Mismatched Snowshoe Hares Stick Out Like Sore Thumb With No Snow Around

Snowshoe hares have adapted the evolutionary defense of shedding their summer brown coats in the winter to blend in with the snow. In general, their coats change color in a response to the amount of daylight in a day (called photoperiodism), so they don't control when this happens. However, when climate change causes snow to come later or melt sooner in the season, these hares stick out like sore thumbs and attract predators. Researchers from North Carolina State University are unsure whether or not these animals will be able to re-adapt before it's too late.

"This is one of the most direct demonstrations of mortality costs for a wild species facing climate change," L. Scott Mills, study co-author and professor at NC State's College of Natural Resources, said in a news release. "In previous research we showed that climate change is causing snow duration to decrease, and that hares have little ability to adjust their molt timing or behaviors to compensate for the mismatch. Here we take the next step of showing that mismatch does indeed kill."

In the latest study, researchers used radio collars to track snowshoe hares in Montana, where the animals are accustomed to hiding in mounds of snow. They found that mismatched snowshoe hares experience a seven percent drop in their weekly survival rate when they can't camouflage to their snowless environments.

"This paper shows that the mismatch costs are severe enough to cause hare populations to steeply decline in the future unless they can adapt to the change," Marketa Zimova, lead author and doctoral at NC State, added in the release.

However, there is good news: Researchers found that some hares molt at different times, which allows natural selection to favor those better suited for changing snowy seasons. That said, given how fast climate change is occurring, researchers are unsure if natural selection can help enough hares evolve different molting cycles in time.

"But in the meantime, we should maintain large and connected populations to foster evolutionary rescue and its ability to allow wild animals to adapt to the changing conditions," Zimova concluded in the university's release.

Snowshoe hares are not the only mismatched animals suffering. Researchers estimate at least 14 other species are impacted by their inability to camouflage with changing seasons. This includes mountain hares, white-tailed jackrabbits, weasels, arctic foxes and many more, which researchers hope to investigate in future studies.

Their findings were recently published in the journal Ecology Letters.

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