White-tailed ptarmigan name "Tetrao (Lagopus) leucurus" by the Arctic explorer John Richardson in 1831. It was later determined that "Lagopus" had sufficient distinguishing features to be regarded as a separate genus and the bird became "Lagopus leucurus". Molecular studies have shown that "Lagopus" is monophyletic, with the rock ptarmigan ("Lagopus muta") and White-tailed ptarmigan being sister species. The position of the willow ptarmigan ("Lagopus lagopus") is less clear cut, it showing some genetic divergence over its wide range. The genus name "Lagopus" is derived from Ancient Greek "lagos" (λαγως), meaning "hare", + "pous" (πους), "foot", in reference to the bird's feathered legs.
Camouflage the brain to vary its opacity. By controlling chromatophores of different colours, cephalopods can rapidly change their skin patterns and colours. On a longer timescale, animals like the Arctic hare, Arctic fox, stoat, and rock ptarmigan have snow camouflage, changing 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. The principle of varying