Spatiotemporal patterns of wolverine (Gulo gulo) harvest: the potential role of refugia in a quota-free system

Abstract

Fur trapping is an important source of mortality for wolverine (Gulo gulo) in northern Canada. However, few populations are monitored for harvest sustainability. An examination of harvest data can be useful to identify areas of concern and direct appropriate management interventions. We used 27 years of harvest data (1988–2014) to examine patterns of wolverine harvest in the Yukon (Canada), where trapping permits are spatially explicit and there are no quotas. We identify spatiotemporal patterns in estimated harvest density, and trapping behavior by fur trappers. We also examined estimated harvest rates and availability of harvest refugia to evaluate if harvest was sustainable. The mean annual harvest in Yukon was 132 ± 31 wolverines, and there was no significant trend over time. Most trappers harvested wolverines infrequently, but 12% of trappers were responsible for 50% of all harvested wolverines, indicating that a small number of trappers had an influence on overall mortality. Relatively high mean annual harvest rates (≥ 8%) were estimated in several ecoregions in southwestern Yukon, where much of the human population and roads are concentrated. Conversely, estimated harvest rates were moderate to low (< 6%) in northern and eastern Yukon, which consist largely of remote wilderness. The mean percent area without harvest was 62 ± 16%. Sustained high harvest rates in southwestern Yukon are likely supported by dispersing animals from harvest refugia. Few putative harvest refugia were formally protected; rather, unsued trapping areas constituted temporal de facto harvest refugia. Our study points to the importance of harvest refugia and the persistence of wilderness regions for sustaining wolverine populations.