The North American river otter, a member of the subfamily Lutrinae in the weasel family (Mustelidae), 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.

Fish is a favored food among the otters, but they also consume various amphibians (such as salamanders and frogs[3]), freshwater clams, mussels, snails, small turtles and crayfish.

[4] Occasional reports also show the river otter eating other small animals, such as mice, squirrels, birds, and even dogs that they've attacked and drowned.

[22][16] North American river otters characteristically approach within a few feet of a boat or a person on shore due to their near-sightedness, a consequence of vision adapted for underwater sight.

[25]: 52–54 A highly active predator, the North American river otter has adapted to hunting in water, and eats aquatic and semiaquatic animals.

[32] Every study done on the food habits of the North American river otter has identified varying fish species as being the primary component of its diet.

[29][37] North American river otters do not generally handle prey of a large size relative to themselves but there are occasions where they have been observed ambushing and killing adult common snapping turtles while the large turtles (which are roughly equal in average body weight to a North American river otter) are hibernating.

Likewise, the potential predatory impact of otters may be considerable whenever fish are physically confined (most commonly in smaller ponds offering sparse cover or other escape options).

Even in larger bodies of water, river otters may take disproportional advantage of any seasonal concentrations of fish when and where only very limited areas of suitable spawning, low-flow, or over-wintering habitat may exist.

North American river otters famously love to play together, which creates strong social bonds, improves hunting skills, and marks territory.

[19] The North American river otters may leave the den by eight weeks and are capable of sustaining themselves upon the arrival of fall, but they usually stay with their families, which sometimes include the father, until the following spring.

Since their reintroduction to Kentucky in the early 1990s, the otters have recovered to the point that a trapping season was implemented in 2006, and the species is now found in all of the state's major waterways.

[45] In 2010, the Colorado Department of Wildlife reported the river otter, reintroduced to the state in the 1980s, was "thriving" and recommended its protection status be reconsidered.

[48] Historical records indicate North American river otters were once populous throughout most major drainages in the continental United States and Canada prior to European settlement.

[22] The diet of the North American River otters is extensive and mostly consists of fish, frogs, crayfish, turtles, insects and some small mammals.

“The North American river otter (Lontra canadensis) is a predator adapted to hunting in water, feeding on aquatic and semi-aquatic animals.

[51] Likewise, the common carp (Cyprinus carpio) is a preferred fish species for the North American river otter in other regions of Colorado.

[51] Fish species frequently found in the diets of the North American river otters include: Catostomidae, which consists of suckers (Catostomus spp.)

[25] Other fish an integral part of the North American river otters' diets are those that are often plentiful and found in large schools: sunfish (Lepomis spp.

[35] North American river otters may prefer to feed on crustaceans, especially crayfish (Cambarus, Pacifasticus, and others) and crabs more than fish where they are locally and seasonally plentiful.

[28] Amphibians, where regionally accessible, have been found in the North American river otter's diet during the spring and summer months, as indicated in many of the food habit studies.

[25][32] Amphibians and reptiles are more obtainable by the North American river otter during the spring and summer as a result of breeding activity, appropriate temperatures, and water supply for the prey.

[33][51] Invertebrates discovered within scats or digestive tracts could most likely be a secondary food item, first being consumed by the fish that are subsequently preyed upon by the North American river otters.

[51] The few occurrences of mammals found in the North American river otter's diet include remains of the muskrat (Ondatra zibethicus); meadow vole (Microtus pennsylvanicus); eastern cottontail (Sylvilagus floridanus); and snowshoe hare (Lepus americanus).

North American river otter inhabitation is affected by type, distribution, and density of aquatic habitats and characteristics of human activities.

Recently, long-term genetic consequences of reintroduction projects on remnant North American river otter populations has been discussed.

Little effort has gone into assessing the threat of disease to wild North American river otter populations, so it is poorly understood and documented.

[1] Lontra canadensis is listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

[62] The North American river otter is considered a species of least concern according to the IUCN Red List, as it is not currently declining at a rate sufficient for a threat category.