Avian top predator and the landscape of fear: responses of mammalian mesopredators to risk imposed by the golden eagle.

Mari S Lyly,Pekka Helle,Erkki Korpimäki,Alexandre Villers,Tuomo Ollila,Elina Koivisto

doi:10.1002/ece3.1370

Mari S Lyly, Pekka Helle + Show 4 more

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https://doi.org/10.1002/ece3.1370

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Abstract

Top predators may induce extensive cascading effects on lower trophic levels, for example, through intraguild predation (IGP). The impacts of both mammalian and avian top predators on species of the same class have been extensively studied, but the effects of the latter upon mammalian mesopredators are not yet as well known. We examined the impact of the predation risk imposed by a large avian predator, the golden eagle (Aquila chrysaetos, L.), on its potential mammalian mesopredator prey, the red fox (Vulpes vulpes, L.), and the pine marten (Martes martes, L.). The study combined 23 years of countrywide data from nesting records of eagles and wildlife track counts of mesopredators in Finland, northern Europe. The predation risk of the golden eagle was modeled as a function of territory density, density of fledglings produced, and distance to nearest active eagle territory, with the expectation that a high predation risk would reduce the abundances of smaller sized pine martens in particular. Red foxes appeared not to suffer from eagle predation, being in fact most numerous close to eagle nests and in areas with more eagle territories. This is likely due to similar prey preferences of the two predators and the larger size of foxes enabling them to escape eagle predation risk. Somewhat contrary to our prediction, the abundance of pine martens increased from low to intermediate territory density and at close proximity to eagle nests, possibly because of similar habitat preferences of martens and eagles. We found a slightly decreasing trend of marten abundance at high territory density, which could indicate that the response in marten populations is dependent on eagle density. However, more research is needed to better establish whether mesopredators are intimidated or predated by golden eagles, and whether such effects could in turn cascade to lower trophic levels, benefitting herbivorous species.

Highlights

The traditional view of trophic dynamics has emphasized the importance of bottom-up effects in ecosystems, but recent studies have provided increasing evidence to show that top-down processes are extensive and influential in shaping communities (e.g., Hebblewhite et al 2005; Borrvall and Ebenman 2006; Terborgh and Estes 2010)
Ecology and Evolution published by John Wiley & Sons Ltd
We examined the abundances of two mammalian mesopredators, the red fox, and the pine marten, in relation to the predation risk imposed by the golden eagle by combining long-term data from monitoring of game animal abundances and eagle nesting

Summary

Introduction

The traditional view of trophic dynamics has emphasized the importance of bottom-up effects in ecosystems, but recent studies have provided increasing evidence to show that top-down processes are extensive and influential in shaping communities (e.g., Hebblewhite et al 2005; Borrvall and Ebenman 2006; Terborgh and Estes 2010). Top predators are often key species in their ecosystems and may induce extensive cascading effects on the lower trophic levels (Estes et al 2011; Ripple et al 2014). Another pathway for top-down effects is intraguild predation (IGP), where predatory species compete over shared prey and prey on each other (Polis et al 1989; Lourenßco et al 2014).

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