Coat color mismatch improves survival of a keystone boreal herbivore: energetic advantages exceed lost camouflage

Abstract

Climate warming is causing asynchronies between animal phenology and environments. Mismatched traits, like coat color change mismatched with snow, can decrease survival. However, coat change does not serve a singular adaptive benefit of camouflage, and alternate coat change functions may confer advantages that supersede mismatch costs. We found that mismatch reduced rather than increased, autumn mortality risk of snowshoe hares in Yukon by 86.5 %. We suggest that the increased coat insulation and lower metabolic rates of winter acclimatized hares confer energetic advantages to white mismatched hares that reduce their mortality risk. We found that white mismatched hares forage 17-77 minutes less per day than matched brown hares between 0 and -10° C, thus lowering their predation risk and increasing survival. We found no effect of mismatch on spring mortality risk, where mismatch occurred at warmer temperatures, suggesting a potential temperature limit where the costs of conspicuousness outweigh energetic benefits.

Survival of a polymorphic species in seasonally snow‐covered forests

“…In addition to cryptic coloration, thermoregulatory properties associated with coloration have been proposed as an alternative or complementary function for polymorphic and seasonally color changing species in winter environments. For example, winter white pelages in seasonally color changing mammals are more insulative than brown summer coats and further, the winter coats of more northerly snowshoe hare are longer and denser than those of hares in lower latitudes (Gigliotti et al 2017, Kennah et al 2023. Similarly for a polymorphic raptor, denser contour feather structure has been found in the gray morph of the tawny owl S. aluco, providing increased plumage insulative capacity over red morph individuals (Koskenpato et al 2016).…”