Roe deer face competing risks between predators along a gradient in abundance

Claudia Melis,John Odden,John D.C Linnell,Erlend B Nilsen,Manuela Panzacchi

doi:10.1890/es13-00099.1

Claudia Melis, John Odden + Show 3 more

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https://doi.org/10.1890/es13-00099.1

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Abstract

Mortality rates and patterns are fundamental demographic traits for understanding the dynamics of populations of large herbivores in different environments. Despite the ongoing recovery of large carnivores in Europe and North America, few European studies on ungulate mortality are available from areas where both large carnivores and human hunters are present. We applied known fate models to estimate cause‐specific mortality rates and Cox proportional hazard models to estimate the effects of environmental covariates on mortality risks of 330 radio‐collared roe deer (Capreolus capreolus) (1995–2005) along a gradient in roe deer abundance in south‐eastern Norway. The study area is characterized by the presence of human hunters, Eurasian lynx (Lynx lynx), red foxes (Vulpes vulpes) and occasionally wolves (Canis lupus). The main mortality causes were: hunter harvest, predation by lynx, predation by foxes (on fawns) and others (including wolves, dogs, diseases, vehicle collisions and accidents). The individual risk of roe deer being killed by lynx or by foxes was differently affected by covariates. In keeping with the specialist foraging behavior of lynx, predation risk by lynx decreased with increasing roe deer abundance. Conversely, consistent with the opportunistic habits of red fox, the risk of being preyed upon by foxes, tended to increase with increasing roe deer abundance, although the pattern was not so marked. Human hunters did not adjust their killing rate to changing roe deer abundance and annually harvested between 11% and 28% of the population according to different sexes and age classes.

Highlights

European wild ungulates represent one of the best studied groups of mammals from the point of view of demography; the best data come from just a few long-term studies
In our study area, where roe deer occur across a spatial gradient in abundance and are sympatric with several predators we found that: (1) the risk of lynx predation was negatively related to roe deer abundance; (2) the risk of fox predation was positively related to roe deer abundance; (3) the risk of being preyed upon by lynx and foxes was similar for the two sexes
The risk of being harvested by hunters did not vary with varying roe deer abundance, which supports the assumption that there is no relationship between these two variables and that harvest statistics is a good index of roe deer abundance

Summary

Introduction

European wild ungulates represent one of the best studied groups of mammals from the point of view of demography; the best data come from just a few long-term studies. European roe deer are the smallest ungulate indigenous to Europe, are found throughout the continent, from Mediterranean to boreal areas, in human-dominated and wilderness areas, and are prey for many carnivores, ranging from red foxes (Vulpes vulpes) to wolves (Canis lupus). They have been widely studied in many areas (mainly without predators or human hunting), resulting in good knowledge of the range of demographic parameters that can be expected, making it possible to recognize shifts in parameters in areas where predation and human hunting coexist. While several studies did not find any sexual bias in fawn survival (Andersen and Linnell 1998, Jarnemo et al 2004, Panzacchi et al 2008), males were found to be at higher risk of neonatal predation from foxes in one study (Aanes and Andersen 1996)

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