Assessing Seasonal Changes in Body Condition for Spotted (Phoca Largha), Ringed (Pusa Hispida), and Bearded (Erignathus Barbatus) Seals

Home , Bearded seal, Leopard seal, Neophoca, Phoca, Pinniped, Pusa

The University of San Francisco USF Scholarship: a digital repository @ Gleeson Library | Geschke Center

Master's Theses Theses, Dissertations, Capstones and Projects

Summer 8-7-2020

Assessing seasonal changes in body condition for spotted (Phoca largha), ringed (Pusa hispida), and bearded (Erignathus barbatus) seals

Michelle Hartwick [email protected]

Follow this and additional works at: https://repository.usfca.edu/thes

Part of the Biology Commons

Recommended Citation Hartwick, Michelle, "Assessing seasonal changes in body condition for spotted (Phoca largha), ringed (Pusa hispida), and bearded (Erignathus barbatus) seals" (2020). Master's Theses. 1344. https://repository.usfca.edu/thes/1344

This Thesis is brought to you for free and open access by the Theses, Dissertations, Capstones and Projects at USF Scholarship: a digital repository @ Gleeson Library | Geschke Center. It has been accepted for inclusion in Master's Theses by an authorized administrator of USF Scholarship: a digital repository @ Gleeson Library | Geschke Center. For more information, please contact [email protected]. Assessing seasonal changes in body condition for spotted (Phoca largha), ringed (Pusa hispida), and bearded (Erignathus barbatus) seals

A thesis submitted by

Michelle N. Hartwick

in partial fulfillment of the requirements for the degree of

Master of Science

Biology

Committee in Charge

Approved: 9/18/20 Dr. Nicole Thometz Date

Approved: 9/21/20 Dr. Scott Nunes Date

Approved: 9/16/20 Dr. Colleen Reichmuth Date

Approved: Dr. Marcelo Camperi, Dean Date

College of Arts and Sciences, Department of Biology

University of San Francisco San Francisco, California September 2020

Acknowledgements

This thesis is the culmination of many years of work conducted by many hard-working people. Thank you to my amazing advisor, Dr. Nicole Thometz, for her support during not only grad school, but over the past 5 years on this project. I have always looked up to and valued working with Nicole and I am so thankful to have her as part of my support system. Thank you to my committee, Drs. Scott Nunes, Colleen Reichmuth, and Nicole, for their valuable feedback on this thesis and for their support and guidance throughout grad school. I feel so fortunate to have been able to work with and learn from Colleen over the past 6 years. Thank you for being an incredible role model and showing me how to thoughtfully and carefully conduct research.

To my fellow graduate students in the Thometz Lab, Mariah Tengler and Sophia Lyon – thank you for being there to solve GIS and stats mysteries and for drinking many glasses of wine together when necessary. I am also grateful to our undergraduate volunteers, particularly

Amanda, Lexy, and Esther for their dedication to data analysis and spending many hours staring at pictures of seals.

I am so grateful for the incredible Pinniped Lab and its staff, grad students, volunteers, and animals past and present who shaped me into the woman in science I am today. Particularly,

Jenna Sullivan, Holly Hermann-Sorenson, Brandi Ruscher-Hill, Sonny Knaub, and Skyla

Walcott, who have mentored and supported me over the past 6 years. I feel so fortunate to be surrounded by such a strong group of scientists and friends that became my family. Thank you to

Taylor, Maddie, and Madilyn for being amazing research techs on the project and accomplishing insane amounts of science-ing every day in Santa Cruz and Alaska. I sincerely thank the many hard-working volunteers and grad students that contributed to this project whether it be through animal care or data collection – none of this would be possible without them. To Nayak, Noatak,

Amak, Tunu, Sura, Kunik, Pimniq, Dutch, Sprouts, Ronan, Rio, Siku, Tuliq, Natchek, Odin, and

Selka for being incredible animal mentors who taught me more than I thought any animal could during my years with the Pinniped Lab and beyond.

Thank you to the incredible husbandry and research staff at the Alaska SeaLife Center who work tirelessly rescuing and rehabilitating marine mammals from all over Alaska while conducting important research. This work would not have been possible without the dedication of Jamie Mullens, Shelby Burman, Juliana Kim, and all of the incredible trainers, interns, and staff at ASLC caring for animals and supporting conservation research.

I am grateful to have such a supportive group of friends, especially my best friend Kirby, who spent hours editing pieces of this thesis. Even though she has lived on a variety of far-away islands while I’ve been in grad school, she has always been there to support me and provide cool places to visit. And to Jessie, who has been with me every step of the way since our first day of kindergarten. Thank you for being there through all of the breakdowns and celebrations over the past 20 years.

I am so thankful for my family, who have supported my dreams of becoming a Marine

Biologist from the beginning after deciding against being an Astrophysicist because I probably wouldn’t get the opportunity to explore space like I could the ocean. Thank you for bringing me on business trips that always included a trip to the nearest zoo, aquarium, or planetarium and inspiring my interest in science.

I am extremely grateful to USF for funding my graduate school education and to the

Student Travel Fund and Biology Department for providing funding that allowed me to present my work at domestic and international conferences while in grad school.

iii

Abstract

Anthropogenic global warming is causing unprecedented changes to occur within Arctic ecosystems. As sea ice continues to decline in both thickness and extent, ice-adapted species will be particularly affected. Specifically, Arctic seals are reliant on sea ice during critical life-history stages and many of their preferred prey depend on reliable patterns in annual sea ice cover. Thus, ongoing changes will likely affect the ability of Arctic seals to carry out key life-history tasks and maintain positive energy balance. One way to assess energy reserves is through examination of body condition. For seals, this is often done by measuring overall blubber content, which individuals use as an onboard energy reserve; however, fat stores can be difficult to accurately assess in free-ranging individuals. Therefore, I worked with captive spotted (n=4), ringed (n=3), and bearded (n=1) seals to determine the most accurate methods to quantify blubber content, defined seasonal changes in body condition, and evaluated best-practices for field assessments of wild seals. I found the traditional truncated cones method [Gales & Burton, 1987, Aus. J. Zool.

35, 207-217] was most accurate in estimating energy stores for all three species. Using this method, I documented predictable changes in body condition that appeared to be linked to specific annual events. Finally, I identified simple indices of body condition to increase efficiency and accuracy in field settings. The results presented here improve our understanding of routine seasonal changes in body condition for three species of Arctic seal and should improve health assessments of wild populations.

Table of Contents

Acknowledgements...... ii

Abstract...... iii

List of Tables...... viii

List of Figures...... x

Abbreviations...... xii

I. Chapter 1: Introduction...... 13

i. Climate Change...... 13

ii. Arctic Mammal Adaptations...... 14

iii. Body Condition...... 15

iv. Blubber...... 16

v. Study Species...... 20

vi. Arctic Seals and Climate Change...... 25

II. Chapter 2: Evaluation of truncated cones methods to estimate body composition in Arctic

seals...... 28

i. Introduction...... 28

ii. Methods...... 31

i. Study Animals...... 31

ii. Photogrammetrics...... 32

iii. Direct Morphometric Measurements...... 32

iv. Measurements of Blubber Depth...... 34

v. Truncated Cones Estimation of Body Composition...... 35

vi. Statistical Analyses...... 38

iii. Results...... 38

iv. Discussion...... 40

v. Chapter 2 Tables and Figures...... 43

III. Chapter 3: Tracking seasonal changes in body condition for ringed, bearded, and spotted

seals...... 51

i. Introduction...... 51

ii. Methods...... 52

i. Study Animals...... 53

ii. Environmental Parameters...... 54

iii. Statistical Analyses...... 54

iii. Results...... 56

iv. Discussion...... 57

i. Seasonal Changes...... 58

ii. Drivers of Seasonal Changes...... 60

iii. Comparison to Wild Seal Blubber Data...... 62

iv. Implications...... 64

v. Chapter 3 Tables and Figures...... 66

IV. Chapter 4: Body condition metrics and applications to field research...... 86

ii. Introduction...... 86

i. Field Research in the Arctic...... 86

ii. Subsistence Hunting...... 86

iii. Current Conservation Issues...... 87

iv. Unmanned Aerial Vehicles...... 88

v. Body Condition Metrics...... 89

iii. Methods...... 91

i. Morphometric Measurements...... 91

ii. Body Condition Metrics...... 92

iii. Statistical Analyses...... 93

iv. Results...... 93

i. Spotted seals...... 93

ii. Ringed seals...... 94

iii. Bearded seals...... 95

v. Discussion...... 95

i. Body Condition Metrics...... 96

ii. Future Directions: Body Condition and Unmanned Aerial Vehicles.... 98

iii. Importance...... 99

vi. Chapter 4 Tables and Figures...... 100

V. Chapter 5: General Discussion...... 112

References...... 115

vii

List of Tables

Chapter 2

Table 2.1. Key characteristics of study animals including, species, sex, age, mass, location, and duration of data collection

Table 2.2. Comparison of ultrasound and CT blubber depth measurements

Table 2.3. Example traditional truncated cone calculation

Table 2.4. Example modified truncated cone calculation

Table 2.5. Comparison of percent error using traditional and modified truncated cones methods

Chapter 3

Table 3.1. Mean air and water temperatures and minutes of daylight for each month by location

Table 3.2. Timing of body condition minimums and maximums in relation to molt for each species

Table 3.3. Results of linear mixed effects models for spotted and ringed seals

Table 3.4. Multiple linear regression results for the bearded seal

Table 3.5. Average blubber depth at all ultrasound locations for spotted, ringed, and bearded seal subjects

Table 3.6. Comparative reference table of body condition data from the literature for a variety of Arctic, temperate, and Antarctic phocid species

Chapter 4

Table 4.1. Percentage of curvilinear length each ultrasound site was located

Table 4.2. Spotted seal body condition metric correlation results

viii

Table 4.3. Ringed seal body condition metric correlation results

Table 4.4. Bearded seal body condition metric correlation results

List of Figures

Chapter 2

Figure 2.1. Measurements of standard and curvilinear lengths, and the locations of ultrasound and girth measurements on a ringed seal subject

Figure 2.2. Two example ultrasound images and a CT image visualizing blubber depth

Figure 2.3. Visual depiction of a truncated cone

Chapter 3

Figure 3.1. Average monthly percent blubber mass plotted for spotted seals

Figure 3.2. Average monthly percent blubber mass plotted for ringed seals

Figure 3.3. Average monthly percent blubber mass plotted for the bearded seal

Figure 3.4. Seasonal changes in body condition relative to photoperiod for spotted seals

Figure 3.5. Seasonal changes in body condition relative to photoperiod for ringed seals

Figure 3.6. Seasonal changes in body condition relative to photoperiod for the bearded seal

Figure 3.7. Seasonal changes in body condition relative to ambient air and water temperatures for spotted seals

Figure 3.8. Seasonal changes in body condition relative to ambient air and water temperatures for ringed seals

Figure 3.9. Seasonal changes in body condition relative to ambient air and water temperatures for the bearded seal

Figure 3.10. Comparison of sternal blubber depth for captive and wild seals using data acquired from the Alaska Department of Fish and Game

Chapter 4

Figure 4.1. Spotted seal blubber mass and body condition metric correlation plots

Figure 4.2. Ringed seal blubber mass and body condition metric correlation plots

Figure 4.3. Bearded seal blubber mass and body condition metric correlation plots

Abbreviations

ADFG Alaska Department of Fish and Game

ASLC Alaska SeaLife Center

IPCC Intergovernmental Panel on Climate Change

NOAA National Oceanic and Atmospheric Administration

NSIDC National Snow and Ice Data Center

UAV Unmanned Aerial Vehicle

UCSC University of California, Santa Cruz

UME Unusual Mortality Event

xii

Chapter 1: Introduction

I. Climate Change

Human-induced climate change—driven by rising levels of greenhouse gases as a result of numerous anthropogenic activities—is raising global air and sea temperatures and promoting rapid sea ice melting at the poles (Comiso, 2002; Johannessen et al., 1999; Meier et al., 2014).

Warming temperatures have already forced many species to shift northward or to higher elevations (Fuller et al., 2010; Levinsky et al., 2007; Parmesan, 2006; Parmesan and Yohe,

2003). Furthermore, the cascading consequences of climate change will modify prey distribution and availability for many species, which may then be forced to alter routine behavior to meet and maintain baseline energy requirements (Fuller et al., 2010; Hetem et al., 2014)

While climate change has widespread effects globally, it is rapidly reshaping Arctic and sub-Arctic ecosystems. The Arctic is warming at a rate twice that of the global mean (IPCC,

2013) and sea ice is decreasing at a rate of almost 13% per decade relative to average sea ice melting rates between 1981 and 2010 (NSIDC, 2020). The lowest regional sea ice extent on record occurred in September 2012, with the second lowest extent occurring in September 2019

(NSIDC, 2019). Not only is sea ice extent drastically decreasing in Arctic waters, but summers are becoming longer, causing sea ice to retreat earlier in the spring and form later in the fall

(Rigor and Wallace, 2004; Stroeve and Notz, 2018). Furthermore, ice cover has a high albedo, meaning it effectively reflects light at a planetary scale, influencing heating of Earth’s surface and extent of sea ice cover (Comiso, 2002; Meier et al., 2014). When sea ice melts, the darker water or land underneath is exposed, absorbing more solar radiation and accelerating warning and melting via a positive feedback loop (Comiso, 2002; Meier et al., 2014). Along with rapid

13 shrinking of sea ice cover, Arctic ecosystems are experiencing changes in the distribution and abundance of many species (Christiansen et al., 2014; Hoegh-Guldberg and Bruno, 2010;

Kovacs et al., 2011; Laidre et al., 2008), which will likely have substantial and rippling ecosystem-wide consequences. Given the speed and severity of changes occurring in the Arctic, species with short life-histories and high adaptive potential or high degrees of behavioral and/or physiological plasticity will likely be the most able to cope with a warming climate.

II. Arctic Mammal Adaptations

An animal’s physiology strongly influences the range of environmental conditions it can tolerate. The Arctic experiences extreme seasonal changes and its inhabitants require specific adaptations to ensure the survival and success of populations in cold, harsh conditions during the winter and warm, ice-free conditions during the summer. Arctic mammals such as reindeer

(Rangifer tarandus) are well-insulated against the cold, but must dispel heat during physical activity to prevent overheating (Aas-Hansen et al., 2000). Reindeer utilize selective brain cooling, sending cooled blood from the nasal mucosa to the brain, to bring brain temperature down (Aas-Hansen et al., 2000). They exhibit open- or closed-mouth panting to cool their nasal venous blood, and the type of panting depends on their heat load (Aas-Hansen et al., 2000).

These adaptations allows reindeer to dissipate heat when needed for thermoregulation during active periods.

Arctic species must also manage long periods of daylight in the summer and darkness in the winter, and associated periods of food scarcity (Blix, 2016; Williams et al., 2015). Many species hibernate during periods of reduced prey availability so that they may conserve energy

(Lyman and Chatfield, 1955; Tøien et al., 2011; Young, 1976). Polar bears (Ursus maritimus) behaviorally adapt to periods of food scarcity by increasing their fat stores to prepare for fasting

(Young, 1976). Pregnant females in Hudson Bay, Canada increase their body fat to up to 40% in preparation for spending two to three months in their dens, where they give birth to their cubs

(Atkinson and Ramsay, 1995). While denning, they do not forage and instead, use their fat reserves for energy. Females lose 43% of their body mass between summer and spring, 93% of which is drawn from fat stores (Atkinson et al., 1996). Males do not undergo a denning period, but must accumulate energy reserves to prepare for fasting when food sources are limited during the open-water season (Atkinson et al., 1996). These adaptations allow polar bears to conserve energy when conditions are not optimal.

Arctic animals exhibit both physiological and behavioral adaptations for polar living; however, the rate at which climate change is altering their environment may be too fast for many long-lived species to successfully adapt. One way to assess the impact of climate change on the health of wild, long-lived populations is through the evaluation of body condition. By tracking overall body condition of individuals within a population as a metric of health, scientists can better assess how well species and populations may adjust to changing conditions.

III. Body Condition

Body condition is defined as an individual’s energy reserves and is representative of both foraging success and reproductive potential (Lockyer, 1986; Ryg et al., 1990a; Schulte-Hostedde et al., 2001; Young, 1976). Therefore, body condition metrics can be used as an indication of overall fitness (Atkinson and Ramsay, 1995; Lockyer, 1986; Schulte-Hostedde et al., 2001;

Young, 1976). Individuals in good body condition likely consume adequate amounts of prey, allowing them to allocate energy towards growth, energy storage, and/or reproduction, while individuals in poor body condition lack sufficient energy reserves (Hammill et al., 2008;

McLaren, 1993; Schulte-Hostedde et al., 2001; Schulte-Hostedde et al., 2005). For example,

15 good body condition is particularly important during energetically taxing life-history stages, such as reproduction. Females in good body condition at parturition generally show increased reproductive success (Atkinson and Ramsay, 1995; Boyd, 1984; Harwood et al., 2000). In mammals, lactating females tend to experience decreases in body condition as they provide for their offspring (Costa et al., 1986; Fedak et al., 1996; Mellish et al., 1999a). Mothers that are capable of providing ample amounts of energy to their offspring by the time of weaning will increasing their offspring’s chances of survival (Costa et al., 1986; Fedak et al., 1996; Mellish et al., 1999b; Schulte-Hostedde et al., 2001). In contrast, poor body condition at the individual level may indicate malnutrition or illness and can lead to reproductive failure and/or death. Further, poor body condition amongst a large number of individuals within a population can inform our understanding of overall population health (Burek et al., 2008; Harwood et al., 2000; Laidre et al., 2008; Laidre et al., 2015; Young, 1976).

In mammals, body condition is often determined by evaluating fat reserves (Pond, 1978;

Young, 1976), which serve as the primary source of energy storage in mammals (Schulte-

Hostedde et al., 2001). Large energy reserves allow individuals to tolerate periods of reduced energy intake, without depleting reserves to lethal levels (Atkinson and Ramsay, 1995). In marine mammals, with the exception of polar bears and sea otters (Enhydra lutris), specialized fat tissue termed ‘blubber’ is the main onboard energy store and it is often used as a metric of body condition (Lockyer 1986, Read 1990).

IV. Blubber

Blubber is a vascularized layer of subcutaneous adipose tissue that is reinforced with structural collagen fibers (Liwanag et al., 2012; Strandberg et al., 2008) and comprises anywhere from 15% to 55% of the total body mass of marine mammals (McLellan et al., 2002; Noren et

16 al., 2015; Ryg et al., 1993). Blubber is primarily composed of adipocytes, which fill and empty with lipids in response to rates of energy intake and metabolic requirements (Ashwell-Erickson et al., 1986; Strandberg et al., 2008; Worthy et al., 1992). It is predominately comprised of unsaturated fatty acids, but varies in its stratification (Iverson and Koopman, 2018; Strandberg et al., 2008).

The outermost blubber layer, composed primarily of monounsaturated fatty acids, provides structural support to the tissue and is more stable over time (Aguilar and Borrell, 1990;

Samuel and Worthy, 2004), while the inner blubber layer comprised of polyunsaturated fatty acids and saturated fatty acids is where the majority of active lipid accumulation and mobilization occurs (Koopman et al., 2002; Samuel and Worthy, 2004). Although the general structural pattern is similar across marine mammal species, blubber thickness can vary significantly; for example, from 2 cm in Australian sea lions to up to 50 cm in bowhead whales

(Ryg et al., 1993). Furthermore, blubber thickness and composition changes with age, nutritional status, health, and reproductive state of individual animals (Beck et al., 2003; Pond, 1978;

Samuel and Worthy, 2004; Schwarz et al., 2015).

Marine mammals utilize this dynamic layer for a variety of critical functions including thermoregulation (Ryg et al., 1990a; Ryg et al., 1990b; Scholander et al., 1950a), streamlining, buoyancy, and energy storage (Beck and Smith, 1995; Webb et al., 1998). Blubber plays a foundational role in thermoregulation, as it is the primary insulator to limit heat loss in the marine environment (Pond, 1978; Scholander et al., 1950b). Blubber allows seals to be hydrodynamic in the water column by reducing drag, increasing streamlining, and reducing the energetic cost of locomotion (Beck and Smith, 1995; Koopman et al., 2002; Liwanag et al.,

2012; Williams and Koopman, 1985). The proportion of blubber to lean tissue determines an

17 animal’s net buoyancy and in turn, influences costs associated with diving and foraging (Beck et al., 2000; Webb et al., 1998). Further, blubber provides a source of lipids for critical energy storage from which they can draw upon during times of nutritional stress (Koopman, 1998;

Koopman et al., 2002; Pond, 1978; Young, 1976).

In phocids (“true seals”), blubber serves as the primary energy store during energetically taxing life-history periods, and blubber mass often varies extensively throughout the year (Beck et al., 2003; Mellish et al., 2007; Shero et al., 2014). Adequate blubber reserves are critical for seals, particularly those that undergo annual periods of extended fasting or reduced foraging such as during breeding periods (Beck et al., 2003; Boness and Bowen, 1996; Fedak and Anderson,

1982). True capital breeding phocids have relatively short, intense lactation periods spanning from as little as three to five days, in the hooded seal (Cystophora cristata) (Bowen et al., 1985), to up to 6 weeks in Mediterranean monk seals (Monachus monachus) (Kenyon, 1981). During lactation, females fast and rely solely on blubber reserves to produce high-fat milk for their pups and sustain their own bodily functions. Income breeders, on the other hand, forage during lactation, expending energy searching for prey while still nursing a pup (Boness and Bowen,

1996; Boyd, 2000; McDonald et al., 2012). Females with inadequate blubber reserves at parturition are unlikely to successfully rear and wean a pup (Costa et al., 1986; Crocker et al.,

2001; Hall and McConnell, 2007). Moreover, inadequate blubber reserves and decreased body condition increase mortality risk for females after lactation (Fedak and Anderson, 1982; Mellish et al., 1999a). Energy reserves are also important for male seals during their breeding season, specifically those that fast while defending territories or competing for female breeding access

(Andersen et al., 1999; Beck et al., 2003; Field et al., 2007; Le Boeuf, 1972). Fasting seals may lose a substantial portion of their body mass – up to half of their total starting mass – by the

18 conclusion of the breeding season, making them more physiologically vulnerable during these periods (Champagne et al., 2012).

Blubber also plays a critical role in meeting energy demands during the annual molt

(Ashwell-Erickson et al., 1986; Boyd et al., 1993; Ling, 1970; Schop et al., 2017). While molting, seals shed all of their hair and several layers of epidermis while growing a new coat

(Ling, 1970). This typically occurs once a year and spans a period of approximately one month; however, total duration varies by species (Ashwell-Erickson et al., 1986; Ling, 1970; Schop et al., 2017). Several studies on seals have found elevated resting metabolic rates during the molt

(Boily, 1996; Chabot and Stenson, 2002; Hedd et al., 1997; Renouf and Gales, 1994), reflecting the energetic cost of tissue regeneration. During this physiologically taxing time, seals remain hauled out for extended periods to maintain high skin temperatures and send blood to the periphery to promote shedding and regrowth of pelage (Ashwell-Erickson et al., 1986; Duyke et al., 2020; Smith and Stirling, 1975).

Many seals fast or reduce foraging effort substantially while molting (Ling, 1970;

Liwanag et al., 2012). Consequently, they rely on blubber reserves to meet metabolic demands

(Ashwell-Erickson et al., 1986; Boily, 1996; Gales and Renouf, 1994a). For many species, the molt occurs immediately following the reproductive period during which adult seals of both sexes expend substantial amounts of energy either rearing a pup or competing for breeding access (Boness and Bowen, 1996; Fedak and Anderson, 1982; Fedak et al., 1996; Ling, 1970).

