page_title: North American river otter
section_title: Form and function
hierarchical_section_title: North American river otter / Description / Form and function
caption_attribution_description: A trip to the River dart and these extremely photogenic Otters were happy to oblige! These Otters are simply mad! They loved the camera and were fairly trusting, I would not of wanted to get too close but they were certainly playful
context_page_description: The North American river otter, also known as the northern river otter or common otter, is a semiaquatic mammal endemic to the North American continent found in and along its waterways and coasts. An adult North American river otter can weigh between 5.0 and 14 kg. The river otter is protected and insulated by a thick, water-repellent coat of fur.
  The North American river otter, a member of the subfamily Lutrinae in the weasel family, is equally versatile in the water and on land. It establishes a burrow close to the water's edge in river, lake, swamp, coastal shoreline, tidal flat, or estuary ecosystems. The den typically has many tunnel openings, one of which generally allows the otter to enter and exit the body of water. Female North American river otters give birth in these burrows, producing litters of one to six young.
  North American river otters, like most predators, prey upon the most readily accessible species. Fish is a favored food among the otters, but they also consume various amphibians, freshwater clams, mussels, snails, small turtles and crayfish. The most common fish consumed are perch, suckers, and catfish.
context_section_description: The North American river otter is physically well-equipped for aquatic life. The ears are short, the neck is the same diameter as the head, the legs are short and powerful, the toes are fully webbed, and the tail (one-third of body length) is tapered. These qualities give the North American river otter a streamlined profile in water, but reduce agility on land. The smell and hearing abilities of the North American river otter are acute. The North American river otter has a delicate sense of touch in the paws in addition to great dexterity. North American river otters characteristically approach within a few feet of a boat or a person on shore because they're near-sighted, a consequence of vision adapted for underwater sight. North American river otters have transparent nictitating membranes to protect their eyes while swimming.
  The right lung of the North American river otter is larger than the left, having four lobes compared with two for the left. Reduced lobulation of the lungs is presumed to be adaptive for underwater swimming. In addition, the length of the trachea of the North American river otter is intermediate between that of terrestrial carnivores and marine mammals. The mean tracheal length of the North American river otter is 15.3 cm (6.0 in), or 23.2% of the body length. A shorter trachea may improve air exchange and increase lung ventilation in diving mammals.
  Most mustelids, including otters, have specialized teeth, including sharp canines and carnassials that inflict lethal bites to prey. Also, North American river otters have large molars used for crushing hard objects, such as the shells of molluscs. An adult North American river otter has a total of 36 teeth. Additional premolars may be present. The dental formula is .
caption: North American river otter have small ears
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