Otter vs Beaver
Verdict: Look at the tail and the build. A beaver has a broad, flat, scaly paddle tail and a stocky body, while an otter has a long, thin, tapered tail and a sleek body. Beavers eat plants, and otters eat fish.
Both are brown, semi-aquatic and often seen in the same stretch of river, but they are unrelated. A beaver is a rodent, North America's largest, with continuously growing front teeth. An otter is a carnivore in the weasel family with sharp canines. Their bodies and diets follow from those roots.
At the water's edge, build is the quickest clue. Beavers are stocky with rounded heads, while otters are long and sleek with dog-like heads. Size separates them too: most adult beavers weigh 40 to 70 pounds, and river otters weigh 15 to 35 pounds. If you see wood chewed to a point or a dam, expect a beaver.
Otter vs Beaver side by side
| Trait | Otter | Beaver |
|---|---|---|
| Classification | Carnivore (weasel family) | Rodent |
| Tail | Long, thin and pointed | Broad, flat and scaly paddle, about 10 in long |
| Body shape | Long and sleek, dog-like head | Stocky with a rounded head |
| Weight | About 15 to 35 lb | Mostly 40 to 70 lb; some reach 100 lb |
| Length | About 40 to 60 in | About 3 to 4 ft including tail |
| Diet | Fish, crabs, frogs, shellfish and sometimes birds | Inner bark, leaves, roots and aquatic plants |
| Teeth | Sharp canines and pointed molars for gripping fish | Long front incisors with orange enamel that never stop growing |
| Home | Uses existing crevices, burrows and tree roots | Builds dams and lodges or bank dens with underwater entrances |
Last verified October 2026. Typical values; individual animals, products and local prices vary.
When you are looking at which
Otter
- The animal is long and slim, swimming low with a thin tail trailing behind.
- It is hunting fish, crabs or frogs and eats them on a bank.
- It is with a family group, a mother and pups, in the water.
- It swims low and may dig tunnels in snow over frozen water.
Beaver
- The animal is chunky with a flat, scaly paddle tail it may slap on the water.
- It is chewing bark or twigs, or has gnawed a tree trunk to a point.
- There is a dam, a stick lodge or a bank den with an underwater entrance.
- It looks heavy and barrel-shaped, around 40 to 70 pounds.
How this works
The quiz scores tail, body shape, diet, nearby signs and estimated weight. Each answer points to otter or beaver, and the side with more answers wins. Tail and body shape are the most reliable, and a close score is reported as too close to call.
It covers North American river otters and American beavers. Sea otters, muskrats and nutria also swim in North American waters and are not covered here. A short or partial view makes size estimates unreliable, so rely on the tail when you can.
Where these numbers come from
The figures and defaults on this page are based on:
- Alaska Department of Fish and Game: Beaver Species Profile, supports beaver size, tail, diet, teeth and dens (checked October 2026)
- Alaska Department of Fish and Game: River Otter Species Profile, supports river otter size, diet and behavior (checked October 2026)
- Discover Wildlife: Beaver vs otter, supports tail, teeth, diet, body shape and classification (checked October 2026)
Field-identification guide. Wild animals can bite, so watch from a distance.
Frequently asked questions
Is an otter related to a beaver?
No. Beavers are rodents, while otters are carnivores in the weasel family. Their similar swimming habits come from living in the same waterways.
Do otters build dams?
No. Otters use existing crevices, burrows and tree roots. Dams and lodges are beaver work.
How big is a beaver compared to an otter?
Alaska Fish and Game says most adult beavers weigh 40 to 70 pounds, while river otters weigh 15 to 35 pounds and have a slimmer build.
What do otters and beavers eat?
Otters eat fish, crabs, frogs and shellfish. Beavers eat the inner bark of trees, leaves, roots and aquatic plants.
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