Bryan McAllister’s personal reference notebook
July 29, 2026Short & citedBlog
Civic Viewpoint.
A quiet encyclopedia with a personal desk
Field Notes • Mammals

Beaver

Beavers are large, semiaquatic rodents in the genus *Castor*.

Updated July 29, 20261 min readCited sources

Beavers are large, semiaquatic rodents in the genus *Castor*, best known for cutting trees and building dams, lodges, and canals in freshwater habitats.

What it is

Beavers are the largest rodents in North America and Eurasia. They have stocky bodies, short legs, webbed hind feet, and a broad flat tail. Two living species exist: the North American beaver (*Castor canadensis*) and the Eurasian beaver (*Castor fiber*). They are herbivores, feeding mainly on bark, twigs, leaves, stems, roots, and aquatic plants.

Why it matters

Beavers are ecosystem engineers. By building dams, they slow water flow, create ponds, and maintain water levels that protect lodges and food stores. This activity benefits many other species and shapes freshwater habitats. In Canada, beavers are widespread and culturally significant, though they are not endangered.

Key details

North American beavers typically live 10–12 years in the wild. Both living species are listed as Least Concern by the IUCN. Beavers prefer freshwater wetlands with woody vegetation like willow, aspen, poplar, birch, and maple. Their populations have rebounded after historical declines from trapping and habitat loss.

In short

  • Beavers are the largest rodents in North America and Eurasia.
  • They build dams to manage water levels and create safe ponds.
  • Diet consists of bark, twigs, leaves, and aquatic plants.
  • Both species are Least Concern and not endangered in Canada.
Canadian angle

Beavers are strongly associated with Canada and are widespread across Canadian freshwater ecosystems. They are also an important cultural symbol and an ecologically significant native species in the country.[1][6][14]

Quick questions

What is a beaver?
A beaver is a large semiaquatic rodent in the genus *Castor*, known for dam building and tree cutting.
Why do beavers build dams?
They build dams to slow water flow and keep water levels high for safety, shelter, and food access.
Are beavers endangered in Canada?
No. Beavers are not generally endangered in Canada; the North American beaver is listed as Least Concern globally.

Sources

  1. Smithsonian's National Zoo & Conservation Biology Institutehttps://nationalzoo.si.edu/animals/beaver
    Supports: Habitat, diet, lifespan, and ecological role of beavers.
  2. Oakland Institute / OAEChttps://oaec.org/our-work/water-institute/beaver-home/beaver-facts/
    Supports: Two species of beaver, native range, and lifespan in the wild.
  3. Trout Unlimited / Wild Trouthttps://www.wildtrout.org/content/beaver-facts
    Supports: Habitats and reason beavers build dams.
  4. World Wide Fund for Nature UKhttps://www.wwf.org.uk/learn/fascinating-facts/beavers
    Supports: Physical description, habitat, diet, and conservation context.
  5. National Geographichttps://www.nationalgeographic.com/animals/mammals/facts/beaver
    Supports: Diet, lifespan, size, and conservation status.
  6. PBS Naturehttps://www.pbs.org/wnet/nature/blog/beaver-fact-sheet/
    Supports: Two species, Canadian range, lifespan, and conservation status.
  7. Chattahoochee Nature Centerhttps://chattnaturecenter.org/visit/experience/wildlife/animal-facts/beaver/
    Supports: Diet and purpose of dams.
  8. Encyclopaedia Britannicahttps://www.britannica.com/animal/beaver
    Supports: General definition, habitat, dam building, and range history.