Ecology, habitat use, and winter thermal dynamics of snowshoe hares in Pennsylvania

Open Access
Author:
Gigliotti, Laura Christine
Graduate Program:
Wildlife and Fisheries Science
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
December 16, 2015
Committee Members:
  • Duane R Diefenbach, Thesis Advisor
Keywords:
  • snowshoe hare
  • Pennsylvania
  • body condition
  • survival
  • home range
  • habitat use
  • adaptation
  • movement
Abstract:
Differences in biotic and abiotic characteristics can lead to geographic variation in the ecology of species and populations. Investigating intraspecific variation over large geographic extents can provide insights into the ecological drivers of population dynamics, which is especially important for predicting how future climatic conditions will affect ecological processes. The snowshoe hare (Lepus americanus) is an excellent species to investigate geographic variation in ecological dynamics because it has a geographic range that encompasses a wide range of climates and habitat types. Although the population dynamics of snowshoe hares in the northern portion of their range are well-studied, information on southern populations is limited. I investigated the ecology, habitat use, and winter thermal dynamics of snowshoe hares in Pennsylvania and compared these data to previous research on other hare populations. From January 2014 – June 2015 I trapped and monitored snowshoe hares to estimate body condition, survival rates, home range size, and home range overlap. I found that hares in Pennsylvania had greater body mass in relation to their structural size, higher annual survival, and larger home ranges than populations from higher latitudes. Home range overlap occurred frequently and I did not find that hares temporally partitioned their home ranges to minimize interaction with nearby hares. Also I trapped three snowshoe hares that exhibited uncharacteristic brown winter coat coloration, indicating potential differences in the winter molt patterns or color morphs. Using locations collected from GPS collars I examined snowshoe hare seasonal habitat use at the stand-level and at fine-scale microhabitats. I determined that during both summer and winter hares preferred areas of mature scrub oak or conifers and avoided open habitats. At the population level, hares preferred areas with dense understory vegetation and high canopy coverage, although I found substantial individual variability in habitat preferences. My research highlights the importance of incorporating multiple scales of analysis into habitat use studies, as well as accounting for individual variation in habitat preferences. Finally, I investigated geographic differences in snowshoe hares’ responses to winter temperatures by comparing winter pelage characteristics and heat production between hares in Pennsylvania and the Yukon, as well as investigated the influence of temperature on resting spot selection and movement rates. I found that hares from Pennsylvania had shorter and less dense winter coats than hares from the Yukon and that the Pennsylvania population had less visible white in their winter coats. Hares in the Pennsylvania population also produced less heat than the Yukon population, indicating a lower metabolic rate. Snowshoe hares did not select for resting spots that offered them thermal advantages, but selected locations providing visual obstruction from predators. Movement rates were associated with ambient temperature, with the lowest hourly movements occurs at the extreme high (>4 ºC) and low (<-10 ºC) ends of the temperature range. Results of this research support the suggestion that snowshoe hares have the ability to adapt to local climatic conditions via their pelage characteristics, metabolism and behavior. Overall snowshoes hares in Pennsylvania exhibited differences in body condition, survival, home range sizes, winter pelage characteristics, and heat production than previously studied populations at northern latitudes, highlighting the importance of understanding southern populations in order to better describe range-wide patterns. In the face of potential changes in climate and habitat quality, recognizing potential range-wide variation in population dynamics will be critical for managing this species, as well as other species with large geographic ranges, in the future.