Therefore, adult seals enter the molt with depleted energy stores following a physiologically intense breeding season. Thus, the period following molt is often associated with minimum annual body condition (Beck et al., 2003; Mellish et al., 2007; Slip et al., 1992).

Ultimately, tracking seasonal changes in blubber reserves can greatly inform understanding of the energetic consequences of specific life-history events as well as help identify populations who may already be experiencing reduced body condition due to ongoing environmental change. This is particularly important for Arctic seal species that rely on blubber stores for critical functions throughout the year.

V. Study Species

There are six species of Arctic phocids: ringed (Pusa hispida), spotted (Phoca largha), bearded (Erignathus barbatus), hooded, harp (Pagophilus groenlandicus), and ribbon

(Histriophoca fasciata) seals. Due to the cryptic nature of these species and challenges associated with working in the Arctic, population estimates are poor for most Arctic seals

(Quakenbush et al., 2011a; Quakenbush et al., 2011b). Arctic seal population estimates range from hundreds of thousands to millions of individuals depending on the species and for which such estimates are available (Laidre et al., 2015; McLaren, 1958a; Quakenbush et al., 2011a;

Quakenbush et al., 2011b).

Arctic seals are important components of their ecosystems and are critical resources for subsistence hunters. They are both predators of fish and invertebrates and prey of apex predators such as polar bears and killer whales (Cameron et al., 2010; Kelly et al., 2010). Although polar bears prey on several Arctic pinnipeds, ringed seals are their primary prey (Stirling and McEwan,

1975). As Arctic seals play important roles within their ecosystems (Fay 1974, Bowen 1997), decreases in their numbers would affect both lower and upper trophic level species (Moore,

2008). Around the Arctic Circle, these seals also provide crucial resources for the livelihood of native people, who legally hunt seals to feed their communities in remote northern locations (Ice

Seal Committee, 2016; Nelson et al., 2019).

The National Oceanic and Atmospheric Administration (NOAA) declared an Unusual

Morality Event (UME) for Alaskan ice seals beginning in 2018 and continuing through at least

August 2020. NOAA declares a UME when a population is experiencing at least one of seven criteria, including increased stranding and death rates and signs of disease (NOAA, 2018).

Previously, from 2011 to 2016, Alaskan ice seals experienced a UME in which seals were found with skin lesions and had abnormal molts; but a definitive cause was not determined (NOAA,

2016). Observations during the current UME indicate an increasing number of spotted, ringed, and bearded seals in poor body condition in the Bering and Chukchi Seas in Alaska (NOAA,

2019), highlighting the need for more detailed information pertaining to routine seasonal patterns in body condition for these species.

For this study, I focus on three threatened seal species included in the current UME: spotted, ringed, and bearded seals. These three species are listed as threatened under the

Endangered Species Act1 due to imminent habitat loss as a result of climate warming by 2100; the southern population of spotted seals is listed as threatened under this order and does not include the Bering Sea population. Although Arctic seals possess some similar physiological and behavioral traits, their life histories and physiology vary within and between species. Thus, directed examination of the attributes of each species is critical for effective conservation and management efforts.

Spotted seals

Spotted seals are moderately sized, ice-associated phocids who move with the margins of seasonal sea ice (Burns, 1970; Lowry et al., 2000). Their range spans the Bering, Chukchi, and

Beaufort Seas, Sea of Japan, Yellow Sea, and Sea of Okhotsk (Lowry et al., 2000; Naito and

1 Ringed: 77 FR 76706-76738, 2012; Spotted: 74 FR 53683, 2009; Bearded: 77 FR 76740-76768, 2012 21

Nishiwaki, 1972; Shaughnessy and Fay, 1977). Spotted seals in the Bering Sea and Sea of

Okhostk are typically 1.6-1.7 m in length and weigh 65-115 kg; however, size varies by location

(Burns, 2002; Heptner et al., 1976). They typically reach full size at sexual maturity at four to five years old for both sexes, but this range varies from three to six years old (Burns, 1970;

Burns, 2002; Naito and Nishiwaki, 1972; Tikhomirov, 1964).

Spotted seals utilize sea ice during the breeding and molting seasons between March and

July. They breed, give birth, and raise pups on ice floes in March and April (Burns, 1970; Burns,

2002). Pups are born on sea ice weighing 7-12 kg and 75-92 cm long and rarely enter the water until weaning (Burns, 2002; Heptner et al., 1976; Tikhomirov, 1964). At weaning, they weigh up to 30 kg, almost tripling in size during the 2-4 week lactation period (Boveng et al., 2009a; Naito and Nishiwaki, 1972). The annual molt takes place two to three months after the breeding season, usually in the summer months, but molt timing varies by age class (Burns, 2002). Age, location, and reproductive status determine the timing of molt, where subadults molt first, about one month before adults, followed by newborns and adults (Burns, 2002). Adult seals molt over a period of two to two and a half months from late April to July (Boveng et al., 2009a;

Tikhomirov, 1964).

Ringed seals

Ringed seals are the smallest pinniped species ranging from 1.3-1.5 m in length and typically weighing 23-70 kg as adults (Duyke et al., 2020; Smith and Stirling, 1975), although they may weigh up to 110 kg (Stewart et al., 2002). Ringed seals are ice-dependent, often associated with land-fast ice and seldom seen on shore (Fedoseev 1975; Smith and Lydersen

1991). They exhibit a circumpolar distribution and there are five recognized subspecies (P.h. hispida, P.h. ochotensis, P.h. botnica, P.h. ladogensis, and P.h. saimensis) in the Arctic (Kelly et

22 al., 2010). Sexual maturity occurs between five to seven years for males and four to eight years for females (McLaren, 1958a), at which time they reach their maximum body length.

Ringed seals depend on subnivean lairs carved in the snow for resting, whelping, nursing, and protection from predators including polar bears, killer whales, and Arctic foxes (Burns,

1970; McLaren, 1958a; Smith and Hammill, 1981; Smith and Stirling, 1975). They require adequate snow cover to dig their caves, which encompass a single hole in the sea ice for entry to and from the water (Smith and Stirling, 1975). Females give birth once per year in spring

(March-May) to pups weighing 4.5-5.0 kg at birth, which increase to four times their size during the four to six week lactation period (Hammill et al., 1991; Lydersen et al., 1992; McLaren,

1958a). Molting occurs following the pupping season between May and July in adults, with peak molting occurring in June (McLaren, 1958a; Smith and Hammill, 1981) but varying somewhat by latituide (Kelly et al., 2010).

While ringed seals are thought to number in the millions (Kelly et al., 2010), the status of ringed seals varies among subspecies. Two subspecies (P.h. ladogensis, and P.h. saimensis) are currently listed as endangered under the Endangered Species Act2. Arctic ringed seals (P.h. hispida) were first declared threatened due to imminent habitat loss in 2012, delisted following multiple lawsuits in March 2016, and relisted in 2018. In March 2019, the State of Alaska, North

Slope Borough, Arctic Slope Regional Corporation, and Iñupiat Community of the Arctic Slope petitioned to delist the Arctic population of ringed seals from the Endangered Species Act due to their apparently large population and the limitations the label poses for subsistence communities and oil exploration (Center for Biological Diversity, 2019); the current status of this petition is

2 P.h. saimensis: 58 FR 26920, P.h. ladogensis: 77 FR 76706 23 unclear, but the 90-day finding period has passed (ADFG, March 2019). In the meantime, they retain threatened status in the United States.

Bearded seals

Bearded seals are the largest Arctic phocid, growing to 2.1-2.4 m in length and weighing

250-360 kg as adults (Burns and Frost, 1979; McLaren, 1958b). Bearded seals reach sexual maturity between five to six years old for females and six to seven years old for males (Andersen et al., 1999; Burns and Frost, 1979; McLaren, 1958a). They are an ice-dependent species with circumpolar distribution, and there are two recognized subspecies (E.b. barbatus and E.b. nauticus) (Burns and Frost, 1979). Bearded seals are generally found in coastal areas and shallow waters less than 200 m (Gjertz et al., 2000). Their movements closely follow the seasonal movements of pack ice, which they rely on for reproduction and molting (Burns and Frost, 1979;

Gjertz et al., 2000).

Bearded seals are thought to breed in spring from March through May, but this varies geographically (McLaren, 1958b). Females give birth to one pup per year on pack ice, and attend their pups for 18 to 24 days (Cameron et al., 2010; McLaren, 1958b). Pups are born weighing 33 kg, with 10% body fat, and grow to 110 kg by the time they are weaned (Burns and Frost, 1979;

Kovacs and Lavigne, 1986). Pups begin swimming shortly after birth and forage with their mothers during the lactation period (Burns and Frost, 1979; Lydersen and Kovacs, 1999).

Despite their large size, bearded seal pups are composed of 25% lipids and are so proportionally are the leanest of all weaned Arctic seal pups (Kovacs et al., 1996; Lydersen and Kovacs, 1999;

Ryg et al., 1990b). Females lose about 4.5 kg per day during lactation, but experience a lower proportional loss of total mass compared to other ice-dependent seals that may not feed at all during lactation (Andersen et al., 1999; Lydersen and Kovacs, 1999).

Following the breeding period, bearded seals undergo their annual molt. Based on irregular observations, the molt appears to occur between April and August with peak molting occurring mid-June, but accounts of timing vary geographically (Burns and Frost, 1979;

Cameron et al., 2010). During this period, bearded seals haul out more frequently than during the rest of the year (Burns and Frost, 1979; Kovacs, 2017). The bearded seal molt remains undefined, but is thought to occur over a period of several months, longer than that of other phocids (Cameron et al., 2010). Bearded seals apparently have a slow-shedding molt and may shed hair throughout the year (Burns and Frost, 1979; Kovacs, 2017).

VI. Arctic Seals and Climate Change

Ice-dependent Arctic seals such as spotted, ringed, and bearded seals rely on sea ice as a platform for rest, predator avoidance, and to carry out important life-history processes (Kovacs et al., 2011; Laidre et al., 2008). Particularly, sea ice is a critical substrate during annual breeding and molting periods when seals spend a considerable amount of time hauled out on sea ice

(Laidre et al., 2008). Continued increases in global temperatures in the coming decades will further amplify dramatic seasonal reductions in sea ice cover (Meier et al., 2014), restricting the availability of haul out substrate during these critical periods. Reduced haul out substrate may force seals to increase time spent in water during the annual molt; this in turn could reduce the likelihood of a successful molt and/or increase the overall cost of molting if body heat is lost to the environment at greater rates (DeJours, 1989).

Many prey species rely on the conditions that sea ice creates below the surface

(Grebmeier et al., 2006). Further, primary production is heavily influenced by seasonal advances and retreats of sea ice (Arrigo et al., 2008; Rigor and Wallace, 2004). Reduced sea ice area provides less substrate for phytoplankton growth on the underside of the ice to fuel ocean

25 productivity that supports marine mammals and their prey sources (Arrigo et al., 2008;

Chambellant et al., 2013; Christiansen et al., 2014; Yurkowski et al., 2016). Bearded seals, along with other marine mammals such as walrus (Odobenus rasmarus) and gray whales (Eschrichtius robustus), forage on benthic organisms that feed on phytoplankton (Bowen, 1997; Cameron et al., 2010). Changes in prey distribution and abundance resulting from alterations in sea ice persistence and extent may force seals to increase foraging effort and/or change routine behavior, ultimately affecting energy reserves and overall body condition (Ochoa-Acuña et al., 2009).

Subdermal blubber stores fluctuate throughout the year, so knowledge about routine fluctuations in body condition of seals will support recognition of abnormal changes in body condition attributable to climate change. The current UME for spotted, ringed, and bearded seals appears to be characterized by poor body condition (NOAA, 2020) and highlights the urgent need for a better understanding of the physiology of these species.

In the following chapters, I examine longitudinal patterns in body condition in spotted, ringed, and bearded seals, as well as examine methods used for defining and tracking body condition in these species. In Chapter 2, I assess the accuracy of two commonly used methods for quantifying blubber mass—as an indicator of body condition—for each species. In Chapter 3,

I track seasonal changes in blubber mass for captive seals over a two-year period and identify potential drivers of observed fluctuations. Lastly, in Chapter 4, I utilize morphometric data from the previous two chapters to determine the best simple metrics of overall body condition for each species that can be quickly and effectively used in the field with wild seals. Together, this information should inform future conservation and management decisions by describing routine changes in body condition for each species as well as providing data-driven guidance to

26 researchers studying wild Arctic seal populations. Ultimately, improving understanding of routine seasonal changes in body condition for these species will increase our ability to identify abnormal changes and track the consequences of climate change in real time.

Chapter 2: Evaluation of truncated cones methods to estimate body composition in Arctic seals

Introduction

Because marine mammals spend most of their lives under water, there are few opportunities to measure blubber mass and assess overall body condition in free-ranging individuals. Often, body condition measurements require invasive procedures or extensive sampling. There are several methods for measuring blubber mass and overall body composition in seals, including hydrogen isotope dilution, bioelectric impedance analysis, collecting direct measurements on live and deceased animals, and truncated cone calculations using morphometric measurements. Method comparisons both within and across seal species have shown that these approaches vary in their accuracy and efficacy, but are used interchangeably in a range of species (Bowen et al., 1999; Gales and Renouf, 1994a; Hall and McConnell, 2007;

Schwarz et al., 2015; Shero et al., 2014; Slip et al., 1992; Webb et al., 1998; Worthy et al., 1992).

Hydrogen isotope dilution is commonly used to measure lipid content in seals (Bowen et al., 1998; Mellish et al., 1999a; Reilly and Fedak, 1990). Isotope dilutions utilize tritium and/or deuterium to measure the total body water of a seal, which can then be used to determine proportions of body lipid and protein (Bowen et al., 1998; Mellish et al., 1999a). Previously defined values for this relationship are drawn from direct measurements of carcasses (Ortiz et al.,

1978) and tissue hydration state to determine total lipid mass. This method can overestimate total body water and therefore lipid and protein content, providing a higher lipid mass value than estimated by other methods (Arnould et al., 1996; Reilly and Fedak, 1990). While hydrogen isotope dilution is fairly accurate, it is an invasive method requiring sedation and/or restraint over a several hour long period of detainment or multiple procedures to acquire samples.

Bioelectric impedance analysis uses electrical currents passed through a subject to estimate fat content (Bowen et al., 1998; Gales and Renouf, 1994b). To use this method with seals, individuals are typically anesthetized and placed on a non-conductive mat. Needle electrodes are inserted into the muscle at anterior and posterior regions between the ears and just anterior to the hind flippers, respectively (Gales and Renouf, 1994b), while a current is sent between the two pairs of electrodes to measure total body water (Bowen et al., 1998). Bioelectric impedance analysis is less accurate than hydrogen isotope dilution, with a percent error from measured mass of up to 25% when compared to isotope dilution in seals (Bowen and Iverson,

1998; Bowen et al., 1999).

Blubber mass can be directly measured from deceased seals to determine blubber content

(Ryg et al., 1990b; Ryg et al., 1990a; Ryg et al., 1993). The seal’s entire skin and blubber layer, referred to as sculp, is dissected from the core mass and weighed (Ryg et al., 1988; Ryg et al.,

1990a). While sculp weights can be compared to other methods, this is problematic as body fluids are lost during the dissection of sculp mass, affecting the accuracy of body mass estimates derived from this approach. Further, unlike hydrogen isotope dilution and bioelectric impedance analyses, sculp weights do not include internal lipid deposits and thus underestimate total lipid stores (Schwarz et al., 2015).

The truncated cones method uses morphometric measurements and geometry to model seals as a series of partial truncated cones to determine body size and composition. This method was first introduced by Gales and Burton (1987) to calculate blubber mass in southern elephant seals (Mirounga leonina) and has been used to study body condition in a number of pinnipeds

(Bell et al., 1997; Crocker et al., 2001; Gales and Burton, 1987; McDonald et al., 2008; Noren et al., 2015; Rosen and Renouf, 1997; Schwarz et al., 2015; Shero et al., 2014; Slip et al., 1992;

Webb et al., 1998; Worthy et al., 1992) and cetaceans (Adamczak et al., 2019; Christiansen et al.,

2019; Noren and Wells, 2009). Truncated cone methods are most often used to estimate lean and blubber mass in marine mammals, but are also utilized to estimate body surface area and volume as a means of investigating thermoregulation and buoyancy (Ryg et al., 1988; Webb et al., 1998).

The traditional method models animals as a series of concentric circular truncated cones, where the inner cone represents lean mass and the outer cone represents blubber mass (Gales and

Burton, 1987). The method was later modified by Slip et al. (1992) to model the cross-section of a seal as an ellipse, accounting for fat ‘slump’ created by the force of gravity when a seal is hauled out on land (Schwarz et al., 2015; Shero et al., 2014; Slip et al., 1992). The traditional truncated cone method utilizes curvilinear lengths, girths, and ultrasound measurements of blubber depth to calculate lean mass and blubber mass; the modified method uses body height and width, curvilinear body length, and blubber depth measurements to create elliptical cones.

The accuracy of both truncated cones methods can be assessed by weighing animals and comparing total measured body mass to calculated total body mass (Gales and Burton, 1987;

Shero et al., 2014).

Truncated cone methods have been utilized with Weddell seals (Shero et al., 2014), southern elephant seals (Bell et al., 1997; Field et al., 2007; Gales and Burton, 1987; Slip et al.,

1992), northern elephant seals (Crocker et al., 2001; Schwarz et al., 2015; Webb et al., 1998;

Worthy et al., 1992), crabeater seals (McDonald et al., 2008), harbor seals (Rosen and Renouf,

1997), harp seals (Gales and Renouf, 1994a), and walrus (Noren et al., 2015). Both variants of the method allow for blubber mass to be measured non-invasively and inexpensively across species that vary in body size and shape; however, many studies report different results when comparing the accuracy of the traditional and modified truncated cones methods within species.

Thus, although both approaches are used to evaluate body condition, it appears that the efficacy of each method should be assessed on a species-by-species basis to ensure accuracy of results.

Here, I longitudinally assess body composition of captive spotted, ringed, and bearded seals over a 13-month period using both truncated and circular cones referenced to body weight to determine the accuracy and efficacy of each method by species.

Methods

I. Study Animals

Longitudinal morphometric measurements were collected for 13 months from December

2017 – December 2018 on captive spotted (n=4), ringed (n=3), and bearded (n=1) seals trained using operant conditioning techniques to cooperatively participate in research activities. Study animals were housed at Long Marine Laboratory at the University of California, Santa Cruz

(UCSC) in Santa Cruz, CA, and at the Alaska SeaLife Center (ASLC) in Seward, AK (Table

2.1). The seals were born in the wild in Alaska, but housed in human care following stranding and rehabilitation or collection from the wild. Study animals represent differences in sex, ontogeny, and location (Table 2.1).

Seals were fed herring and capelin diets year-round, which were managed according to each individual’s weekly body mass and daily appetite and motivation. Motivation was scored daily on a scale of 1-5, where one indicated no interest in food or participation, and five indicated intense behavior and hunger. Feeding to optimal motivation (maintaining scores of 3 to

3.5) allowed seals to experience natural fluctuations in body condition experienced by wild individuals whose foraging effort and success vary seasonally.

All research was conducted under National Oceanic and Atmospheric Administration and

National Marine Fisheries Service (NMFS) Permit 18902 with oversight from the Institutional

Animal Care and Use Committees at the University of California, Santa Cruz and the Alaska

SeaLife Center.

II. Photogrammetrics

Scaled photographs of each animal were taken weekly to track changes in body morphology (Fig. 2.1). For each image, a 0.5 m or 1 m long scale bar was held above each animal and aligned with the spine. The scale bar provided a known reference distance to allow for accurate body proportion measurements (standard length, curvilinear length, and vertical body heights) using the software program ImageJ (Version 1.52a). Standard length extended from the nose to the tip of the tail, straight across the length of the seal. Curvilinear length spanned from the nose to the tip of the tail along the curvature of the seal. Vertical body heights were determined at six pre-defined locations (Fig. 2.1) along the length of the body: the neck, located in the cervical area of the animal’s spine, anterior to the front flipper; axilla, located directly behind the flipper pit with the flipper tucked to the side; middle, located at the end of the ribs; umbilicus, directly in line with the animal’s umbilicus; pelvis, located at the anterior region of the pelvis; and ankle, located posterior from the hip and anterior to the back flippers.

III. Direct Morphometric Measurements

Direct morphometric measurements of length and girth were collected by a research technician weekly using a standard measuring tape with seals trained to relax in sternal recumbency. Girth measurements were collected at the same six locations along the length of the

32 animal as identified for photogrammetrics methods (Fig. 2.1). Standard and curvilinear lengths were measured in the same manner as defined for photogrammetrics; however, for direct measurements we recorded curvilinear length at each of the corresponding girth locations in addition to the full curvilinear length measure (Fig. 2.1). At UCSC, large animal veterinary calipers were used to measure height and width for the adult female ringed seal and bearded seal at each position along the primary axis of the animal. Direct morphometric and ultrasound measurements were taken consistently by an experienced technician at each location (UCSC and

ASLC).

Direct measurements were compared to photogrammetric measurements to assess accuracy. In addition, when direct width measurements were not collected, I solved for body width using data obtained from photogrammetric analyses. Specifically, I measured body height using ImageJ and used the circumference of an ellipse equation (equation 1) to solve for width

(equation 2):

퐶 ≈ 휋(3(푟푚푎푗표푟 + 푟푚푖푛표푟) − √(푟푚푎푗표푟 + 3푟푚푖푛표푟)(푟푚푖푛표푟 + 3푟푚푎푗표푟)) (1)

−4휋푟 ± √(−20휋2푟 2 + 12휋푟 퐶 + 3퐶2) + 3퐶 푟 = 푚푖푛표푟 푚푖푛표푟 푚푖푛표푟 (2) 푚푎푗표푟 6휋

where rmajor is the radius of the width (cm), rminor is the radius of the height (cm), and C is girth

(cm) at the corresponding location. Total width was calculated by multiplying rmajor by 2.

IV. Measurements of Blubber Depth

Blubber depth was measured weekly with a hand-held portable ultrasound machine

(Sonosite Vet180; SonoSite Inc., Bothell, Washington, USA). Following the methods outlined by

Mellish et al. (2004) and with the consultation of a veterinary ultrasound expert (Martin Haulena,

Vancouver Aquarium, pers. comm.), we measured blubber depth from the top of the skin to the bottom of the blubber layer (Fig. 2.2) (Mellish et al., 2004). I will refer to the skin and blubber layer combined as blubber depth for the duration of this thesis. Blubber depth was systematically measured along the length of each animal at 13 locations. These locations correspond to the six axial height and girth locations, both dorsally, and laterally, and above the xiphoid process on the ventral side of the seal, referred to as the sternal point (Fig. 2.1). Dorsal and lateral points were measured while seals were in sternal recumbency. Ultrasound images (Fig. 2.2A,B) contain white and dark bands that indicate the boundary between the blubber layer and underlying muscle. In ultrasound images containing one dark band between two white bands, blubber depth was measured to the bottom of the first white band, at the base of the blubber layer (Fig. 2.2A).

When only one white band was present, blubber depth was measured to the base of that band

(Fig 2.2B). Original technichians trained any new technicians and cross-checked data to maintain measurement consistency between individuals for ultrasound and direct morphometric measurements.

