Beavers are the largest rodents in North America. It belongs to the genus Castor. Eurasian Beaver is native to Asia and Europe whereas North American beaver is a resident of North America. In the years gone by, beavers’ range has reduced to its historical habitat. The physical appearance of these two extant species appears to be same but they show significant difference in their behaviors.
Beaver Facts For Kids
- Beaver is highly nocturnal and it lives a semi-aquatic life. It is generally known for building canals, lodges, and dams.
- Beaver is one of the largest rodents in the world—second only to Capybara.
- They are dark brown rodents with flat tail. The tail lacks hair.
- The length measures around 80 – 140 cm with the tail making one-third of its total length.
- Many adult beavers weigh up to 16 – 31.5 kg with the total length measuring at 120 cm. These rodents have powerful bulky body which is supported by large legs.
- The hind legs are shorter than forelegs. This means that they are greater in height at the hips than at shoulders.
- Beavers are short but they have a thick neck which because of which their shoulders are not so prominent.
- Beaver’s tail is yet another distinguishing physical feature. This paddle-like tail averages 230 – 323 mm in length along with the width of 110 – 180 mm.
- Beavers typically wobble on land but they are able to gallop when threatened. Adult beavers can even walk straight like humans (bipedal walk) while carrying some food with their chin.
- Beavers are not bad swimmers. They move slowly and deliberately by kicking hind legs in an alternate fashion.
- It is reasonable to assume that beavers are marine mammals instead of simply terrestrial mammals. They have 200 mm long webbed toes which helps the animal in swimming. These toes are absolutely movable and beavers also use them for brushing their hair.
- They build many dams not only to seek protection from potential predators but also due to the fact that the food floats on the surface.
- Beaver’s size and growth depends on several factor including climate, extent of exploitation, quality and availability of food, and latitude.
- Beavers have million years old settlement in North America—they had lived some 40 – 600 million years before. This shows that beavers had started living well before the European settlement.
- These rodents used to live in the northern tundra and subarctic mainland of Canada—ranging from the mouth of MacKenzie River to the Northwest Territories.
- Beavers were once present in large numbers in Alaska, not occurring in the Arctic Slope including Canadian border (Hakala 1952).
- With the vast increase in the United States land, beavers were forced to occupy wetlands and riparian habitats, in the arid southwest.
- Beavers had almost completely disappeared from several regions of southern Nevada and southern California.
- It’s true that beavers’ historical distribution (in Mexico) is hard to determine, they had existed in large numbers in Rio Grande River and Colorado River. A handful number of these species still occurred along the Gulf of Mexico.
Beaver is capable to adapt an altogether new habitat and thus it has enabled their population to grow in natural and human-made habitats. Over the years they have established their colonies in riparian areas in hot and cold deserts; in taiga and tundra in the far North; marshes and bottom-land hardwood forests in the Deep South, and elevations as high as 3,400 meters above sea level.
Beavers like to build habitats in Rocky Mountains probably because they prefer wide alleys. Generally they would live near flowing streams and water but they can adjust in bogs that lack open water.
Beavers fancy living in semiaquatic and riparian habitats. The height of the dams which they build is 10 ft (3 m) with length measuring hundreds of feet but on average they are 65 – 98 ft (20 – 30 m). Beavers build dams only when food is scarce but if food is abundant they will not build such dams.
Beavers live in wood lodge, bank den, and bank burrows.
Ecology and Diet
- Beaver is extremely opportunistic herbivores and they feed on a variety of woody plants. In the southern part beavers like to eat many plants species whereas the northern tip rarely feeds on plants.
- Herbaceous plants make most of the beaver’s diet when they are readily available.
- In the southern and central United States beaver consumes riparian and aquatic grasses and forbs together with cultivated grains and crops.
- Woody Material 53%
- Grasses 25%
- In summer herbaceous plants make up 90% of the feeding time. In spring and fall these plants constitute 40 – 50%. In the West and Southwest beavers consume cattails, rushes, sedges, and grasses.
- Deciduous woody plants are important sources of food for beavers. Other foods include buds, roots, barks, leaves, twigs, noncorky bark, fruits of woody plants, and acorns.
Want to Learn More? What Do Beavers Eat?
Reproduction and Development
- Beavers reach maturity at the age of 1.5 – 3.0 years although they are able to breed few months before first breeding. Some species however reach maturity as early as 2 years.
- These animals generally breed in winter and females litter in late spring. They give birth to only 1 litter each year. The breeding season is fairly long—from November to March and parturition between February and November.
- The gestation period averages 100 days.
- Beavers of southeastern United States typically have smaller litters. The litter size can go up to four or even six. Western and northern beavers usually have larger litters. Perhaps the varied size of litters is due to the weight of mother and the quality of habitat.
- Beaver kits weigh no more than 0.5 kg and their entire body is covered with fur. In captivity they can learn to swim at 4 days. Kits can walk bipedal 90 days after birth. They drink 25 ml milk each day. Kits will start eating solid food after 1 – 4 weeks.
- Beavers spend a large amount of time in small colonies. They are known to produce seven vocal sounds including a hiss, growl, and a whine. Beavers repeat whine in quick succession.
- Although beavers are quite passive towards humans, at times they can become aggressive. However, the most common which they produce is by striking water by its tail. They do this either to send warning signals to other family members; or to drive away potential predators.
- Beavers use scent marking in order to communicate with each other.
- They are nocturnal and crepuscular. Home range depends on the social organization of beavers.
- Unlike other rodents, beaver builds dams, canals, and ponds just to have a favorable aquatic habitat. They use woody vegetation along with other materials to build dams. Other materials include tamarisk, plastic, aquatic plants, metal, corncobs, cornstalks, sagebrush, and conifers. Beavers also build lodges in shallow lakes and ponds with the help of dead sticks and freshly cut tree branches. In regions without ice, beavers build dams all year round but they are less active in summer.
- They become highly active in evening around 6:00 p.m. Adult beavers typically spend much of their time in foraging, travelling, and sitting in the lodge. When ice covers land beavers conserve energy by staying close to their homes.
- They have a maximum lifespan of 24 years in the wild but they mostly live up to seven to eight years.
Mortality and Predation
Timber wolf is the potential predator of beaver. Wolf hunts beaver on an ice-free land when almost half of their diet must be composed of beavers. Coyotes and mountain lions are also known to kill beaver which led to the population reduction of beaver in much of the major habitats. Other predators include bobcat, river otters, wolverines, mink, and bears.
- In 1988, beaver’s population was estimated at 6 – 23 million. At present they are living in much of North America, although habitat loss and other degradation led to the reduction of beaver’s population in its original habitat.
- Since 1834 humans have converted around 195,000 – 200,000 km2 of wetlands to agricultural use in the United States. This was thought to be the original habitat of beavers.
- Thanks to animal’s nature, beavers are highly adaptable as they are able to reside above timberline in mountainous regions. But these rodents have failed to colonize much of Canadian or Alaskan arctic tundra probably because these lands do not offer suitable woody plants.
- Reintroduction continued for many years until 1950s after which the animal’s population remained relatively stable. The last three or four decades saw a remarkable increase in beaver’s population (especially in southeastern states) so much so that it had caused a major nuisance to the timber industry.
- Beavers have also successfully established their colonies in the Colorado River and in the Santa Ana.
- Many countries had introduced these species. Prominent among these countries are Argentina, Finland, and Asian Kamchatka. This indeed had made the original population living in North America to grow beyond their original habitat range.