceratotherium_simum 1.20 3.35 Herbivore Terrestrial Pienaar et al. 1993 Cercartetus_nanus -2.15 -1.62 Omnivore Terrestrial Laidlaw and Wilson 1996 Cercopithecus_cephus -0.46 0.54 Omnivore Terrestrial Jones et al. 2009 Cercopithecus_diana 0.28 0.64 Omnivore Terrestrial Jones et al. 2009 Cercopithecus_mitis -0.80 0.70 Omnivore Terrestrial Jones et al. 2009 Cercopithecus_nictitans 0.24 0.72 Omnivore Terrestrial Jones et al. 2009 Cerdocyon_thous 0.48 0.76 Omnivore Terrestrial MacDonald and Courtenay 1996, Sunquist et al. 1989 Catt and Staines 1987, Cole et al. 1997, Craighead et al. 1973, Edge et al. 1985, Franklin and Cervus_elaphus 1.87 2.37 Herbivore Terrestrial Lieb 1979, Georgii 1980, Irwin and Peek 1983, Jenkins and Starkey 1982, McCorquodale et al. 1989, Strohmeyer and Peek 1996, Waldrip and Shaw 1979 Cervus_nippon -0.07 1.47 Herbivore Terrestrial Borkowsky and Furubayashi 1998, Feldhamer et al. 1982 Cheirogaleus_major -1.40 -0.35 Omnivore Terrestrial Jones et al. 2009 147 Chrysocyon_brachyurus 1.43 1.38 Omnivore Terrestrial Dietz 1984 Chrysospalax_trevelyani -3.21 -0.36 Carnivore Terrestrial Jones et al. 2009 Clethrionomys_californicus -1.80 -1.65 Herbivore Terrestrial Tallmon and Mills 1994 Coendou_prehensilis -0.73 0.63 Herbivore Terrestrial Montgomery and Lubin 1978 Condylura_cristata -2.44 -1.32 Carnivore Terrestrial Jones et al. 2009 Conepatus_humboldtii -0.79 0.12 Omnivore Terrestrial Fuller et al. 1987 Conepatus_semistriatus -0.45 0.38 Omnivore Terrestrial Sunquist et al. 1989 Crocidura_russula -3.63 -2.00 Carnivore Terrestrial Jones et al. 2009 Crocuta_crocuta 2.24 1.81 Carnivore Terrestrial Gasaway et al. 1989, Sillero Zubiri and Gottelli 1992 Cryptomys_damarensis -1.89 -0.83 Herbivore Terrestrial Lovegrove 1988 Cryptomys_hottentotus -2.80 -1.19 Herbivore Terrestrial Davies and Jarvis 1986 Cryptoprocta_ferox -0.05 0.98 Carnivore Terrestrial Jones et al. 2009 Cryptotis_parva -2.76 -2.30 Omnivore Terrestrial Jones et al. 2009 Cuon_alpinus 1.84 1.20 Carnivore Terrestrial Venkataraman et al. 1995 Cyclopes_didactylus -1.40 -0.58 Carnivore Terrestrial Jones et al. 2009 Cynictis_penicillata -0.23 -0.21 Carnivore Terrestrial Cavallini 1993 Cystophora_cristata 4.72 2.56 Carnivore Marine Bajzak et al. 2009 Dactylopsila_trivirgata -1.10 -0.38 Omnivore Terrestrial Jones et al. 2009 Dama_dama -0.01 1.85 Herbivore Terrestrial Nugent 1994 Dasypus_novemcinctus -1.52 0.60 Omnivore Terrestrial Jones et al. 2009 Dasyurus_geoffroii 0.36 0.04 Carnivore Terrestrial Jones et al. 2009 Dasyurus_maculatus 0.16 0.52 Omnivore Terrestrial Jones et al. 2009 Dasyurus_viverrinus -0.44 0.04 Omnivore Terrestrial Jones et al. 2009 Daubentonia_madagascariensi -0.96 0.44 Omnivore Terrestrial Jones et al. 2009 s Delphinapterus_leucas 3.52 3.18 Carnivore Marine Hobbs et al., 2005 Dendrolagus_lumholtzi -1.71 0.82 Herbivore Terrestrial Newell 1999 148 Desmana_moschata -2.28 -0.37 Omnivore Terrestrial Jones et al. 2009 Diceros_bicornis 1.62 3.02 Herbivore Terrestrial Frame 1980, Goddard 1967, Kiwia 1989, Mukinya 1973 Didelphis_marsupialis -0.25 0.04 Omnivore Terrestrial Sunquist et al. 1987 Didelphis_virginiana -0.28 0.70 Omnivore Terrestrial Gillette 1980, Shirer and Fitch 1970 Dipodomys_ingens -3.36 -0.81 Herbivore Terrestrial Braun 1985 Dipodomys_merriami -2.13 -1.38 Herbivore Terrestrial Jones 1989, Schroder 1987 Dipodomys_ordii -1.75 -1.25 Herbivore Terrestrial Schroder 1987 Dipodomys_spectabilis -2.52 -0.84 Herbivore Terrestrial Schroder 1979, Schroder 1987 Dipodomys_stephensi -2.83 -1.12 Herbivore Terrestrial Kelly and Price 1995 Dolichotis_patagonum -0.01 0.90 Herbivore Terrestrial Taber and MacDonald 1992 Dugong_dugon 2.12 2.30 Herbivore Marine Sheppard et al., 2006 Echymipera_clara -2.00 0.08 Omnivore Terrestrial Jones et al. 2009 Echymipera_kalubu -1.70 -0.08 Omnivore Terrestrial Jones et al. 2009 Eira_barbara 1.16 0.65 Carnivore Terrestrial Konecny 1989, Sunquist et al. 1989 Elephantulus_rufescens -2.47 -1.24 Carnivore Terrestrial Rathbun 1979 Elephas_maximus 2.04 3.60 Herbivore Terrestrial Sukumar 1989 Enhydra_lutris 0.18 1.44 Carnivore Marine Garshelis and Garshelis 1984 Equus_burchelli 2.21 2.38 Herbivore Terrestrial Smuts 1975 Equus_caballus 1.35 2.63 Herbivore Terrestrial Berger 1987 Equus_zebra 0.97 2.46 Herbivore Terrestrial Penzhorn 1982 Eremitalpa_granti -1.33 -1.64 Carnivore Terrestrial Fielden 1991 Erethizon_dorsatum -0.44 0.94 Herbivore Terrestrial Roze 1987 Erinaceus_europaeus -0.71 -0.10 Carnivore Terrestrial Boitani and Reggiani 1984, Morris 1988, Reeve 1982, Schoenfeld and YomTov 1985 Erythrocebus_patas 1.61 0.90 Omnivore Terrestrial Jones et al. 2009 Eulemur_mongoz -1.15 0.25 Omnivore Terrestrial Jones et al. 2009 Eumetopias_jubatus 4.68 2.44 Carnivore Marine Merrick et al., 1997 149 Euphractus_sexcinctus -0.03 0.67 Omnivore Terrestrial Jones et al. 2009 Apps 1986, Fitzgerald and Karl 1986, Genovesi et al. 1995, Hall et al. 2000, Jones and Coman Felis_catus 0.17 0.53 Carnivore Terrestrial 1982, Konecny 1987, Norbury et al. 1998, Page et al. 1992, Weber and Dailly 1998 Felis_silvestris 