To assess the accuracy of ultrasound measurements, a subset of ultrasound measures from one male ringed seal were compared to available CT scan data from the same animal collected opportunistically during a routine veterinary exam. Because the CT data allowed for three-dimensional imaging of the entire blubber layer, these data can be considered ‘actual’ blubber depth and, when volumetric analyses are performed, mass. During the scan, metal

34 markers were placed along the length of the seal’s body to indicate neck, axilla, and middle ultrasound locations in CT images. CT images were viewed using 3D Slicer (version 4.10.1)

(Fedorov et al., 2012) and cross-sectional images were analyzed in ImageJ to determine blubber depth from CT images at dorsal and lateral locations. Blubber depth was measured from the top of the skin to the interface between the visible blubber layer and the core (Fig. 2.2C). CT scan measurements were compared to ultrasound measurements of blubber depth performed by a trained ultrasound technician during the same week as the CT procedure.

V. Truncated Cone Estimations of Body Composition

I used two variations of the truncated cones method to calculate and track longitudinal changes in blubber mass for each study animal. Truncated cone methods use blubber depth and morphometric measurements (i.e. standard and curvilinear lengths, girth, height, and width) to model a seal as a series of concentric truncated cones (Fig. 2.3A). The head and flippers are excluded from measurements as there is little blubber in those areas (Gales and Burton, 1987;

Shero et al., 2014).

Traditional Truncated Cones Method

Weekly morphometric measurements of standard and curvilinear length, girth and blubber depth were averaged monthly and used to calculate a series of circular truncated cones for each individual (Table 2.3). I calculated the radius of the outer and inner cones using the following equations: 𝑔 푅 = (3) 표 2휋

푅푖 = 푅표 − 푏푎푣 (4)

35 where Ro is the outer radius (cm), g is girth (cm), Ri is the inner radius (cm), and bav is average blubber depth (cm). Once the inner and outer radii were determined, the radius difference was calculated by subtracting Ri from Ro. To calculate the distance between the two ends of the cones, straight length was calculated as:

2 2 푠푙 = √퐶퐿 − (푅표 − 푅푖 ) (5) where sl is straight length (cm) and CL is curvilinear length (cm). Using these calculations, I calculated the volume (L) of outer and inner cones using the following equation:

1 푉 = 휋[(푅 2 + ((푅 )(푅 )) + 푅 2)(푠푙)] (6) 3 1 1 2 2 using the appropriate R1 and R2 for the inner or outer cone.

Modified Truncated Cones Method

Weekly morphometric measurements of standard and curvilinear length, blubber depth, height and width were averaged monthly and used to calculate a series of elliptical truncated cones (Table 2.4). The radii for height and width are referred to as the major and minor radius respectively. I calculated the minor radius (cm) of the outer cone with the following equation:

ℎ 푟 (표푢푡푒푟) = 푚푖푛표푟 2 (7) where h is height. The radius difference and straight length (equation 5) were calculated in the same manner as in the traditional method. Measured height and width were used as the diameters for the outer cone. The diameters of the inner cone (the major and minor axes) were calculated by:

ℎ 퐷 = − (2푏) (8) 푤

36 where D is diameter (cm), h is height, w is width, and b is dorsal or lateral blubber depth. The volume (L) of the outer cone was calculated using the following equation:

푠푙 ∗ 휋 푉 = × (ℎ 푤 + ℎ 푤 + √ℎ 푤 ℎ 푤 ) ∗ 0.001 (9) 12 1 1 2 2 1 1 2 2 where sl is straight length (cm), h1 and w1 were the height and width of the anterior end of the cone (cm), and h2 and w2 were the height and width of the posterior end of the cone (cm). The volume (L) of the inner cone was calculated using the following equation:

푠푙 ∗ 휋 푉 = × (퐷 퐷 + 퐷 퐷 + √퐷 퐷 퐷 퐷 ) ∗ 0.001 (10) 12 1 2 3 4 1 2 3 4 where sl is straight length (cm), D1 and D2 were the major and minor diameters of the anterior end of the cone (cm), and D3 and D4 were the major and minor diameters of the posterior end of the cone (cm), calculated using equation 8.

For both methods, blubber volume was calculated by subtracting the volume of the inner cone from the volume of the outer cone. Core mass (kg) was determined by multiplying the inner cone volume by an assumed lean density of 1.1 g/mL, and blubber mass (kg) was determined by multiplying the blubber volume by an assumed lipid density of 0.94 g/mL (Gales and Burton,

1987; Worthy et al., 1992). Total mass was estimated by summing core and blubber mass calculations and compared to empirically measured total body mass using platform scales (Rice

Lake, Rice Lake, WI, USA; Tree Scales, LW Measurements LLC, Rohnert Park, CA, USA;

Prime USA Scales, San Diego, CA, USA).

VI. Statistical Analyses

To determine the most accurate traditional or modified method for each species, I compared 13 months of data to each seal’s actual weight to determine percent error from measured mass. The method that produced the lowest percent error for each species was used to calculate blubber mass for the remainder of the study (see Chapters 3 & 4).

In addition, paired t-tests were used to compare average calculated and measured masses for each method to determine if calculated mass was significantly different from measured mass using the traditional or modified truncated cones method when calculating mass (Shero et al.,

2014). All data were screened for outliers and checked for normality and homogeneity of variance prior to analysis. Paired t-tests were performed in JMP Pro 15 (SAS Institute Inc.).

Results

Blubber depth measurements obtained from CT images were consistently thicker than measurements obtained from ultrasonography for all 6 sites (Table 2.2). Percent differences

[(max-min/(max+min/2))*100] between ultrasound and CT blubber depths ranged from 2-20%.

Raw and percentage differences at each site are presented in Table 2.2.

Both traditional and modified truncated cones methods successfully calculated body composition for all three species. Example calculations of body composition using traditional and modified methods for the bearded seal for one month are displayed in Tables 2.3 (traditional) and 2.4 (modified).

Evaluations of error terms strongly favored the traditional truncated cones method over the modified truncated cones method. For all three species, masses estimated from the traditional truncated cones method yielded smaller mean percent error from measured mass than those

38 obtained using the modified method. Negative values indicate underestimation of measured mass while positive values indicate overestimation. Mean percent error for masses calculated with the traditional truncated cones method were smaller than those calculated with the modified method

(Table 2.5). For spotted seals, the smallest percent error from measured mass (the one closest to

0) was 0.01%, but the range from maximum underestimation to maximum overestimation was -

3.2 to +18% (mean 6.0%). For ringed seals, the smallest percent error from measured mass was

0.1% and the range from maximum underestimation to maximum overestimation was -9.3 to

+16% (mean 1.3%). The smallest bearded seal percent error was 0.4% and the range from maximum underestimation to maximum overestimation was -2.3 to +11.3% (mean 3.7%) (Table

2.5).

When using the modified truncated cones method, the spotted seals’ smallest percent error from measured mass was 0.3%, but the range from maximum underestimation to maximum overestimation was -27.3 to +11.6% (mean -7.8%). For the ringed seals, the smallest percent error from measured mass was 0.1%, but the range from maximum underestimation to maximum overestimation was -20.6 to +2.7% (mean -10.9%). For the bearded seal, the smallest percent error from measured mass was 2.7%, but the range from maximum underestimation to maximum overestimation was -13.1 to -2.7% (mean -10.3%) (Table 2.5).

Paired t-tests revealed significant differences between calculated and measured masses for all three species. For spotted seals, measured mass differed from calculated mass using both the traditional (t= 6.776, P <0.0001) and modified truncated cones methods (t= -9.428,

P<0.0001). Mass calculated using the traditional method consistently overestimated mass, while the modified method consistently underestimated mass. For ringed seals, mass calculated using the traditional method was not different from total measured mass (t= 0.684, P= 0.498). When

39 using the modified truncated cones method, measured mass was different from calculated mass

(t= -10.59, P<0.0001). Mass calculated using the traditional method was similar to measured mass, but mass calculated using the modified method underestimated measured mass. For the bearded seal, measured mass and calculated mass were different for both the traditional (t=

2.205, P= 0.048) and modified methods (t= -12.160, P<0.0001). Mass calculated using the traditional method slightly overestimated measured mass, while mass calculated using the modified method significantly underestimated mass.

Discussion

Here, I successfully determined the accuracy and efficacy of the traditional and modified truncated cones methods for spotted, ringed, and bearded seals. I found that the traditional method most accurately estimated blubber mass when compared to total measured mass for all study species. In addition, the traditional method requires fewer morphometric measurements, and is therefore the easier method for calculating body composition. The traditional method consistently underestimated mass for all species. The slight compression of the blubber layer during measurements obtained with a handheld ultrasound probe, as demonstrated by thinner blubber depths when comparing ultrasound and CT blubber depth measurements, could contribute to underestimations of total blubber mass using this method. One important factor to consider is that while truncated cones methods can be used to estimate subcutaneous blubber mass, they cannot account for internal fat deposits (McDonald et al., 2008; Schwarz et al., 2015;

Shero et al., 2014). This method can be used to determine body mass of seals irrespective of subject posture (e.g. when resting on its dorsal, ventral, or lateral sides) on the haul out substrate, as this method assumes a circular perimeter with equal diameters on both sides. While calculated

40 mass from the traditional truncated cones method is an underestimation of blubber mass, the percent error in this study was smaller than the modified percent error for all species.

Other studies have found various degrees of agreement between these methods for different phocid species. In Weddell seals, the traditional truncated cones method produced a mean error of 26.9  1.5% from measured mass, while the modified method produced a mean of only -2.8  1.7% error from measured mass (Shero et al., 2014). Using the traditional method,

Crocker et al. (2001) and Webb et al. (1998) found an average error of 4% and 3.05  2.75% for northern elephant seals respectively, while McDonald et al. (2008) found an average error of

0.9% for crabeater seals (Crocker et al., 2001; McDonald et al., 2008; Webb et al., 1998). The traditional truncated cones method is more commonly used among phocid species in the literature and produces fairly accurate estimations of blubber mass (Bell et al., 1997; Crocker et al., 2001; Gales and Burton, 1987; Gales and Renouf, 1994a; McDonald et al., 2008; Pirotta et al., 2019; Rosen and Renouf, 1997; Thordarson et al., 2007; Webb et al., 1998; Worthy et al.,

1992). My results agree with these studies.

Body size and morphology can vary greatly within and between clade Pinnipedia (seals, sea lions, walrus). Specifically, across phocids body size varies greatly from 23-70 kg ringed seals (Duyke et al., 2020; Smith and Hammill, 1981) to 4,000 kg southern elephant seals (Ling and Bryden, 1981). Ringed seals are the smallest pinniped and have a thick, rigid blubber layer with little fat slump. I found that ringed seals had the smallest mean percent error out of the three species. Further, spotted, ringed, and bearded seals are overall smaller and have a narrower width than the large species mentioned above, for which the modified method has been shown to be most accurate in some cases (Schwarz et al., 2015; Shero et al., 2014; Slip et al., 1992).

The truncated cones method is a minimally invasive way to determine blubber and lean mass content of free-ranging and captive seals. Both truncated cones methods have primarily been utilized with larger phocid species: elephant (Gales and Burton, 1987; Slip et al., 1992),

Weddell (Shero et al., 2014), and crabeater (McDonald et al., 2008) seals. I was able to successfully assess the use of these methods in Arctic seals of various body sizes, from the smallest phocid seal (i.e. ringed seal) to the largest Arctic seal (i.e. bearded seal). Ultimately, I found that all three ice seal species I evaluated, regardless of body size, appeared to be more circular than elliptical in cross-section, as demonstrated by the accuracy of the traditional truncated cones method for each species.

This information is relevant for researchers in the field who want to measure total blubber mass without overly invasive or expensive measures in living individuals. The ability to have one uniform truncated cones method for spotted, ringed, and bearded seals simplifies field efforts and allows for more direct comparisons between species. This process can be used by researchers working with wild seals during various field procedures (e.g. satellite tagging); however, there may not always be enough time to collect a full suite of measurements on every seal when overall body condition assessments are not the primary goal. In the following chapters

I use longitudinal measurements of blubber mass proportions calculated with the traditional truncated cones method to assess seasonal changes in body condition for captive spotted, ringed, and bearded seal individuals (Chapter 3). Then, using these fine-scale measurements of blubber mass, I assess the best metrics for rapid assessment of body condition in the field (Chapter 4).

Chapter 2 Tables and Figures

Table 2.1. Species, sex, age, mass, location, and duration of data collection for individual study animals in captive care. Age and mass are presented as ranges (min-max) across the sampling period. Mass ranges represent monthly averages of weekly measurements. Individual Species Sex Age (yrs) Mass (kg) Location Amak Phoca largha M 7 – 9 49.8 – 86.0 ASLC Tunu Phoca largha M 7 – 9 61.3 – 85.4 ASLC Kunik Phoca largha M 2 – 4 42.6 – 72.0 ASLC Sura Phoca largha F 3 – 5 40.9 – 72.3 ASLC Pimniq Pusa hispida M 3 – 5 25.6 – 36.8 ASLC Dutch Pusa hispida F 1 – 3 19.4 – 30.2 ASLC Nayak Pusa hispida F 6 – 8 27.7 – 33.3 UCSC Erignathus Noatak M 2 – 4 113.7 – 144.4 UCSC barbatus

Table 2.2. Comparison of blubber depth measurements determined via portable ultrasound and CT image analysis for one male ringed seal (Pimniq) over a two-day period (ultrasound images taken on 1 Feb 2018; CT images taken on 2 Feb 2018). Variations between measurements are presented as both absolute (cm) and percent differences. D indicates dorsal points and L indicates lateral points for neck (1), axilla (2), and middle (3) locations (see Fig. 2.1). Blubber depth Blubber depth Raw difference Location % difference CT image (cm) Ultrasound (cm) (cm) D1 2.9 2.6 -0.3 11 D2 2.5 2.3 -0.2 7 D3 3.4 2.8 -0.6 20 L1 3.1 2.7 -0.5 16 L2 4.3 4.2 -0.1 2 L3 3.9 3.7 -0.3 7

Table 2.3. An example traditional truncated cone calculation for bearded seal Noatak in Dec 2017 where girth, total curvilinear length, and dorsal/lateral blubber depth were measured directly. Body volume was converted to mass using tissue density values (gmL-1) from Gales and Burton 1987 and Worthy et al. 1992. Equations are displayed below. Outer Cone Inner Cone Body Volume Mass Total Dorsal Lateral Average 1Outer Radius Curvilinear Curvilinear 2Straight Blubber Blubber Blubber Inner 3Outer 3Inner Total Girth Radius Difference Length Length Length Depth Depth Depth Radius Cone Cone Blubber Core Blubber Mass (cm) (cm) (cm) (cm) (cm) (cm) (cm) (cm) (cm) (cm) (L) (L) (L) (kg) (kg) (kg) Nose 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Neck 74.2 11.8 11.8 32.8 32.8 30.6 3.81 4.05 3.93 7.9 4.5 2.0 2.5 2.2 2.3 4.5 Axilla 114.3 18.2 6.4 60.0 27.3 26.5 3.11 4.57 3.84 14.4 19.0 10.6 8.4 11.6 7.9 19.6 Mid 123.8 19.7 1.5 94.8 34.8 34.7 3.66 3.18 3.42 16.2 39.2 25.7 13.6 28.2 12.7 41.0 Umbi 112.6 17.8 2.0 116.3 21.5 21.4 3.49 3.25 3.37 14.4 23.6 15.9 7.8 17.4 7.3 25.8 Pelvis 89.2 14.2 3.6 136.3 20.0 19.7 3.12 3.44 3.28 10.9 15.8 10 5.9 11.0 5.5 16.5 Ankle 72.8 11.6 2.6 147.4 11.1 10.8 3.13 3.5 3.31 8.3 5.7 3.1 2.5 3.5 2.4 5.8 Total: 73.9 38.2 112.1 65.9% 34.1% Measured mass 113.7 (kg): Percent error: -1.5

1 Outer radius: Ro=girth/2π 2 2 2 Straight length: sl=√(CL -(Ro-Ri )) 3 2 2 Volume: V=1/3π[(R1 +((R1)(R2))+R2 )(sl)]*0.001

Table 2.4. An example modified truncated cone calculation for bearded seal Noatak in Dec 2017 where, total curvilinear length, and dorsal/lateral blubber depth were measured directly and width and height were measured via photometric methods. Body volume was converted to mass using tissue density values (gmL-1) from Gales and Burton 1987 and Worthy et al. 1992. Equations are displayed below. Outer Cone Inner Cone Body Volume Mass Minor Total Dorsal Lateral Minor Major Body Body 1Minor Radius Curvilinear Curvilinear 2Straight Blubber Blubber Axis Axis 3Outer 4Inner Total Girth Height Width Radius Difference Length Length Length Depth Depth Diameter Diameter Cone Cone Blubber Core Blubber Mass (cm) (cm) (cm) (cm) (cm) (cm) (cm) (cm) (cm) (cm) (cm) (cm) (L) (L) (L) (kg) (kg) (kg) Nose 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Neck 74.2 19.1 26.2 9.6 9.6 32.8 32.8 31.3 3.81 4.05 11.5 18.1 4.1 1.7 2.4 1.9 2.3 4.5 Axilla 114.3 31.2 39.0 15.6 6.1 60.0 27.3 26.6 3.11 4.57 25.0 29.9 17.4 9.4 8.0 10.3 7.5 19.6 Mid 123.8 32.4 43.0 16.2 0.6 94.8 34.8 34.7 3.66 3.18 25.1 37.0 35.7 22.8 12.9 25.1 12.2 41.0 Umbi 112.6 27.5 40.3 13.8 2.5 116.3 21.5 21.4 3.49 3.25 20.5 33.8 21.0 13.6 7.5 14.9 7.0 25.8 Pelvis 89.2 23.1 31.4 11.6 2.2 136.3 20.0 19.9 3.12 3.44 16.9 24.5 14.2 8.5 5.7 9.4 5.3 16.5 Ankle 72.8 16.8 27.1 8.4 3.2 147.4 11.1 10.7 3.13 3.5 3.5 20.1 4.9 2.6 2.3 2.8 2.2 5.8 Total: 64.4 36.5 100.8 63.8% 36.2% Measured mass 113.7 (kg): Percent error: -11.4

1 Minor radius (outer): r=h/2 2 2 2 Straight length: sl=√(CL -(Ro-Ri )) 3 Outer Cone Volume: V=(sl* π/12)[h1w1+h2w2+√( h1w1h2w2)]*0.001 4 Inner Cone Volume: V=(sl*π/12)[D1D2+D3D4+√(D1D2D3D4)]*0.001

Table 2.5. A comparison of traditional and modified truncated cones methods for spotted, ringed, and bearded seals. Grand means of percent error were taken for each species using 13 months of data (Dec 2017 – Dec 2018) for each method, and are shown with standard devation values. Ranges are presented in parentheses below with a comma separating the lower and upper ranges. Positive error indicates an overestimation, while negative error indicates an underestimation of total body mass. Traditional Method Modified Method Species n Mean Error (%) Mean Error (%) 6.0  2.0 -7.8  2.6 Spotted seals 4 (-3.2, +18.0) (-27.3, +11.6) 1.3  4.2 -10.9  3.5 Ringed seals 3 (-9.3, +16.0) (-20.6, +2.7) 3.7  3.3 -10.3  2.6 Bearded seals 1 (-2.3, +11.3) (-13.1, -2.7)

6 5 4 3 2 1

Fig. 2.1. Measurements of standard length (SL), curvilinear length (CL), and the locations of ultrasound sites (represented by white circles), girth, and height measurements (represented by black lines) where 1 = neck, 2 = axilla, 3 = middle, 4 = umbilicus, 5 = pelvis, and 6 = ankle. The scale bar above the seal is 0.5m in length.

A B C

Fig. 2.2. Ultrasound images and a CT image taken on one ringed seal, one day apart. (A) An ultrasound image containing two bands separating blubber and muscle layers, (B) an ultrasound image containing a single band separating blubber and muscle layers, (C) and a cross-sectional image from a CT scan viewed in 3D Slicer. The red lines on ultrasound images (A,B) indicate blubber depth measurements; the radiopaque marker on the dorsal surface of the seal in (C) cross references the standard morphometric site that bubber depth measurements are taken at. Blubber depth in the CT image was directly measured from the lower boundary of the skin to the base of the blubber layer (shaded here in dark grey).

A B C blubber

r1 rminor

r1 rmajor

Fig. 2.3. (A) A visual depiction of a truncated cone, where the shaded area is the inner core and the white outer portion is blubber. (B) A circular cross section of the traditional truncated cone method where r is the radius for both body height and width. (C) An elliptical cross section of the modified truncated cone method.

Chapter 3: Tracking seasonal changes in body condition for spotted, ringed, and bearded seals

Introduction

Body condition in terrestrial and marine mammals fluctuates seasonally in response to physiological and environmental changes. Further, many species undergo routine periods of fattening and depletion of fat stores concomitantly with seasonal life-history events. Mammals undergo seasonal patterns such as hibernation in female polar bears (Atkinson and Ramsay,

1995) and migration between feeding and breeding grounds in humpback (Megaptera novaeangliae) and fin (Balaenoptera physalus) whales (Aguilar and Borrell, 1990; Christiansen et al., 2016). Appropriate matching of natural fluctuations in body condition to food availability is particularly important to an individual’s fitness and survival. However, many species are experiencing dramatic changes in environmental conditions that affect the phenology of annual cycles. These changes may result in the misalignment of optimal environmental conditions and physiological events that are likely established over evolutionary time. The timing of annual physiological events is of great importance to ice seals, and this may lead to insufficient energy stores with which to draw upon during energetically taxing life stages or during periods of food scarcity.

Photoperiod is a strong indicator of time of year for animals and influences their migratory patterns, physiological cycles, and dormancy periods (Bradshaw and Holzapfel, 2007).

Daylight hours are consistent between years, making photoperiod a reliable cue (Bradshaw and

Holzapfel, 2007; Williams et al., 2015). Photoperiod influences physiological patterns and informs animals about seasonality, prompting changes in behavior and utilization of energy

51 reserves. Animals innately prepare for taxing life-history periods by building up crucial energy stores at appropriate times (Bradshaw and Holzapfel, 2008; Gili et al., 2000).

Energetically challenging arctic seal life-history events have evolved to occur during specific times of year when environmental conditions, including sea ice thickness and extent, are optimal. As outlined in Chapter 1, Arctic seals undergo annual energetically taxing periods during events such as lactation and molt during which they must utilize their blubber reserves to maintain their own bodily functions while nursing a pup or growing a new coat (Boyd et al.,

1993; Kovacs and Lavigne, 1986; Ling, 1970). Molting typically occurs in the late spring or summer, during periods of longer daylight hours and warmer air temperatures but when ice haul out platforms are still available prior to the open water season. For the majority of Arctic seals, maximum sea ice extent in March coincides with reproductive and/or molting seasons (Ashwell-

Erickson et al., 1986; Boveng et al., 2009b; Burns and Frost, 1979; Young and Feguson, 2013), when seals spend an increased amount of time hauled out on ice (Ling, 1970). Whelping, lactation, mating, and molting occur at roughly the same time each year by species, and may be influenced by regional differences in environmental conditions corresponding to latitude.

Here, I evaluate seasonal changes in proportion of blubber mass for ringed, bearded, and spotted seals using the traditional truncated cones method (see Chapter 2). I utilize longitudinal data spanning two years for captive individuals to evaluate changes in blubber mass by species and age class. In addition, I assess the environmental and physiological parameters that drive these changes in body condition for each species. These comprensive body condition data collected with trained individuals provide the opportunity to capture fine-scale changes in body condition that are presently impossible to document in free ranging seals.

Methods

I assessed longitudinal changes in blubber mass in four spotted seals, three ringed seals, and one bearded seal over a two year period from December 2017 – December 2019. I used the traditional truncated cones method (Gales and Burton, 1987) to determine total blubber mass, as outlined in Chapter 2. I then used these longitudinal and fine-scale measurements of blubber content the association between seasonal changes in body condition and specific environmental parameters (air and water temperature, photoperiod) and age to identify which of these variables might influence body condition.

