To match their environment and avoid predators, some animals change their coat colour with the seasons – switching from brown to white in winter, for instance. But climate change has left certain species mismatched with their habitat at particular times of year.
Snowshoe hares (Lepus americanus), which live in Canada and northern parts of the US, turn white in autumn when snow usually begins to fall in their environment. But the animals may become mismatched and lose their camouflage if snowfall is delayed.
“With climate change increasing the variability of the snow seasons and snow cover duration, hares are more likely to become colour mismatched, as their coat colour change initiation is likely driven by changes in daylight hours, which is fixed,” says at the Memorial University of Newfoundland in Canada.
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Mismatched hares stand out more to potential predators, so their mortality rates might be expected to be higher. But Kennah and her colleagues have found that for some mismatched hares, the risk of mortality actually decreases.
The team captured and monitored 347 snowshoe hares in south-west Yukon, Canada for three autumns and four springs between 2015 and 2018. About one in seven captured hares were mismatched.
Kennah and her colleagues found that the autumn mortality risk of the mismatched hares was 86.5 per cent lower than that of the matched hares.
The researchers think they know why white hares on a brown background fare so well. Snowshoe hares gain more insulation when they turn white. This means that the white mismatched hares in Yukon may have an advantage over brown hares when it comes to their energetic demands.
“If you can be a [white hare] that happens to be mismatched, you actually don’t need to move [as much],” says team member , also at the Memorial University of Newfoundland. “You can move less, hunker down, hide in a spot, and if you’re not moving, you’re less likely to bump into a predator or a predator [is less likely] to bump into you.”
White mismatched snowshoe hares foraged for 17 to 77 fewer minutes per day than brown matched hares, according to data from accelerometers fitted to the animals. This decreased their predation risk.
“I think what the findings suggest is that the thermal and energetic benefits of the winter coat during cold temperatures outweigh the mortality costs of camouflage mismatch and I actually find that pretty compelling,” says  at the Appalachian State University, North Carolina.
at the University of Montana believes that this advantage may be short-lived. “We’re dealing with climate change, which means temperatures are warming,” he says. “They found this effect most pronounced when you had cold fall days, but those days are gonna become less and less frequent in the future.”
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