Point out to students that beavers do NOT breathe under water; they hold their breath by conserving oxygen. Compare the beaver, as a mammal with lungs, to a fish that can breathe underwater with gills.

How long can a beaver hold its breath?

Aquatic Adaptations

These attributes allow beavers to swim at speeds of up to five miles an hour. They can remain underwater for 15 minutes without surfacing, and have a set of transparent eyelids that function much like goggles. Their fur is naturally oily and waterproof.

How do beavers breathe?

They can close their mouths by closing a flap located behind their teeth, allowing them to clamp onto logs or chew while holding their breath. Like all rodents, their teeth continue to grow their entire lives. When beavers go below the surface, they close their ears and nostrils with flaps of skin that act as valves.