I. Study Animals

Study animals were individuals maintained in long-term captive care at UCSC and

ASLC, representative of multiple species, age classes, and sexes. Spotted seal subjects included two adults, both males, and two subadults, one male and one female. Ringed seals included one adult female, one male who reached sexual maturity in 2019, and one subadult female. The bearded seal was a subadult male. Subadults were classified as ages up to four years old and adults as five years or older for all species (McLaren, 1958a; Quakenbush et al., 2009;

Quakenbush et al., 2011b). Molt status was determined according to the visible molt, beginning when first loose hair was observed on haul-out spaces or on the seal and ending when seals were no longer shedding and had a completely new coat. Seals were considered actively molting in any month that active hair loss and regrowth was observed. As in the previous chapter, the food intake of each seal was allowed to vary weekly in a naturalistic manner.

II. Environmental Parameters

Seals were housed in ambient air and water temperatures and natural lighting conditions at both facilities. Animals were maintained in natural seawater, which was filtered and pumped directly into pools from Monterey Bay, California and Resurrection Bay, Alaska for UCSC and

ASLC, respectively. TidbiT v2 temperature loggers (Onset Computer Corporation, Bourne, MA,

USA) were used to measure fine-scale air and water temperatures of seal habitats at each facility

(Table 3.1). Temperature was logged once per hour and averaged daily for hours between 00:01-

23:59. Daily averages were pooled monthly to obtain a grand mean temperature for the month.

Photoperiod (total daylight hours from sunrise to sunset) for each location was calculated from the Sun or Moon Rise/Set Table for One Year generated by the Astronomical Applications

Department of the U.S. Naval Observatory. Monthly average temperatures and day lengths were used in statistical analyses.

III. Statistical analyses

To determine the physiological and environmental drivers of seasonal changes in blubber mass, I used linear mixed effects models for spotted and ringed seals and a multiple linear regression for the bearded seal (Kastelein et al., 2019; Ladds et al., 2017; Mellish et al., 2007;

Noren et al., 2008). The dependent variable of interest was percent blubber mass. Given that this variable was a proportion, percent blubber mass was arcsine transformed prior to analysis for mixed effects models and logit transformed prior to analysis for the multiple linear regression.

Fixed effects included air and water temperatures, photoperiod, age, and molt status. Spotted and ringed seal mixed effects models were run separately, and individual was included as a random effect to account for repeated measures.

As photoperiod has been shown to be highly correlated with molt status in phocid seals

(Ashwell-Erickson et al., 1986; Gili et al., 2000; Ling, 1970), I dropped molt from consideration in all models and only evaluated the effect of photoperiod on changes in blubber mass.

For spotted seal variables, I considered air and water temperatures, photoperiod, and age.

I used age class (subadult or adult) rather than age as a continuous variable due to a bimodal distribution of age when defined as a continuous variable. Air and water temperatures were highly correlated, as were air temperature and photoperiod. The final effects considered in the model were water temperature, age class, and photoperiod.

For ringed seal variables, I considered air and water temperatures, photoperiod, and age.

Air and water temperatures were highly correlated, as were water temperature and age. The final effects considered in the mixed effects model were air temperature, age as a continuous variable, and photoperiod.

For the bearded seal multiple linear regression, I considered air and water temperatures, age, and photoperiod. Air and water temperatures were significantly correlated, with water temperature being less correlated with photoperiod than air temperature. The final variables included in model selection were age as a continuous variable, water temperature, and photoperiod.

All environmental variables were checked for normality, homogeneity of variance, and collinearity prior to analyses. I used backward model selection and lowest Akaike information criteria (AIC) values to determine the best model for each species. Following analyses, residuals were plotted and assessed for normality and homoscedasticity. All statistical analyses were performed in JMP Pro 15 (SAS Institute Inc.). Average values are presented as mean  standard deviation.

Results

Enviornmental parameters varied through the year at both locations (Table 3.1). Body condition data for seals both within individuals and between species. Ringed seals had the highest annual average percent blubber mass at 42.0  3.4% (subadults: 43.5  2.6%; adults: 40.5

 3.4%), followed by spotted seals at an average 33.0  4.6% blubber mass (subadults: 34.7 

3.6%; adults: 31.2  4.8%) and the bearded seal at an average 33.0  1.3% blubber mass (Table

3.2).

Body condition clearly varied by season in spotted and ringed seals. Blubber mass for the spotted seals ranged from a monhly minimum of 28.6  0.7% to a maximum of 39.5  0.3% for subadults, and from 31.2  4.8% to 37.2  1.4% for adults (Table 3.2). Minimum blubber mass occurred in May and June and maximum blubber mass occurred from November to January, with exact timing dependent on individual (Table 3.2, Fig. 3.1). Overall, spotted seals displayed an average difference of 39.0  12.0% between their annual minimum and maximum percent blubber mass values (Fig. 3.1). Specifically, adults showed an average 45.8  15.4% difference between minimum and maximum percent blubber mass, while subadults showed a 35.5  4.9% difference (Table 3.2).

For the ringed seals, blubber mass ranged from a minimum of 43.5  2.6% to a maximum of 46.8  1.2% blubber mass for subadults and a minimum of 45.5  3.4% to a maximum of 45.3

 0.7% blubber mass for adults (Table 3.2). In general, minimum blubber mass occurred between

April and June, depending on the location and individual (Table 3.2, Fig. 3.2). Overall, ringed seals exhibited a difference of 21.8  7.4% between average annual minimum and maximum percent blubber mass. Subadults showed an average 16.6  6.3% difference between minimum

56 and maximum percent blubber mass, while adults incurred a 21.3  10.9% difference (Table

3.2).

The bearded seal exhibited more subtle changes in body condition annually. Bearded seal blubber mass ranged from mean minimums of 31.8% in June 2018 and 30.3% in November

2019, to a mean maximum of 34.5  0.2% blubber mass in August of both years (Table 3.2, Fig.

3.3). The bearded seal exhibited an average 10.8  2.8% difference between his annual mean minimum and maximum percent blubber masses (Table 3.2).

Age class and photoperiod (Table 3.3, Fig. 3.4) had the strongest effect on seasonal patterns of body condition in spotted seals (age class: p= 0.04; photoperiod: p<0.0001; AIC= -

364.656). Similarly, for ringed seals, age and photoperiod (Table 3.3, Fig. 3.5) were found to be potential drivers of changes in body condition (age: p= 0.04; photoperiod: p<0.0001; AIC= -

263.71). For the bearded seal, age was the only significant variable included in the analysis (age: p=0.002; water temp: p= 0.052; AIC= -74.0184), but the inclusion of water temperature improved the AIC value and was thus included in the best-fitting model (Table 3.4, Fig 3.6).

Relationships between blubber content and air and water temperatures for each species are presented in Figs. 3.7-3.9.

Discussion

I was able to document annual changes in blubber mass for ringed, bearded, and spotted seals over two years. Spotted and ringed seals exhibited consistent seasonal changes in percent blubber mass, while relatively minimal changes were observed for the bearded seal. Notable changes coincided with the onset of the annual molt, during which time seals experienced substantial decreases in blubber mass. Blubber stores subsequently increased following the

57 molting period for spotted and ringed seals, with a less defined pattern for the single bearded seal in this study. Molt is an energetically taxing physiological process (Boily, 1996; Boyd et al.,

1993; Chabot and Stenson, 2002), and therefore we would expect seals to draw on blubber reserves at this time. Given that the captive seals did not have to expend energy searching for their own food and were fed to motivation year-round, the patterns described here may be less dramatic than those that occur in wild seals, however are still reflective of innate physiological cycles entrained in these seals (Nitto et al., 2001; Renouf and Noseworthy, 1990; Rosen and

Renouf, 1998).

I. Seasonal Changes

Spotted, ringed, and bearded seals exhibited differences in their proportion of blubber and the in the magnitude of their seasonal changes in body condition. Of these species, ringed seals had by far the overall highest proportion of blubber mass, with blubber comprising up to half their body mass. Because ringed seals are smaller bodied, they require more insulation than a seal of large body size that can retain heat more easily (Lovegrove, 2005; Ryg et al., 1988; Ryg et al.,

1993). Bearded seals are large-bodied and spotted seals are intermediate in body size, both requiring different levels of insulation. Spotted and bearded seals had the same average blubber mass, but did not exhibit the same seasonal patterns, annual minimums, or maximums of proportion of blubber. Spotted seals displayed much greater seasonal variation in blubber thickness than the bearded seal.

Changes in blubber mass have been shown to coincide with species-specific life-history events in phocids (Mellish et al., 2007; Rosen and Renouf, 1997; Ryg et al., 1990a; Thordarson et al., 2007). My data indicate that the timing of seasonal changes in body condition for these

58 species are closely tied to the annual molt. Spotted and ringed seals both experienced annual minimum blubber mass, and therefore body condition, during or at the completion of the annual molt. While the timing and duration of the molt is similar for spotted and ringed seals, it varies in timing and length by age class and individual. The bearded seal’s molt was significantly prolonged compared to spotted and ringed seals, which may explain the differential magnitude of changes in blubber mass. Further, the bearded seal’s comparatively small percent difference in blubber mass did not clearly or consistently align with his molt.

In addition to regular seasonal changes in blubber mass, spotted and ringed seals demonstrated ontogenetic patterns that shifted the magnitudes of these changes for subadults and adults. Ontogenetic patterns were confirmed by linear mixed effects models, which revealed that age was a significant driver of changes in percent blubber mass for all species. The younger, smaller subadult seals had proportionally more blubber than the older, larger adult seals. The adult spotted seals (Amak & Tunu) showed more dramatic fluctuations in blubber mass than the subadult seals (Sura & Kunik). Seasonal patterns were similar for both adult seals, although

Amak had a more dramatic decrease in blubber mass in 2018 due to frequent regurgitation events and decreased appetite for which he received veterinary treatment. As a result, Tunu’s changes were more consistent between years (34.9  2.5%) than Amak’s (56.7  17.5%). Among the subadult seals, at three to five years old, Sura was approaching sexual maturity and demonstrated a higher percent difference than Kunik, who was two to four years old at the same time.

The three ringed seals of different ages exhibited similar ontogenetic patterns. Dutch, the subadult female housed in Alaska, was the youngest of the three seals and exhibited the smallest seasonal fluctuations in blubber mass. The male ringed seal Pimniq, who entered adulthood during the study demonstrated seasonal changes in blubber mass that increased in magnitude as

59 he reached the beginning of sexual maturity at five years old. Nayak, the adult female housed in

California, and Pimniq both displayed larger seasonal differences than Dutch. As the magnitude of seasonal changes increases in adults, proportion of blubber mass relative to total mass decreases. Subadult seals here had a higher proportion of blubber than adults, possibly due to higher surface area to volume ratios, causing them to lose heat at a faster rate than larger seals

(Noren et al., 2008; Ryg et al., 1988; Ryg et al., 1993); therefore, they must maintain greater amounts of insulation to stay warm in cold Arctic conditions.

The bearded seal did not demonstrate large seasonal changes in body condition. Noatak’s molt extended for four months across winter and spring, prolonging the energetically taxing period of shedding and regrowth of pelage (Ashwell-Erickson et al., 1986; Boily, 1996; Gales and Renouf, 1994a). Unlike spotted and ringed seals, photoperiod was not a significant driver of changes in blubber mass. This prolonged molt period may be part of the reason why photoperiod was decoupled from seasonal changes in body condition for this individual. In addition, age was the only significant driver of changes in body condition. Percent difference between annual minimum and maximum body condition showed a small increase from 2018 to 2019; suggesting a similar ontogenetic pattern as observed in the other two species. Noatak was a subadult for the duration of this study and steadily grew in size over this period. The bearded seal’s lack of clear seasonal changes could be attributed to his relatively young age, and may amplify as he reaches sexual maturity. More fine-scale data for bearded seals would be useful to this analysis.

II. Potential Drivers of Seasonal Changes

Photoperiod was a significant driver of changes in percent blubber mass for spotted and ringed seals. Photoperiod has a strong influence on seasonality and the triggering of innate

60 physiological processes, such as molt (Bradshaw and Holzapfel, 2007; Ling, 1970). Changes in photoperiod correspond with changes in season; daylight hours increase in the summer and decrease in the winter (Bradshaw and Holzapfel, 2007; Bradshaw and Holzapfel, 2008). In the model, increased daylight hours corresponded to decreases in percent blubber mass. The annual molt occurs during or just prior to lowest annual percent blubber mass and aligns with extended daylight hours (Figs. 3.4, 3.5, 3.6). For study seals in Alaska, the molt coincided directly with greatest number of daylight hours and minimum blubber mass in May and June, the same timing as their wild counterparts.

Air and water temperatures did not appear to directly influence changes in blubber mass.

Air temperature was not a significant factor in the mixed effects models, but air temperatures increased during longer daylight hours during the summer in both locations (Figs. 3.7, 3.8, 3.9).

The combination of longer days with more exposure to sunlight and warmer temperatures create ideal conditions for increased skin perfusion to promote hair growth and tissue regeneration while limiting energetic expense (Ling, 1970; Schop et al., 2017).

Between the facilities in Alaska and California, ringed seals showed similar seasonal patterns in percent blubber mass. The adult female ringed seal, Nayak, housed at UCSC showed a greater percent difference between minimum and maximum blubber mass than Pimniq and

Dutch at ASLC. Nayak’s increased percent difference could be attributed to adulthood, or is potentially an artifact of being housed in a warmer climate where she has lower thermoregulatory constraints. A thick blubber layer could be detrimental in warm conditions and cause overheating. Dutch, the youngest animal, had the smallest difference and the highest blubber mass of the three individuals. The ringed seals in Alaska maintained a higher blubber mass year- round, apparently to manage the colder Arctic temperatures. Their small body size gives them a

61 larger surface area to volume ratio from which to dissipate heat into the environment (Noren et al., 2008; Ryg et al., 1988; Ryg et al., 1993). Spotted and bearded seals have smaller surface area to volume ratios and are sufficiently insulated with a smaller proportion of blubber mass than that of the ringed seals.

III. Comparisons to Wild Seal Blubber Data

Body condition patterns in captive seals can be compared to available data from wild spotted, ringed, and bearded seals to better understand typical proportions and changes in body condition for these species. Using data obtained from ADFG, I compared three to four years of sternal blubber depth data from individuals in this study to average point sampled sternal blubber depth acquired for wild seals over many decades. ADFG sampled subsistence-caught Arctic seals over a 50-year period for 1104 spotted (1968-2018), 943 ringed (1972-2018), and 445 bearded (1973-2018) seals from 15 villages covering most of the spotted, ringed, and bearded seal range in Alaska. These data are presented in Fig. 3.10 along with mean sternal blubber data from all study animals. For full 50-year reports by species, see Quakenbush et al. 2009, 2011a,

2011b.

Captive seals showed thinner sternal blubber thickness than wild seals year-round – on average 0.9-1.9 cm thinner – but there was some overlap in thickness within the confidence intervals of average wild seal blubber depth and this varied by species (Fig 3.10). Wild individuals likely displayed thicker blubber layers than captive individuals because they occurred at higher latitudes where they experience more extreme environmental conditions and colder temperatures that necessitate greater insultation. However, timing of blubber losses and gains were relatively consistent between captive and wild seals.

The available data describing body condition in phocid seals is reviewed in Table 3.6.

When comparing seasonal changes in proportion of blubber mass that I documented in the captive study animals were similar to those documented in wild seals (Burns and Frost, 1979;

Ferguson et al., 2017; Ryg et al., 1990b; Ryg et al., 1990a), but to a lesser magnitude. When compared to data from wild individuals, proportion of blubber mass for ringed and bearded seals in this study fell within the reported ranges for wild seals (ringed: 15-60%; bearded: 25-39%).

The blubber content values of the ringed seals here tracked with studies completed with wild seals in Svalbard and Hudson Bay, located at the lowest latitude of their range (Ryg et al., 1990a;

Young and Feguson, 2013). Body condition decreases before and during molt and increases directly following the completion of molting (Ryg et al., 1990a; Young and Feguson, 2013). Ryg et al. (1990a) evaluated blubber content in ringed seal females during several different months and found a minimum of 31% blubber in June, following the molt, and a maximum of 53% blubber in March. While the captive bearded seal’s proportion of blubber was within range of wild values, he did not exhibit the seasonal patterns observed in limited studies of free-ranging bearded seals using blubber depth and body condition metrics (Andersen et al., 1999; Ryg et al.,

1990b). Total blubber mass has not previously been described for wild spotted seals, but the values found here are similar to those reported for the closely related harbor seal (range 21-55%), with which their habitats overlap (Pitcher, 1986). Arctic seals exhibit similar patterns in body condition, but still exhibit species-specific differences in body condition across species.

Year-round captive measurements show longitudinal changes in blubber mass that are impossible to repeatedly sample from single wild individuals. Further, these types of fine-scale body condition data collected with captive seals can support interpretation of morphometric data that are point-sampled on wild individuals. Although the magnitude of changes in blubber

63 content seen in the captive seals are different, the timing and general pattern are comparable to their wild counterparts. Body condition patterns in captive seals can therefore inform our understanding body condition dynamics and fat mobilitation in wild seals.

IV. Implications

Wild ice seals have been exhibiting declines in body condition in recent decades

(Harwood et al., 2012; Harwood et al., 2015; Laidre et al., 2008). These declines coincide with the rapid melting of sea ice in the Arctic due to climate change (Harwood et al., 2020; Kovacs et al., 2011; Parkinson, 2014). For example, ringed seal body condition appears to be steadily declining in some parts of their range (Ferguson et al., 2017; Harwood et al., 2000; Harwood et al., 2020). Between 2003 and 2013, researchers and subsistence hunters measured sculp mass data from harvested ringed seals in Hudson Bay, Canada (Ferguson et al., 2017). They documented a marked decline in body condition throughout the 10-year period, ranging from

55.4% blubber in 2004 to 48.1% blubber in 2013, where 2012 had the lowest percent fat at

40.3% (Ferguson et al., 2017). Long-term studies such as those conducted by ADFG provide morphometric data to monitor health of seals over decades. Directed studies of body condition using fine-scale data can support the interpretation of these long-term datasets of Arctic seal health.

Most blubber mass values reported for wild seals are collected on single individuals at a single timepoint (often post-mortem) and do not represent the full range of values from minimum to maximum body condition of individuals. Thus, longitudinal data collected on captive individuals provides a unique opportunity to reveal the underlying nature of seasonal patterns in body composition. These results provide quantitative data for assessing fluctuations in body

64 condition for spotted, ringed, and bearded seals, allowing for a more comprehensive look at the health of wild individuals. The rapid advancement of climate change in the past few decades appears to be impacting body condition of ice seals in Alaska at an accelerated rate. Indeed,

NOAA has declared two UMEs for ice seals in Alaska over the past decade due to increased numbers of seals stranding along the coast of Alaska that are presenting in poor health (NOAA,

2019). Baseline health data for Arctic seal species allow scientists to measure the impacts of changes in habitat on individuals and population health. Thus, more information pertaining to baseline changes in ice seal body condition are needed to better assess potential causes of these

UMEs. Knowledge of periods during which ice seals may be most vulnerable to changes within their environment can aid in management efforts.

Chapter 3 Tables and Figures

Table 3.1. Air and water temperature (C) and photoperiod (minutes of daylight from sunrise to sunset) for Seward, AK and Santa Cruz, CA, averaged monthly for each location for 2018-2019. Alaska California Air Water Photoperiod Air Water Photoperiod Month (C) (C) (min daylight) (C) (C) (min daylight) Jan -0.6 8.1 411 12.5 13.1 597 Feb 0.2 7.6 551 11.5 12.4 651 Mar 3.0 7.0 712 12.8 13.0 718 Apr 5.6 7.6 879 13.9 13.6 789 May 8.5 8.1 1035 14.5 14.1 849 Jun 13.3 8.5 1125 16.1 15.0 879 Jul 15.2 8.5 1076 16.9 15.9 864 Aug 15.3 8.6 932 17.0 16.2 811 Sep 11.9 9.0 769 16.8 15.8 743 Oct 6.9 9.1 604 15.7 15.2 673 Nov 4.9 9.5 449 12.9 13.9 612 Dec 1.4 8.6 359 11.8 13.2 580

Table 3.2. General characteristics of seasonal changes in blubber mass and molt parameters for Arctic seals in this study. Displayed are species- and age-specific timing of average minimum and maximum percent blubber masses (monthly averages, averaged by year) and percent difference (from min to max). All values are presented as mean  s.d. For subadult ringed seals, Dutch had a minimum blubber mass in July both years and maximum in April (2018) or May (2019), while Pimniq’s minimum occurred in May both years and his maximum in Oct (2018) and Dec (2019). Mean Min Max Molt Age % Molting Blubber Blubber Month Blubber Month Duration Class difference Period Mass (%) Mass (%) Mass (%) (days) Spotted Subadult 34.7  3.6 28.6  0.7 May/Jun 39.5  0.3 Nov/Dec 35.5  4.9 May-June 25 ± 1.9 seals Adult 31.2  4.8 26.1  0.8 Jun 37.2  1.4 Dec/Jan 45.8  15.4 April-May 27 ± 2.8 Ringed Apr/May Subadult 43.5  2.6 38.8  2.6 May/Jul 46.8  1.2 16.6  6.3 May-June 24 ± 4.3 seals Oct/Dec Adult 40.5  3.4 35.7  3.0 Apr/May 45.3  0.7 Dec/Jan 21.3  10.9 Mar-April 40 ± 6.4 Bearded Subadult 33.0  1.3 31.0  1.1 Jun/Nov 34.5  0.2 Aug 10.8  2.8 Dec-April 118 ± 1.4 seal

Table 3.3. Results of best fitting linear mixed effects models for spotted and ringed seals. For spotted seals, age class (F= 23.19, p= 0.0402) and photoperiod (F= 121.14, p<0.0001) were significant. For ringed seals, age (F= 63.56, p= 0.0439) and photoperiod (F= 28.5, p<0.0001) were significant. Individual accounted for 2.37% of total variance for spotted seals and 0% of the total variance for ringed seals.

