Population regulation of a mesocarnivore: Relative influence of landscape, predators, and prey.
Thompson, Craig*,1, Gese, Eric2, 1 Department of Forest, Range, and Wildlife Sciences, Logan, UT, USA2 US Department of Agriculture, Wildlife Services, National Wildlife Research Center, Logan, UT, USA
ABSTRACT- The relative influence of top-down versus bottom-up regulation has been argued for decades. Today most ecologists accept that population regulation results from complex interacting forces in both directions and is subject to environmental, geographic, and system characteristics. While there is general acceptance of this interaction, there is very little empirical evidence regarding the mechanisms through which regulation is achieved. Here we present the idea of landscape-mediated predation: that population density may be maintained through predation but that the risk of being depredated varies according to the vegetation structure of a landscape. From 2001 to 2004, we investigated the relative influence of vegetation structure, predators, and prey density on swift fox (Vulpes velox) population ecology on and around the Pinon Canyon Maneuver Site in southeastern Colorado. We monitored 116 foxes on six transects exposed to different disturbance regimes. Coyote predation was the major cause of mortality, though swift fox populations were not related to coyote abundance or prey base. Swift fox populations appear to more heavily influenced by vegetation than community structure. As a native Great Plains mesocarnivore, swift foxes depend on disturbance regimes to maintain open grassland habitat, and changes in the regime may push the landscape into trajectories unsuitable for fox persistence. Likewise, managers may use disturbance regimes to create higher quality grassland habitat for native mesocarnivores.
Key words: mesocarnivore, regulation, Swift fox, Vulpes velox
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