FaunaHub

Otter

MammalMustelidSemi-aquatic

Sea otters (Enhydra lutris) floating in Glacier Bay National Park, Alaska.

Sea otters (Enhydra lutris) in Glacier Bay National Park, Alaska.

Image: Diego Delso, CC BY-SA 4.0, via Wikimedia Commons.

Overview

Otters are semi-aquatic to fully aquatic mustelids of the subfamily Lutrinae. The group includes the Eurasian otter (Lutra lutra), the North American river otter (Lontra canadensis), the giant otter (Pteronura brasiliensis) of South America, and the sea otter (Enhydra lutris) of the North Pacific. Body plans vary from sleek riverine forms to the heavier, sea-adapted body of the sea otter.

Habitat & Range

Otter habitats range from cold marine kelp forests (sea otter) to tropical rivers (giant otter) and temperate rivers, lakes, and coasts (Eurasian and river otters). Most species are highly dependent on clean water with abundant prey. Pollution, water-quality decline, and habitat loss are recurring conservation pressures across the group.

Diet

Most otters are carnivorous, with fish, crustaceans, and molluscs forming the bulk of the diet. The sea otter is a specialist on sea urchins, abalone, and other invertebrates and is well-known for using stones as tools to open prey. Diet varies substantially by species and habitat.

Behavior

Some otter species are largely solitary, others are highly social. Giant otters live in close-knit family groups. Sea otters form "rafts" of resting individuals at sea. Otters are agile swimmers and often exhibit visible play behaviour with conspecifics and with objects.

Human Interaction & Conservation

Conservation status varies widely. The sea otter, giant otter, and several Asian otter species are particularly threatened by historical hunting, illegal trade, habitat loss, and pollution. The Eurasian otter has recovered in several European populations after substantial 20th-century declines. Otters are wildlife, not pets; private keeping is restricted or banned in most jurisdictions. Confirm species-specific status and law with the IUCN Red List and local wildlife agencies.

Similar Animals

Other mustelids include weasels, ferrets, badgers, wolverines, and martens. The sea otter is sometimes confused at distance with the unrelated marine mammals, but its dense fur and floating posture are characteristic.

Frequently Asked Questions — Otter

How are sea otters different from river otters?
Sea otters (Enhydra lutris) are larger, denser-furred, and almost entirely marine, often living their whole lives in nearshore ocean kelp habitats. River otters and the various Old World otters are smaller, more sleekly built, and primarily inhabit fresh or brackish waterways. They are different species in different genera.
Why do sea otters use rocks?
Sea otters are documented tool users, employing stones to break open hard-shelled prey such as urchins and bivalves. This is one of the best-known examples of mammalian tool use outside the great apes.
Can otters be kept as pets?
Most jurisdictions restrict or prohibit private keeping of otters. They are highly active, highly social, and require specialised aquatic housing far beyond what private owners can typically provide. Many otter species are also protected under CITES or domestic law.
Are otters endangered?
Conservation status varies sharply by species. The giant otter and sea otter are particularly threatened by historical hunting and continuing habitat pressures, while the Eurasian otter has recovered in several European populations. Verify per species on the IUCN Red List.

Sources and further reading

Authoritative wildlife references used for general educational context. Conservation status should always be verified against current IUCN Red List data. External links open in a new tab.