Parameters ß S.E. DFDEN t ratio p Spotted Intercept 0.4313 0.009 48.46 45.68 <0.0001 seals Age class -0.0183 0.004 2.01 -4.82 0.0402 Photoperiod -0.00013 0.00001 94.02 -11.01 <0.0001 Ringed Intercept 0.5488 0.014 17.41 38.57 <0.0001 seals Age -0.0109 0.001 1.33 -7.97 0.0439 Photoperiod -0.00008 0.00002 67.34 -5.34 <0.0001

Table 3.4. Multiple linear regression results for the bearded seal. Parameters ß S.E. t ratio p Intercept -1.0820 0.278 -3.89 0.0008 Age -0.0611 0.017 -3.60 0.0016 Water temp 0.2273 0.1104 2.06 0.0516

Table 3.5. Annual mean blubber depth ± s.d. (cm) at each standard body site by species and age class. The range of mean minimum to mean maximum blubber depth at each location for each species and age class is presented below the mean. Spotted seals Ringed seals Bearded seal Subadults Adults Subadults Adults Subadult Dorsal 2.98 ± 0.44 3.25 ± 0.43 3.19 ± 0.38 3.33 ± 0.29 3.54 ± 0.3 Neck (2.20-3.64) (2.61-3.94) (2.56-3.77) (2.82-3.70) (3.06-3.91) 2.31 ± 0.47 3.25 ± 0.60 2.74 ± 0.35 2.31 ± 0.25 3.07 ± 0.19 Axial (1.66-3.14) (1.51-3.16) (2.19-3.22) (1.99-2.75) (2.76-3.38) 3.05 ± 0.52 3.25 ± 0.66 3.28 ± 0.30 2.85 ± 0.36 3.68 ± 0.22 Middle (2.17-3.70) (2.08-3.97) (2.70-3.60) (2.21-3.38) (3.34-3.99) 3.23 ± 0.53 3.24 ± 0.63 3.33 ± 0.39 2.79 ± 0.30 3.46 ± 0.2 Umbilical (2.36-3.95) (2.13-3.96) (2.64-3.78) (2.23-3.18) (3.1-3.78) 2.80 ± 0.48 2.78 ± 0.57 3.05 ± 0.34 2.53 ± 0.30 3.12 ± 0.19 Pelvic (2.02-3.48) (1.81-3.51) (2.56-3.62) (2.06-2.95) (2.84-3.42) 2.46 ± 0.26 2.55 ± 0.42 2.80 ± 0.21 2.37 ± 0.22 3.17 ± 0.17 Ankle (1.99-2.80) (1.82-3.08) (2.41-3.10) (1.99-2.71) (2.91-3.45)

Lateral 2.65 ± 0.33 2.75 ± 0.32 3.28 ± 0.30 2.92 ± 0.19 3.96 ± 0.22 Neck (2.10-3.24) (2.26-3.37) (2.78-3.71) (2.62-3.28) (3.63-4.28) 3.71 ± 0.67 3.79 ± 0.72 3.86 ± 0.34 3.64 ± 0.39 4.71 ± 0.26 Axial (2.52-4.62) (2.47-4.59) (3.29-4.45) (2.97-4.23) (4.4-5.14) 3.28 ± 0.55 3.08 ± 0.56 3.54 ± 0.30 3.58 ± 0.42 3.4 ± 0.17 Middle (2.40-4.14) (2.15-3.73) (3.00-4.01) (2.83-4.23) (3.15-3.67) 3.33 ± 0.55 3.18 ± 0.61 3.41 ± 0.33 3.26 ± 0.32 3.33 ± 0.14 Umbilical (2.40-4.08) (2.15-3.93) (2.67-3.82) (2.62-3.67) (3.16-3.58) 2.54 ± 0.49 2.59 ± 0.53 3.16 ± 0.31 3.04 ± 0.33 3.5 ± 0.24 Pelvic (1.81-3.29) (1.75-3.25) (2.61-3.60) (2.48-3.54) (3.06-3.92) 1.94 ± 0.24 1.99 ± 0.26 2.36 ± 0.18 2.36 ± 0.22 3.45 ± 0.16 Ankle (1.54-2.30) (1.56-2.46) (2.08-2.71) (1.98-2.68) (3.21-3.72)

Ventral 2.84 ± 0.47 2.68 ± 0.56 2.90 ± 0.34 2.67 ± 0.27 3.31 ± 0.19 Sternum (2.20-3.63) (1.84-3.38) (2.38-3.41) (2.12-3.04) (2.97-3.64)

Table 3.6. Summary of body condition data for Arctic, temperate, and Antarctic phocids. Percent blubber mass and blubber depths are presented as means or ranges depending on data available in the literature. Values with ~ denote values estimated from figures. Where age class is specified, P indicates pup, Y indicates young of the year, J indicates juvenile, A indicates adult, and C indicates a combination of age classes. Sex, when specified, is denoted as M for male and F for female. For methods, TTC represents traditional truncated cones, VOL represents volumetric calculations, ID represents isotope dilution, and SCULP represents direct measurements of sculp mass. Species mass ranges were acquired from the Encyclopedia of Marine Mammals*. For bearded, ringed, and spotted seals, masses in parentheses are the mass ranges seals in this study.

Blubber/Lipid Blubber Blubber Depth Species Mass (kg) Method Time of year Location Source Mass (%) Depth (cm) Location

Arctic Phocids Bearded seal 250-425 33.0 TTC 3.3 Sternum Jan-Dec Captive This study Erignathus barbatus (114-144) (30.3-34.7) (3.0-3.7) 29-39 SCULP 4.4-7.2 Sternum Jan-Dec Alaska Burns and Frost 1979

- - ~4.3-6.4 Sternum Jan-Dec Alaska Quakenbush et al. 2011

25-38 SCULP - - May Svalbard Ryg et al. 1990

- - 5.6/4.4 (A) Sternum May/July Alaska Crawford et al. 2015 4.7/3.2 (P) - - 3.7-6.0 Dorsal, 60% of May-Sept Svalbard Andersen et al. 1999 length Ringed seal 23-100 42.0 TTC 2.8 Sternum Jan-Dec Captive This study Pusa hispida (19-37) (31.7-47.9) (2.0-3.6) - - ~2.5-5.4 Sternum Jan-Dec Alaska Quakenbush et al. 2011

~36-53 SCULP - - Jan-Dec Hudson Bay Young and Ferguson 2013 40.3-55.4 SCULP - - Oct-Dec Hudson Bay Ferguson et al. 2017

Blubber/Lipid Blubber Blubber Depth Species Mass (kg) Method Time of year Location Source Mass (%) Depth (cm) Location

23.2-60.3 VOL 1.7-4.5 Multiple - Captive Parsons 1977

15-50 SCULP - - Feb-Sept Svalbard Ryg et al. 1990a

52.5 (F) SCULP - - Mar Svalbard Ryg et al. 1990b 41.0 (M) 47.0 SCULP - - Apr Svalbard Ryg et al. 1990b

- - ~1.0-4.5 Sternum Apr-Jun Svalbard Ryg et al. 1988

31 (F) SCULP - - June Svalbard Ryg et al. 1990b 29 (M) 49 (F) SCULP - - Sept Svalbard Ryg et al. 1990b 39,46 (M) - - 2.7/1.9 (P) Sternum May/July Alaska Crawford et al. 2015

22-31 SCULP - - Sept-Oct Canada Yurkowski et al. 2020

Spotted seal 65-115 33.0 TTC 2.8 Sternum Jan-Dec Captive This study Phoca largha (41-86) (18.6-41.3) (1.8-4.0) - - 2.6-6.5 Sternum Jan-Dec Alaska Quakenbush et al. 2009 Harp seal 120-140 15-39 SCULP - - Jan-Feb Norway Ryg et al. 1990 Phoca groenlandica 29.3 Multiple - - Mar-Jun Newfoundland Gales and Renouf 1994 (18.5-37.8) - - 3.3 Sternum Mar-Apr Barents/White Nilssen et al. 1997 Seas, Norway

Blubber/Lipid Blubber Blubber Depth Species Mass (kg) Method Time of year Location Source Mass (%) Depth (cm) Location

- - 2.2 Sternum June Barents/White Nilssen et al. 1997 Seas, Norway - - 8.8 Sternum Oct Barents/White Nilssen et al. 1997 Seas, Norway Hooded seal 200-400 38 TTC ~2.7-4.9 Multiple May Iceland Thordarson et al. 2007 Cystophora cristata

37 TTC ~2.3-4.0 Multiple Aug Iceland Thordarson et al. 2007

42 TTC ~2.8-5.2 Multiple Oct Iceland Thordarson et al. 2007 Ribbon seal 70-110 - - 0.8-6.0 Sternum Jan-Dec Alaska Quakenbush et al. 2008 Histriophoca fasciata

Temperate Phocids Gray seal 100-400 34.2 ID - - Jan Canada Beck et al. 2000 Halichoerus grypus (30.1-37.6) 14.4 ID - - May Canada Beck et al. 2000 (4.7-27.3) 21.2 (M) ID - - Feb Canada Beck et al. 2003 17.7 (F) 18.7 (M) ID - - May Canada Beck et al. 2003 23.0 (F) 11.5 (M) ID - - June Canada Beck et al. 2003 15.6 (F) 22.5 (M) ID - - Oct Canada Beck et al. 2003 21.4 (F)

Blubber/Lipid Blubber Blubber Depth Species Mass (kg) Method Time of year Location Source Mass (%) Depth (cm) Location

27.5 (M) ID - - Dec/Jan Canada Beck et al. 2003 32.5 (F) Harbor seal 60-170 33.2/36.2 SCULP 2.03-3.41 Sternum Jan-Dec Alaska Pitcher 1986 Phoca vitulina (21-55) 26-33 SCULP - - - North Sea Ryg et al. 1990 - - 1.8-2.7 (A) Multiple Jan-Dec Captive Mellish et al. 2007 Northern elephant 400-2300 26.2/25.9 TTC - - Pre-/post-molt Año Nuevo, CA Worthy et al. 1992 seal Mirounga 24.2-43.7 TTC - - Spring; autumn Año Nuevo, CA Webb et al. 1998 angustirostris

Antarctic Phocids Southern elephant 400-3700 27.2 (F) HID - - End lactation South Georgia Boyd et al. 1993 seal Mirounga leonina 29.1 (F) HID - - Start molt South Georgia Boyd et al. 1993 27.5 (F/J) TTC - - Molt (Nov-Dec) Macquarie Isl. Field et al. 2007

26.6 (M/J) 29.9 (F/J) TTC - - Mar-Jun Macquarie Isl. Field et al. 2007

28.7 (M/J) Weddell seal 400-600 - - 3.0 (A) Average of 6 sites Dec-Feb Antarctica Castellini et al. 2009 Leptonychotes 2.7 (J) weddellii Crabeater seal 200-300 20.4 SCULP - - Jan-Feb Antarctica Bryden and Erickson Lobodon (17.5-24.9) 1976 carcinophaga 2.7-4.7 Sternum Feb-Mar Antarctica Laws et al. 2003 30.9-42.5 TTC 4.2 Sternum Apr-May; Antarctica McDonald et al. 2008 Aug-Sept - - 2.0 Average of 6 sites Dec-Feb Antarctica Castellini et al. 2009

Blubber/Lipid Blubber Blubber Depth Species Mass (kg) Method Time of year Location Source Mass (%) Depth (cm) Location

- - 5.7 Sternum Sept-Oct Antarctica Øritsland 1970 Ross seal 129-216 21.8 SCULP - - Jan-Feb Antarctica Bryden and Erickson Ommatophoca rossii (21.6-22.1) 1976 - - 2.3 (A) Average of 6 sites Dec-Feb Antarctica Castellini et al. 2009 - - 5.6 Sternum Sept-Oct Antarctica Øritsland 1970 Leopard seal 300-500 - - 4.6 Sternum Sept-Oct Antarctica Øritsland 1970 Hydrurga leptonyx - - 2.4 Average of 6 sites Dec-Feb Antarctica Castellini et al. 2009

* Encyclopedia of Marine Mammals, 2nd edition (2008), ed. W. Perrin, B. Würsig, J.G.M. Thewissen.

Fig. 3.1. Average monthly percent blubber mass for Dec 2017-2019 for four spotted seals. See Table 2.1 in Chapter 2 for information on individual age and sex. Open circles represent 2017, squares represent 2018, and triangles represent 2019. Percentages in bottom right corners of each graph show the range of percent differences from annual minimum to annual maximum percent blubber mass for each individual. Gray bars indicate visible molt.

Fig. 3.2. Average monthly percent blubber mass for Dec 2017-2019 for three ringed seals. See Table 2.1 in Chapter 2 for information on individual age and sex. Open circles represent 2017, squares represent 2018, and triangles represent 2019. Percentages in bottom right corners of each graph show the range of percent differences from annual minimum to annual maximum percent blubber mass for each individual. Gray bars indicate visible molt. For individuals with both gray and purple bars, gray represents the 2018 molt and purple represents the 2019 molt. Individuals with 1 gray bar had similar start and end molt dates other years.

Fig. 3.3. Average monthly percent blubber mass for Dec 2017-2019 for one bearded seal. See Table 2.1 in Chapter 2 for information on individual age and sex. Open circles represent 2017, squares represent 2018, and triangles represent 2019. Percentages in bottom right corners of each graph show the range of percent differences from annual minimum to annual maximum percent blubber mass for each individual. Gray bars indicate visible molt.

Fig. 3.4. Seasonal changes in body condition relative to photoperiod for spotted seals housed in Seward, AK. The left y-axis shows average monthly blubber mass (black circles) as a percentage of total mass. The right y-axis shows average monthly photoperiod (blue solid line) in minutes of daylight from sunrise to sunset. Gray bars indicate the visible molt.

Fig. 3.5. Seasonal changes in body condition relative to photoperiod for ringed seals housed in Seward, AK (Pimniq and Dutch) and Santa Cruz, CA (Nayak). The left y-axis shows average monthly blubber mass (black circles) as a percentage of total mass. The right y-axis shows average monthly photoperiod (blue solid line) in minutes of daylight from sunrise to sunset. Gray bars indicate the visible molt.

Fig. 3.6. Seasonal changes in body condition relative to photoperiod for the bearded seal housed in Santa Cruz, CA. The left y-axis shows average monthly blubber mass (black circles) as a percentage of total mass. The right y-axis shows average monthly photoperiod (blue solid line) in minutes of daylight from sunrise to sunset. Gray bars indicate the visible molt.

Fig. 3.7. Seasonal changes in body condition relative to air and water temperature for spotted seals housed in Seward, AK. The left y-axis shows average monthly blubber mass (black circles) as a percentage of total mass. The right y-axis shows average monthly temperature (C) for air (dark gray solid line) and water (blue dashed line) temperatures. Gray bars indicate the visible molt.

Fig. 3.8. Seasonal changes in body condition relative to air and water temperature for ringed seals. Pimniq and Dutch were housed in Seward, AK and Nayak was housed in Santa Cruz, CA. The left y-axis shows average monthly blubber mass (black circles) as a percentage of total mass. The right y-axis shows average monthly temperature (C) for air (dark gray solid line) and water (blue dashed line) temperatures. Gray bars indicate the visible molt.

Fig. 3.9. Seasonal changes in body condition relative to air and water temperature for the bearded seal housed in Santa Cruz, CA. The left y-axis shows average monthly blubber mass (black circles) as a percentage of total mass. The right y-axis shows average monthly temperature (C) for air (dark gray solid line) and water (blue dashed line) temperatures. Gray bars indicate the visible molt.

Figure 3.10. Average sternal blubber depth and 95% confidence intervals for wild and captive spotted (A), ringed (B), and bearded (C) seals by month. Symbols in black represent data from wild seals, while open symbols represent data from captive seals in this study. Circles indicate subadults, while squares indicate adults. Wild data were provided by the the Alaska Department of Fish and Wildlife Marine Mammals Program with permission from L. Quakenbush.

85 Chapter 4: Body condition metrics and applications to field research

Introduction

I. Field Research in the Arctic

It is difficult to conduct research on wild Arctic seals due to their remote, ice-covered habitats and cryptic behavior. Ice seals spend the majority of the year in open water or under sea ice, only spending prolonged amounts of time hauled out during breeding and molting seasons

(i.e. late spring and summer) (Boveng et al., 2009b; Burns and Frost, 1979; Champagne et al.,

2012; Smith and Hammill, 1981). During the spring, a relatively small number of wild seals are outfitted with various tags (e.g. VHF, satellite, etc.) during research expeditions, providing data on movement and haul out behavior (NOAA Vessel-Based Studies of Ice-Associated Seals,

2020) (Beck et al., 2003; Bowen et al., 1985; Duyke et al., 2020; Gjertz et al., 2000). It is impossible to recapture individual seals over extended periods of time in the Arctic, thus fine- scale archival tags cannot be used and repeated sampling of the same individuals cannot be conducted. Further, even when hauled-out, seals are often dispersed across vast regions of the

Arctic and dangerous environmental conditions pose challenges for researchers working in these remote locations. Together, these issues result in a narrow timeframe and hazardous conditions with which to conduct field research on wild seals.

II. Subsistence Hunting

In Alaska, the heath of wild seal populations is often assessed during subsistence hunts in remote Alaskan villages. ADFG partners with Alaskan villages across the state during subsistence hunts to collect a suite of morphological and physiological data for long-term study.

86 This allows ADFG to assess Arctic seal health and gain an understanding of population status using distribution, age, growth rate, body condition, pregnancy rate and sex ratio data

(Quakenbush et al., 2009; Quakenbush et al., 2011a; Quakenbush et al., 2011b). Some of these data were presented in the previous chapter (see Figure 3.10 in Chapter 3). Villages rely on

Arctic seal harvests to sustain their remote communities and are invested in conserving Arctic seal populations and maintaining their health for both cultural and subsistence reasons

(Huntington et al., 2016; Ice Seal Committee, 2016; Nelson et al., 2019). Significant numbers of harvested seals in poor condition may indicate shifts in the ecosystem such as changing prey resources, diseases, or alterations in oceanographic conditions, among others (Harwood et al.,

2015; Kovacs et al., 2011; Laidre et al., 2015). Further, wild Arctic seal health directly impacts the health of people consuming seals, as some diseases carried by seals can be transmitted to humans (Burek et al., 2008; Waltzek et al., 2012) and changes in seal abundance can have dire conseuqences on the availability of food in subsistence communities (Huntington et al., 2016; Ice

Seal Committee, 2019).

III. Current Conservation Issues

Arctic seals in Alaska are currently experiencing a UME, the second such event declared this decade. During the 2011-2016 UME, Alaskan pinnipeds stranded in record numbers, presenting with skin lesions and abnormal hair loss (NOAA, 2016). An official cause was not determined (NOAA, 2016), but Arctic seals are again facing increased mortality without a definitive cause; however, this time they are presenting in more obvious poor body condition

(NOAA, 2019).

87 When attempting to repeatedly sample Arctic seals, it is nearly impossible to re-capture individuals to take serial measurements. Consequently, much of the morphological and physiological data collected on ice seals are taken at a single time point during certain months of the year and based on population averages. Further, researchers often do not have the time or resources to collect full suites of morphometric data on seals during sampling events. Thus, simple species-specific indices of body condition are needed to quickly and accurately assess body condition in the field (Castrillon and Bengtson Nash, 2020).

IV. Unmanned Aerial Vehicles

More recently, field researchers have begun utilizing new technology for collecting data on marine mammals that are difficult to access due to their location, body size, and behavior.

The use of unmanned aerial vehicles (UAVs) is becoming widespread for assessing the health of wild marine mammals (Allan et al., 2019; Christiansen et al., 2016). UAVs allow researchers to access difficult areas that may be inpenetrable to humans, and collect data on marine mammals in a non-invasive way (Christiansen et al., 2016; Christiansen et al., 2019; Fearnbach et al.,

2018). Scaled photographs taken from directly above a seal can be measured at specific locations using computer software to determine body proportions (Allan et al., 2019; Hodgson et al.,

2020). Further, those metrics that cannot be directly measured can often be calculated from other measurements. For example, widths measured from aerial images of seals hauled out in any orientation can be used to calculate girth by solving for the circumference of a circle (Allan et al., 2019). The use of UAVs allows researchers to collect data on more individuals in a shorter timeframe than if they were on the ground and handling each seal.

88 V. Body Condition Metrics

Whether working with live or harvested seals, or collecting images with UAVs, some combination of morphometric measurements (e.g. mass, standard length, axillary girth, blubber depth) are often used to determine the overall body condition of individuals. Blubber depth measurements are often only obtained at the sternum on the ventral side of seals. This site has long been the recommended blubber sample location for pinnipeds (Committee on Marine

Mammals (1966-67), 1967). However, although the sternal measurement has been deemed the standard for pinnipeds, due to the large range of body sizes and proportions across this group, this location is not always the most representative of overall body condition for every species.

For instance, in studies on harbor (Pitcher, 1986) and harp (Beck et al., 1993) seals, sternal blubber thickness was weakly correlated to sculp mass and therefore likely not a reliable indicator of body condition.

In many studies, the body site with the highest seasonal variation in blubber depth has been identified as the most indicative of overall body condition (Lockyer et al., 1985; Ryg et al.,

1988; Ryg et al., 1990b). Ryg et al. (1988) found that in ringed seals, the best indicator site was located dorsally and at 60% of the standard length of the seal (Ryg et al., 1988). Beck et al.

(1993) found that blubber was most variable dorsally between 40-70% of length in harp seals

(Beck et al., 1993). In captive walruses, blubber depth at the shoulder was most indicative of body condition; this location was found to be a better indicator than the sternal site (Noren et al.,

2015).

Along with individual morphometric measurements, the condition index (girth/standard length x 100) (Smirnov 1924; McLaren 1958; Ryg et al. 1990) and LMD index [(√(퐿 ⁄ 푀) ×

푑), where L is standard length, M is mass, and d is blubber thickness], are commonly used as

89 metrics of overall body condition (Hall and McConnell, 2007; Harwood et al., 2012; Nilssen et al., 1997; Pitcher and Pendleton, 2000; Ryg et al., 1990b). The suggested blubber thickness site for the LMD index is located at 60% of the standard length of the seal (Andersen et al., 1999;

Gales et al., 1994; Ryg et al., 1988; Ryg et al., 1990a) based on the most variable blubber depth site found in ringed seals (Ryg et al., 1988). These indices are sometimes calculated with, or in addition to, singular blubber thickness measurements when given a combination of standard length, mass, and blubber thickness data to give a more comprehensive picture of body condition. The LMD index has been used in a variety of phocid species, but some studies use blubber depths from different measurement locations (e.g. at the sternum over the xiphoid process) (Gales and Renouf, 1994a; Harwood et al., 2012; Pitcher and Pendleton, 2000) in place of Ryg’s standard site (Ryg et al., 1988).

In recent studies on varying age classes of ribbon, spotted, and harbor seals in Alaska,

NOAA researchers used mass/standard length as a metric of body condition with which to compare blubber depth at the right lateral hip and axillary girth measurements (Zeil et. al., 2020).

They found that the lateral hip blubber depth location was good indicator of body condition for all species when compared to this metric (Zeil et. al., 2020). Interestingly, body condition studies of a variety of pinniped species reveal that the best body condition indices are species-specific

(Mellish et al., 2007; Noren et al., 2015; Ryg et al., 1990b; Schwarz et al., 2015). Thus, given the importance of understanding body condition in Arctic seals, defining species-specific metrics will improve field techniques and provide a clearer picture of the health of wild ice seals.

Captive seals provide the opportunity to repeatedly sample individuals and obtain fine- scale data that are difficult or impossible to acquire on wild Arctic seals. The fine-scale data

90 presented here capture seasonal variability in body condition that cannot be discerned from a single interaction with a wild seal, and allow us to assess the efficacy of various methods used in the field. Here, I compare morphometric measurements and body condition indices to calculated total proportion of blubber mass to determine the best species-specific body condition metrics for spotted, ringed, and bearded seals. Using these data, I hope to aid in improving body condition assessments of wild seals—both on the ground and through the use of UAVs—to help field researchers maximize their time and limited resources.

Methods

In this chapter, I use morphometric measurements (see Chapter 2) to calculate a variety of body condition metrics commonly used in the field. I use linear regressions to compare each metric with calculated percent blubber mass (see Chapter 3), and determine the best body condition metrics for each species and, when possible, age class.

I. Morphometric Measurements

We obtained a variety of morphometric measurements weekly on four spotted, three ringed, and one bearded seal living in captive care from 2016-2019. Note that all data streams were not collected over this entire time frame. Height and width data were only obtained directly with large veterinary calipers for a 10-month period from 2018-2019 on the ringed and bearded seals housed at UCSC. Blubber depth measurements were collected weekly using a portable ultrasound machine at 13 locations (see Fig. 2.1 in Chapter 2) on each individual starting in

2016. Girth measurements were collected weekly starting at the end of 2017 with a standard measuring tape at 6 locations corresponding to blubber depth measurements. The percentage of

91 length (curvilinear length) where each ultrasound, girth, and width location described above occurred for each species are presented in Table 4.1. In addition to girth, standard length was measured from the tip of the nose to the tip of the tail (see Fig. 2.1 in Chapter 2). All seals were weighed weekly on a calibrated platform scale. Weekly morphometric measurements were averaged monthly to determine average length, blubber depth, and girth at each location each month.

