Grey Wolf (Canis Lupus) Predation on Livestock in Relation to Prey Availability
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Biological Conservation 243 (2020) 108433 Contents lists available at ScienceDirect Biological Conservation journal homepage: www.elsevier.com/locate/biocon Review Grey wolf (Canis lupus) predation on livestock in relation to prey T availability ⁎ Andrea Janeiro-Oteroa, , Thomas M. Newsomeb, Lily M. Van Eedenc, William J. Rippled, Carsten F. Dormanna a Department of Biometry and Environmental System Analysis, Faculty of Environment and Natural Resources, University of Freiburg, Tennenbacher Straße 4, 79106 Freiburg, Germany b Global Ecology Lab, School of Life and Environmental Sciences, University of Sydney, NSW 2006, Australia c Desert Ecology Research Group, School of Life and Environmental Sciences, University of Sydney, NSW 2006, Australia d Global Trophic Cascades Program, Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, USA ARTICLE INFO ABSTRACT Keywords: Wolf diet Feeding ecology 1. Conflict between humans and large carnivores hinders carnivore conservation worldwide. Livestock de- Prey selection predations by large carnivores is the main cause of conflict, triggering poaching and retaliatory killings by Human-wildlife conflict humans. Resolving this conflict requires an understanding of the factors that cause large carnivores toselect Conservation livestock over wild prey. Individual studies to date report contradictory results about whether wild prey density affects livestock depredation by large carnivores. 2. We carried out a systematic review of grey wolf (Canis lupus) dietary preferences. We reviewed and analysed 119 grey wolf dietary studies from 27 countries to determine whether wild prey or livestock density affects grey wolf dietary selection. 3. We also assessed whether there are traits that predispose species to be preyed upon (body size, group size, defence mechanisms, speed), and whether livestock management is a factor that affects selection of livestock by grey wolves. 4. Overall, wild prey (65% of the total frequency of occurrence in all reviewed grey wolf diet studies) was selected for even when livestock was abundant. The average proportion of biomass percentage in grey wolf diets was 13% for livestock and 19% for wild species. 5. Wild prey species in possession of defence mechanisms (horns, antlers, spikes, and fangs), with high body weight and present in high density were more likely to be depredated by grey wolves. 6. Even when prey abundance significantly affected selection of wild prey, livestock predation was muchlower considering their substantially higher density. Areas where livestock were left to graze freely in small numbers (<20 individuals/km2) were more vulnerable to grey wolf attacks. 7. Our results suggest that the adoption of attack prevention measures on pastures and the increase of wild prey abundance could reduce depredation on livestock by grey wolves, and in turn, provide better opportunities for coexistence between humans, grey wolves and livestock. 1. Introduction created widespread conflict (Behdarvand et al., 2014, Fall and Jackson, 1998; Messmer et al., 1997; Treves et al., 2004). Such conflict is in- Large carnivores have long been perceived as a threat to people's creasing as large carnivores recolonise human-dominated landscapes lives and livelihoods (Ripple et al., 2014). Changing attitudes towards (Chapron et al., 2014; Madhusudan and Mishra, 2003; Treves and large carnivores and their conservation have resulted in implementa- Karanth, 2003), mainly because they sometimes prey on livestock and tion of measures to protect them. At the same time increasing human game species also valued by humans, incurring economic costs (Graham expansion and subsequent destruction of (semi-)natural habitat has et al., 2005; Promberger et al., 1997; Treves and Karanth, 2003). ⁎ Corresponding author. E-mail addresses: [email protected] (A. Janeiro-Otero), [email protected] (T.M. Newsome), [email protected] (L.M. Van Eeden), [email protected] (W.J. Ripple), [email protected] (C.F. Dormann). https://doi.org/10.1016/j.biocon.2020.108433 Received 30 September 2019; Received in revised form 17 December 2019; Accepted 24 January 2020 0006-3207/ © 2020 Elsevier Ltd. All rights reserved. A. Janeiro-Otero, et al. Biological Conservation 243 (2020) 108433 Deeply held cultural views and hostility towards large carnivores can Here we evaluate for the grey wolf (a) which ungulate species are lead to their localised extermination (Jones, 2002; Kruuk, 2002), even the most preferred prey items, (b) whether prey consumption is de- if direct attacks on humans are rare (Brain, 1981; Karanth and termined by prey abundance at a given location, (c) whether there are Madhusudan, 