Climate change catches snowshoe hares off guard

Midwesterners aren’t the only ones perplexed by unpredictable winter weather. Several mammal species annually swap out their brown drab summer coat for a stylish camouflaged white coat in time for snow season. Over the past few decades, shorter periods of snowpack from warmer temperatures are exposing snowshoe hares to predators when their coats molt out of sync with snow cover. That could be a problem for hare populations, an important resource in northern food webs, unless individuals recognize the mismatch and compensate with less risky behavior.

western snowpack trends

To see how the hares responded to standing out, wildlife biologists in Montana marked and released almost 200 snowshoe hares at two sites over three years. They recorded the relative brownness and whiteness of the hares’ coats, the percentage of snow cover at resting sites, and the degree of mismatch between coat and background colors. As a measure of behavioral adjustment to any mismatch, the researchers estimated concealment by vegetation cover and the distance at which hares flushed when approached by observers.

The timing of molt remained fixed in autumn even though the timing of snow pack differed between years. Hares were more likely to follow spring trends and delayed losing their white coats in years with longer snow persistence. Even so, coat color was often mismatched and it seemed to make little difference to the hares. They did not seek cover more often when less cryptic, nor did mismatched hares flee earlier from a potential bipedal predator. Patches of bare ground were preferred over snowy spots as resting sites, independent of coat color.

The hares’ apparent disregard for conspicuousness is a bit of a mystery. Given that predation accounts for 85 to 100 percent of hare mortality, they should be a little more cautious in territory prowled by bobcats, coyotes, lynx, and great horned owls. It may be that mismatched hares do change behaviors, but only at night or dawn and dusk when predators are more active than biologists. A shift from a reliance on camouflage to other adaptive predator avoidance strategies, such as running faster, may also help hares keep pace with climate change.Miles Becker | 24 March 2014

Source: Zimova, M. et al. 2014. Snowshoe hares display limited phenotypic plasticity to mismatch in seasonal camouflage. Proceedings of the Royal Society – Series B doi:10.1098/rspb.2014.0029

Photo © Tom Reichner

Figure ©  U.S. EPA