0.45 0.68 Carnivore Terrestrial Stahl et al. 1988 Fossa_fossana -0.05 0.27 Omnivore Terrestrial Jones et al. 2009 Funambulus_pennantii -2.74 -0.99 Herbivore Terrestrial Prakash et al. 1968 Galago_senegalensis -0.96 -0.67 Omnivore Terrestrial Jones et al. 2009 Galemys_pyrenaicus -2.86 -1.22 Carnivore Terrestrial Jones et al. 2009 Galerella_pulverulenta -0.23 -0.23 Omnivore Terrestrial Cavallini and Nel 1990 Galictis_vittata 0.62 0.24 Carnivore Terrestrial Sunquist et al. 1989 Galidia_elegans -0.70 -0.09 Omnivore Terrestrial Jones et al. 2009 Gazella_gazella 0.27 1.33 Herbivore Terrestrial Dunham 1998 Genetta_genetta 0.89 0.24 Carnivore Terrestrial Palomares and Delibes 1994 Genetta_tigrina -1.24 0.33 Carnivore Terrestrial Ikeda et al. 1982 Georychus_capensis -3.57 -0.62 Herbivore Terrestrial Jarvis and Beviss-Challinor unpublished data, cited in Reichman and Smith 1990 Gerbillurus_paeba -2.00 -1.59 Omnivore Terrestrial Jones et al. 2009 Giraffa_camelopardalis 2.14 3.13 Herbivore Terrestrial Berry 1978, duToit 1990, Langman 1973, Leuthold and Leuthold 1978 Glaucomys_sabrinus -1.10 -0.83 Herbivore Terrestrial Fridell and Litvaitis 1991, Witt 1992 Glaucomys_volans -1.53 -1.19 Herbivore Terrestrial Bendel and Gates 1987, Madden 1974, Stone et al. 1997 Graphiurus_ocularis -0.96 -1.16 Herbivore Terrestrial vanHensbergen and Channing 1989 Banci and Harestad 1990, Gardner 1985 MS Alaska, Hornocker and Hash 1981, Landa et al. Gulo_gulo 2.56 1.33 Carnivore Terrestrial 1998, Magoun 1985, Whitman et al. 1986 Halichoerus_grypus 3.42 1.92 Carnivore Marine Sjoberg and Ball, 2000 Heliophobius_argenteocinereus -3.76 -0.81 Herbivore Terrestrial Jarvis and Sale 1971 cited in Reichman and Smith 1990 Helogale_parvula -0.55 -0.55 Carnivore Terrestrial Jones et al. 2009 Hemiechinus_auritus -1.39 -0.53 Carnivore Terrestrial Schoenfeld and YomTov 1985 Herpestes_ichneumon 0.45 0.47 Omnivore Terrestrial Delibes and Beltran 1985 150 Herpestes_javanicus -1.50 -0.36 Omnivore Terrestrial Nellis and Everard 1983 Herpestes_naso -0.28 0.56 Omnivore Terrestrial Ray 1997 Heterocephalus_glaber -2.27 -1.41 Herbivore Terrestrial Jarvis 1985 cited in Reichman and Smith 1990 Hyaena_brunnea 1.32 1.68 Carnivore Terrestrial Viljoen 1986 Hyaena_hyaena 1.77 1.60 Carnivore Terrestrial Kruuk 1976, vanAarde et al. 1988 Hydrurga_leptonyx 4.18 2.54 Carnivore Marine This study Hyemoschus_aquaticus -0.72 1.04 Herbivore Terrestrial Dubost 1978citedinEmmons 1983 Hylaeamys_megacephalus -2.11 -1.18 Herbivore Terrestrial Guillotin 1982 Hylobates_agilis -0.57 0.77 Omnivore Terrestrial Jones et al. 2009 Hylobates_klossii -0.68 0.77 Omnivore Terrestrial Jones et al. 2009 Hylobates_lar -0.34 0.75 Omnivore Terrestrial Jones et al. 2009 Hylobates_moloch -0.77 0.77 Omnivore Terrestrial Jones et al. 2009 Hylobates_muelleri -0.42 0.77 Omnivore Terrestrial Jones et al. 2009 Hylobates_pileatus -0.48 0.74 Omnivore Terrestrial Jones et al. 2009 Hylomys_suillus -2.74 -1.24 Omnivore Terrestrial Jones et al. 2009 Hypogeomys_antimena -1.46 0.07 Herbivore Terrestrial Cook et al. 1991 Hystrix_africaeaustralis 0.23 1.23 Herbivore Terrestrial Corbet and vanAarde 1996 Hystrix_cristata -0.24 1.13 Omnivore Terrestrial Jones et al. 2009 Hystrix_indica 0.15 1.18 Herbivore Terrestrial Saltz and Alkon 1989 Ichneumia_albicauda -0.41 0.56 Carnivore Terrestrial Ikeda et al. 1982, Waser and Waser 1985 Isoodon_auratus -0.93 -0.41 Carnivore Terrestrial Southgate et al. 1996 Isoodon_macrourus -1.70 0.18 Omnivore Terrestrial Jones et al. 2009 Isoodon_obesulus -1.68 -0.11 Carnivore Terrestrial Broughton and Dickman 1991 Lagostomus_maximus -2.00 0.72 Herbivore Terrestrial Branch 1993 Lagothrix_lagotricha 0.60 0.80 Omnivore Terrestrial Jones et al. 2009 Lasiorhinus_krefftii -0.60 1.41 Herbivore Terrestrial Johnson 1991 151 Lemmus_sibiricus -2.08 -1.04 Herbivore Terrestrial Banks et al. 1975 Leontopithecus_chrysopygus 0.07 -0.18 Omnivore Terrestrial Jones et al. 2009 Leontopithecus_rosalia -0.43 -0.23 Omnivore Terrestrial Jones et al. 2009 Leopardus_geoffroyi 0.85 0.56 Carnivore Terrestrial Johnson and Franklin 1991 Crawshaw and Quigley 1989, Emmons 1988, Konecny 1989, Lopez 1985, Ludlow and Sunquist Leopardus_pardalis 0.84 1.00 Carnivore Terrestrial 1987, Sunquist et al. 1989 Leopardus_wiedii 1.04 0.56 Carnivore Terrestrial Konecny 1989 Lepilemur_edwardsi -2.02 -0.09 Omnivore Terrestrial Jones et al. 2009 Leptailurus_serval 0.38 1.08 Carnivore Terrestrial vanAarde and Skinner 1986 Leptonychotes_weddelli 1.98 2.62 Carnivore Marine This study Lepus_americanus -1.49 0.13 Herbivore Terrestrial Boutin 1979, Ferron and Ouellet 1992 Lepus_arcticus 0.46 0.61 Herbivore Terrestrial Hearn et al. 1987 Lepus_californicus 0.20 0.36 Herbivore Terrestrial Smith 1990 Lepus_capensis -0.28 0.55 Herbivore Terrestrial Parkes 1984 Lepus_europaeus -0.54 0.72 Herbivore Terrestrial Broekhuizen and Maaskamp 1982 Lepus_nigricollis -1.86 0.50 Herbivore Terrestrial Kirk and Bathe 1994 Lepus_timidus -0.34 0.45 Herbivore Terrestrial Flux 1970, Hewson and Hinge 1990, Hulbert et al. 1996 Liomys_salvini -2.76 -1.38 Omnivore Terrestrial Jones et al. 2009 Lobodon_carcinophagus 5.57 2.40 Carnivore Marine This study Lophocebus_albigena 0.61 0.87 Omnivore Terrestrial Jones et al. 2009 Loris_tardigradus -2.00 -0.60 Omnivore Terrestrial Jones et al. 2009 DeVilliers and Kok 1997, Dunham 1986, Leuthold 1977, Lindeque and Lindeque 1991, Tchamba Loxodonta_africana 3.24 3.60 Herbivore Terrestrial et al. 1994, Thouless 1996, Viljoen 1989 Lutra_canadensis 1.63 0.97 Carnivore Marine Blundell et al., 2000 Lutra_lutra 1.41 0.95 Carnivore Terrestrial Jones et al. 2009 Lutreolina_crassicaudata -2.73 -0.26 Carnivore Terrestrial Jones et al. 2009 Lutrogale_perspicillata 0.80 0.95 Carnivore Terrestrial Jones et al. 2009 152 Lycaon_pictus 2.64 1.43 Carnivore Terrestrial Anderka et al. 1999, Fuller and Kat 1990 Lynx_canadensis 1.92 1.01 Carnivore Terrestrial Bailey et al. 1986, Koehler 1990, Poole 1994, Slough and Mowat 1996 Lynx_lynx 2.26 1.48 Carnivore Terrestrial Haller and Breitenmoser 1986, Schmidt et al. 1997 Lynx_pardinus 0.98 1.04 Carnivore Terrestrial Ferreras et al. 1997 Bailey 1974, Berg 1981, Bradley and Fagre 1988, Buie et al. 1979, Conner et al. 1992, Fuller et al. 1985, Knick 1990, Koehler and Hornocker 1989, Litvaitis et al. 1987, Lovallo and and erson Lynx_rufus 1.60 1.05 Carnivore Terrestrial 1996, Major and Sherburne 1987, Rolley 1983, Rucker et al. 1989, Whitaker et al. 1987, Witmer and deCalesta 1986, Zezulak and Schwab 1979, Zwank et al. 1985 Macaca_silenus -0.07 0.78 Omnivore Terrestrial Jones et al. 2009 Macropus_antilopinus -0.19 1.44 Herbivore Terrestrial Croft 1987 Macropus_dorsalis -0.04 1.05 Herbivore Terrestrial Evans 1996 Macropus_fuliginosus 0.51 1.34 Herbivore Terrestrial Arnold et al. 1992, Coulson 1993, Priddell et al. 1988 Macropus_giganteus 0.79 1.02 Herbivore Terrestrial Jarman and Taylor 1983 Macropus_robustus -0.01 1.33 Herbivore Terrestrial Clancy and Croft 1990, Croft 1987, Jarman and Taylor 1983 Macropus_rufogriseus -0.79 1.23 Herbivore Terrestrial Johnson 1987 Macropus_rufus 0.89 1.67 Herbivore Terrestrial Priddell et al. 1988 Macroscelides_proboscideus 0.00 -1.41 Omnivore Terrestrial Jones et al. 2009 Madoqua_guentheri -1.56 0.66 Herbivore Terrestrial Ono et al. 1988 Manis_temminckii 1.12 1.10 Carnivore Terrestrial Heath and Coulson 1997 Marmosa_robinsoni -2.66 -1.22 Omnivore Terrestrial Jones et al. 2009 Marmota_flaviventris -1.24 0.53 Herbivore Terrestrial Salsbury and Armitage 1994, Van Vuren unpubl. data Marmota_monax -0.78 0.53 Herbivore Terrestrial Ferron and Oellet 1989, Meier 1992, Swihart 1992 Archibald and Jessup 1984, Bateman 1986, Burnett 1981, Buskirk 1983, Clark et al. 1989, Davis 1983, Katnik et al. 1994, Major 1979, Mech and Rogers 1977, Simon 1980, Slough 1989, Martes_americana 0.85 -0.05 Carnivore Terrestrial Spencer 1981, Steventon 1979, Steventon and Major 1982, Thompson and Colgan 1987, Wynne and Sherburne 1984 Martes_foina 0.64 0.26 Carnivore Terrestrial Genovesi et al. 1997 Martes_martes 0.96 0.39 Carnivore Terrestrial Clevenger 1993, Pulliainen 1984, Schropfer et al. 1997, Zalewski et al. 1995 Martes_pennanti 1.22 0.50 Carnivore Terrestrial Arthur et al. 1989, Garant and Crete 1997 153 Mastomys_natalensis -2.93 -1.18 Omnivore Terrestrial Leirs et al. 1996 Megaptera_novaeangliae 4.68 4.52 Carnivore Marine Dalla Rosa et al., 2008 Meles_meles 0.34 1.09 Omnivore Terrestrial Broseth et al. 1997, Kruuk 1987 Melursus_ursinus 1.00 1.99 Carnivore Terrestrial Melquist 1982 Mephitis_mephitis 0.47 0.66 Omnivore Terrestrial Lariviere and Messier 1998, Shirer and Fitch 1970, Storm 1972 Meriones_hurrianae -3.88 -1.05 Herbivore Terrestrial Fitzwater and Prakash 1969 Microdipodops_megacephalus -2.33 -1.91 Omnivore Terrestrial Jones et al. 2009 Microtus_agrestis -3.15 -1.42 Herbivore Terrestrial Agrell et al. 1996 Microtus_californicus -4.07 -1.15 Herbivore Terrestrial Heske 1987 Microtus_montanus -3.82 -1.25 Herbivore Terrestrial Douglas 1976 Danielson and Swihart 1987, Gaulin and FitzGerald 1988, Harvey and Barbour 1965, Jike et al. Microtus_ochrogaster -3.17 -1.45 Herbivore Terrestrial 1988 Collins and Barrett 1997, Douglas 1976, Gaulin and FitzGerald 1988, Jones 1990, Jones and Microtus_pennsylvanicus -3.39 -1.30 Herbivore Terrestrial Sherman 1983 Microtus_pinetorum -4.44 -1.53 Herbivore Terrestrial Gettle 1975 Microtus_richardsoni -3.38 -1.07 Herbivore Terrestrial Ludwig 1981 Miopithecus_talapoin 0.08 0.10 Omnivore Terrestrial Jones et al. 2009 Mirounga_angustirostris 3.90 3.08 Carnivore Marine LeBoeuf et al., 2000 Mirounga_leonina 5.69 3.18 Carnivore Marine This study Mirza_coquereli -1.40 -0.49 Omnivore Terrestrial Jones et al. 2009 Monachus_schauinslandi 4.00 2.31 Carnivore Marine Curtice et al., 2011 Monodelphis_americana -3.33 -1.71 Carnivore Terrestrial Jones et al. 2009 Monodon_monoceros 4.72 3.11 Carnivore Marine Dietz et al., 2008 Mungos_mungo 0.33 0.10 Carnivore Terrestrial Jones et al. 2009 Muntiacus_reevesi -0.79 1.13 Herbivore Terrestrial Chapman et al. 1993 Mus_musculus -3.21 -1.71 Carnivore Terrestrial Jones et al. 2009 