Otter — aquatic mustelids: overview, behavior, habitat and conservation

Physical characteristics and behaviour

Otters have thick, insulating fur rather than blubber, which helps them remain warm in cold water. Many species are playful and highly agile swimmers. Social organization ranges from solitary to group-living; a common collective noun for a group of otters is a "romp" due to their energetic social play. They shelter in dens often called holts or bank dens; more on aquatic habitats is available at water habitat resources.

Classification and species

Otters belong to the mustelid family, which also includes weasels, badgers and wolverines. There are around a dozen species of otters worldwide, each adapted to specific environments. For taxonomic details consult mustelid references.

Distribution and habitats

Different species occupy rivers, lakes, wetlands and coastal seas. River otters are commonly associated with inland waterways while sea otters live along rocky shorelines in the northern Pacific. Otters are found on most continents; see regional distribution notes at river habitats, marine habitats and specific information on the sea otter at sea otter resources. Broad continental occurrence is summarized in distribution summaries, with none native to Australia and Antarctica.

Diet, ecology and conservation

Otters are primarily fish and invertebrate eaters; some species use stones or tools to open shells. They can act as ecological indicators and, in coastal systems, keystone predators that help maintain healthy kelp forests. Major threats include habitat degradation, pollution (including oil spills), entanglement in fishing gear and historical hunting for fur. Conservation status varies by species and region; many benefit from habitat protection, pollution controls and legal safeguards.

• Key facts: dens called holts, groups often called romps.
• Adaptations: dense fur, webbed feet, aquatic hunting skills.
• Human relevance: ecological role, cultural value, conservation concern.