Eroding Cycles Along a Southern Range Boundary: Snowshoe Hares in the Great Lakes Region

ABSTRACT Aim The regular cycling of animal populations has fascinated ecologists for over a century. Some cycling populations have recently however, exhibited instability, often attributed to climate change. Snowshoe hare ( Lepus americanus ) cycles are well documented, displaying peaks every 8–11 years. While these cycles have been studied extensively in the core of their distributional range, less is known about snowshoe hare cyclic dynamics along their southern range boundary. We tested the hypotheses that the cycling of southern snowshoe hare populations varies across a latitudinal cline and that populations have exhibited dampening in recent years. Location Six latitudinal degrees (44°–49° N) in the Great Lakes region. Taxon Snowshoe hare ( Lepus americanus ). Methods Utilising a series of snow track transects across Minnesota and Wisconsin, we examined snowshoe hare cyclicity across a 40‐year time series from 1978 to 2022. These transects were grouped into four bands across the Great Lakes region to identify changes across a latitudinal cline. Wavelet analysis was then used to examine shifts in cyclic behaviour across time. Results We found evidence of cyclicity across all latitudinal zones and detected a gradient of fading cyclicity along their southern range boundary. Main Conclusions Our findings reveal that while snowshoe hare populations along their southern range boundary have previously cycled, in recent years they appear to be destabilising. These observed shifts in cyclic behaviour may be linked to other regional shifts including range contraction and climate change; however, further research investigating the causal mechanisms behind this cyclic loss is needed.