Muscardinus_avellanarius -2.36 -1.51 Herbivore Terrestrial Bright and Morris 1991 154 Mustela_erminea 0.12 -0.57 Carnivore Terrestrial Alterio 1998, Murphy and Dowding 1994, Murphy and Dowding 1995 Mustela_frenata -0.75 -0.82 Carnivore Terrestrial DeVan 1982 Mustela_lutreola -0.68 -0.25 Carnivore Terrestrial Jones et al. 2009 Mustela_nigripes 0.00 -0.04 Carnivore Terrestrial Jones et al. 2009 Mustela_nivalis -0.19 -1.06 Carnivore Terrestrial Norbury et al. 1998 Mustela_putorius_furo -0.05 -0.09 Carnivore Terrestrial Jedrzejewski et al. 1995 Mustela_sibirica 0.61 -0.28 Carnivore Terrestrial Jones et al. 2009 Myocastor_coypus -1.52 0.80 Omnivore Terrestrial Jones et al. 2009 Myodes_californicus -2.80 -1.65 Herbivore Terrestrial Tallmon and Mills 1994 Myodes_gapperi -3.26 -1.70 Omnivore Terrestrial Jones et al. 2009 Myodes_glareolus -2.92 -1.68 Omnivore Terrestrial Jones et al. 2009 Myopus_schisticolor -3.01 -1.52 Herbivore Terrestrial Andreassen and Bondrup Nielsen 1991 Myrmecobius_fasciatus -0.46 -0.29 Carnivore Terrestrial Jones et al. 2009 Myrmecophaga_tridactyla 0.51 1.48 Carnivore Terrestrial Shaw et al. 1987 Nasua_narica 0.24 0.67 Omnivore Terrestrial Gompper 1997, Lanning 1976, Ratnayeke et al. 1994 Nasua_nasua -0.02 0.58 Omnivore Terrestrial Jones et al. 2009 Nectomys_squamipes -2.66 -0.73 Omnivore Terrestrial Jones et al. 2009 Neomys_fodiens -3.77 -1.82 Omnivore Terrestrial Jones et al. 2009 Neophoca_cinervea 2.78 1.95 Carnivore Marine Fowler et al. 2007 Neotoma_cinerea -1.32 -0.40 Herbivore Terrestrial Topping and Millar 1996 Neotoma_fuscipes -2.60 -0.51 Herbivore Terrestrial Cranford 1977, Kelly 1990, Lynch et al. 1994, Sakai and Noon 1997 Neotoma_lepida -3.27 -0.88 Herbivore Terrestrial Thompson 1982 Neotoma_micropus -3.24 -0.59 Herbivore Terrestrial Condit and Ribble 1997 Nesomys_audeberti -2.02 -0.67 Herbivore Terrestrial Ryan et al. 1994 Nesomys_rufus -2.30 -0.78 Herbivore Terrestrial Ryan et al. 1994 Nyctereutes_procyonoides 0.40 0.81 Omnivore Terrestrial Ikeda et al. 1979, Kauhala et al. 1993, Ward and Wurster Hill 1989 155 Ochotona_curzoniae -2.86 -0.81 Herbivore Terrestrial Smith et al. 1986 Ochotona_princeps -2.73 -0.83 Herbivore Terrestrial Kawamichi 1976, Smith and Ivins 1984 Ochrotomys_nuttalli -2.38 -1.64 Omnivore Terrestrial Jones et al. 2009 Dickinson and Garner 1979, Eberhardt et al. 1984, Hayes and Krausman 1993, Kohl et al. 1987, Odocoileus_hemionus 1.54 1.73 Herbivore Terrestrial Kufeld et al. 1989, Leach and Edge 1994, Livesey 1991, Loft et al. 1989, Nicholson et al. 1997, Schoen and Kirchhoff 1985, Stephenson et al. 1996 Beier and McCullough 1990, Holzenbein and Marchinton 1992, Hoskinson and Mech 1976, Ivey and Causey 1981, McShea and Schwede 1993, Mooty et al. 1987, Nelson and Mech 1981, Odocoileus_virginianus 0.40 1.94 Herbivore Terrestrial Sargent and Labisky 1995, Scanlon and Vaughan 1985, Tierson et al. 1985, Vanderhoof and Jacobson 1993, Vercauteren and Hygnstrom 1998, Wiles and Weeks 1986 Okapia_johnstoni 0.77 2.36 Herbivore Terrestrial Hart and Hart 1989 Ondatra_zibethicus -2.47 0.00 Omnivore Terrestrial Jones et al. 2009 Ondatra_zibethicus_ -2.22 0.13 Herbivore Terrestrial Dell et al. 1983 Onychogalea_fraenata -0.37 0.70 Herbivore Terrestrial Evans 1996 Onychomys_torridus -1.59 -1.66 Carnivore Terrestrial Frank and Heske 1992 Orcaella_heinsohni 2.28 2.11 Carnivore Marine Parra, 2006 Orcinus_orca 3.72 3.75 Carnivore Marine Andrews et al., 2008 Oreamnos_americanus 1.37 2.80 Herbivore Terrestrial Rideout 1975 Ornithorhynchus_anatinus -1.16 0.18 Carnivore Terrestrial Gust and Handasyde 1995 Oryctolagus_cuniculus -1.20 0.20 Herbivore Terrestrial Hulbert et al. 1996 Oryzomys_palustris -2.56 -1.27 Omnivore Terrestrial Jones et al. 2009 Otaria_flavescens 3.86 2.37 Carnivore Marine Campagna et al., 2001 Otocyon_megalotis 0.55 0.62 Carnivore Terrestrial Malcolm 1986 Otolemur_crassicaudatus -1.15 0.08 Omnivore Terrestrial Jones et al. 2009 Otolemur_garnettii -0.89 -0.09 Omnivore Terrestrial Jones et al. 2009 Ovis_ammon 0.77 2.06 Herbivore Terrestrial DuBois et al. 1993 Bissonette and Steinkamp 1996, Bristow et al. 1996, Krausman et al. 1989, Leslie and Douglas Ovis_canadensis 1.44 1.96 Herbivore Terrestrial 1979, Payer and Coblentz 1997 Ozotoceros_bezoarticus 0.90 1.54 Herbivore Terrestrial Leeuwenberg et al. 1997 156 Paguma_larvata 0.57 0.48 Omnivore Terrestrial Rabinowitz 1991 Pan_troglodytes 1.10 1.65 Omnivore Terrestrial Jones et al. 2009 Panthera_leo 2.31 2.31 Carnivore Terrestrial Schaller 1972 Panthera_onca 1.92 1.92 Carnivore Terrestrial Crawshaw and Quigley 1991, Rabinowitz and Nottingham 1986 Panthera_pardus 2.70 1.68 Carnivore Terrestrial Bailey 1993, Bothma et al. 1997, Jenny 1996, Norton and Lawson 1985, Stander et al. 1997 Panthera_tigris 1.73 2.05 Carnivore Terrestrial McDougal 1977, Schaller 1967, Sunquist 1981 Paradoxurus_hermaphroditus 0.73 0.54 Omnivore Terrestrial Dhungel and Edge 1985, Rabinowitz 1991 Parascalops_breweri -4.35 -1.29 Omnivore Terrestrial Jones et al. 2009 Paraxerus_cepapi -2.41 -0.65 Omnivore Terrestrial Jones et al. 2009 