Proc. Natl Acad. Sci. USA http://doi.org/mgz (2013)

Having a coat that changes colour with the seasons enables many mammals to maintain camouflage against contrasting white landscapes in winter versus a green/brown summer background. Changes in the pattern of the seasons — for example, earlier snowmelt — associated with climate change have the potential to mismatch seasonal coat colour with that of the environment. The degree of this mismatch depends to a large extent on whether plasticity in the initiation or rate of coat colour change can compensate for changes in seasonal timings.

Scott Mills, from the Wildlife Biology Program, University of Montana, USA and co-workers studied natural populations of snowshoe hares exposed to 3 years of varying snowpack. They found that the hares show plasticity in the rate of the spring white-to-brown moult, but not in the initiation dates of colour change or in the rate of the autumn brown-to-white moult. Mills et al. estimate that without evolution in the timing of seasonal colour change, the reduced snow duration will increase the number of days that white hares will be mismatched on a snowless background by four- to eightfold by the end of the century. Loss of camouflage potentially has serious implications for predation risk for these small mammals.