Species Guide

Otters

Semi-aquatic mammals found on every continent but Antarctica and Australia — including the sea otter, the smallest marine mammal in North America.

Classification

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Mustelidae
Genus: Varies (13 species)

Quick Facts

Smallest: Oriental Small-Clawed: 12–24 in
Largest: Giant Otter: up to 6 ft
Heaviest: Sea Otter: up to 95 lbs
Lifespan: 15–20 years
Diet: Carnivore
Status: 7 of 13 species Endangered/Vulnerable

Habitat & Range

Otters are found across Africa, Asia, and parts of North, Central, and South America — Antarctica and Australia are the only continents without them. Sea otters live in the Pacific Ocean, while most other otter species live in rivers, lakes, and marshes close to land, often in swamp and marsh habitat that helps them avoid predators. Otters defend their land territory but are not territorial in the water.

Sea otter floating with a rock, cracking shellfish

Diet & Senses

An otter's diet varies by species: European and African clawless otters hunt fish, octopus, and frogs, while sea otters specialize in shellfish. To crack open hard abalone shells, sea otters float on their backs and strike the shell against a rock balanced on their belly. Otters eat 15–25% of their body weight a day and can spend up to five hours a day eating, guided by a keen sense of smell.

Did You Know?

Sea otters use tools — floating on their backs and cracking hard abalone shells against a rock balanced on their belly.

Behavior & Life Cycle

Otters are highly social and playful, spending much of their time grooming their dense, two-layer waterproof coat — among the thickest fur of any animal, with at least 250,000 hairs per square inch (up to a million in some species). Gestation lasts 2–5 months depending on species; most litters have 2–5 pups, though high mortality means usually only one survives. Pups typically stay with their mother for their first year and reach sexual maturity between 3 and 6 years old. Otters communicate through clicks, screams, chirps, and squeals, as well as touch and scent marking.