<P> Most mustelids, including otters, have specialized teeth, including sharp canines and carnassials that inflict lethal bites to prey . Also, river otters have large molars used for crushing hard objects, such as the shells of molluscs . An adult river otter has a total of 36 teeth . Additional premolars may be present . The dental formula is 3.1. 4.1 3.1. 3.2 . </P> <P> River otters are active year - round, and are most active at night and during crepuscular hours . They become much more nocturnal in the spring, summer, and fall seasons, and more diurnal during winter . They may migrate as a result of food shortages or environmental conditions, but they do not migrate annually . River otters only settle in areas that consist of vegetation, rock piles, and sufficient coverage . </P> <P> River otters swim by quadrupedal paddling, forelimb paddling, alternate hind - limb paddling, simultaneous hind - limb paddling, or body and tail dorsoventral undulation . The tail, which is stout and larger in surface area than the limbs, is used for stability while swimming and for short bursts of rapid propulsion . While swimming at the surface, the dorsal portion of the river otter's head, including nostrils, ears, and eyes, is exposed above water . It must remain in motion to maintain its position at the surface . </P> <P> On land, the river otter can walk, run, bound, or slide . Foot falls during walking and running follow the sequence of left limb, right limb, right limb, left limb . During walking, the limbs are moved in a plane parallel to the long axis of the body . Bounding is the result of simultaneous lifting of the limbs off the ground . As the front feet make contact with the ground, the back feet are lifted and land where the front paws first contacted the ground, producing a pattern of tracks in pairs typical of most mustelids . Sliding occurs mostly on even surfaces of snow or ice, but can also occur on grassy slopes and muddy banks . Sliding across snow and ice is a rapid and efficient means of travel, and otters traveling over mountain passes, between drainages, or descending from mountain lakes often slide continuously for several hundred meters . Rear leg paddling enables continuous sliding where gravity is an insufficient or an opposing force . During winter, the river otters heavily use openings in the ice, and may excavate passages in beaver dams for accessing open water . </P>

What does a baby river otter look like