River otters are well suited to life in the water. They have streamlined bodies, webbed feet and long, tapered tails. Their ears and nose close when they go underwater. Dense, oily fur and heavy layers of body fat insulate them in the water. The have an acute sense of smell, and prominent facial whiskers, which are extremely sensitive to touch. Otters are dark brown with pale brown or gray bellies. The muzzle and throat are silvery. Males and females look alike, although males are larger. Otters are relatively long-lived. In captivity, some bred at 17 years and lived to 19 years of age. They are graceful, powerful swimmers and can remain submerged for 3 to 4 minutes. On land, they travel with a loping gate. On snow or ice, they alternate loping with sliding.