Paraxerus_palliatus -1.56 -0.43 Herbivore Terrestrial Skinner and van Aarde 1987 Pecari_tajacu 0.40 1.37 Herbivore Terrestrial Bellantoni and Krausman 1993, Ilse and Hellgren 1995, Schweinsburg 1971, Taber et al. 1994 Perameles_bougainville -1.15 -0.64 Omnivore Terrestrial Jones et al. 2009 Perodicticus_potto -0.92 0.03 Omnivore Terrestrial Jones et al. 2009 Perognathus_inornatus -3.75 -1.99 Omnivore Terrestrial Jones et al. 2009 Perognathus_merriami -2.05 -2.16 Omnivore Terrestrial Jones et al. 2009 Perognathus_parvus -2.73 -1.67 Omnivore Terrestrial Jones et al. 2009 Peromyscus_attwateri -2.74 -1.55 Omnivore Terrestrial Jones et al. 2009 Peromyscus_boylii -2.44 -1.55 Omnivore Terrestrial Ribble and Stanley 1998 Peromyscus_californicus -2.92 -1.34 Omnivore Terrestrial Ribble and Salvioni 1990 Peromyscus_crinitus -2.47 -1.79 Omnivore Terrestrial Jones et al. 2009 Peromyscus_gossypinus -2.30 -1.56 Carnivore Terrestrial Jones et al. 2009 Peromyscus_leucopus -1.91 -1.64 Omnivore Terrestrial Mineau and Madison 1977, Ormiston 1985 Peromyscus_maniculatus -2.88 -1.57 Omnivore Terrestrial Mullican 1988 Peromyscus_truei -1.85 -1.60 Omnivore Terrestrial Hall and Morrison 1997, Ribble and Stanley 1998 Petauroides_volans -1.81 0.11 Herbivore Terrestrial Comport et al. 1996 Petaurus_australis -0.34 -0.24 Omnivore Terrestrial Goldingay and Kavanagh 1993 157 Petaurus_breviceps -1.37 -1.14 Omnivore Terrestrial Quin 1995, Quin et al. 1992 Petaurus_norfolcensis -1.42 -0.64 Omnivore Terrestrial Quin 1995 Petrodromus_tetradactylus -1.92 -0.70 Carnivore Terrestrial FitzGibbon 1995 Petrogale_assimilis -0.92 0.67 Herbivore Terrestrial Horsup 1994 Phacochoerus_aethiopicus 0.24 1.91 Herbivore Terrestrial Cumming 1975 Philander_opossum -2.51 -0.37 Omnivore Terrestrial Jones et al. 2009 Phoca_vitulina 2.60 1.50 Carnivore Marine Smith et al., 2006 Phocarctos_hookeri 2.41 2.11 Carnivore Marine Auge et al. 2011 Phocoena_phocoena 4.28 1.74 Carnivore Marine Johnston et al., 2005 Piliocolobus_badius -0.15 0.93 Omnivore Terrestrial Jones et al. 2009 Podomys_floridanus -2.52 -1.51 Omnivore Terrestrial Jones et al. 2009 Pongo_pygmaeus 0.74 1.73 Omnivore Terrestrial Jones et al. 2009 Potorous_longipes -0.43 0.28 Herbivore Terrestrial Green et al. 1998 Potos_flavus -0.55 0.46 Herbivore Terrestrial Julien-LaFerriere 1993, Kays and Gittleman 1995 Priodontes_maximus 0.66 1.61 Carnivore Terrestrial Jones et al. 2009 Prionailurus_bengalensis 0.38 0.40 Carnivore Terrestrial Rabinowitz 1990 Fritzell 1978, Gehrt and Fritzell 1997, Hoffman and Gottschang 1977, Sherfy and Chapman Procyon_lotor 0.52 1.03 Omnivore Terrestrial 1980, Shirer and Fitch 1970, Urban 1970 Proechimys_brevicauda -2.30 -0.55 Omnivore Terrestrial Jones et al. 2009 Proechimys_cuvieri -2.24 -0.46 Herbivore Terrestrial Guillotin 1982 Proechimys_longicaudatus -2.68 -0.69 Omnivore Terrestrial Jones et al. 2009 Proechimys_semispinosus -2.98 -0.37 Herbivore Terrestrial Seamon and Adler 1999 Proechimys_simonsi -2.50 -0.55 Omnivore Terrestrial Jones et al. 2009 Proteles_cristatus 0.58 1.00 Carnivore Terrestrial Skinner and van Aarde 1986 Pseudalopex_culpaeus 0.69 0.87 Carnivore Terrestrial Johnson and Franklin 1994, Salvatori et al. 1999 Pseudalopex_griseus 0.30 0.60 Carnivore Terrestrial Johnson and Franklin 1994 Pseudomys_chapmani -1.13 -2.00 Omnivore Terrestrial Anstee et al. 1997 158 Pseudomys_fuscus -3.20 -0.91 Herbivore Terrestrial Bubela et al. 1991 Pseudomys_higginsi -2.67 -1.20 Omnivore Terrestrial Jones et al. 2009 Pteromys_volans -1.40 -0.84 Omnivore Terrestrial Jones et al. 2009 Pteronura_brasiliensis 2.01 1.41 Carnivore Terrestrial Jones et al. 2009 Pudu_puda -0.70 0.88 Herbivore Terrestrial Eldridge et al. 1987 Belden et al. 1988, Hemker et al. 1984, Logan et al. 1986, Maehr et al. 1991, Pittman et al. Puma_concolor 2.49 1.95 Carnivore Terrestrial 1995, Ross and Jalkotzy 1992, Seidensticker et al. 1973, Spreadbury et al. 1996 Puma_yagouaroundi_ 1.83 0.83 Carnivore Terrestrial Konecny 1989 Pygeretmus_pumilio -2.50 -1.28 Herbivore Terrestrial Rogovin et al. In press Rangifer_tarandus 3.55 2.01 Herbivore Terrestrial Bradshaw et al. 1995, Edmonds 1988, Stuart Smith et al. 1997 Raphicerus_campestris -0.21 1.05 Herbivore Terrestrial du Toit 1990 Rattus_everetti -2.37 -0.60 Omnivore Terrestrial Jones et al. 2009 Rattus_exulans -3.10 -1.30 Omnivore Terrestrial Jones et al. 2009 Rattus_rattus -2.70 -0.85 Omnivore Terrestrial Jones et al. 2009 Rattus_verecundus -2.82 -1.01 Omnivore Terrestrial Jones et al. 2009 Reithrodontomys_fulvescens -2.77 -1.94 Omnivore Terrestrial Jones et al. 2009 Reithrodontomys_montanus -2.61 -1.96 Omnivore Terrestrial Jones et al. 2009 Reithrodontomys_raviventris -2.67 -1.96 Herbivore Terrestrial Bias and Morrison 1999 Rhynchocyon_chrysopygus -1.54 -0.27 Carnivore Terrestrial FitzGibbon 1995, Rathbun 1979 Rupicapra_rupicapra 0.53 1.49 Herbivore Terrestrial Clarke and Henderson 1984 Saguinus_fuscicollis -0.48 -0.40 Omnivore Terrestrial Jones et al. 2009 Saguinus_midas -1.05 -0.27 Omnivore Terrestrial Jones et al. 2009 Saguinus_oedipus -0.77 -0.34 Omnivore Terrestrial Jones et al. 2009 Saimiri_sciureus -0.19 -0.13 Omnivore Terrestrial Jones et al. 2009 Scalopus_aquaticus -2.13 -0.99 Carnivore Terrestrial Harvey 1976 Scapanus_orarius -2.82 -1.21 Omnivore Terrestrial Jones et al. 2009 Sciurus_aberti -0.88 -0.10 Herbivore Terrestrial Farentinos 1979, Hall 1981, Patton 1975, Patton et al. 1985 159 Sciurus_carolinensis -2.31 -0.27 Herbivore Terrestrial Doebel and McGinnes 1974 Sciurus_granatensis -2.00 -0.50 Omnivore Terrestrial Jones et al. 2009 Sciurus_lis -0.77 -0.58 Herbivore Terrestrial Tamura 1998 Sciurus_niger -0.89 -0.02 Herbivore Terrestrial Benson 1980, Kantola and Humphrey 1990, Sheperd and Swihart 1995 Sciurus_vulgaris -1.13 -0.48 Herbivore Terrestrial Wauters et al. 1994, Wiegand 1995 Sigmodon_hispidus -2.55 -0.96 Omnivore Terrestrial Jones et al. 2009 Sminthopsis_leucopus -1.94 -1.64 Carnivore Terrestrial Laidlaw et al. 1996 Sorex_araneus -3.28 -2.04 Omnivore Terrestrial Jones et al. 2009 Sorex_arcticus -2.32 -2.09 Carnivore Terrestrial Jones et al. 2009 Sorex_cinereus -2.30 -2.38 Carnivore Terrestrial Jones et al. 2009 Sorex_coronatus -3.43 -2.03 Carnivore Terrestrial Jones et al. 2009 Sorex_gracillimus -3.56 -2.36 Carnivore Terrestrial Jones et al. 2009 Sorex_minutus -2.85 -2.36 Omnivore Terrestrial Jones et al. 2009 Sorex_monticolus -2.78 -2.16 Omnivore Terrestrial Jones et al. 2009 Sorex_palustris -2.59 -1.88 Omnivore Terrestrial Jones et al. 2009 Sorex_unguiculatus -4.11 -1.85 Carnivore Terrestrial Jones et al. 2009 Sotalia_fluviatilis 1.18 1.74 Carnivore Marine Flores et al., 2004 Sotalia_guianensis 0.90 1.90 Carnivore Marine Oshima et al., 2010 Sousa_chinensis 2.29 2.33 Carnivore Marine Parra, 2006 Spalacopus_cyanus -4.39 -1.00 Herbivore Terrestrial TorresMura 1990 Spermophilus_beecheyi -3.28 -0.14 Herbivore Terrestrial Boellstorff and Owings 1995 Spermophilus_columbianus -3.27 -0.24 Herbivore Terrestrial Festa Bianchet and Boag 1982 Spermophilus_franklinii -0.77 -0.20 Herbivore Terrestrial Choromanski Norris et al. 1989 Spermophilus_parryii -1.52 -0.10 Herbivore Terrestrial Hubbs and Boonstra 1998 Spermophilus_spilosoma -1.82 -0.97 Herbivore Terrestrial Streubel 1975 Spermophilus_tereticaudus -2.00 -0.83 Omnivore Terrestrial Jones et al. 2009 160 Spermophilus_tridecemlineatus -1.81 -0.70 Herbivore Terrestrial Streubel 1975 Spermophilus_variegatus -1.37 -0.13 Herbivore Terrestrial Ortega 1990, Shriner and Stacey 1991 Spilogale_putorius -0.63 -0.23 Omnivore Terrestrial Crooks and Van Vuren 1995 Stylodipus_telum -2.35 -1.22 Herbivore Terrestrial Heske et al. 1995 Suricata_suricatta 1.15 -0.14 Carnivore Terrestrial Jones et al. 2009 Baber and Coblentz 1986, Boitani et al. 1994, Caley 1997, Coblentz and Baber 1987, Ilse and Sus_scrofa 0.90 1.92 Omnivore Terrestrial Hellgren 1995, Massei et al. 1997, Saunders and Kay 1996, Van Vuren and Coblentz 1989, Wood and Brenneman 1980 Sylvilagus_aquaticus -1.74 0.33 Herbivore Terrestrial Kjolhaug and Woolf 1988 Sylvilagus_floridanus -1.54 0.13 Herbivore Terrestrial Allen et al. 1982, Althoff and Storm 1989, Anderson and Pelton 1976, Trent and Rongstad 1974 Sylvilagus_palustris -1.40 0.13 Herbivore Terrestrial Forys and Humphrey 1996 Synaptomys_cooperi -2.34 -1.42 Herbivore Terrestrial Danielson and Swihart 1987 Syncerus_caffer 1.91 2.77 Herbivore Terrestrial Funston et al. 1994, Leuthold 1972, Stark 1986 Tachyglossus_aculeatus -0.35 0.65 Carnivore Terrestrial Abensperg Traun 1991, Augee et al. 1992, Wilkinson et al. 1998 Tachyoryctes_splendens -4.00 -0.59 Herbivore Terrestrial Jarvis 1973 cited in Reichman and Smith 1990 Talpa_europaea -2.52 -1.02 Carnivore Terrestrial Macdonald et al. 1997 Talpa_romana -2.55 -1.09 Carnivore Terrestrial Loy et al. 1994 Tamandua_mexicana -0.60 0.62 Carnivore Terrestrial Jones et al. 2009 Tamandua_tetradactyla 0.48 0.68 Carnivore Terrestrial Jones et al. 2009 Tamias_amoenus -2.09 -1.57 Herbivore Terrestrial Martinsen 1968 Tamias_minimus -1.83 -1.37 Herbivore Terrestrial Bergstrom 1988, Martinsen 1968, Sheppard 1972 Tamias_quadrimaculatus -2.22 -1.08 Omnivore Terrestrial Jones et al. 2009 Tamias_quadrivittatus -1.27 -1.37 Herbivore Terrestrial Bergstrom 1988 Tamias_senex -2.00 -1.05 Omnivore Terrestrial Jones et al. 2009 Tamias_sibiricus -2.71 -1.02 Herbivore Terrestrial Geinitz 1980 Tamias_speciosus -2.00 -1.22 Omnivore Terrestrial Jones et al. 2009 Tamias_townsendii -2.14 -1.10 Omnivore Terrestrial Jones et al. 2009 161 Tamias_umbrinus -1.49 -1.37 Herbivore Terrestrial Bergstrom 1988 Tamiasciurus_douglasii -2.49 -0.65 Omnivore Terrestrial Jones et al. 2009 Tamiasciurus_hudsonicus -2.32 -0.65 Herbivore Terrestrial Benhamou 1996, Boutin and Schweiger 1988 Tarsius_bancanus -1.70 -0.94 Omnivore Terrestrial Jones et al. 2009 Tarsius_tarsier -1.70 -0.77 Omnivore Terrestrial Jones et al. 2009 Tatera_indica -2.76 -0.86 Omnivore Terrestrial Jones et al. 2009 Taxidea_taxus 0.58 0.94 Carnivore Terrestrial Lindzey 1978, Messick and Hornocker 1981, Minta 1990 Tayassu_pecari 1.16 1.31 Herbivore Terrestrial Fragoso 1998 Thomomys_bottae -4.15 -0.80 