The reindeer, also known as caribou in North America, is a species of deer found in northern Europe, Siberia and North America. Both male and female reindeer grow antlers annually, with the size being typically larger for males. They have the largest antlers relative to their body size among any living deer species. The color of the fur varies between individuals, both depending on subspecies and season. With reindeer in northern areas having typically a lighter coat than individuals found in the south part of their range. Males weigh between 159 - 182 kg (350 - 401 lb) while females are smaller and weigh between 80 - 120 kg (176 - 264 lb). Reindeer are migratory and can be found in huge herds with up to 500,000 individuals during migration periods. During the rut, they gather in smaller mixed gender groups with a few males guarding a group of females. Reindeer prefer open areas both for feeding and for resting as it allows them to keep an eye out for predators such as lynx and brown bears.