 On a longer timescale , animals like the Arctic hare , Arctic fox , stoat , and rock ptarmigan change their coat colour ( by moulting and growing new fur or feathers ) from brown or grey in the summer to white in the winter ; the Arctic fox is the only species in the dog family to do so . However , Arctic hares which live in the far north of Canada , where summer is very short , remain white year @-@ round . 
