Beavers are the second-largest living rodents, after the capybaras. They have a head-body length of , with a tail, a shoulder height of and a weight of . Males and females are almost identical externally. Their bodies are streamlined like marine mammals and their robust build allows them to pull heavy loads. A beaver coat has 12,000–23,000 hairs/cm2 (77,000–148,000 per in2) and functions to keep the animal warm, to help it float in water, and to protect it against the teeth and claws of predators. Guard hairs are long and typically reddish brown, but can range from yellowish brown to nearly black; while the underfur is long and dark gray. Beavers molt during the summer.