II. Body Condition Metrics

I calculated the following body condition metrics commonly used in the field with wild seals for all animals in this study: (1) the condition index (girth/SL) (Smirnov 1924; Ryg et al.

1990a; Gales et al. 1994); (2) the LMD index (√(퐿 ⁄ 푀) × 푑) (Ryg et al., 1990b); (3) mass divided by standard length (mass/SL) (Noren et al., 2015; Pitcher and Pendleton, 2000); (4) individual blubber depth measurements at 13 locations; and (5) girth at six locations for all seals.

Due to availability of applicable data, widths at six locations and widths divided by standard length (width/SL) were only evaluated as potential metrics for the female ringed seal, Nayak, and male bearded seal housed at UCSC. I calculated the LMD index using blubber depth at the ultrasound site most correlated to blubber mass, as determined for each age class. In addition to using the most correlated blubber depth location, I also used blubber depth at the dorsal middle site (D3), located at 60% of standard length to calculate the LMD index in the equation to conform to the standard location outlined by Ryg et al. (1990a, 1990b).

92 III. Statistical Analyses

I used simple linear regressions to investigate relationships between percent blubber mass and each body condition metric, outlined above. Data were separated by age class and species, such that separate linear regressions were performed for each metric for subadults and adults of each species. All data were screened for outliers and checked for normality prior to analysis. All statistical analyses were performed in JMP 14.0 (SAS Institute Inc.).

Results

I. Spotted seals

Percent blubber mass was strongly correlated with blubber depth at multiple ultrasound locations for spotted seals (Table 4.2, Fig 4.1), but was most strongly correlated at single locations between the axial and pelvic regions. Correlations were weakest at neck and ankle sites. For spotted seal subadults, the strongest relationship between percent blubber mass and blubber depth at a particular site occurred at the dorsal hip location (D5: p<0.0001, R2=0.887) followed by the lateral umbilicus (L4: p<0.0001, R2=0.864), lateral middle (L3) (p<0.0001,

R2=0.838), and dorsal umbilical (D4) (p<0.0001, R2=0.839) locations. For adults, the strongest relationship occurred at the dorsal umbilicus (D4: p<0.0001, R2=0.935) followed by the lateral mid (L3: p<0.0001, R2=0.932) and lateral umbilicus (L4: p<0.0001, R2=0.926) locations. The sternal measurement was more strongly correlated with percent blubber mass in adults

(p<0.0001, R2=0.899) than subadults (p<0.0001, R2=0.768).

The metrics best correlated with percent blubber mass varied for subadults and adults

(Table 4.2, Fig 4.1). Mass/SL was a fair estimator for adults (p<0.0001, R2=0.758) but a reasonable, but less predictictable indicator for subadults (p<0.0001, R2=0.377). Individual girth

93 measurements and the condition index proved to be good metrics, but correlation strength varied by site. For adults, axial girth was most strongly correlated to percent blubber mass (p<0.0001,

R2=0.737) and for subadults, the mid girth was most strongly correlated (p<0.0001, R2=0.527).

The condition index was significantly correlated to body condition when using girth at the axilla for adults (p<0.0001, R2=0.627) and umbilicus for subadults (p<0.0001, R2=0.676). Overall, the

LMD index using the D4 blubber depth location for adults (p<0.0001, R2=0.942) and the D5 blubber depth location for subadults (p<0.0001, R2=0.819) provided one of the best metrics of body condition.

II. Ringed seals

Individual ultrasound measurements of blubber depth were correlated with percent blubber mass for both subadult and adult ringed seals (Table 4.3, Fig 4.2). All sites were significant (p<0.05) for adults and all but the lateral ankle site (L6) were significant for subadults. For subadults, the dorsal umbilical site (D4) had the strongest correlation (p<0.0001,

R2=0.753) to blubber mass. For adults, the lateral pelvis location (L5) had the strongest correlation (p<0.0001, R2=0.748) to blubber mass, but all sites between the mid and pelvis locations had similar correlations. Overall, blubber depth was more strongly correlated to blubber mass in adults. In contrast, girth measurements were not strongly correlated for either age class. Mid girth proved to be a weaker indicator of body condition for subadults (p<0.0001,

R2=0.270) and ankle girth was most correlated for adults (p<0.0001, R2=0.160).

Mass/SL did not predict body condition for adult ringed seals (p=0.119, R2=0.172), but did better for subadults (p=0.0073, R2=0.210) but with low R2 values. The condition index using girth at the pelvis was more correlated for subadults (p<0.0001, R2=0.357) than adults

(p<0.0001, R2=0.265). The LMD index using the D4 blubber depth location for subadults

94 (p<0.0001, R2=0.713) and the L5 blubber depth location for adults (p<0.0001, R2=0.743) were the most strongly correlated metrics to percent blubber mass of all analyzed metrics. The LMD index calculated with the standard blubber depth site outlined by Ryg et al. (1990), which corresponded to D3, was less correlated than when using the most significant blubber depth locations. None of the width or width/SL locations were significant for the female ringed seal

(p>0.05) (Table 4.3).

III. Bearded seals

Of the individual blubber depth sites, all but the lateral neck (L1) location were significantly correlated to blubber mass (Table 4.4, Fig 4.3). Blubber thickness at the dorsal midpoint (D3) was significant and the most highly correlated to body condition in this individual

(p<0.0001, R2=0.814). None of the 6 girth locations were significantly correlated to body condition, and the condition index using girth at the middle point was only weakly correlated

(p<0.0001, R2=0.243). Mass/SL was not a reliable indicator of blubber mass (p=0.03, R2=0.042).

Width was significantly correlated to body condition at the neck, axilla, and pelvis locations, but was most strongly correlated at the axilla (p<0.0001, R2=0.642). Width/SL was only significant at the axilla (p<0.0001, R2=0.380). There was not enough data to form a relationship between the condition index using girth at the midpoint and blubber mass. Overall for the bearded seal, the

LMD index proved to be the best estimator of body condition using the D3 site (p<0.0001,

R2=0.849) for blubber depth in the equation.

Discussion

The results presented here suggest that simple metrics of body condition can be used to reasonably estimate percent blubber mass, and thus overall body condition, of wild spotted,

95 ringed, and bearded seals. Importantly, I found multiple body condition metrics that can be used for each species in the field, and when possible, I identified the best metrics by age class.

I. Body Condition Metrics

In other studies with various species, the LMD index was an accurate estimator for ringed

(Harwood et al., 2012; Ryg et al., 1990b), bearded (Andersen et al., 1999), and harp (Gales et al.,

1994; Ryg et al., 1990b) seal body condition. I was able to confirm the validity of this metric for spotted, ringed, and bearded seals when using blubber content as an indicator of body condition.

The LMD index and individual blubber thickness measurements are the metrics best correlated with percent blubber mass for all species, although the best blubber thickness location varied by species.

For spotted seals, the best body condition metrics are singular blubber depth measurements at the dorsal umbilicus (adults) and pelvis (subadults) and the LMD index using the blubber depth location most correlated with blubber mass in the equation. These two metrics are ideal for subadult and adult spotted seals when the required data are available.

The best body condition metrics for ringed seals are the LMD index using the blubber depth location most correlated to blubber mass in the equation, and singular blubber depth measurements at the dorsal umbilicus (subadults) and lateral pelvis (adults). These two metrics are ideal for subadult and adult ringed seals when these data are available.

The most correlated metrics for bearded seals are the LMD index, and blubber depth at the dorsal middle measurement site, the same the location that Ryg et al. (1988) outlined as the best indicator of body condition (Andersen et al., 1999; Ryg et al., 1988; Ryg et al., 1990b).

These two metrics are ideal for subadult bearded seals when the necessary data are available, but

96 could likely be used for all age classes. More data are needed for bearded seals in particular to determine the best indices for this species.

While these species share common body condition metrics, the differences seen between age classes are likely attributable to patterns in growth leading up to maturity (Andersen et al.,

1999; Benjaminsen, 1973; McLaren, 1993). For example, subadult seals have a higher proportion of blubber mass relative to adults (see Chapter 3), likely due to their smaller body size and need for increased insulation (Burns, 1970; Liwanag, 2008). Adults are no longer growing, so their annual changes in mass, blubber depth, girth, and blubber mass remain more consistent. Changes in body condition metrics for adults indicate changes in blubber reserves, whereas changes in subadult metrics may reflect changes in both somatic growth and blubber reserves.

Given my results, it appears that some of the current metrics widely used for Arctic seals are not the most optimal. Although mass/SL and the condition index are commonly used for numerous pinniped species, mass/SL was weakly correlated for spotted seal subadults, ringed seals, and the bearded seal, and girth/SL was moderately correlated for spotted seals, but weakly correlated for ringed and bearded seals. I recommend using individual blubber thickness measurements at specific sites or the LMD index as opposed to mass/SL or girth/SL for all species, although the condition index is a fair estimator for spotted seals. Although I did not find the exact same blubber depth location results as Ziel et al. in spotted seals of all age classes

(lateral hip) that NOAA used for an indicator site (Ziel et al., 2020), the location presented here for subadult spotted seals was similarly placed, although dorsally on the body. For adults, this location was just anterior to this location. Here, mass/SL was a strong metric of body condition for adults, but was less tightly correlated for subadults (Table 4.2).

97 For the LMD index, the addition of blubber depth improves upon the metrics above to provide a better estimate of percent blubber mass and therefore, body condition (Shuert et al.,

2015). In several studies on ringed, harp and bearded seals as well as Steller sea lions, the LMD index was found to be the best indicator of body condition when compared to the condition index and blubber thickness alone (Andersen et al., 1999; Gales and Renouf, 1994a; Harwood et al.,

2012; Pitcher and Pendleton, 2000; Ryg et al., 1990b). I used the most correlated blubber depth sites for each species and age class to perform LMD index calculations, but blubber depth collected at various locations could be used in the calculation (Tables 4.2, 4.3). In addition to measuring body condition with metrics that utilize direct measurements on animals, such as those required for the LMD index, photographic data allowing for assessments of body condition can be collected remotely with minimal disturbance to the animal.

II. Future Directions: Body Condition and Unmanned Aerial Vehicles

When measured using UAV images, body condition is often quantified using standard length and width at various locations along the length of the body (Allan et al., 2019; Durban et al., 2016; Krause et al., 2017). UAVs are used to measure body condition in a variety of marine mammal species including Australian fur seals (Arctocephalus pusillus) (Allan et al., 2019), leopard seals (Hydrurga leptonyx) (Krause et al., 2017), humpback whales (Christiansen et al.,

2016; Christiansen et al., 2020), Australian sea lions (Neophoca cinerea) (Hodgson et al., 2020), short- and long-finned pilot whales (Globicephala spp.) (Adamczak et al., 2019), and right whales (Eubalaena spp.) (Christiansen et al., 2019). The findings presented here using width measurements are limited due to a small sample size of one individual each for ringed and bearded seals over a relatively short period. I did not determine an aerial metric for body

98 condition for the ringed seal, but the available data for the bearded seal indicated that measurements of width at the axilla were correlated with blubber content. Simple width measurements obtained from aerial images of wild bearded seals could give researchers information about the overall body condition of a large number of individuals. The relative circular body shape of these species (see Chapter 2) makes them amenable for width measurements from above. As it is becoming more important to collect body condition data on wild ice seal populations, UAVs will likely be more widely used in health assessments. Directed studies of the use of UAVs with captive ice seals with known body condition would provide valuable information for establishing best practices for UAV use with wild ice seals.

III. Importance

With rapidly changing Arctic conditions, management agencies need quick and easy ways to assess the health of wild individuals. Since the declaration of the current Alaskan ice seal UME in 2018, increasing numbers of spotted, ringed, and bearded seals are stranding in poor body condition (NOAA, 2020) and subsistence hunters are landing seals with thinner blubber layers (Savage, 2018). With limited opportunities to study these seals in the wild, researchers need to know the best data points to determine body condition of individual seals in real time to optimize data collection and how best to work with the data that may be gathered in different situations. Declining body condition and increased mortality amongst ice seals (NOAA, 2020) accelerates the need for accurate assessments of body condition, particularly those made with

UAV data. New information about how to efficiently evaluate body condition will hopefully improve our ability to answer outstanding questions pertaining to UMEs and climate-related trends for spotted, ringed, and bearded seals.

99 Chapter 4 Tables and Figures

Table 4.1. The percentage of total curvilinear length that each measurement site is located. Curvilinear length was measured from the tip of the nose to each location and was and divided by the total curvilinear length extending to the tip of the tail. Spotted seals Ringed seals Bearded seal Neck 23 ± 0.6% 24 ± 0.7% 20 ± 0.5% Axilla 40 ± 0.7% 42 ± 1.8% 35 ± 1.0% Mid 57 ± 0.8% 59 ± 0.9% 59 ± 4.2% Umbi 65 ± 1.2% 67 ± 1.0% 71 ± 0.8% Pelvis 76 ± 1.4% 76 ± 1.6% 82 ± 1.4% Ankle 85 ± 1.5% 84 ± 1.6% 91 ± 1.4%

100

Table 4.2. Results of simple linear regressions between percent blubber mass and different body condition metrics for two subadult and two adult spotted seals. Separate regressions were performed for each metric and age class. R2 values highlighted in green indicate an R2 greater than 0.8 and values highlighted in orange, a value greater than 0.6. Where multiple locations are significant, the most significant R2 value is bolded. Data displayed in gray have a p-value greater than 0.05 and are not significant. Spotted seal subadults Spotted seal adults Body condition metric p R2 ß SE t df p R2 ß SE t df Mass/SL <0.0001 0.377 50.428 9.557 5.28 1, 46 <0.0001 0.758 74.113 6.182 11.99 1, 46 LMD index Most significant site <0.0001 0.819 4.997 0.351 14.25 1, 45 <0.0001 0.942 5.435 0.199 27.34 1, 46 D3 <0.0001 0.744 4.350 0.377 11.55 1,46 <0.0001 0.886 4.919 0.260 18.90 1, 46 Condition index (girth/SL) Neck 0.567 0.007 5.101 8.834 0.58 1, 46 0.0005 0.233 30.348 8.129 3.73 1, 46 Axilla <0.0001 0.378 74.450 14.096 5.28 1, 46 <0.0001 0.627 86.713 9.854 8.80 1, 46 Mid <0.0001 0.468 80.290 12.627 6.36 1, 46 <0.0001 0.406 69.356 12.373 5.61 1, 46 Umbi <0.0001 0.676 107.10 10.926 9.80 1, 46 <0.0001 0.485 76.328 11.593 6.58 1, 46 Pelvis <0.0001 0.489 105.94 15.972 6.63 1, 46 <0.0001 0.564 103.13 13.372 7.71 1, 46 Ankle <0.0001 0.294 65.042 14.851 4.38 1, 46 0.0002 0.256 67.147 16.884 3.98 1, 46 Girth Neck 0.0326 0.092 0.170 0.077 2.20 1, 48 <0.0001 0.340 0.277 0.056 4.92 1, 47 Axilla <0.0001 0.454 0.388 0.061 6.32 1, 48 <0.0001 0.737 0.594 0.052 11.46 1, 47 Mid <0.0001 0.517 0.427 0.060 7.17 1, 48 <0.0001 0.603 0.558 0.066 8.45 1, 47 Umbi <0.0001 0.499 0.395 0.057 6.91 1, 48 <0.0001 0.548 0.495 0.066 7.55 1, 47

101 Spotted seal subadults Spotted seal adults Body condition metric p R2 ß SE t df p R2 ß SE t df

Pelvis <0.0001 0.489 0.488 0.072 6.77 1, 48 <0.0001 0.706 0.727 0.068 10.63 1, 47 Ankle <0.0001 0.416 0.456 0.078 5.85 1, 48 <0.0001 0.387 0.578 0.106 5.45 1, 47 Blubber depth D1 <0.0001 0.588 4.945 0.598 8.27 1, 48 <0.0001 0.645 6.994 0.756 9.25 1, 47 L1 <0.0001 0.322 5.203 1.090 4.77 1, 48 <0.0001 0.443 7.111 1.164 6.11 1, 47 D2 <0.0001 0.780 6.052 0.464 13.03 1, 48 <0.0001 0.852 6.610 0.402 16.46 1, 47 L2 <0.0001 0.764 4.741 0.381 12.45 1, 48 <0.0001 0.862 5.287 0.308 17.17 1, 47 D3 <0.0001 0.804 5.869 0.419 14.02 1, 48 <0.0001 0.885 5.767 0.304 18.98 1, 47 L3 <0.0001 0.838 5.963 0.378 15.76 1, 48 <0.0001 0.932 6.483 0.256 25.31 1, 47 D4 <0.0001 0.829 6.071 0.399 15.23 1, 48 <0.0001 0.935 6.237 0.239 26.10 1, 47 L4 <0.0001 0.864 6.085 0.348 17.49 1, 48 <0.0001 0.926 6.278 0.258 24.29 1, 47 D5 <0.0001 0.887 6.831 0.355 19.25 1, 48 <0.0001 0.898 7.050 0.346 20.38 1, 47 L5 <0.0001 0.803 6.587 0.472 13.97 1, 48 <0.0001 0.870 7.506 0.424 17.71 1, 47 D6 <0.0001 0.733 11.591 1.009 11.48 1, 48 <0.0001 0.743 7.834 0.673 11.65 1, 47 L6 <0.0001 0.507 9.996 1.422 7.03 1, 48 <0.0001 0.602 11.931 1.414 8.44 1, 47 Sternum <0.0001 0.768 6.664 0.529 12.60 1, 48 <0.0001 0.899 7.477 0.365 20.50 1, 47

102 Table 4.3. Results of simple linear regressions between percent blubber mass and different body condition metrics for two subadult and two adult ringed seals. Separate regressions were performed for each metric for each age class. R2 values highlighted in green indicate an R2 greater than 0.8 and values highlighted in orange, a value greater than 0.6. Where multiple locations are significant, the most significant R2 value is bolded. Data displayed in gray have a p-value greater than 0.05 and are not significant. Results for width and width/SL were only obtained for the female adult ringed seal at UCSC. Dashes denote no data collected. Ringed seal subadults Ringed seal adults Body condition metric p R2 ß SE t df p R2 ß SE t df Mass/SL 0.0073 0.210 56.967 19.841 2.87 1, 31 0.0119 0.172 76.973 28.947 2.66 1, 34 LMD index Most significant site <0.0001 0.713 2.889 0.329 8.78 1,31 <0.0001 0.743 5.175 0.522 9.92 1, 34 D3 <0.0001 0.574 2.677 0.414 6.46 1, 31 <0.0001 0.529 4.344 0.703 6.18 1, 34 Condition index

(girth/SL) Neck 0.2522 0.042 7.349 6.298 1.17 1, 31 0.1434 0.062 22.786 15.212 1.50 1, 34 Axilla 0.059 0.110 11.298 5.763 1.96 1, 31 0.9869 8.02e-6 0.411 24.898 0.02 1, 34 Mid 0.0034 0.246 16.460 5.182 3.18 1, 31 0.1010 0.077 25.523 15.140 1.69 1, 34 Umbi 0.0009 0.305 19.980 5.412 3.69 1, 31 0.0410 0.117 30.350 14.290 2.12 1, 34 Pelvis 0.0002 0.357 27.109 6.530 4.15 1, 31 0.0013 0.265 47.878 13.683 3.50 1, 34 Ankle 0.0069 0.213 22.810 7.876 2.90 1, 31 0.0017 0.254 48.416 14.213 3.41 1, 34 Girth Neck 0.7504 0.003 0.027 0.084 0.32 1, 33 0.4971 0.014 0.098 0.143 0.69 1, 34 Axilla 0.1194 0.072 0.173 0.108 1.60 1, 33 0.1200 0.070 -0.35 0.219 -1.59 1, 34 Mid 0.0014 0.270 0.296 0.085 3.50 1,33 0.4858 0.014 0.113 0.161 0.70 1, 34 Umbi 0.0008 0.291 0.308 0.083 3.68 1, 33 0.2339 0.041 0.171 0.141 1.21 1, 34

103 Ringed seal subadults Ringed seal adults Body condition metric p R2 ß SE t df p R2 ß SE t df

Pelvis 0.0014 0.270 0.340 0.097 3.50 1, 33 0.0205 0.148 0.363 0.149 2.43 1, 34 Ankle 0.0949 0.082 0.171 0.010 1.72 1, 33 0.0155 0.160 0.401 0.157 2.55 1, 34 Blubber depth D1 <0.0001 0.419 4.053 0.832 4.87 1, 33 0.0066 0.203 4.253 1.467 2.90 1, 33 L1 0.0401 0.122 2.867 1.342 2.14 1, 33 0.0003 0.326 4.630 1.142 4.05 1, 34 D2 <0.0001 0.725 5.324 0.571 9.33 1, 33 <0.0001 0.361 7.602 1.733 4.39 1, 34 L2 <0.0001 0.679 6.226 0.745 8.36 1, 33 <0.0001 0.480 5.468 0.976 5.60 1, 34 D3 <0.0001 0.653 4.744 0.602 7.89 1, 33 <0.0001 0.529 6.700 1.084 6.18 1, 34 L3 <0.0001 0.462 5.227 0.982 5.32 1, 33 <0.0001 0.745 6.349 0.636 9.98 1, 34 D4 <0.0001 0.753 4.750 0.474 10.02 1, 33 <0.0001 0.647 6.970 0.883 7.90 1, 34 L4 <0.0001 0.714 6.598 0.727 9.08 1, 33 <0.0001 0.722 8.523 0.907 9.39 1, 34 D5 <0.0001 0.579 4.747 0.715 6.64 1, 32 <0.0001 0.502 6.071 1.036 5.86 1, 34 L5 <0.0001 0.590 6.193 0.898 6.90 1, 33 <0.0001 0.748 8.163 0.813 10.04 1, 34 D6 0.0030 0.243 5.851 1.825 3.21 1, 32 <0.0001 0.459 6.177 1.151 5.37 1, 34 L6 0.7691 0.003 -0.45 1.525 -0.30 1, 32 <0.0001 0.467 6.169 1.130 5.46 1, 34 Sternum <0.0001 0.498 5.025 0.879 5.72 1, 33 <0.0001 0.590 7.475 1.068 7.00 1, 34 Width Neck ------0.9216 0.001 0.106 1.047 0.10 1, 8 Axilla ------0.2659 0.152 -1.66 1.384 -1.20 1, 8 Mid ------0.2558 0.158 -0.53 0.430 -1.22 1, 8

104 Ringed seal subadults Ringed seal adults Body condition metric p R2 ß SE t df p R2 ß SE t df

Umbi ------0.2073 0.190 -2.13 1.554 -1.37 1, 8 Pelvis ------0.2647 0.152 -2.76 2.302 -2.10 1, 8 Ankle ------0.4153 0.084 1.271 1.479 0.86 1, 8 Width/SL Neck ------0.2753 0.146 122.24 104.40 1.17 1, 8 Axilla ------0.4381 0.077 158.64 194.43 0.82 1, 8 Mid ------0.1484 0.242 257.49 160.99 1.60 1, 8 Umbi ------0.6057 0.035 121.02 225.26 0.54 1, 8 Pelvis ------0.4015 0.089 167.83 189.44 0.89 1, 8 Ankle ------0.1446 0.246 158.93 98.30 1.62 1, 8

