Cyclic Population Dynamics & Community Disassembly in Wisconsin’s Tension Zone


Cyclic population dynamics are one of the cornerstone concepts in population ecology. Alterations in the dynamics of a single species can alter trophic relationships and community dynamics. Historically snowshoe hare (Lepus americanus), ruffed grouse (Bonasa umbellus) and porcupine (Erethizon dorsatum) all coexisted in the Tension Zone at the southern edge of their range distributions, exhibited cyclic abundance and shared common predators, particularly fisher (Pekania pennanti). Recently snowshoe hare have undergone a northerly range shift and are now uncommon in the tension zone. This community disassembly has coincided with declines in porcupines and ruffed grouse abundance. This research will build upon a framework of long-term monitoring and previous research in the Pauli lab and by Wisconsin DNR examining this community within the Tension Zone of Wisconsin to disentangle the mechanisms behind cyclic population dynamics through experimental manipulation of a snowshoe hare population within the Tension Zone. We will attempt to temporarily resurrect the historic density of snowshoe hare within our study area by translocating snowshoe hare from their core range in northern Wisconsin to a site within the tension zone, and quantify the effects of this translocation on porcupine and ruffed grouse population dynamics, and fisher spatial ecology and diet. We predict that the increased density of snowshoe hare will: 1) lead to a functional response in fisher, reflected in individual space use, obtained using GPS collars, and diet, using stable isotope analysis, 2) decrease predation on juvenile porcupines and ruffed grouse and precipitate population growth and increased density 3) be only a short-term phenomenon, with hare once again vanishing from the landscape due to predation, resulting in only a temporary return to historic dynamics. Identifying and understanding the mechanisms that have led to the collapse of historical population dynamics and trophic relationships within this system can have important conservation, management and ecological implications.

This work is funded by a USDA Hatch Grant and the Wisconsin DNR.