Facts About Otters
Published October 18, 2026 · FactsSeeker
Otters are mammals closely tied to water, but they are not all the same. The source describes differences between river otters and sea otters in buoyancy, habitat, feeding, family life, and the challenges they face.
Otters are water-specialized mustelids
Otters are mammals in the family Mustelidae, the weasel family. Unlike their relatives, they are described as the only serious swimmers in that family, so water is central to how their bodies and behavior work. [1]
Their bodies help them dive and steer
An otter’s body is built for efficient movement through water. A streamlined shape helps with diving and swimming, while the flattened tail supplies sideways propulsion and the back feet help steer. [1]
They can seal out water while swimming
Most otters have webbed feet, although the amount of webbing varies. They can close their ears and nose underwater, and the source says they can remain submerged for five to eight minutes, depending on species, because the heart rate slows and oxygen use drops. [1]
Otters can swim in more than one posture
Otters are not limited to a single swimming position. The source says they like swimming on their backs and sides, and it adds that they can see just as well underwater as above water. [1]
Fur is essential for warmth and buoyancy
Otter fur is functional equipment, not just covering. A dense undercoat traps air beneath longer waterproof guard hairs, so grooming is important; matted fur, including oil fouling, can interfere with hunting and staying warm. [1]
Sea otters float differently from river otters
Sea otters are especially buoyant because air trapped in their fur helps them float at the surface. River otters are less buoyant and must actively swim to keep afloat, showing that otter species differ in how they rest or move at the surface. [1]
Whiskers help otters sense water and prey
Otter whiskers are sensitive tools for hunting and awareness. The source explains that whiskers above the lips detect changes in water currents as well as prey or potential predators in the water. [1]
Play is part of social behavior
Otters are described as energetic, curious, and playful, with behaviors such as throwing objects, wrestling, twirling, chasing, and sliding. This activity is not merely entertainment; the source links it to courtship, social bonding, communication, and practice for young otters. [1]
Otters communicate with sounds and scent
Otters use many sounds, including whistles, growls, screams, barks, chirps, moans, and coos. River otters also scent mark with glands near the tail base, and repeated urination or defecation sites can serve as communication. [1]
They live on most continents but not everywhere
Otters occur across a wide geographic range, but the source excludes Australia and Antarctica. It also says they do not live in deserts, polar regions, or mountains, and that typical otter habitat includes both water and land except for the sea otter. [1]
Many otters use dens they did not build
Except for sea otters, otters usually live in dens, and many of those dens were made by other wildlife. Beaver habitat can be especially useful because otters benefit from the dams and dens beavers create. [1]
River otters and sea otters eat different mixes of prey
River otters mostly eat fish along with frogs, crayfish, crabs, mollusks, and occasional small mammals or birds. Sea otters eat many similar foods but are especially associated with sea urchins, abalone, crabs, fish, octopuses, mussels, and clams, and they are the otters described as using rocks as tools to open shellfish. [1]
Feeding demands can be high
Otters can need frequent meals because of their energetic lifestyles. The source says river otters use lots of energy and digest food very quickly, while sea otters need to eat nearly a third of their body weight each day. [1]
Typical social groups center on mothers and pups
For most otters, the source describes social groups as a mother with her older offspring and newest pups. Males often spend much of their time alone or with a few other males, although larger gatherings may form during breeding time or where food is abundant. [1]
Most pups begin life helpless in a den
Most otter pups are born in dens with their eyes closed and depend on their mother. They begin exploring the den at about one month, learn to swim at two months, and typically stay with their mother and siblings until about one year old. [1]
Sea otter pups start life differently
Sea otter pups are born in the ocean setting with their eyes open and a coat that lets them float before they can swim. Their mothers carry them on the stomach until about two months old, when they start swimming and diving independently. [1]
Threats and predators vary by species and habitat
The source emphasizes that what otters must fear depends on where they live. It lists different predators for different otters, and it also describes conservation pressures such as water pollution, oil spills, habitat destruction, trapping, hunting, fishing nets, and changes to rivers. [1]
Sources & further reading
Otter traits vary by species and habitat. The source also cautions that native populations are hard to determine because otters can be secretive and widely distributed, so broad statements about abundance should be treated carefully.
Sources checked 2026-10-17. Our approach to facts · Suggest a correction