This amphibious mammal's sleek coat is composed of double-layered, tightly packed hair. Many hours are spent grooming and oiling the fur to keep it water repellent. The river otter has webbed feet for swimming and numerous stiff whiskers called vibrissae around the snout for detecting movement of prey underwater. Some of the funniest contortions in and out of the water are important behaviors for the otter. Rolling around on grasses or logs may be done to dry off or leave a scent trail behind. Scent markers communicate territorial boundaries, identity, and sex to neighboring animals. Once widespread across North America, river otters have declined and disappeared from many states because of overhunting and loss of freshwater habitats.