A master's degree student in wildlife and fisheries science when the research was done, Gigliotti is now a doctoral degree student at Clemson University.
The researchers discovered that hares in Pennsylvania had shorter, less-dense and less-white winter coats than their northern counterparts, suggesting lower coat insulation. Hares in the southern population had lower coat temperatures, indicating that they produced less heat than those in the northern population.
In addition, hares in Pennsylvania did not select for resting spots that offered thermal advantages, instead selecting locations offering obstruction from predators. Hare-movement rates were related to air temperature, with the smallest movements occurring at the lower and upper range of observed ambient temperatures — the animals did not move much in winter when it was very cold or very warm.
Snowshoe hares are ideal to investigate the potential for species to alter winter adaptations in response to climate change, explained Gigliotti, because unlike other small mammals that hibernate, group huddle, or use nests as means of coping with cold temperatures, hares remain active on the surface throughout winter. And they are active at night when temperatures are typically the lowest.
"Snowshoe hares also have well-documented morphological and physiological adaptations to cope with winter, such as an increase in fur density — in addition to their coat color change — and a low metabolic rate," she said. "Hares also have a broad geographic range, which permits comparison of winter adaptations from populations that experience very different conditions."
Pennsylvania hares were, on average, significantly larger than hares in the Yukon, Gigliotti pointed out, and to their surprise, researchers found specimens that did not completely molt, or change coloration from brown to white, in the winter. That development, of course, helps hares camouflage and elude predators in winters with scant snowfall.
"We trapped three hares in January that were almost completely brown, and it's the first time that has been recorded in eastern North America," she said. "There are hare populations in the Cascades in Washington that don't molt completely, but that had not been documented elsewhere."
Researchers, right now, can only speculate over what time scale Pennsylvania snowshoe hares' adaptations to warmer winters have occurred, and they don't know, yet, whether genetic modifications are triggering the changes. But, in tandem, the adaptations may allow hares to survive warming long term, Gigliotti hopes.
"Our results indicate that snowshoe hares may be able to adapt to future climate conditions via changes in pelage characteristics, metabolism and behavior," said Gigliotti. "Unfortunately, we don't know if they can adapt as quickly as climate change is occurring."
The Pennsylvania Game Commission supported this research.