Average size :  38 to 51 cm (15 to 20 in), 1.3 to 2.3 kg (3 to 5 lb), females slightly larger than males

Coloration :  White in winter (base of hairs dark), tips of ears black; rusty brown or grayish-brown in summer, tips of ears black, tail brown on upper side with white underside.

External characteristics :  Ears from 62 to 68 mm (2 to 3 in); hind feet robust and very long (121 to 150 mm / 5 to 6 in).