‘That mismatch does indeed kill’
For millennia, snowshoe hares have camouflaged themselves from predators by blending in with their surroundings, turning pure white in the winter to blend in with the snow, then brown in the summer.
But climate change is shifting the timing of the snow season, and the hares may not be able to adapt in time, according to a North Carolina State University study published in the journal Ecology Letters.
Based on field research with radio-collared snowshoe hares in Montana, mismatched snowshoe hares suffer a 7 percent drop in their weekly survival rate when snow comes late or leaves early and white hares stand out to predators like “light bulbs” against their snowless backgrounds.
Snowshoe hares are a critical food source for predators, especially lynx, and population-level impacts could ripple through ecosystems. The study suggests that evolutionary rescue efforts may be needed to give the species time to adapt.
“This is one of the most direct demonstrations of mortality costs for a wild species facing climate change,” said L. Scott Mills, professor at NC State’s College of Natural Resources and study co-author. “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.”
“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,” says Marketa Zimova, lead author of the journal article in Ecology Letters and doctoral student with Mills at NC State.
The good news for snowshoe hares is the finding that different individuals molt at different times, enabling natural selection to favor those better suited for the changing snow conditions. However, whether evolution through natural selection can save hares quickly enough is uncertain, especially given the rapid rate of change.
“Ultimately, to promote species persistence in the face of climate change induced mismatch, the reduction of its cause is essential and must be done via climate change mitigation,” Zimova says. “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.”
Camouflage mismatch has the potential to impact at least 14 species worldwide that change coat colors seasonally, Mills says. His team of researchers is expanding the coat color research to other species globally, including mountain hares, white-tailed jackrabbits, weasels and arctic foxes.