There are only two living species of beavers in the world, and they are among the most remarkable rodents for their engineering skills and ecological influence. These two species are:
- The North American Beaver (Castor canadensis)
- The Eurasian Beaver (Castor fiber)
Beavers are the second-largest living rodents, after capybaras, weighing up to 50 kg (110 lb).
They have stout bodies with large heads, long chisel-like incisors, brown or gray fur, hand-like front feet, webbed back feet, and tails that are flat and scaly. The two species differ in skull and tail shape and fur color. Beavers can be found in a number of freshwater habitats, such as rivers, streams, lakes and ponds. They are herbivorous, consuming tree bark, aquatic plants, grasses and sedges.
North American Beaver (Castor canadensis)
Distribution and Habitat
The North American beaver is native to North America, found throughout Canada, the United States, and parts of northern Mexico. It thrives in freshwater environments like rivers, streams, ponds, and lakes, especially in forested areas with abundant trees for building materials and food.
Physical Description
This species is a large, semi-aquatic rodent, usually weighing between 16 and 32 kilograms (35–70 pounds). It has a broad, flat tail covered in scales, webbed hind feet, and dense, waterproof fur that ranges from chestnut brown to almost black. Its strong front teeth (incisors) are orange due to iron content, which keeps them sharp and strong for gnawing wood.
Behavior and Ecology
North American beavers are master builders. They construct dams to create ponds that provide protection from predators and easy access to food during winter. They also build lodges, dome-shaped homes made of branches and mud, with underwater entrances for safety. These activities have a profound ecological impact — beaver dams slow water flow, reduce erosion, create wetlands, and support diverse wildlife.
Diet
Their diet mainly consists of tree bark, twigs, and leaves, especially from willow, aspen, birch, and poplar. In summer, they also eat aquatic plants and herbs. Beavers do not eat the wood itself but rather the cambium, the soft layer beneath the bark.
Reproduction and Lifespan
Beavers are monogamous, mating for life. Breeding occurs in late winter, and after a gestation of about 3.5 months, females give birth to 2–4 kits in spring. Kits stay with the family for two years before dispersing. Beavers can live up to 10–12 years in the wild.
Eurasian Beaver (Castor fiber)
Distribution and Habitat
The Eurasian beaver once ranged widely across Europe and Asia, but due to overhunting for fur and castoreum (a gland secretion once used in perfumes and medicines), it was nearly extinct by the early 20th century. Through extensive conservation efforts and reintroductions, it has recovered and is now found in Scandinavia, Russia, parts of Central Europe, the UK, and Western Asia.
Physical Description
Similar in general appearance to its North American relative, the Eurasian beaver is slightly larger, with adults weighing up to 38 kilograms (84 pounds). Its head is narrower, its tail more elongated and less broad, and its fur generally lighter in color. Another distinction is in the skull and dental structure, which differ subtly but consistently between the two species.
Behavior and Ecology
Like its North American cousin, the Eurasian beaver builds dams and lodges, though the materials and scale can differ depending on local resources. It also shapes entire ecosystems, creating wetlands that filter water and provide habitat for birds, fish, and amphibians. Eurasian beavers tend to live in family groups and maintain well-marked territories using scent mounds made from mud and castoreum.
Diet
Their feeding habits are nearly identical to those of the North American beaver. They prefer deciduous trees such as willow, birch, alder, and aspen, and in warmer months they consume a wide variety of aquatic vegetation and grasses.
Reproduction and Lifespan
Eurasian beavers also form monogamous pairs. Breeding typically occurs from January to March, with kits born around May or June. Litter sizes are smaller than those of the North American species, usually 1–3 kits. In the wild, they can live for around 12–15 years.
Differences Between the Two Species
| Trait | North American Beaver (C. canadensis) | Eurasian Beaver (C. fiber) |
|---|---|---|
| Geographic Range | North America | Europe and Asia |
| Tail Shape | Broader and more oval | Longer and narrower |
| Size | Slightly smaller | Slightly larger |
| Fur Color | Darker, often chestnut to black | Lighter, often tan to reddish-brown |
| Litter Size | 2–4 kits | 1–3 kits |
| Chromosome Number | 40 | 48 |
| Interbreeding | Cannot interbreed | Cannot interbreed |