Most snowshoe hares, to cope with the changes in their environment over the course of the year, change their colour to match the season. As autumn days grow shorter and colder, many of the hares shed their brown fur for coats of bright white, which provides camouflage in their snowy wintertime habitats. However, while white-winter hares predominate, in areas where winter snow is less extensive some hares remain brown year-round.
A recent genomic study, confirmed by an examination of the genetic parent-offspring relationships of captive hares, identified expression of the Agouti pigmentation gene as the underlying driver of the autumnal colour change.
However, the difference between winter-white and winter-brown hares was not found to be a product of a recent mutation, but rather the introduction of genetic material from another species – the black-tailed jackrabbit, which does not change its colour.
According to the authors of the study, the evolution of winter-brown coats in snowshoe hares through hybridization may have allowed them to survive in less snowy regions. Genetic exchange, they argue, is a critical component of local adaptation to rapidly changing environments.