Climate change and reduced snow cover is forcing snowshoe hares to move farther north. New research from the University of Wisconsin-Madison revealed that the historic range of snowshoe hares is advancing north by about five and a half miles per decade.
With enormous feet and a snow-white fur coat, snowshoe hares are well equipped for winter. However, as climate warms, northern winters become shorter and milder.
Therefore, the annual blanket of snow many northern animals have evolved to depend on is in steady retreat, forcing the animals to move with it.
"The snowshoe hare is perfectly modeled for life on snow," explained Jonathan Pauli, a University of Wisconsin-Madison professor of forest and wildlife ecology and co-author of the recent study. "They're adapted to glide on top of the snow and to blend in with the historical colors of the landscape."
The recent study demonstrates how the composition of plants and animals in northern ecosystems is gradually changing in a warming world. It also indicates that climate change far surpasses land use as the dominant driver of such ecological change.
"This is one of the first studies to really identify how changing climate factors influence a southern range boundary," added Ben Zuckerberg, co-author and professor from the University of Wisconsin-Madison.
Research on snowshoe hares in Wisconsin dates back to at least 1945, when famed ecologist Aldo Leopold first noted the animals' range, which at the time spanned roughly half of the state from the Mississippi north of St. Paul to Green Bay.
The latest study, led by graduate student Sean M. Sultaire, used observational data collected from 148 of the 249 historic survey sites where snowshoe hares have been documented in the past. Surprisingly, snowshoe hares can no longer be found in 78 percent of the places where they once thrived, likely due to the overwhelming lack of snow.
"Color mismatch - white fur on a brown background - will continue to occur and have a significant impact [on the species]," Pauli said. "For a snowshoe hare, being cryptic is a fundamental requirement for making a living. It is a relatively fixed phenotype, so it is pretty clear that snow cover is one of the most important constraints in terms of where the animal can and can't be."
In other words, the animals can't stay in snowless environments since their bright white fur makes them a prime target for predators such as lynx and coyotes.
Researchers say a diminished abundance of snowshoe hares in Wisconsin will likely have both ecological and economic consequences as the animal is an important game species and prey for larger animals.
Their study was recently published in the journal Proceedings of the Royal Society B.