Herbivore Terrestrial Gettinger 1984, Reichman et al. 1982 Thylamys_elegans -3.15 -1.54 Carnivore Terrestrial Jones et al. 2009 Thylogale_stigmatica -1.45 0.67 Herbivore Terrestrial Vernes et al. 1995 Thylogale_thetis -0.86 0.73 Herbivore Terrestrial Johnson 1980 Tragelaphus_oryx 1.72 2.80 Herbivore Terrestrial Hillman 1988 Tragelaphus_scriptus -1.43 1.74 Herbivore Terrestrial Allsopp 1978 Tragelaphus_strepsiceros 3.03 2.30 Herbivore Terrestrial Allen Rowlandson 1980, duToit 1990 Trichosurus_vulpecula -1.30 0.46 Herbivore Terrestrial Statham and Statham 1997 Tupaia_glis -2.06 -0.88 Omnivore Terrestrial Jones et al. 2009 Tursiops_aduncus 2.00 2.33 Carnivore Marine Hung et al., 2004 Tursiops_truncates 1.71 2.56 Carnivore Marine Gubbins et al. 2002 Uncia_uncia 1.24 1.48 Carnivore Terrestrial Jackson and Ahlborn 1989, Oli 1997, Schaller et al. 1994 Urocyon_cinereoargenteus 0.44 0.66 Omnivore Terrestrial Fuller 1978, Hallberg 1973, Haroldson and Fritzell 1984 Urocyon_littoralis -0.71 0.29 Omnivore Terrestrial Crooks and Van Vuren 1995 Urotrichus_talpoides -2.66 -1.74 Omnivore Terrestrial Jones et al. 2009 Amstrup and Beecham 1976, Garshelis and Pelton 1981, Hellgren and Vaughan 1989, Hellgren and Vaughan 1990, Lindzey and Meslow 1977, Novick and Stewart 1982, Piekielek and Burton Ursus_americanus 1.59 2.18 Omnivore Terrestrial 1975, Warburton and Powell 1985, Young and Ruff 1982, Blanchard and Knight 1991, Huber and Roth 1993, Mace and Waller 1998, Servheen 1983, Wielgus et al. 1994 Ursus_arctos 2.91 2.34 Omnivore Terrestrial Blanchard and Knight 1991, Huber and Roth 1993, Mace and Waller 1998, Servheen 1983, 162 Wielgus et al. 1994 Ursus_maritimus 5.10 2.41 Carnivore Marine Ferguson et al., 1999 Viverra_zibetha 1.08 0.90 Carnivore Terrestrial Rabinowitz 1991 Viverricula_indica 0.49 0.53 Omnivore Terrestrial Rabinowitz 1991 Vombatus_ursinus -0.97 1.41 Herbivore Terrestrial Taylor 1993 Vulpes_lagopus 1.45 0.70 Carnivore Terrestrial Anthony 1997, Eberhardt et al. 1982, Landa et al. 1998, Prestrud 1992 Vulpes_macrotis 0.94 0.65 Carnivore Terrestrial O'Neal et al. 1987, Spiegel and Bradbury 1992, White and Ralls 1993, Zoellick and Smith 1992 Vulpes_rueppelli 1.48 0.51 Carnivore Terrestrial Lindsaey and MacDonald 1986 Vulpes_velox 0.74 0.32 Carnivore Terrestrial Jones et al. 2009 Ables 1969, Adkins and Stott 1998, Blanco 1986, Boitani et al. 1984, Cavallini 1992, Cavallini and Lovari 1994, Coman et al. 1991, Goszczynski 1989, Harrison et al. 1989, Jones and Theberge 1982, Kolb 1986, Lindsaey and MacDonald 1986, Lovari et al. 1994, Major and Vulpes_vulpes 0.69 0.81 Omnivore Terrestrial Sherburne 1987, Meia and Weber 1995, Pandolfi et al. 1997, Phillips and Catling 1991, Poulle et al. 1994, Sargeant et al. 1987, Servin et al. 1991, Travaini et al. 1993b, White et al. 1996, Woollard and Harris 1990 Wallabia_bicolor -0.82 1.18 Herbivore Terrestrial Troy and Coulson 1993 Xerus_erythropus -0.91 -0.30 Herbivore Terrestrial Linnandkey 1996 Xerus_rutilus -1.38 -0.50 Omnivore Terrestrial O'Shea 1976 Zalophus_californianus 3.72 1.93 Carnivore Marine Kuhn et al., 2006 Zapus_hudsonius -2.64 -1.73 Omnivore Terrestrial Jones et al. 2009 Zapus_princeps -2.61 -1.57 Omnivore Terrestrial Jones et al. 2009 Table S2.1 References Abensperg-Traun, M. 1991. 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A comparison of density, home range and habitat utilization of bobcat populations at Lava Beds and Joshua Tree National Monuments,California. Nat. Wild. Fed. Sci. Tech. Ser. 6:74-79. Zoellick, B. W., and N. S. Smith. 1992. Size and spatial organization of home ranges of kit foxes in Arizona. Journal of Mammalogy 73:83-88. Zwank, P. J., B. L. Shiflet, and J. D. Newsom. 1985. Habitat use by bobcats in upland forests of Louisiana. Proc. Ann. Conf. S. E. Assoc. Fish and Wildlife Agencies 39:313- 320. 186 Table S2.2 Summary tracking information for leopard seals, Weddell seals, crabeater seals, southern elephant seals, Sub-Antarctic fur seals and Antarctic fur seals. Species No. Sex No. Location Source Individuals days (min- max) Hydrurga leptonyx 26 M,F 23 – Western (Rogers et al., (Leopard seal) 347 Antarctic 2005) Peninsula & East Antarctica Leptonychotes 4 M,F 25 – 81 Neumayer See Table S4 weddellii Station, (Weddell seal) Ekström Shelf Ice, Atka Bay, Antarctica Lobodon 26 M,F 30 - 95 Neumayer See Table S5 carcinophagus Station, (Crabeater seal) Ekström Shelf Ice, Atka Bay, Antarctica & East Antarctica Mirounga leonina 21 M,F 25 - 412 King George (Bornemann et al., (Southern Island, 2000) elephant seal) Antarctica Arctocephalus 8 F 23 – Marion Island (de Bruyn et al., tropicalis 121 2009) (Sub-Antarctic fur seals) Arctocephalus 87 F 2 – 16 Heard Island (Staniland et al., gazella and Bird 2010) (Antarctic fur Island seals) S2.2.1 Leopard Seals Satellite telemetry data was collected from two locations in Antarctica; one population off the Western Antarctic Peninsula (64°09′S, 60°57′E) and one population in Prydz Bay, eastern Antarctica (69°00’S, 76°00’E). Protocols and ethics for the data from the eastern population (n=10) as per (1). 