105 Table 4.4. Results of simple linear regressions between percent blubber mass and different body condition metrics for one subadult bearded seal. Separate regressions were performed for each metric. R2 values highlighted in green indicate an R2 greater than 0.8 and values highlighted in orange, a value greater than 0.6. Where multiple locations are significant, the most significant R2 value is bolded. Data displayed in gray have a p-value greater than 0.05 and are not significant. Dashes denote an insufficient amount of data for analysis. Bearded seal subadult Body condition metric p R2 ß SE t df Mass/SL 0.03238 0.042 10.211 10.127 1.01 1, 23 LMD index <0.0001 0.849 4.964 0.436 11.38 1, 23 Condition index

(girth/SL) Neck 0.5619 0.015 9.821 16.690 0.59 1, 23 Axilla 0.3042 0.046 11.200 10.656 1.05 1, 23 Mid 0.0124 0.243 23.026 8.481 2.71 1, 23 Umbi 0.1093 0.108 19.390 11.640 1.67 1, 23 Pelvis 0.7724 0.004 -3.08 10.526 -0.29 1, 23 Ankle 0.9751 0.00004 0.395 12.499 0.03 1, 23 Girth Neck 0.4304 0.027 -0.07 0.083 -0.80 1, 23 Axilla 0.4969 0.020 -0.06 0.084 -0.69 1, 23 Mid 0.1641 0.082 0.121 0.084 1.44 1, 23 Umbi 0.8937 0.0007 -0.01 0.094 -0.14 1, 23 Pelvis 0.1020 0.112 -0.10 0.056 -1.70 1, 23 Ankle 0.0744 0.132 -0.17 0.089 -1.87 1, 23

106 Bearded seal subadult Body condition metric p R2 ß SE t df

Blubber depth D1 0.0089 0.262 2.281 0.798 2.86 1, 23 L1 0.4758 0.022 0.927 1.278 0.72 1, 23 D2 <0.0001 0.585 5.022 0.882 5.69 1, 23 L2 0.006 0.285 2.236 0.739 3.03 1, 23 D3 <0.0001 0.814 5.217 0.520 10.04 1, 23 L3 <0.0001 0.550 5.130 0.968 5.30 1, 23 D4 <0.0001 0.571 4.677 0.846 5.53 1, 23 L4 <0.0001 0.490 6.176 1.313 4.70 1, 23 D5 0.0004 0.426 4.452 1.077 4.13 1, 23 L5 0.0019 0.347 2.824 0.807 3.50 1, 23 D6 0.0331 0.183 2.997 1.322 2.27 1, 23 L6 0.0417 0.168 3.127 1.450 2.16 1, 23 Sternum 0.0003 0.444 4.606 1.076 4.28 1, 23 Width Neck 0.02 0.469 0.347 0.123 2.82 1, 9 Axilla 0.003 0.642 0.249 0.062 4.02 1, 9 Mid 0.1358 0.237 0.522 0.294 1.78 1, 9 Umbi 0.1186 0.249 0.381 0.221 1.73 1, 9 Pelvis 0.0275 0.434 0.308 0.117 2.63 1, 9

107 Bearded seal subadult Body condition metric p R2 ß SE t df

Ankle 0.2202 0.162 0.279 0.212 1.32 1, 9 Width/SL Neck 0.3443 0.099 38.14 38.214 1.00 1, 9 Axilla 0.0433 0.380 62.083 26.421 2.35 1, 9 Mid ------Umbi 0.3010 0.118 -41.5 37.823 -1.10 1, 9 Pelvis 0.2262 0.158 47.077 36.239 1.30 1, 9 Ankle 0.9458 0.0005 -2.934 41.976 -0.07 1, 9

108

Figure 4.1. Spotted seal body condition metric correlations with percent blubber mass for mass/SL, LMD index, condition index, girth, and blubber depth. Subadults (n=2) are in the left column represented by open circles. Adults (n=2) are in the right column represented by closed circles. All p-values were the same at <0.0001. R2 values and equations are reported in the lower right-hand corner.

109

Figure 4.2. Ringed seal body condition metric correlations with percent blubber mass for mass/SL, LMD index, condition index, girth, and blubber depth. Subadults (n=2) are in the left column represented by open circles. Adults (n=2) are in the right column represented by closed circles. R2, p-values and equations are reported in the lower right-hand corner.

110

Figure 4.3. Bearded seal body condition metric correlations with percent blubber mass for mass/SL, LMD index, condition index, blubber depth, width, and width/SL. R2, p-values, and equations are reported in the lower right-hand corner.

111 Chapter 5: General Discussion

Climate change is causing Arctic sea ice to melt at unprecedented rates, causing rapid declines in both its thickness and extent (Grebmeier et al., 2006; Meier et al., 2014). Further, sea ice is breaking up earlier each year and open water seasons are becoming longer (Rigor and

Wallace, 2004), reducing available habitat for Arctic seals and impacting the ecosystems that sustain them. Good body condition is vital for these species to cope with alterations in their habitat, but insufficient haul-out substrate (i.e. sea ice) and changes in prey resources may prevent seals from acquiring adequate energy reserves and/or cause them to deplete these reserves too quickly.

Because of expected changes in the Arctic and associated predicted declines in ice seal populations, several ringed, bearded, and spotted seal populations have been listed as threatened under the United States Endangered Species Act (NOAA, 2010; 2018). This is concerning for both ice seals and Arctic ecosystems, as ice seals are indicators of marine ecosystem health and may act as sentinel species of serious habitat changes (Moore, 2008). Over the past decade, spotted, ringed, and bearded seal populations in the north Pacific have been impacted by prolonged UMEs, during which large numbers of seals have stranded. Each UME has been defined by a suite of different physiological symptoms, but the current UME is characterized by seals in poor body condition (NOAA, 2020). Mass marine mammal die-offs and UMEs happening worldwide are indicators that ocean ecosystems are changing dramatically and the

Arctic is no exception (Grebmeier et al., 2006; Kovacs et al., 2011).

Subsistence hunters in Arctic and sub-Arctic regions have noticed that the rate of catching seals in poor body condition has accelerated in past decades (Ferguson et al., 2017;

112 Sheffield, 2020). Typically, good body condition and high blubber content causes seals to float after death (Webb et al., 1998) making them easier to hunt and harvest. More recently, subsistence-caught seals have been appearing sickly with thinner blubber layers than historically documented (Ferguson et al., 2017) and in poorer body condition (Savage, 2018). Poor body condition can indicate lack of prey resources or poor prey health, making ice seals more susceptible to illness and disease (Harvell et al., 1999; Kovacs et al., 2011). These seals provide critical food resources to remote Alaskan communities that do not have easy access to a consistent flow of provisions, and therefore, the long-term viability of ice seal populations is of both ecosystem and human importance.

This thesis provides one of the first fine-scale, repeated-measures evaluations of body condition for Arctic seals. Using direct morphometrics, body mass, and blubber ultrasound measurements, I was able to determine the most accurate truncated cones method for body composition analysis in spotted, ringed, and bearded seals. Subsequently, I used longitudinal data for individual seals in long-term human care to provide insight into the drivers of seasonal patterns in body condition for these species. Finally, using these year-round measurements to calculate percent blubber mass, I was able to determine the best simple metrics for estimating body condition by species—indices which can be used by field biologists and management agencies to evaluate trends in population health.

Although the findings presented here are constrained by inherently small sample sizes, they still represent an importance advancement in our understanding of Arctic seal physiology.

Moving forward, it would be beneficial to provide better representation of each species and age class across seasons to validate the patterns presented here; however, this will be challenging due to difficulties associated with accessing ice seals.

113 While this thesis provides fine-scale body condition data and best practices for captive individuals, there is much to be expanded upon for future research. A larger sample of aerial images from UAVs containing free-ranging ice seals in optimal positioning are needed to investigate optimal body condition metrics for these three species. Here, I provided preliminary options for UAV body condition metrics for the bearded seal using available data. A more robust, directed study using individuals with known body condition determined using the best possible methods could be compared to estimates derived from calibrated UAV images to expand upon these data. There is great potential for the creation of novel methods to safely and accurately evaluate body condition using UAVs.

Ultimately, this research contributes to our understanding of routine changes in body condition for spotted, ringed, and bearded seals and provides recommendations for field sampling efforts, both of which will improve our ability to monitor the health of wild populations and hopefully inform decision making.

114 References

Aas-Hansen, Ø., Folkow, L. P. and Blix, A. S. (2000). Panting in reindeer (Rangifer tarandus). Am. J. Physiol. - Regul. Integr. Comp. Physiol. 279, 1190–1195. Adamczak, S. K., Pabst, A., McLellan, W. A. and Thorne, L. H. (2019). Using 3D Models to Improve Estimates of Marine Mammal Size and External Morphology. Front. Mar. Sci. 6, 1–12. Aguilar, A. and Borrell, A. (1990). Patterns of Lipid Content and Stratification in the Blubber of Fin Whales (Balaenoptera physalus). J. Mammal. 71, 544–554. Allan, B. M., Ierodiaconou, D., Hoskins, A. J. and Arnould, J. P. Y. (2019). A Rapid UAV Method for Assessing Body Condition in Fur Seals. Drones 3, 24. Andersen, M., Hjelset, A. M., Gjertz, I., Lydersen, C. and Gulliksen, B. (1999). Growth, age at sexual maturity and condition in bearded seals (Erignathus barbatus) from Svalbard, Norway. Polar Biol. 21, 179–185. Arnould, J. P. Y., Boyd, I. L. and Speakman, J. R. (1996). Measuring the Body Composition of Antarctic Fur Seals (Arctocephalus gazella): Validation of Hydrogen Isotope Dilution. Physiol. Zool. 69, 93–116. Arrigo, K. R., van Dijken, G. and Pabi, S. (2008). Impact of a shrinking Arctic ice cover on marine primary production. Geophys. Res. Lett. 35, 1–6. Ashwell-Erickson, S., Fay, F. H., Elsner, R. and Wartzok, D. (1986). Metabolic and hormonal correlates of molting and regeneration of pelage in Alaskan harbor and spotted seals ( Phoca vitulina and Phoca largha ). Can. J. Zool. 64, 1086–1094. Atkinson, S. N. and Ramsay, M. A. (1995). The Effects of Prolonged Fasting of the Body Composition and Reproductive Success of Female Polar Bears (Ursus maritimus). Funct. Ecol. 9, 559. Atkinson, S. N., Nelson, R. A. and Ramsay, M. A. (1996). Changes in the Body Composition of Fasting Polar Bears ( Ursus maritimus ): The Effect of Relative Fatness on Protein Conservation. Physiol. Zool. 69, 304–316. Beck, G. G. and Smith, T. G. (1995). Distribution of blubber in the northwest Atlantic harp seal, Phoca groenlandica . Can. J. Zool. 73, 1991–1998. Beck, C. G., Smith, T. C. and Hammill, M. (1993). Evaluation of Body Condition in the Northwest Atlantic Harp Seal (Phoca groenlandica). Can. J. Fish. Aquat. Sci. 50, 1372– 1381. Beck, C. A., Bowen, W. D. and Iverson, S. J. (2000). Seasonal changes in buoyancy and diving behaviour of adult grey seals. J. Exp. Biol. 203, 2323–2330. Beck, C., Bowen, W. and Iverson, S. (2003). Sex differences in the seasonal patterns of energy storage and expenditure in a phocid seal. J. Anim. Ecol. 72, 280–291. Bell, C. M., Hindell, M. A. and Burton, H. R. (1997). Estimation of body mass in the southern elephant seal, Mirounga leonina, by photogrammetry and morphometrics. Mar. Mammal Sci. 13, 669–682. Benjaminsen, T. (1973). Age determination and the growth and age distribution from cementum growth layers of bearded seals at Svalbard. FiskDir.Skr.Ser.HavUnders 16, 159–170. Blix, A. S. (2016). Adaptations to polar life in mammals and birds. J. Exp. Biol. 219, 1093–1105. Boily, P. (1996). Metabolic of captive and hormonal changes gray seals (Halichoerus grypus) during the molt mvwud. 1051–1058. Boness, D. J. and Bowen, W. D. (1996). The Evolution of Maternal Care in Pinnipeds.

115 Bioscience 46, 645–654. Boveng, P. L., Bengtson, J. L., Buckley, T. W., Cameron, M. F., Dahle, S. P., Kelly, B. P., Megrey, B. A., Overland, J. E. and Williamson, N. J. (2009a). Status review of the spotted seal (Phoca largha). U.S. Dep. Commer. NOAA Tech. Memo. NMFS-AFSC-200 153. Boveng, P. L., Bengtson, J. L., Buckley, T. W., Cameron, M. F., Dahle, S. P., Kelly, B. P., Megrey, B. a, Overland, J. E. and Williamson, N. J. (2009b). Status review of the spotted seal (Phoca largha). NOAA Tech. Memo. NMFS-AFSC 1–153. Bowen, W. D. (1997). Role of marine mammals in aquatic ecosystems. Mar. Ecol. Prog. Ser. 158, 267–274. Bowen, W. D. and Iverson, S. J. (1998). Estimation of Total Body Water in Pinnipeds Using Hydrogen‐Isotope Dilution. Physiol. Zool. 71, 329–332. Bowen, W. D., Oftedal, O. T. and Boness, D. J. (1985). Birth to weaning in 4 days: remarkable growth in the hooded seal, Cystophora cristata. Can. J. Zool. 63, 2841–2846. Bowen, W. D., Boness, D. J. and Iverson, S. J. (1998). Estimation of Total Body Water in Harbor Seals: How Useful Is Bioelectrical Impedance Analysis? Mar. Mammal Sci. 14, 765–777. Bowen, W. D., Beck, C. A. and Iverson, S. J. (1999). Bioelectrical impedance analysis as a means of estimating total body water in grey seals. Can. J. Zool. 77, 418–422. Boyd, I. L. (1984). The relationship between body condition and the timing of implantation in pregnant Grey seals (Halichoerus grypus). J. Zool. 203, 113–123. Boyd, I. L. (2000). State-dependent fertility in pinnipeds: Contrasting capital and income breeders. Funct. Ecol. 14, 623–630. Boyd, I., Arnbom, T. and Fedak, M. (1993). Water Flux, Body Composition , and Metabolic Rate during Molt in Female Southern Elephat Seals (Mirounga leonina). Physiol. Zool. 66, 43–60. Bradshaw, W. E. and Holzapfel, C. M. (2007). Evolution of Animal Photoperiodism. Annu. Rev. Ecol. Evol. Syst. 38, 1–25. Bradshaw, W. E. and Holzapfel, C. M. (2008). Genetic response to rapid climate change: It’s seasonal timing that matters. Mol. Ecol. 17, 157–166. Burek, K. A., Gulland, F. M. D. and O’Hara, T. M. (2008). Effects of Climate Change on Arctic Marine Mammal Health. Ecol. Appl. 18, S126–S134. Burns, J. J. (1970). Remarks on the Distribution and Natural History of Pagophilic Pinnipeds in the Bering and Chukchi Seas. J. Mammal. 51, 445. Burns, J. J. (2002). Harbor seal and spotted seal, Phoca vitulina and Phoca largha. In Encyclopedia of Marine Mammals (ed. Perrin, W. F.), Würsig, B.), and Thewissen, J. G. M.), pp. 552–560. San Diego: Academic Press. Burns, J. J. and Frost, K. J. (1979). Natural history and ecology of the bearded seal, Erignathus barbatus. Cameron, M., Bengtson, J. L., Boveng, P., Jansen, J. K., Kelly, B. P., Dahle, S. P., Logerwell, E. A., Overland, J. E., Sabine, C. L., Waring, G. T., et al. (2010). Status review of the bearded seal (Erignathus barbatus). U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-211. Castrillon, J. and Bengtson Nash, S. (2020). Evaluating cetacean body condition; a review of traditional approaches and new developments. Ecol. Evol. 1–19. Chabot, D. and Stenson, G. B. (2002). Growth and seasonal fluctuations in size and condition of male Northwest Atlantic harp seals Phoca groenlandica: An analysis using sequential

116 growth curves. Mar. Ecol. Prog. Ser. 227, 25–42. Chambellant, M., Stirling, I. and Ferguson, S. H. (2013). Temporal variation in western Hudson Bay ringed seal Phoca hispida diet in relation to environment. Mar. Ecol. Prog. Ser. 481, 269–287. Champagne, C. D., Crocker, D. E., Fowler, M. A. and Houser, D. S. (2012). Fasting Physiology of the Pinnipeds. In Comparative Physiology of Fasting, Starvation, and Food Limitation, pp. 309–336. Christiansen, J. S., Mecklenburg, C. W. and Karamushko, O. V. (2014). Arctic marine fishes and their fisheries in light of global change. Glob. Chang. Biol. 20, 352–359. Christiansen, F., Dujon, A. M., Sprogis, K. R., Arnould, J. P. Y. and Bejder, L. (2016). Noninvasive unmanned aerial vehicle provides estimates of the energetic cost of reproduction in humpback whales. Ecosphere 7, 1–18. Christiansen, F., Sironi, M., Moore, M. J., Di Martino, M., Ricciardi, M., Warick, H. A. and Uhart, M. M. (2019). Estimating body mass of free-living whales using aerial photogrammetry and 3D volumetrics. Methods Ecol. Evol. 00, 1–11. Christiansen, F., Sprogis, K. R., Gross, J., Castrillon, J., Warick, H. A., Leunissen, E. and Bengtson Nash, S. (2020). Variation in outer blubber lipid concentration does not reflect morphological body condition in humpback whales. J. Exp. Biol. 223, jeb213769. Comiso, J. C. (2002). A rapidly declining perennial sea ice cover in the Arctic. Geophys. Res. Lett. 29, 17-1-17–4. Committee on Marine Mammals (1966-67) (1967). Standard Measurements of Seals. J. Mammal. 48, 459–462. Costa, D. P., Le Boeuf, B. J., Huntley, A. C. and Ortiz, C. L. (1986). The energetics of lactation in the northern elephant seal. J. Zool. 209, 21–33. Crocker, D., Williams, J., Costa, D. P. and Le Boeuf, B. J. (2001). Maternal Traits and Reproductive Effort in Northern Elephant Seals. Ecology 82, 3541–3555. DeJours, P. (1989). From Comparative Physiology of Respiration to Several Problems of Environmental Adaptations and Evolution. J. Physiol. 1–19. Durban, J. W., Moore, M. J., Chiang, G., Hickmott, L. S., Bocconcelli, A., Howes, G., Bahamonde, P. A., Perryman, W. L. and LeRoi, D. J. (2016). Photogrammetry of blue whales with an unmanned hexacopter. Mar. Mammal Sci. 32, 1510–1515. Duyke, A. L. Von, Douglas, D. C., Herreman, J. and Morris, A. W. (2020). Ringed seal (Pusa hispida) spatial use, dives, and haul-out behavior in the Beaufort, Chukchi , and Bering Seas ( 2011-2016 ). Ecol. Evol. 00, 1–22. Fearnbach, H., Durban, J. W., Ellifrit, D. K. and Balcomb, K. C. (2018). Using aerial photogrammetry to detect changes in body condition of endangered southern resident killer whales. Endanger. Species Res. 35, 175–180. Fedak, M. A. and Anderson, S. S. (1982). The energetics of lactation : Accurate measurements from a large wild mammal , the grey seal ( Halichoerus. Zool. Soc. London 473–479. Fedak, M. A., Arnbom, T. and Boyd, I. L. (1996). The Relation between the Size of Southern Elephant Seal Mothers , the Growth of Their Pups , and the Use of Maternal Energy , Fat , and Protein during Lactation. Physiol. Zool. 69, 887–911. Fedorov, A., Beichel, R., Kalpathy-Cramer, J., Finet, J., Jennings, D., Fennessy, F., Sonka, M., Buatti, J., Aylward, Stephen, Miller, J. V., Pieper, S., et al. (2012). 3D Slicer as an Image Computing Platform for the Quantitative Imaging Network. Genet. Improv. F. Crop. 30, 1323–1341.

117 Ferguson, S. H., Young, B. G., Yurkowski, D. J., Anderson, R., Willing, C. and Nielsen, O. (2017). Demographic, ecological, and physiological responses of ringed seals to an abrupt decline in sea ice availability. PeerJ 2017, 1–17. Field, I. C., Bradshaw, C. J. A., Burton, H. R. and Hindell, M. A. (2007). Differential resource allocation strategies in juvenile elephant seals in the highly seasonal Southern Ocean. Mar. Ecol. Prog. Ser. 331, 281–290. Fuller, A., Hetem, R. S., Dawson, T., Mitchell, D., Helmuth, B. and Maloney, S. K. (2010). Physiological Mechanisms in Coping with Climate Change. Physiol. Biochem. Zool. 83, 713–720. Gales, N. J. and Burton, H. R. (1987). Ultrasonic Measurement of Blubber Thickness of the Southern Elephant Seal, Mirounga leonina (Linn.). Aust. J. Zool. 35, 207–217. Gales, R. and Renouf, D. (1994a). Assessment of body condition of harp seals. Polar Biol. 14, 381–387. Gales, R. and Renouf, D. (1994b). Use of Bioelectrical Impedance Analysis to Assess Body Composition of Seals. Mar. Mammal Sci. 10, 1–12. Gales, R., Renouf, D. and Noseworthy, E. (1994). Body composition of harp seals. Can. J. Zool. 72, 545–551. Gili, C., Mo, G., Ponte, G. and Ferrando, P. (2000). Do Photoperiod and Temperature Influence the Moult Cycle of Phoca vitulina in Captivity ? Mar. Mammal Sci. 16, 570–577. Gjertz, I., Kovacs, K. M., Lydersen, C. and Wiig (2000). Movements and diving of bearded seal (Erignathus barbatus) mothers and pups during lactation and post-weaning. Polar Biol. 23, 559–566. Grebmeier, J. M., Overland, J. E., Moore, S. E., Farley, E. V, Carmack, E. C., Cooper, L. W., Frey, K. E., Helle, J. H., McLaughlin, F. A. and McNutt, S. L. (2006). A Major Ecosystem Shift in the Northern Bering Sea. Science (80-. ). 311, 1461–1464. Hall, A. J. and McConnell, B. J. (2007). Measuring changes in juvenile gray seal body composition. Mar. Mammal Sci. 23, 650–665. Hammill, M. O., Lydersen, C., Ryg, M. and Smith, T. G. (1991). Lactation in the ringed seal (Phoca hispida). Can. J. Fish. Aquat. Sci. 48, 2471–2476. Hammill, M. O., Kingsley, M. C. S., Beck, G. G. and Smith, T. G. (2008). Growth and condition in the Northwest Atlantic harp seal. Can. J. Fish. Aquat. Sci. 52, 478–488. Harvell, C. D., Kim, K., Burkholder, J. M., Colwell, R. R., Epstein, P. R., Grimes, D. J., Hofmann, E. E., Lipp, E. K., Osterhaus, A. D. M. E., Overstreet, R. M., et al. (1999). Emerging marine diseases - Climate links and anthropogenic factors. Science (80-. ). 285, 1505–1510. Harwood, L. A., Smith, T. G. and Melling, H. (2000). Variation in reproduction and body condition of the ringed seal (Phoca hispida) in western Prince Albert Sound, NT, Canada, as assessed through a harvest-based sampling program. Arctic 53, 422–431. Harwood, L. A., Smith, T. G., Melling, H., Alikamik, J., Kingsley, M. C. S., Harwood, L. A., Smith, T. G., Melling, H., Alikamik, J. and Kingsley, M. C. S. (2012). Ringed Seals and Sea Ice in Canada’s Western Arctic: Harvest-Based Monitoring 1992-2011. Arctic 65, 377–390. Harwood, L. A., Smith, T. G., George, J. C., Sandstrom, S. J., Walkusz, W. and Divoky, G. J. (2015). Change in the Beaufort Sea ecosystem: Diverging trends in body condition and/or production in five marine vertebrate species. Prog. Oceanogr. 136, 263–273. Harwood, L. A., Smith, T. G., Alikamik, J., Lea, E., Stirling, I., Wright, H., Melling, H. and

