COS 6-5 - CANCELLED - The impacts of climate change induced coat-colour mismatch in snowshoe hares

Background/Question/Methods

Snowshoe hares are an important prey species in the boreal forest that undergo seasonal colour change to match the presence or absence of snow. This species is vulnerable to climate change, as reduced snow cover duration causes increased mismatch with their background, which can undermine their camouflage and increase predation risk. However, to develop a comprehensive understanding of the effects of coat-colour mismatch on this species, we require research across the snowshoe hare range. Coat change provides other advantages such as increased insulation, which may supersede the costs of mismatch in northern population exposed to colder temperatures. Additionally, individuals may mitigate the increased predation risk associated with lost camouflage through other antipredator behaviour, such as altered foraging decisions. We examined this potential by conducting studies in two populations of snowshoe hares at the climatic extremes of their range. First, we monitored the survival, foraging behaviour, and coat-colour mismatch of wild snowshoe hares in the southwestern Yukon. Next, we artificially simulated mismatch using enclosures on wild-caught snowshoe hares in Newfoundland, and measured their intake rate, intraspecific selection for forage quality, and resulting body mass loss.

Results/Conclusions

Surprisingly, mismatch reduced autumn mortality risk of snowshoe hares in the Yukon. By measuring foraging rates using accelerometers, we found that white mismatched hares forage 17-77 minutes less per day than matched brown hares between 0 and -10 ºC, potentially lowering their predation risk and driving this survival pattern. We found no effect of mismatch on mortality risk or foraging behaviour in the spring, where mismatch occurred at warmer temperatures. This suggests a potential temperature limit where the costs of conspicuousness outweigh energetic benefits.

In our experimental manipulations in Newfoundland, we found minimal evidence that hares alter their intake rate or selection for forage quality to mitigate increased predation risk associated with mismatch. Instead, mismatched hares lost 4.55 % more body mass than their matched counterparts, potentially due to increased stress. These results suggest that in relatively warmer climates such as Newfoundland, indirect effects of coat-colour mismatch may occur in tandem with survival costs. Taken together, our results highlight that temperature may drive the associated effects of coat-colour mismatch across the snowshoe hare range. Elucidating the mechanisms through which phenological mismatches may be operating is essential to enable predictions on broad-scale changes in species distributions.