Castor canadensis, is the largest rodent in North America. It is easily recognized by its large, flat, bare, scaled tail and fully webbed rear feet.
Beaver range in North America includes most of the United States and southern Canada. The beaver had an important role in early colonization of North America, as trappers came in search of pelts.
Habitat
Beavers are found in Vermont along wooded streams, marshes, small lakes, and ponds. They seek areas of flowing water where the volume of water is reliable or still waters where water levels are consistent. An abundance of desirable trees for food and construction of their lodges and dams is also important. Dams, lodges, burrows, and canals are built in the selected area. Beavers actually create a large portion of their environment with their dams, some of which are very large. The dams create a pond that allows the beavers to access food more easily without having to move too far from the water.
Beavers live in bank dens (hollowed out tunnels in the banks of rivers or ponds) or in lodges. The lodges are built out of sticks, stones, leaves, grass, sod, and mud. Branches are first piled together, then the beavers swim up underneath the pile to hollow out a central living quarter. This inside chamber is built above the waterline and is connected to the outside with one or more underwater tunnels.
The outside of the lodge is covered with sticks and mud, which insulates it in the winter. The inside chamber is then lined with grass and shredded bark. There is also a ventilation hole to the outside that allows fresh air to circulate inside the chamber.
The lodges are almost always well placed at a natural low point with solid anchor points on each side of the brook or stream. A long dam is often zigzagged to make use of intermediate anchor points. Structures are constantly maintained when they are not iced in. Additional dams are often built upstream or downstream from the main dam to create smaller reservoirs that increase the safe foraging range.
Beavers are most active in late afternoon and throughout the night. They try to stay in the water or as close to the water as possible. Beavers swim at speeds of about 2 mph, and can stay underwater for as long as 15 minutes without coming up.
Reproduction
A beaver colony is usually comprised of three generations: the adult male and female, their yearlings, and the kits of the year. These colonies average a half dozen or so individuals, although as many as twelve have been recorded.
Beavers tend to mate for life, but there are exceptions to this rule. The breeding season peaks in mid-February. The gestation period averages 106 days, and a single litter is born each year. Litters vary from one to nine kits, but three to five is normal.
Kits are born from mid-May through early June. They are fully furred at birth but their eyes can only open slightly. They weigh 8 to 22 ounces and are about 12 inches in length (including the tail). The kits begin to swim when they are only a few days old. At two to three weeks, they begin to eat solid food and are weaned at about six weeks.
In late winter, before the litter of the year is born, the mature two-year-old beavers are either driven away by their parents or leave on their own to establish a new colony. Beavers communicate by leaving a scent and by making soft whining sounds. The young beavers vocalize often. Splashes motivate the kits to swim and tail slapping on the surface of the water teaches them how to signal for danger. Beavers live up to 11 years in the wild, but those in captivity have reached 20 years of age.
Diet
Beavers are herbivores and consume bark, leaves, twigs, and roots growing near water. The most preferred food is the inner bark of deciduous trees, called the cambium layer.
During warm months, the beaver's menu includes bulrushes, sedges, pond lily roots and other aquatic plants. Their woody diet includes the bark of poplar, alder, paper birch, willow, gray birch, red oak, red maple, cherry, and viburnum. White cedar, hemlock, black spruce, red spruce, white pine, pitch pine, balsam fir, and tamarack (larch) are also eaten, sometimes even when more preferred foods are readily available.
Since beavers do not hibernate, they store their food (branches of edible trees) in a large underwater pile near the lodge (food cache), pulling mud or rocks over the base stems. The pile soon becomes waterlogged and settles to the bottom. A family of eight beavers requires one ton of bark to survive the winter.
Management
The Fish & Wildlife Department strives to maintain as high a beaver population as possible while still maintaining levels that are compatible with public uses of land and minimizing conflicts between beaver and people. Information on beaver is collected annually from each of the watersheds in Vermont.
The beaver trapping season begins on the fourth Saturday in October and runs to the end of March. The length and time of the open season for different areas is based on population levels determined by biologists.
Status
Prior to European settlement, there may have been as many as ten times the number of beaver that presently exist in New England. The unregulated trapping that occurred as a result of the early fur trade, coupled with the clearing of the New England forests in the early to mid-1800s for farming, virtually eliminated beaver from Vermont by the middle of the 1800s.
In 1910, beaver were protected by state law and began to make a slow comeback. The Vermont Fish & Wildlife Department reintroduced beaver into Vermont from New York and Maine in the 1920s and 1930s. The reintroduction coincided with the abandonment of many of Vermont's farms and the subsequent reforestation created an excellent habitat for the growing beaver population.
By the 1940s and 1950s, beaver had again become well established in the state. The first open trapping season for 15 days was set in 1950. Aerial surveys conducted on the Green Mountain National Forest in the 1980s and 1990s indicated that beaver population levels had increased by 120% in the ten years between surveys.
Vermont's beaver population is healthy, prospering, and growing. The Vermont Fish & Wildlife Department recognizes beaver as a valuable renewable natural resource. The maintenance of beaver populations ensures the continued production and enhancement of valuable wetland habitat, and provides a broad array of social benefits.
The Fish & Wildlife Department strives to maintain as high a beaver population as possible while still maintaining levels that are compatible with public uses of land and minimizing conflicts between beaver and people.