Comments on Brodie and Post: Climate-driven declines in wolverine populations: causal connection or spurious correlation?

The recent paper by Brodie and Post ("Nonlinear responses of wolverine populations to declining winter snowpack", Popul Ecol 52:279-287, 2010) reports conclusions that are unsupportable, in our opinion, due to both mis-interpretations of current knowledge regarding the wolverine's (Gulo gulo) association with snow, and the uncritical use of harvest data to index wolverine populations. The authors argue that, because the wolverine is a snow-dependent species, average annual provincial snowfall, based on weather station data, can be expected to correlate strongly and positively with wolverine population numbers, which in turn can be accurately indexed by trapper harvests. Thus, correlations between declines in wolverine harvests and declining average snowpack are interpreted to reflect a climate-driven decrease in wolverine populations. This conclusion overstates the nature of the wolverine's association with snow, and makes unsupportable assumptions about the reliability of harvest data as a proxy for population size.