Scavenging patterns of generalist predators in forested areas: The potential implications of increase in carrion availability on a threatened capercaillie population

Jorge Tobajas,Josep Piqué,Antoni Margalida,Rubén Moreno‐Opo,Diego García‐Ferré,Ivan Afonso‐Jordana,Pilar Oliva‐Vidal

doi:10.1111/acv.12735

Abstract

AbstractThe increases in ungulate populations and hunting bags throughout Europe and North America have resulted in higher carcass numbers available for mesocarnivore species in temperate and boreal forests. The increase in food resources can sustain denser predator populations, potentially affecting prey species such as the threatened western capercaillie Tetrao urogallus. We investigated the ungulate population trends in recent decades and the carrion use by facultative scavengers in areas of the Pyrenees occupied by capercaillie to assess the potential effects on predation of nests and adult birds, and on its population trend. We found a significant increase in the number of ungulates harvested during the period of sharp capercaillie population decline. Carrion was provided experimentally in forested areas occupied by capercaillie showing that remains were mainly consumed by red fox Vulpes vulpes, followed by wild boar Sus scrofa and marten species (Martes sp.). Season (cold or warm) was the most important factor determining scavenging activity in most species. Main predators of capercaillie nests and adults were martens and red fox, with no predation by wild boar. Our data show that main predators of capercaillie are the same species that mainly consume carrion, especially in winter, and that plentiful carrion resources could maintain higher populations of these species, potentially increasing predation pressure on the capercaillie population. This study shows that managing carrion arising from hunting activity in areas of capercaillie distribution is a necessary management action to reduce the available carrion biomass and so reduce the impact of mesocarnivores on capercaillie conservation.

Highlights

The extirpation of large carnivores and the legal protection of mesocarnivores has triggered increases in mesocarnivore populations in many areas, resulting in increasing predation pressure on mesocarnivore prey species (Ritchie & Johnson, 2009; Jimenez et al 2019), in some cases affecting prey populations conservation (K€ammerle et al 2017)
We investigated the ungulate population trends in recent decades and the carrion use by facultative scavengers in areas of the Pyrenees occupied by capercaillie to assess the potential effects on predation of nests and adult birds, and on its population trend
We found a significant increase in the number of ungulates harvested during the period of sharp capercaillie population decline

Summary

Introduction

The extirpation of large carnivores and the legal protection of mesocarnivores has triggered increases in mesocarnivore populations in many areas, resulting in increasing predation pressure on mesocarnivore prey species (Ritchie & Johnson, 2009; Jimenez et al 2019), in some cases affecting prey populations conservation (K€ammerle et al 2017). The abundance of generalist mesocarnivores generally depends on food availability, the abundance of their main prey being especially relevant (Oaten & Murdoch, 1975; Delibes-Mateos et al 2008). If their main prey or food resource becomes less abundant, or is drastically reduced, generalist predators shift their diet to other food resources, which can induce spillover predation on alternative prey species (Marcstr€om, Kenward & Engren, 1988). Carrion is especially important in habitats and at times when the availability of prey or other food resources is low, such as in temperate and alpine ecosystems and in cold weather (Needham et al 2014; Pereira et al 2014; Carricondo-Sanchez et al 2016). Carrion can occur in temporal pulses, or be scattered across

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