1. Short, heavily furred, rounded ears - Limits dispersal of heat 2. Coat changes colour - In summer, the fur is reddish brown - In winter, it develops a layer of insulating fat, and a thick white coat, including fur on the bottom of its paws 3. Phenomenal breeding rate - Females give birth to as many as 25 cubs per year - However, most of these do not survive for more than 6 months - Thus, the high birth rate helps to maintain population growth 4. Able to remain active at temperatures of around -50 degrees Celsius - Remains active without a corresponding increase in metabolic rate - However, mature foxes rarely live for more than a few years in the harsh arctic climate