An otter hunts fish with a sleek, streamlined body, while a beaver is a stockier rodent famous for gnawing down trees to build dams. One tell-tale clue: beavers build things, otters don't.
The core difference
Otters are slim, fish-hunting mammals, while beavers are larger rodents known for felling trees and building dams.
- otter — a sleek, semi-aquatic mammal with dense fur that hunts fish in rivers or coastal waters: A pair of otters played in the shallows near the dock.
- beaver — a large semi-aquatic rodent known for gnawing down trees and building dams: A family of beavers had dammed the stream, flooding part of the meadow.
How to tell them apart
Look at what each animal is doing. An otter in the water is usually hunting fish, moving with a lean, sinuous body built for speed. A beaver is more often seen gnawing at a tree trunk or patching a dam with mud and branches, and its body is stockier, built for construction rather than the chase.
Beaver has picked up a second life as a verb, too: to "beaver away" at something means to work hard and steadily, a nod to the animal's reputation for tireless building. Otter carries an informal use of its own, describing a slim, hairy build, but it doesn't extend into a verb the way beaver does.
