Otters eat, mate, play, and sleep in water. They are the only mammals that can do this. Bundled in the densest fur on the planet, otters are warm and buoyant thanks to air bubbles trapped by their hairs (600,000 to a million per square inch) and blubber. They can stay in the water for up to 20 years.
Sea otters are known to rest by wrapping themselves in kelp to avoid drifting away while they nap. They also hold hands to stay close to each other while they sleep. A group of sleeping otters is called a raft and researchers have recorded over 1,000 in a single raft.
River otters may find a secluded spot in the mud or under a log to snooze. They are also known to take over abandoned beaver lodges and burrows near rivers. They are generally crepuscular animals and are most active at dawn and dusk.
As members of the Mustelidae family, otters are closely related to weasels, badgers, ferrets and mink. But they are not the same as those other animals, and their habitats are different. While otters cannot hibernate, they can get pretty cozy in the winter with their thick waterproof fur and insulating body heat. In the wild, otters are found year-round, but many find a safe place to spend the winter in burrows, nooks and crannies of trees or even in old beaver lodges. Their cozy homes help them survive harsh cold and predation while they await warmer temperatures and new opportunities to romp and frolic in the water.