16 seals from the west population were instrumented (Table S3). The satellite tags and deployment procedure is the same used in Rogers, Hogg and Irvive (2005). However, there were modifications to the anaesthetic protocol from Higgins et al. (2002), see Table S3. This study was conducted under the approval of the University of New South Wales Animal Care and Ethics Committee, ACEC number 08/103B and 11/112A. 187 Table S2.3 Western Antarctic leopard seal ID, sex, length and satellite transmission summary. Date Days Seal ID Sex Tag Anesthetic Protocol Transmitting attached LS0719 M 28/02/2008 328 Zoletil/Atropine LS0801 M 10/02/2009 29 Midazolam/Flumazenil LS1707 M 27/02/2008 84 Zoletil/Atropine LS1607 F 20/02/2008 137 Zoletil/Atropine LS0907 M 18/02/2008 23 Zoletil/Atropine LS0803 F 11/02/2009 258 Midazolam/Isoflurane LS0720 F 12/02/2009 47 Midazolam LS0808 M 03/01/2009 336 Zoletil/Adrenalin LS0812 M 03/01/2009 341 Zoletil/Ketamine LS0814 M 20/02/2009 52 Zoletil/Ketamine LS0715 M 21/02/2009 86 Zoletil/Ketamine LS0816 F 03/01/2009 337 Zoletil/Ketamine LS0817 F 26/02/2009 311 Zoletil LS0818 F 27/02/2009 53 Zoletil/Ketamine LS0819 F 27/02/2009 303 Zoletil/Ketamine LS1012 F 05/02/2011 105 Zoletil/Ketamine/Midazolam S2.3.2 Weddell seals Weddell seal raw telemetry data was obtained from Plötz et al. (2009), and is available via open access through the data library PANGAEA– Publishing Network for Geoscientific and Environmental data (see Table S4). Table S2.4 Weddell seal data sources ID Source Institution* 714633 DOI: AWI 10.1594/PANGAEA.714633 714634 DOI: AWI 10.1594/PANGAEA.714634 714635 DOI: AWI 10.1594/PANGAEA.714635 714636 DOI: AWI 10.1594/PANGAEA.714636 * AWI: Alfred Wegener Institute 188 S2.2.3 Crabeater Seals Crabeater seal raw telemetry data was obtained from two sources; Bornemann & Plötz (2005), data is available via open access through the data library PANGAEA– Publishing Network for Geoscientific and Environmental data Table S4). The second source is from Southwell (2007), data may be accessed from Australian Antarctic Data Centre http://data.aad.gov.au/aadc/argos/profile_list.cfm?taxon_id=25), see Table S5. For the tagging protocol and ethics of Southwell (2007), see Wall et al. (2007). Table S2.5 Crabeater seal data sources. ID Source Institution* 19126 Southwell (2007) AAD 19127 Southwell (2007) AAD 19129 Southwell (2007) AAD 19130 Southwell (2007) AAD 19131 Southwell (2007) AAD 19132 Southwell (2007) AAD 19133 Southwell (2007) AAD 20709 Southwell (2007) AAD 23196 Southwell (2007) AAD 23197 Southwell (2007) AAD 23198 Southwell (2007) AAD 23199 Southwell (2007) AAD 26438 Southwell (2007) AAD 26439 Southwell (2007) AAD 26441 Southwell (2007) AAD 26442 Southwell (2007) AAD 26443 Southwell (2007) AAD 26444 Southwell (2007) AAD 26445 Southwell (2007) AAD 26447 Southwell (2007) AAD 26448 Southwell (2007) AAD 4781 Southwell (2007) AAD 26125 DOI: 10.1594/PANGAEA.261725 AWI 26126 DOI: 10.1594/PANGAEA.261726 AWI 26127 DOI: 10.1594/PANGAEA.261727 AWI 26129 DOI: 10.1594/PANGAEA.261729 AWI *AAD: Australian Antarctica Division; AWI: Alfred Wegener Institute 189 Appendix S2.2 References Bornemann, H. & Plötz, J. (2005) At surface behaviour at location on spot of crabeater seal DRE1998_cra_y_m_15 from Drescher Inlet. doi:10.1594/PANGAEA.264706. Bornemann, H., Kreyscher, M., Ramdohr, S., Martin, T., Carlini, A., Sellmann, L. & Plötz, J. (2000) Southern elephant seal movements and Antarctic sea ice. Antarctic Science, 12, 3-15. de Bruyn, P.J.N., Tosh, C.A., Oosthuizen, W.C., Bester, M.N. & Arnould, J.P.Y. (2009) Bathymetry and frontal system interactions influence seasonal foraging movements of lactating subantarctic fur seals from Marion Island. Marine Ecology Progress Series, 394, 263-276. Higgins, D.P., Rogers, T.L., Irvine, A.D. & Hall-Aspland, S.A. (2002) Use of midazolam/pethidine and tiletamine/zolazepam combinations for the chemical restraint of leopard seals (Hydrurga leptonyx). Marine Mammal Science, 18, 483-499. Plötz, J., McIntyre, T., Bester, M.N. & Bornemann, H. (2009) At surface behaviour at location on spot of Weddell seal NEU2008_wed_u_m_17 from Atka Bay. Alfred Wegener Institute for Polar and Marine Research, Bremerhaven. doi:10.1594/PANGAEA.714638. Rogers, T.L., Hogg, C.J. & Irvine, A. (2005) Spatial movement of adult leopard seals (Hydrurga leptonyx) in Prydz Bay, Eastern Antarctica. Polar Biology, 28, 456- 463. Southwell, C. (2007) 1994 to 2000 - Antarctic Pack Ice Seals APIS) Survey, Australian Antarctic Data Centre - ARGOS satellite tracking record < http://data.aad.gov.au/aadc/argos/profile_list.cfm?taxon_id=25 >. Staniland, I., Gales, N., Warren, N., Robinson, S., Goldsworthy, S. & Casper, R. (2010) Geographical variation in the behaviour of a central place forager: Antarctic fur seals foraging in contrasting environments. Marine Biology, 157, 2383-2396. Wall, S.M., Bradshaw, C.J.A., Southwell, C.J., Gales, N.J. & Hindell, M.A. (2007) Crabeater seal diving behaviour in eastern Antarctica. Marine Ecology Progress Series, 337, 265-277. 190