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Scientific name: Castor canadensis

It is a little known fact that the beaver is our New York State mammal. It may also be our most appealing rodent with its amazing building skills and diligent work ethic. Why does the beaver build a dam? To create a safe shelter. If a pond is deep enough and safe enough, often they will only build a lodge. The  lodge has two entrances, and provides shelter and room for food storage during the long winter months. Their underground tunnels can be quite long and elaborate. They do their work under the cover of darkness as they are largely nocturnal animals.

Beaver are called “ecosystem engineers” because the expanded wetland that they create furnish habitat for a great variety of birds and other wildlife (see Floodplain Forests in our Habitats section).

It is believed that there were many more wetlands hundreds of years ago, when the beaver was more prevalent.


They are large, ranging from 24 to 70 pounds!


Its distinctive flat tail is about a foot long, with the main body being 2 to 3 feet.

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Woody plants from bark and twigs of trees in the winter to the aquatic vegetation such as water lilies in the summer.


They will rarely leave the water but for short periods of time. Wooded streams, ponds and reservoirs are all home to the beaver.

Life Cycle

Beaver will often mate for life. They have a litter in the spring and these “kits” will stay with the family anywhere from one to three years.

Similar Species

You might see muskrats locally, too in wet locations. They are only 4 pounds and much small than the beaver, and they have a thin, rather than a paddle-like, tail. For more information on the differences between these two read this.

Ecosystem Connections

The dams that beavers create can have both positive and negative effects. On the plus side, they create valuable habitats for wildlife by creating deep wetlands and ponds.  This supports a very diverse ecosystem with many benefits, providing habitat for waterfowl and other mammals, and also reducing downstream flooding while bio-retaining pollutants from stormwater runoff.

Human Connections

  • In the past, beaver were trapped and killed for their skins which made warm garments.
  • Beaver dams can create flooding and damage to roads, property, trails and more.

To learn more about what to do with nuisance beavers, go here to the New York State DEC webpage.

Did You Know?

A beaver will slap its tail to warn others of a threat.

Fun Facts

The beaver is the largest rodent in North America!

Family Structure

Beaver live in colonies. There might just be a couple or an extended family of up to 12, consisting of parents, the current year litter and perhaps older offspring.

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