Mule deer live throughout western North America in deserts, wooded areas, and mountains. They're called 'mule deer' because of their big ears that look like they could belong to a mule. The male mule deer, called bucks, have antlers. They lose their antlers in the winter and then grow new ones each year. Mule deer are know to change colours - they are tan and brown during the summer but turn grey and brown in the winter.