Mesocarnivore response to wolf presence, prey availability, and snowpack

Background/Question/Methods

Alaska is home to a diverse carnivore community, including the coyote (Canis latrans), which was first documented in the early 1900s and has expanded throughout Alaska in recent years. Increased coyote abundance could have community-wide consequences, including competition with native furbearers, such as red foxes (Vulpes vulpes) and Canada lynx (Lynx canadensis). Wolves (Canis lupus) strongly regulate coyotes through direct killing, therefore it is possible that fluctuations in wolf density as a result of predator control could contribute to the expansion of coyotes in Alaska via mesopredator release. However, it is unknown how biotic factors (i.e., prey abundance) and abiotic factors (i.e., climate change) will influence the strength and consequences of this ecological cascade, which is especially relevant for arctic ecosystems characterized by long winters and dominated by prey cycling. This study evaluates the relative importance of limiting factors such as wolf activity, prey availability, and climate (e.g., snow characteristics) on mesocarnivore communities in interior Alaska. In winter 2013, we used two snow track survey methods and motion-sensor trail cameras to document presence/absence of wolves, and mesocarnivores in two distinct study areas representing high (Denali National Park) and low (Upper Susitna River Basin) wolf abundance.  

Results/Conclusions

We constructed single season, single species occupancy models for wolves, coyotes, red fox, and lynx to account for the effect of survey method and detectability (i.e., failure to detect a species when it is present) on occupancy estimates in each study area. Preliminary occupancy estimates in the high wolf area (Denali) were 0.370 +/-0.165 for wolf, 0.319 +/- 0.081 for coyote, 0.275+/-0.060 for red fox, and 0.402 +/-0.135 for lynx. In the low wolf area (Susitna), occupancy was 0.164 +/- 0.106 for wolf, 0.519 +/- 0.122 for coyote, 0.532 +/- 0.083 for red fox, and 0.445 +/- 0.155 for lynx. Where wolf occupancy was low (Susitna), occupancy of coyote, red fox, and lynx was greater compared to areas with higher wolf occupancy (Denali). These initial estimates suggest that the mesocarnivore community as a whole could be responding to wolf presence, as opposed to a mesopredator release cascade. Final analysis including data collected winter 2014 and prey abundance, snow pack, and habitat factors is currently underway. The results of this study enhance scientific understanding of factors that determine the strength of mesopredator release, and provide important baseline information regarding interior Alaska's mesocarnivore community.