Small rodent cycles influence interactions among predators in a boreal forest ecosystem

Rocío Cano-Martínez,Morten Odden,David Carricondo-Sanchez,Olivier Devineau

doi:10.1007/s13364-021-00590-7

Rocío Cano-Martínez, Morten Odden + Show 2 more

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https://doi.org/10.1007/s13364-021-00590-7

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Abstract

Cyclic fluctuations of prey have profound effects on the functioning of ecosystems, for example, by changing the dynamics, behavior, and intraguild interactions of predators. The aim of this study was to assess the effect of rodent cyclic fluctuations in the interspecific interactions of a guild of small- and medium-sized predators: red fox (Vulpes vulpes), pine marten (Martes martes), and weasels (Mustela erminea and Mustela nivalis) in the boreal ecosystem. We analyzed eight years (2007–2014) of snow tracking data from southeastern Norway using structural equation models to assess hypothesized networks of causal relationships. Our results show that fluctuations in rodent abundance alter the strength of predator’s interactions, as well as the effect of determinant environmental variables. Pine marten and weasel abundances were positively associated with rodent population growth rate, but not red fox abundance. All predators were positively associated with each other; however, the association between red fox and the other predators weakened when rodents increased. Rodent fluctuations had variable effects on the habitat use of the predators. The presence of agricultural land was important for all predators, but this importance weakened for the mustelids as rodent abundance increased. We discuss the shifting role of interference and exploitative competition as possible mechanisms behind these patterns. Overall, we highlight the importance of accounting for the dynamics of prey resources when studying interspecific interactions among predators. Additionally, we demonstrate the importance of monitoring the predator populations in order to anticipate undesirable outcomes such as increased generalist predator abundances to the detriment of specialists.

Highlights

Cyclic fluctuations of small mammals are characteristic of northern ecosystems and have been comprehensively studied in the last century (Korpimäki and Krebs 1996; Krebs and Myers 1974; Norrdahl 1995)
15,257 red fox, 2752 pine marten, and 3164 weasel tracks were observed along 1713.78 km of transects during the 8-year survey
We assessed whether interactions between sympatric predators in a boreal ecosystem are affected by the fluctuations of their shared cyclic prey

Summary

Introduction

Cyclic fluctuations of small mammals are characteristic of northern ecosystems and have been comprehensively studied in the last century (Korpimäki and Krebs 1996; Krebs and Myers 1974; Norrdahl 1995). (Microtus spp.) and lemmings (Lemmus spp.) (Korpimäki and Krebs 1996), ptarmigan (Lagopus spp.), black grouse (Tetrao tetrix), hazel grouse (Tetrastes bonasia) (Lindén 1988; Ranta et al 1995; Watson et al 1998), and forest Lepidoptera (Myers 1988) These population cycles have profound effects in the functioning of the ecosystems where they occur (Ims and Fuglei 2005; Stoessel et al 2018), influencing the dynamics and behavior of predators (Klemola et al 1999; Korpimäki et al 1991) and of other sympatric herbivores (i.e., the Alternative Prey Hypothesis; Angelstam et al 1984; Breisjøberget et al 2018). These interactions are largely based on exploitation competition, which operates when a

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