Snowshoe Hares May Not be Able to Adapt Quickly Enough to Climate Pressures

A new study in The Proceedings of the Royal Society B, by SE Climate Science Center affiliated researchers, Marketa Zimova and L. Scott Mills, investigates whether snowshoe hares can adjust the timing of when they undergo seasonal coat color molts and their anti-predatory behaviors to reduce camouflage mismatch and evaluated whether such adjustments (= phenotypic plasticity) may facilitate adaptation to climate change. The paper extends their previous research on plasticity in the timing of coat color molts to a second study site which differed dramatically in climate and photoperiod. They compared the timing at the two sites and jointly tested the effects of variables influencing the molt timing. They confirmed their previous finding that hares initiate both the spring and fall molts at the same time each year, consistent with a photoperiod modulator of timing. Next, they confirmed that hares exhibit some ability to adjust the rate of the spring white-to-brown molt to the immediate snow conditions.
Finally, they investigated, for the first time in any mammal species, whether hares modify their anti-predatory behaviors (hiding, fleeing, or micro-site selection) in a manner that reduces camouflage mismatch. They found that hares do not hide more in vegetation or do not increase the distance at which they flee from predators when color mismatched against their background. Additionally, hares do not select their hiding spots with background color that matches their coat color. Conversely, they prefer spots with relatively little snow which in turn increases the camouflage mismatch in the fall and spring.
Based on these findings, they concluded that the current levels in phenotypic plasticity are insufficient to facilitate adaptation to camouflage mismatch and any future adaptation to climate change will require natural selection on the molt timing or on hare behavior.
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