Otters are semiaquatic mammals that belong to the weasel family (Mustelidae) and are noted for their playful behaviour. They are found on every continent except Australia and Antarctica.
There are 13 species in total, ranging from the small-clawed otter to the giant otter. Though most live in freshwater rivers, lakes, and wetlands, the sea otter and the smaller marine otter are found in the Pacific Ocean.
Otters have long, slim bodies and relatively short limbs. Their most striking anatomical features are the powerful webbed feet used to swim, and their seal-like abilities holding breath underwater. Most have sharp claws on their feet and all except the sea otter have long, muscular tails. All otters are expert hunters that eat fish, crustaceans, and other critters.
Otters also have particularly stinky poop, which even has its own name: spraints. It’s thought to get its special odor, which some scientists describe as smelling like violets, from the seafood diet otters eat.
The 13 species of otters range in adult size from 0.6 to 1.8 m in length and 1 to 45 kg in weight. The Asian small-clawed otter is the smallest otter species and the giant otter and sea otter are the largest. They have very soft, insulated underfur, which is protected by an outer layer of long guard hairs. This traps a layer of air which keeps them dry, warm, and somewhat buoyant under water.
Most otter species come ashore to give birth in dens, which sometimes have been used by other animals such as beavers. Sea otters are the exception, giving birth in the water. Baby otters, called pups or kittens, stay with their mothers until they’re up to a year old, or until she has another litter.
Beavers are the second-largest living North-America rodents after the capybaras. Beavers can be found in a number of freshwater habitats, such as rivers, streams, lakes and ponds. They are herbivorous, consuming tree bark, aquatic plants, grasses and sedges.
Adults can be up to four feet long and weigh over 60 pounds. The beaver has webbed hind feet and a large, flat, nearly hairless tail. It uses its tail to help maintain its balance when it is gnawing on trees. It will also slap its tail against the water to signal danger or to warn away predators.
The beaver has short front legs with heavy claws. Their rear legs are longer, and they use their rear webbed feet help propel themselves through the water. When the beaver is under water, its nose and ears close up and a special membrane covers its eyes. It also has dark brown fur on its back and sides and lighter brown fur on its chest and belly.
Most of the beaver’s diet is made up of tree bark and cambium – cambium is the soft tissue that grows under the bark of a tree. They especially like the bark of willow, maple, birch, aspen, cottonwood, beech, poplar, and alder trees.
Beavers live in family groups or colonies. A colony is made up of a breeding male and female beaver and their offspring. Beavers are very territorial and protect their lodges from other beavers. They mark their territory by building piles of mud and marking it with scent.
The beaver can be found throughout North America, except for most of Florida, the desert Southwest, central and southern Mexico, and the northern most parts of Alaska and Canada.
Beavers vs Otters: Key Differences
|Larger, typically 30-60 lbs
|Smaller, typically 10-30 lbs
|Broad, flat, and paddle-like
|Long, tapered, and muscular
|Brown with waterproof, dark underfur
|Dark brown to reddish-brown
|Aquatic, primarily freshwater
|Aquatic, freshwater and marine
|Herbivorous, mainly tree bark and aquatic plants
|Carnivorous, fish, and invertebrates
|Large, chisel-like incisors for cutting wood
|Sharp, pointed teeth for hunting
|Dams and Lodges
|Build large dams and lodges with entrances underwater
|Do not build dams or lodges
|Swim slowly and gracefully
|Live in family groups, colonies
|Often solitary or in small family groups
|Slapping tails on water for warning signals
|Use vocalizations and body language
|Give birth to fully developed young
|Give birth to partially developed young
|10-15 years in the wild
|10-15 years in the wild
|Some species are endangered
|Some species are threatened