The beaver is a large semi-aquatic rodent, which is primarily nocturnal, pertaining to the genus Castor. This genus includes two main species, the North American beaver (Castor canadensis) and Eurasian beaver (Castor fiber). They are best known for building dams, canals and lodges, as they are the second largest rodent in the world after the capybara. They live in colonies and work to construct dams to gather deep still water which protects them from predators. This is what also includes them in the pest category, as they can sometimes provoke flooding and they can gravely damage the topography around them by diverting water courses through their constructions.
Description and distribution of beavers
Although similar to each other, there are some differences between the two species mentioned above. The European beaver tends to be larger than the American one, with with larger, less rounded heads, longer, narrower muzzles, thinner, shorter and lighter underfur, narrower, less oval-shaped tails and shorter shin bones, making them less capable of bipedal locomotion. Fur color is also different, as the 66% of the European ones have pale brown or beige fur, 20% have reddish brown, nearly 8% are brown and only 4% have blackish coats. In North American beavers, 50% have pale brown fur, 25% are reddish brown, 20% are brown and 6% are blackish.
The two species are also not genetically compatible, as several attempts to hybridize the two species have been made, but they all resulted in stillborn kits.
The European beaver was nearly hunted to extinction, for its fur, but also for its gland secretion knows as castoreum, as it was believed to have medicinal purposes. It is currently spread in areas such as Scandinavia, Poland, Slovakia, and it has been recently reintroduced in Scotland, Bavaria, Austria, Netherlands and is spreading to new locations.
The North American beaver is mainly native to Canada and the United States, but also to the northern part of Mexico. It has a different diet, as it prefers the inner bark of aspen and poplar trees. They are also usually trapped for their fur, which is used for clothing or the production of hats. Native peoples and early settlers also ate this animal’s meat.
Breeding and dietary information
Beavers are social animals, living in large family groups of monogamous parents, young kits, and the yearlings from the previous spring. The families can have additional members alongside the monogamous pair, even as many as ten members. Larger groups build more lodges, while smaller ones usually only need one. It is known that beaver pairs mate for life, however, should a beaver’s mate die, the remaining one will pair with a different beaver. Both male and female individuals take part in raising their offspring, and they also both participate in building and defending their lodge or territory.
The breeding season commences in January and February. Female North American beavers are usually pregnant for around 107 days in total, after which the beaver mothers typically give birth to their little ones either during the late spring or the beginning of the summer each year. On average, North American beaver litters are made up of three or four little ones. Baby beavers, also know as “kits”, are born well-developed, with open eyes and ample body fur. They are comfortable with the water in the span of a single day post-birth, and are even able to swim by that point. Weaning occurs at approximately 2 weeks in age, although the male and female beavers, as a parental team, rear the kits together for a maximum of 2 years. For the most part, Eurasian beaver litters include between one and three youngsters. However, some litters in rare cases can actually exceed six kits. Weaning generally finishes once the kits are 6 weeks in age, although as with North American beavers, the offspring tend to stay close to mom until their second year.
Beaver diets are not fully consistent as they change by the season. In terms of diet, woody plants are their favorite, especially the inner bark of trees. During the warm summer, a beaver’s diet only consists of only 10% of woody plants. Aspen trees are usually their preference, although beavers feed on black cherry, beech, maple, alder and birch trees as well. Apart from just the bark, they enjoy eating the “cambium” of trees, which is the name for the very soft and smooth layer just below the bark. They also frequently consume the twigs and foliage of various trees, especially red maples, willows and aspens. Rhizomes, pond weeds, bulrush, cattails and water lilies are just a couple of common summertime beaver “dishes.” In the spring and summer, ferns, leaves and grasses are all big components of beaver meals. Although they are good swimmers, beavers do not eat fish, as these animals are vegetarian, as opposed to their cousins, the muskrats.
When it comes to their predators, the most common ones include fishers, coyotes, hawks, brown and black bears, northern river otters, lynx, eagles, mountain lions, owls, wolverines and wolves. People are also serious threats to North American beavers, as they sometimes hunt them for their skins and fur. The European beavers also have a diverse array of predators, some of which are red foxes, brown bears, lynx and Eurasian wolves. They are also hunted for they fur, so humans can also be considered a common predator as well.
Beavers as pests
The beaver works as a keystone species in an ecosystem by creating wetlands that are used by many other species. Next to humans, no other extant animal appears to do more to shape its landscape. This is part of why they are also considered pests, as the damage they can create with their dams and lodges, can cause costly damages properties and the areas around them. Beaver dams are created as a protection against predators, such as coyotes, wolves and bears, and to provide easy access to food during winter. They are avid builders, that work at night and can rebuild a damaged dam overnight. The ponds created by their well maintained dams will isolate the beavers’ home, but the harvesting of trees and flooding of waterways may interfere with other land uses. It is estimated that beavers cause $100 million worth of damage every year in the United States alone. This sum is predominantly made up of property costs that are incurred as a result of their behavior.
They can manipulate their environment quite dramatically, redesigning it to suit their needs by building dams, canals and lodges. A clear proof of this is the fact that the largest dam that has been built by beavers in Wood Buffalo National Park, Alberta, Canada reaches an amazing 2,790 feet, or 850 meters, in length, making it is so big that it is actually visible from space.
Beavers are known to maintain and defend territories, which are areas for feeding, nesting and mating. They mark their territories by constructing scent mounts made of mud, debris and castoreum on the border of their territory. Due to the fact that they invest so much energy in their territories, beavers are intolerant of intruders. They have been constantly trapped, and they are trapped to this day, even if not in the same amount. As the demand for fur started to decrease, beavers have begun to spread and to be reintroduced in several other parts of the world.
Having to deal with these rodents as pests can prove to be quite troublesome, as they are very persistent and highly adaptable creatures. Prevention measures are always useful, to be able to avoid such nuisance as the invasion of beavers on your territory. You can find relevant preventive measures in our article about how to “Prevent infestation with beavers”.