Midwest Fish & Wildlife Conference 2016

AUTHORS: Benjamin Zuckerberg*, University of Wisconsin-Madison; Lars Y. Pomara, USDA Forest Service

ABSTRACT: Cyclic population dynamics are one of the most studied aspects of population ecology, yet the relationship between climate and population cycling in high-latitude species remains poorly understood. There is increasing concern that modern climate change will lead to the collapse of some of ecology’s classic examples of cyclic populations. Unpacking the role of climate variability in population cycling can be greatly aided by linking species demographics to climate across broad geographic regions. We identified demographic sensitivities of ruffed grouse Bonasa umbellus, a northerly bird species, to temperature and precipitation anomalies, and to landscape-scale land use intensity, using survival and nest success estimates derived from multiple studies throughout eastern North America. We then used these relationships to simulate spatially-explicit population dynamics from 1982 to 2069, and evaluated model-based predictions against long-term monitoring data. We found that climate variability has been an important driver of spatiotemporal variation in demographic rates, and that decadal population cycling emerges from these climate-demographic relationships, even when individual climate variables do not show decadal periodicity. Population cycling and spatial synchronization were stronger at more northerly latitudes, but this geographic transition occurred abruptly rather than gradually, a pattern linked to regional variation in winter weather conditions. Projected future dynamics indicated regular, decadal cycling out to mid-century, followed by irregular changes which occurred differently across a latitudinal gradient. Our findings suggest a climate-driven de-synchronization of population dynamics and the potential dampening of cyclic dynamics.