118 Zhu, X. (2020). Long-term, harvest-based monitoring of ringed seal body condition and reproduction in Canada’s Western Arctic: an update through 2019. Arctic in press, 206– 220. Hedd, A., Gales, R. and Renouf, D. (1997). Inter-annual consistency in the fluctuating energy requirements of captive harp seals Phoca groenlandica. Polar Biol. 18, 311–318. Heptner, L. V. G., Chapskii, K. K., Arsen’ev, V. A. and Sokolov, V. T. (1976). Common seal, larga, Phoca (Phoca) vitulina Linnaeus, 1758. In Mammals of the Soviet Union (ed. Heptner, L. V. G.), Naumov, N. P.), and Mead, J.), pp. 307–369. Moscow, Russia: Vysshaya Shkola Publishers. Hetem, R. S., Fuller, A., Maloney, S. K. and Mitchell, D. (2014). Responses of large mammals to climate change. Temperature 1, 115–127. Hodgson, J. C., Holman, D., Terauds, A., Koh, L. P. and Goldsworthy, S. D. (2020). Rapid condition monitoring of an endangered marine vertebrate using precise, non-invasive morphometrics. Biol. Conserv. 242, 108402. Hoegh-Guldberg, O. and Bruno, J. F. (2010). The impact of climate change on the world’s marine ecosystems. Science (80-. ). 328, 1523–1528. Huntington, H. P., Nelson, M. and Quakenbush, L. T. (2016). Traditional Knowledge Regarding Ringed Seals, Bearded Seals, Walrus, and Bowhead Whales near Kivalina, Alaska. Final report to the Eskimo Walrus Commission, the Ice Seal Committee, and the Bureau of Ocean Energy Management for contract #M13PC00015. 8pp. Ice Seal Committee (2016). The Subsistence Harvest of Ice Seals in Alaska — a Compilation of Existing Information, 1960 – 2012. Ice Seal Committee (2019). The subsistence harvest of ice seals in Alaska - a compliation of existing information, 1960-2017. Iverson, S. J. and Koopman, H. N. (2018). Blubber. In Encyclopedia of Marine Mammals (ed. Würsig, B.), Thewissen, J. G. M.), and Kovacs, K. M.), pp. 107–110. New York, NY: Academic Press. Johannessen, O. M., Shalina, E. V. and Miles, M. W. (1999). Satellite evidence for an Arctic sea ice cover in transformation. Science (80-. ). 286, 1937–1939. Kastelein, R. A., Helder-Hoek, L., Jennings, N., van Kester, R. and Huisman, R. (2019). Reduction in Body Mass and Blubber Thickness of Harbor Porpoises (Phocoena phocoena) Due to Near-Fasting for 24 Hours in Four Seasons. Aquat. Mamm. 45, 37–47. Kelly, B. P., Bengston, J. L., Boveng, P. L., Cameronm, M. F., Dahle, S. P., Jansen, J. K., Logerwell, E. A., Overland, J. E., Sabine, L. C. and Wilder, J. M. (2010). Status Review of the Ringed Seal (Phoca hispida). NOAA Tech. Memo. NMFS-AFSC-212. Kenyon, K. W. (1981). Monk seals. In Handbook of Marine Mammals, pp. 195–220. London: Academic Press. Koopman, H. N. (1998). Topographical Distribution of the Blubber of Harbor Porpoises (Phocoena phocoena). J. Mammal. 79, 260–270. Koopman, H. N., Pabst, D. A., McLellan, W. A., Dillaman, R. M. and Read, A. J. (2002). Changes in Blubber Distribution and Morphology Associated with Starvation in the Harbor Porpoise ( Phocoena phocoena ): Evidence for Regional Differences in Blubber Structure and Function. Physiol. Biochem. Zool. 75, 498–512. Kovacs, K. M. (2017). Bearded Seal. In Encyclopedia of Marine Mammals, pp. 83–86. Elsevier Inc. Kovacs, K. M. and Lavigne, D. M. (1986). Maternal Investment and Neonatal Growth in

119 Phocid Seals. J. Anim. Ecol. 55, 1035–1051. Kovacs, K. M., Lydersen, C. and Gjertz, I. (1996). Birth-Site Characteristics and Prenatal Molting in Bearded Seals (Erignathus barbatus). J. Mammal. 77, 1085–1091. Kovacs, K. M., Lydersen, C., Overland, J. E. and Moore, S. E. (2011). Impacts of changing sea-ice conditions on Arctic marine mammals. Mar. Biodivers. 41, 181–194. Krause, D. J., Hinke, J. T., Perryman, W. L., Goebel, M. E. and LeRoi, D. J. (2017). An accurate and adaptable photogrammetric approach for estimating the mass and body condition of pinnipeds using an unmanned aerial system. PLoS One 12, 1–20. Ladds, M. A., Slip, D. J. and Harcourt, R. G. (2017). Intrinsic and extrinsic influences on standard metabolic rates of three species of Australian otariid. Conserv. Physiol. 5, 1–14. Laidre, K. L., Stirling, I., Lowry, L. F., Wiig, Ø., Heide-Jørgensen, M. P. and Ferguson, S. H. (2008). Quanifying the sensitivity of Arctic marine mammals to climate-induced habitat change. Ecol. Appl. 18, S97–S125. Laidre, K. L., Stern, H., Kovacs, K. M., Lowry, L., Moore, S. E., Regehr, E. V., Ferguson, S. H., Wiig, Ø., Boveng, P., Angliss, R. P., et al. (2015). Arctic marine mammal population status, sea ice habitat loss, and conservation recommendations for the 21st century. Conserv. Biol. 29, 724–737. Le Boeuf, B. J. (1972). Sexual Behavior in the Northern Elephant Seal Mirounga angustirostris. Behavior 41, 1–26. Levinsky, I., Skov, F., Svenning, J. C. and Rahbek, C. (2007). Potential impacts of climate change on the distributions and diversity patterns of European mammals. Biodivers. Conserv. 16, 3803–3816. Ling, J. K. (1970). Pelage and Molting in Wild Mammals with Special Reference to Aquatic Forms. Q. Rev. Biol. 45, 16–54. Ling, J. K. and Bryden, M. M. (1981). Southern elephant seal (Mirounga leonina) Linnaeus, 1758. In Handbook of Marine Mammals (ed. Ridgway, S. H.) and Harrison, R. J.), pp. 297– 327. London: Academic Press. Liwanag, H. E. (2008). Fur versus Blubber: A comparative look at marine mammal insulation and its metabolic and behavioral consequences. Liwanag, H. E. M., Berta, A., Costa, D. P., Abney, M. and Williams, T. M. (2012). Morphological and thermal properties of mammalian insulation. Biol. J. Linn. Soc. 107, 774–787. Lockyer, C. (1986). Body Fat Condition in Northeast Atlantic Fin Whales, Balaenoptera physalus, and Its Relationship with Reproduction and Food Resource. Can. J. Fish. Aquat. Sci. 43, 142–147. Lockyer, C. H., McConnell, L. C. and Waters, T. D. (1985). Body condition in terms of anatomical and biochemical assessment of body fat in North Atlantic fin and sei whales. Can. J. Zool. 63, 2328–2338. Lovegrove, B. G. (2005). Seasonal thermoregulatory responses in mammals. J. Comp. Physiol. B Biochem. Syst. Environ. Physiol. 175, 231–247. Lowry, L. F., Burkanov, V., Frost, K. J., Simpkins, M. A., Davis, R., DeMaster, D. P., Suydamn, R. and Springer, A. (2000). Habitat use and habitat selection by spotted seals (Phoca largha) in the Bering Sea. Can. J. Fish. Aquat. Sci. VO - 47 78, 1959–1971. Lydersen, C. and Kovacs, K. M. (1999). Behaviour and energetics of ice-breeding, North Atlantic phocid seals during the lactation period. Mar. Ecol. Prog. Ser. 187, 265–281. Lydersen, C., Hammill, M. O. and Ryg, M. S. (1992). Water flux and mass gain during

120 lactation in free‐living ringed seal (Phoca hispida) pups. J. Zool. 228, 361–369. Lyman, C. P. and Chatfield, P. O. (1955). Physiology of hibernation in mammals. Physiol. Rev. 35, 403–425. McDonald, B. I., Crocker, D. E., Burns, J. M. and Costa, D. P. (2008). Body condition as an index of winter foraging success in crabeater seals (Lobodon carcinophaga). Deep. Res. Part II Top. Stud. Oceanogr. 55, 515–522. McDonald, B. I., Goebel, M. E., Crocker, D. E. and Costa, D. P. (2012). Dynamic influence of maternal and pup traits on maternal care during lactation in an income breeder, the antarctic fur seal. Physiol. Biochem. Zool. 85, 243–254. McLaren, I. A. (1958a). The biology of the ringed seal (Phoca hispida Schreher) in the eastern Canadian Arctic. Fish. Reasearch Board Canada 118, 1–97. McLaren, I. A. (1958b). Some Aspects of Growth and Reproduction of the Bearded Seal, Erignathus barbatus. J. Fish. Res. Board Canada 15, 219–227. McLaren, I. A. (1993). Growth in Pinnipeds. Biol. Rev. 68, 1–79. McLellan, W. A., Koopman, H. N., Rommel, S. A., Read, A. J., Potter, C. W., Nicolas, J. R., Westgate, A. J. and Pabst, D. A. (2002). Ontogenetic allometry and body composition of harbour porpoises (Phocoena phocoena, L.) from the western North Atlantic. J. Zool. 257, 457–471. Meier, W. N., Hovelsrud, G. K., van Oort, B. E. H., Key, J. R., Kovacs, K. M., Michel, C., Haas, C., Granskog, M. A., Gerland, S., Perovich, D. K., et al. (2014). Arctic sea ice in transformation: A review of recent observed changes and impacts on biology and human activity. Rev. Geophys. 51, 185–217. Mellish, J. E., Iverson, S. J. and Bowen, W. D. (1999a). Variation in Milk Production and Lactation Performance in Grey Seals and Consequences for Pup Growth and Weaning Characteristics. Physiol. Biochem. Zool. 72, 677–690. Mellish, J. E., Iverson, S. J. and Bowen, W. D. (1999b). Variation in Milk Production and Lactation Performance in Grey Seals and Consequences for Pup Growth and Weaning Characteristics. Physiol. Biochem. Zool. 72, 677–690. Mellish, J.-A. E., Tuomi, P. a and Horning, M. (2004). Assessment of ultrasound imaging as a noninvasive measure of blubber thickness in pinnipeds. J. Zoo Wildl. Med. 35, 116–118. Mellish, J. E., Horning, M. and York, A. E. (2007). Seasonal and Spatial Blubber Depth Changes in Captive Harbor Seals (Phoca Vitulina) and Steller’s Sea Lions (Eumetopias Jubatus). J. Mammal. 88, 408–414. Moore, S. E. (2008). Marine mammals as ecosystem sentinels. J. Mammal. 89, 534–540. Naito, Y. and Nishiwaki, M. (1972). The Growth of Two Species of the Harbour. Sci. Reports Whales Res. Inst. 127–144. Nelson, M., Quakenbush, L., Taras, B. and Ice Seal, C. (2019). Subsistence harvest of ringed, bearded, spotted, and ribbon seals in Alaska is sustainable. Endanger. Species Res. 40, 1– 16. Nilssen, K. T., Haug, T., Grotnes, P. E. and Potelov, V. (1997). Seasonal Variation in Body Condition of Adult Barents Sea Harp Seals (Phoca groenlandica). J. Northwest Atl. Fish. Sci. 22, 17–25. Nitto, H., Kawamura, T. and Baba, N. (2001). Changes in body weight of the Steller sea lion (Eumetopias jubatus) in Captivity. 1998 40, 8–13. NOAA (2016). 2011 Arctic Pinniped Unusual Mortality Event (UME). Noren, S. R. and Wells, R. S. (2009). Blubber Deposition during Ontogeny in Free-Ranging

121 Bottlenose Dolphins: Balancing Disparate Roles of Insulation and Locomotion. J. Mammal. 90, 629–637. Noren, S. R., Boness, D. J., Iverson, S. J., McMillan, J. and Bowen, W. D. (2008). Body condition at weaning affects the duration of the postweaning fast in gray seal pups (Halichoerus grypus). Physiol. Biochem. Zool. 81, 269–277. Noren, S. R., Udevitz, M. S., Triggs, L., Paschke, J., Oland, L. and Jay, C. V. (2015). Identifying a reliable blubber measurement site to assess body condition in a marine mammal with topographically variable blubber, the Pacific walrus. Mar. Mammal Sci. 31, 658–676. Ochoa-Acuña, H. G., McNab, B. K. and Miller, E. H. (2009). Seasonal energetics of northern phocid seals. Comp. Biochem. Physiol. - A Mol. Integr. Physiol. 152, 341–350. Ortiz, C. L., Costa, D. and Le Boeuf, B. J. (1978). Water and Energy Flux in Elephant Seal Pups Fasting under Natural Conditions. Physiol. Zool. 51, 166–178. Parkinson, C. L. (2014). Global sea ice coverage from satellite data: Annual cycle and 35-yr trends. J. Clim. 27, 9377–9382. Parmesan, C. (2006). Ecological and Evolutionary Responses to Recent Climate Change. Annu. Rev. Ecol. Evol. Syst. 37, 637–669. Parmesan, C. and Yohe, G. (2003). A globally coherent fingerprint of climate change. Nature 421, 37–42. Pirotta, E., Schwarz, L. K., Costa, D. P., Robinson, P. W. and New, L. (2019). Modeling the functional link between movement, feeding activity, and condition in a marine predator. Behav. Ecol. 30, 434–445. Pitcher, K. W. (1986). Variation in Blubber Thickness of Harbor Seals in Southern Alaska. J. Wildl. Manage. 50, 463–466. Pitcher, W. and Pendleton, W. (2000). Stellar Sea Lion Body Condition Indices. Mar. Mammal Sci. 16, 427–436. Pond, C. M. (1978). Morphological Aspects and the Ecological and Mechanical Consequences of Fat Deposition in Wild Vertebrates. Annu. Rev. Ecol. Evol. Syst. 9, 519–570. Quakenbush, L., Citta, J. and Crawford, J. (2009). Biology of the Spotted Seal (Phoca largha) in Alaska from 1962 to 2008. Quakenbush, L., Citta, J. and Crawford, J. (2011a). Biology of the ringed seal (Phoca hispida) in Alaska, 1960-2010. Final Rep. to Natl. Mar. Fish. Serv. 72. Quakenbush, L., Citta, J. and Crawford, J. (2011b). Biology of the bearded seal (Erignathus barbatus) in Alaska, 1961-2009. Final Rep. to Natl. Mar. Fish. Serv. 1961–2009. Reilly, J. J. and Fedak, M. A. (1990). Measurement of the body composition of living gray seals by hydrogen isotope dilution. J. Appl. Physiol. 69, 885–91. Renouf, D. and Gales, R. (1994). Seasonal variation in the metabolic rate of harp seals: Unexpected energetic economy in the cold ocean. Can. J. Zool. 72, 1625–1632. Renouf, D. and Noseworthy, E. (1990). Feeding cycles in captive harbour seals (Phoca vitulina): Weight gain in spite of reduced food intake and increased thermal demands . Mar. Behav. Physiol. 17, 203–212. Rigor, I. G. and Wallace, J. M. (2004). Variations in the age of Arctic sea-ice and summer sea- ice extent. Geophys. Res. Lett. 31, 2–5. Rosen, D. A. S. and Renouf, D. (1997). Seasonal Changes in Blubber Distribution in Atlantic Harbor Seals: Indications of Thermodynamic Considerations. Mar. Mammal Sci. 13, 229– 240.

122 Rosen, D. A. S. and Renouf, D. (1998). Correlates of seasonal changes in metabolism in Atlantic harbour seals (Phoca vitulina concolor). Can. J. Zool. 76, 1520–1528. Ryg, M., Smith, T. G. and Øritsland, N. A. (1988). Thermal Significance of the Topographical Distribution of Blubber in Ringed Seals ( Phoca hispida ). Can. J. Fish. Aquat. Sci. 45, 985–992. Ryg, M., Smith, T. G. and Øritsland, N. A. (1990a). Seasonal changes in body mass and body composition of ringed seals ( Phoca hispida ) on Svalbard. Can. J. Zool. 68, 470–475. Ryg, M., Lydersen, C., Markussen, N. H., Smith, T. G. and Øritsland, N. A. (1990b). Estimating the Blubber Content of Phocid Seals. Can. J. Fish. Aquat. Sci. 47, 1223–1227. Ryg, M., Lydersen, C., Knutsen, L., Bjørge, A., Smith, T. G. and ØRitsland, N. A. (1993). Scaling of insulation in seals and whales. J. Zool. 230, 193–206. Samuel, A. M. and Worthy, G. A. . (2004). Variability in fatty acid composition of bottlenose dolphin ( Tursiops truncatus ) blubber as a function of body site, season, and reproductive state. Can. J. Zool. 82, 1933–1942. Savage, K. (2018). Health Evaluation of Ringed Seals Documented in the Southern Bering Region, Winter 2017-Spring 2018. Scholander, P., Hock, R., Walters, V. and Irving, L. (1950a). Adaptation to cold in arctic and tropical mammals and birds in relation to body temperature, insulation, and basal metabolic rate. Biol. Bull. 99, 259–271. Scholander, P., Walters, V. and Hock, R. (1950b). Body Insulation of some arctic and tropical mammals and birds. Biol. Bull. 99, 225–236. Schop, J., Aarts, G., Kirkwood, R., Cremer, J. S. M. and Brasseur, S. M. J. M. (2017). Onset and duration of gray seal (Halichoerus grypus) molt in the Wadden Sea, and the role of environmental conditions. Mar. Mammal Sci. 33, 830–846. Schulte-Hostedde, A. I., Millar, J. S. and Hickling, G. J. (2001). Evaluating body condition in small mammals. Can. J. Zool. 79, 1021–1029. Schulte-Hostedde, A., Zinner, B., Millar, J. S. and Hickling, G. J. (2005). Restution of mass- size residual: validating condition indices. Ecology 86, 155–163. Schwarz, L. K., Villegas-Amtmann, S., Beltran, R. S., Costa, D. P., Goetsch, C., Hückstädt, L., Maresh, J. L. and Peterson, S. H. (2015). Comparisons and uncertainty in fat and adipose tissue estimation techniques: The northern elephant seal as a case study. PLoS One 10, 1–24. Shaughnessy, P. D. and Fay, F. H. (1977). A review of the taxonomy and nomenclature of North Pacific Harbour seals. J. Zool. 385–419. Sheffield, G. (2020). Lessons Learned: Moving Forward Marine Wildlife Response, Health Investigations, and Research in Western and Northern Coastal Alaska During Unparalleled Ecosystem Transition. In Alaska Marine Science Symposium, p. Anchorage, AK. Shero, M. R., Pearson, L. E., Costa, D. P. and Burns, J. M. (2014). Improving the precision of our ecosystem calipers: A modified morphometric technique for estimating marine mammal mass and body composition. PLoS One 9,. Shuert, C. R., Skinner, J. P. and Mellish, J. E. (2015). Weighing our measures: Approach- appropriate modeling of body composition in juvenile Steller sea lions (Eumetopias jubatus). Can. J. Zool. 93, 177–180. Slip, D., Burton, H. and Gales, N. (1992). Determining Blubber Mass in the Southern Elephant Seal by Ultrasonic and Isotopic Techniques. Aust. J. Zool. 40, 143–152. Smith, T. G. and Hammill, M. O. (1981). Ecology of the ringed seal, Phoca hispida , in its fast

123 ice breeding habitat. Can. J. Zool. 59, 966–981. Smith, T. G. and Lydersen, C. (1991). Availability of suitable land-fast ice and predation as factors limiting ringed seal populations, Phoca hispida, in Svalbard. Polar Res. 10, 585– 594. Smith, T. G. and Stirling, I. (1975). The breeding habitat of the ringed seal ( Phoca hispida ). The birth lair and associated structures . Can. J. Zool. 53, 1297–1305. Stewart, B. S., Claphap, P. J. and Powell, James, A. (2002). Ringed Seal. In Guide to Marine Mammals of the World, pp. 125–127. New York, NY: Andrew Stewart Publishing Inc. Stirling, I. and McEwan, E. H. (1975). The caloric value of whole ringed seals ( Phoca hispida ) in relation to polar bear ( Ursus maritimus ) ecology and hunting behavior. Can. J. Zool. 53, 1021–1027. Strandberg, U., Käkelä, A., Lydersen, C., Kovacs, K. M., Grahl‐Nielsen, O., Hyvärinen, H. and Käkelä, R. (2008). Stratification, Composition, and Function of Marine Mammal Blubber: The Ecology of Fatty Acids in Marine Mammals. Physiol. Biochem. Zool. 81, 473–485. Stroeve, J. and Notz, D. (2018). Changing state of Arctic sea ice across all seasons. Environ. Res. Lett. 13,. Thordarson, G., Vikingsson, G. A. and Hersteinsson, P. (2007). Seasonal variation in body condition of adult male hooded seals (Cystophora cristata) in Skjalfandi-Bay, northeast Iceland. Polar Biol. 30, 379–386. Tikhomirov, E. A. (1964). Distribution and biology of pinnipeds in the Bering Sea. In Soviet Fisheries Investigations in the Northeast Pacific (ed. Moiseev, P. A.), pp. 277–285. Moscow, Russia. Tøien, Ø., Blake, J., Edgar, D. M., Grahn, D. A., Heller, H. C. and Barnes, B. M. (2011). Hibernation in black bears: Independence of metabolic suppression from body temperature. Science (80-. ). 331, 906–909. Waltzek, T. B., Cortés-Hinojosa, G., Wellehan, J. F. X. and Gray, G. C. (2012). Marine mammal zoonoses: A review of disease manifestations. Zoonoses Public Health 59, 521– 535. Webb, P. M., Crocker, D. E., Blackwell, S. B., Costa, D. P. and Le Boeuf, B. J. (1998). Effects of buoyancy on the diving behavior of northern elephant seals. J. Exp. Biol. 201, 2349–58. Williams, T. M. and Koopman, H. N. (1985). Swimming Performance and Hydrodynamic Characteristics of Harbor Seals Phoca Vitulina. Physiol. Biochem. Zool. 58, 576–589. Williams, C. T., Barnes, B. M. and Loren Buck, C. (2015). Persistence, entrainment, and function of circadian rhythms in polar vertebrates. Physiology 30, 86–96. Worthy, G. A. J., Morris, P. A., Costa, D. P. and Le Boeuf, B. J. (1992). Moult energetics of the northern elephant seal. J. Zool. 227, 257–265. Young, R. A. (1976). Fat, energy and mammalian survival. Am. Zool. 16, 699–710. Young, B. G. and Feguson, S. H. (2013). Seasons of the ringed seal: pelagic open-water hyperphagy, benthic feeding over winter and spring fasting during molt. Wildl. Res. 50, 52– 60. Yurkowski, D. J., Semeniuk, C. A. D., Harwood, L. A., Rosing-Asvid, A., Dietz, R., Brown, T. M., Clackett, S., Grgicak-Mannion, A., Fisk, A. T. and Ferguson, S. H. (2016). Influence of sea ice phenology on the movement ecology of ringed seals across their latitudinal range. Mar. Ecol. Prog. Ser. 562, 237–250.

124 Ziel, H., McClintock, B. and Boveng, P. (2020). Relationships among blubber depth, body condition, and morhpometric measurements in Alaska phocids. In Alaska Marine Science Symposium, p. Anchorage, AK.

125