OOS 48-3 - A Great Escape: The role of climate, resource availability, and density-dependence on trailing edge populations

Thursday, August 18, 2022

4:00 PM – 4:15 PM EDT

Location: 520D

Presenting Author(s)

AS

Alexej Sirén

Postdoctoral Researcher
Vermont Cooperative Fish and Wildlife Research Unit, University of Vermont, Burlington, VT, United States

Co-author(s)

MZ

Marketa Zimova, PhD

Assistant Professor
Appalachian State University
CS

Chris Sutherland, PhD

Reader
University of St. Andrews
JF

John Finn, PhD

Emeritus Professor
University of Massachusetts
JK

Jillian Kilborn, MSc

Wildlife Biologist
New Hampshire Fish and Game Department
RC

Rachel Cliche, BS

Wildlife Biologist
US Fish and Wildlife Service
LP

Leighlan Prout, MSc

Wildlife Biologist
US Forest Service
LM

L Scott Mills, PhD

Associate Vice President of Research for Global Change and Sustainability
University of Montana
Toni Lyn Morelli

Research Ecologist
U.S. Geological Survey Northeast Climate Adaptation Science Center, Massachusetts, United States

Background/Question/Methods
Populations along range limits are often exposed to highly variable climates and resource availability. As such, there has been a revival to understand the causes of range limits to better predict how species will respond to global change. Using recent theory on range limits and classical understanding of density dependence, we evaluated the influence of resource availability on the snowshoe hare (Lepus americanus) along its trailing southern edge. We collected data on population density and fluctuations, habitat use, and survival to test the hypothesis, here referred to as the Great Escape Hypothesis, that density dependence determines, in part, a species’ persistence along trailing edges.

Results/Conclusions
From a 6-year study (2014–2019), we found that variability in resource availability affected density and population fluctuations and led to trade-offs in survival for snowshoe hare populations in the northeastern US. Hares living in resource-limited environments had lower and stable population density, yet higher survival compared to populations living in resource-rich environments. We suggest that density-dependent dynamics, elicited by resource availability, provide hares a unique survival advantage and partly explains persistence along their trailing edge. We hypothesize that this low-density escape from predation and parasitism occurs for other prey species along trailing edges, but the extent to which it occurs is likely conditional on the quality of matrix habitat. Given the range of a species is shaped by several factors other than climate, including biotic and intraspecific factors, a more careful examination of factors influencing populations along trailing edges is needed to better inform conservation and management decisions.