Abstract

Where lynx prevail, foxes will fail - limitation of a mesopredator in Eurasia.

Aim: Climate change and loss of apex predators can impact ecosystem structure and function through modified limitation processes. We investigated, on a continental scale, whether mesopredator abundance is limited top-down by large predators as predicted by the mesopredator release hypothesis, or limited by bottom-up factors. The mesopredator in focus is the red fox Vulpes vulpes, a key predator in many ecosystems due to its strong effects on prey abundance.

Location: Europe and northern Asia.

Methods: Data on red fox density was compiled from published papers and reports. For each site, we collated presence-absence data on large carnivores (Lynx lynx, Canis lupus, C. aureus), and remote sensing data for factors potentially related to bottom-up limitation (winter severity, summer temperature, human density, primary productivity, tree cover). The data were analyzed through structural equation modeling.

Results: Presence of lynx had a direct negative effect on red fox suppressing fox abundance. Also winter severity had a negative effect on red fox abundance, and in Eurasia as a whole this effect was partially mediated through lynx. Within the lynx distribution range winter severity was the only bottom-up factor significantly affecting red fox abundance. Outside the lynx distribution range, primary productivity, summer temperature and human density had a positive effect on red fox abundance.

Main conclusions: Our results show that apex predatorscan limit mesopredator abundance on a continental scale, thus supporting the mesopredator release hypothesis. Winter severity also affected red fox abundance, partially due to an interaction between lynx and winter conditions. On the continental scale a complex network of processes operates with varying effects depending on mediation processes. Our results imply thatapex predators can have an important effect on ecosystem structure by limiting mesopredator abundance, and we suggest that apex predators may dampen increases in mesopredator abundance driven by global warming.

Reference
Pasanen-Mortensen M, Pyykönen M, Elmhagen B (2013) Where lynx prevail, foxes will fail - limitation of a mesopredator in Eurasia. Global Ecology and Biogeography 22: 868-877.