2002; Linnell et al., 2002; Linnell et al., 2003). Public traits that predispose species to be preyed upon (body size, group size, reports of attacks on livestock are somewhat unreliable, as exaggerating defence mechanisms, speed), and, (d) whether livestock management is them is occasionally part of lobbying activities, even when evidence a factor that affects the selection of livestock as wolf prey. We usethe indicates that other factors, such as falling meat prices, threaten live- results to test the broad hypothesis that depredation on livestock by stock farming to a greater extent (Chapron and López-Bao, 2014). Some grey wolves would be lower under circumstances where abundant wild administrations manage livestock-carnivore conflicts with compensa- prey is available and where nonlethal livestock protection measures are tion and carnivore relocation programs (Agarwala et al., 2010; Boitani in place. et al., 2011, Nyhus et al., 2003; Treves and Karanth, 2003; Vos, 2000). Improvements in husbandry techniques appear to be the most effective 2. Methods means of preventing attacks (Ciucci and Boitani, 1998; Mishra, 1997), but uptake of such methods remains low at a global scale (van Eeden 2.1. Literature review and data collection et al., 2018a, 2018b). In human-dominated landscapes, balancing large carnivore con- We conducted a systematic review of the available literature re- servation and farming interests is politically desirable. However, ten- garding grey wolf diet and prey densities. All studies used by a previous sions run high when carnivores return to farming or hunting regions review (Newsome et al., 2016) were included when accessible. Addi- (Bangs et al., 1998; Jhala and Giles, 1991; Landa et al., 1999). Game- tional studies were located by searches in JSTOR, Web of Science, keepers, farmers and ranchers typically oppose what they perceive to be Google Scholar, Wiley Online Library and Science Direct using the cumbersome protective measures (Andersson, 1977; Bath and search terms (“diet” OR “food habits” OR “frequency of occurrence”) Buchanan, 1989) and may even support illegal killing and eradication AND (“wolf” OR “Canis lupus”) without date or language restrictions programs (Blanco et al., 1992; Boitani and Ciucci, 1993; Huber et al., (Appendices A and C). Bibliographies of relevant articles were searched 1993; Jackson and Hunter, 1996). Social studies of human-large car- for secondary studies. The last search was made in September 2018. nivore relationships have documented improving attitudes following a Studies usually included information about prey consumed by grey reduction of livestock killed (Gyorgy, 1984; Huber et al., 1993), sug- wolves and the other species occurring in the area. However, when this gesting that mitigating attacks on livestock is crucial for managing information was not available, we searched for studies undertaken at stakeholder attitudes to facilitate conservation. While several reviews the same time period and location using articles from the same author have recently explored evidence of the effectiveness of different live- or authors who conducted the grey wolf dietary study first, and then stock protection measures (van Eeden et al., 2018b; Eklund et al., 2017; from other authors using the same search engines as above. We also Miller et al., 2016; Treves et al., 2016), further research is needed to searched for books, academic theses, conference presentations, national understand the broader context that shapes large carnivore attacks on park and protected site reports, and official government sites. livestock. Data regarding prey densities were collected the same way The grey wolf (Canis lupus) is considered an opportunist predator (Appendices A and D). From this search, we selected papers containing species (Carbyn, 1988; Salvador and Abad, 1987). As such, it usually information about frequency of occurrence (FO) and biomass of prey consumes the food which occurs most abundantly, changing its diet species from scat contents, excluding studies where authors only ana- depending on food availability (Glasser, 1982). Grey wolves are one of lysed stomach contents. Then, we performed a bootstrap analysis in R the most widely distributed large carnivores, and they frequently come (R Development Core Team, 2016) to evaluate whether the total into conflict with humans because they prey on livestock (Graham number of papers screened was sufficient to represent the biomass et al., 2005; Sillero-Zubiri and Laurenson, 2001). Because of legal frequencies of wolves. The bootstrap method is a resampling approach protections, recolonisations, and reintroduction effects, grey wolves are that enables estimation of the accuracy of an estimator by random now returning to parts of their former range,