Beavers in Massachusetts
Natural History, Description, and Status
Beavers are abundant throughout most of Massachusetts, but are uncommon in southeastern Massachusetts and absent from Cape Cod and the islands. Beavers favor habitat containing shrubs and softwood trees, flat terrain, and perennial streams that can be dammed to create ponds. They are unique among wild mammals in that they alter their habitat to meet their needs. They do this primarily by damming up small rivers and streams to form ponds.
Beavers are North America's largest native rodents, weighing between
35 and 80 pounds as adults. They can be 2-3 feet in length, with an
additional 10-18 inches for the tail. Males and females are similar
in size. Beavers typically have a dark brown to reddish brown fur coat.
Large, webbed hind feet and a flat, wide leathery tail help them to
move swiftly in water. An animal often mistaken for the beaver is the
much smaller muskrat, which is another aquatic rodent. However, muskrats
weigh only 2-3 pounds and have a narrow, rat-like tail.
Adult beavers have few predators and may live up to 20 years or more. They stay with the same mate for life and breed during winter (January through March). The females give birth to 1-9 kits inside a lodge between April and June. These kits stay with their parents through two winters before dispersing the following spring. A single family unit is called a colony, and is typically made up of 6-8 individuals; two adults, that year's kits, and the young from the previous year.
Beavers are herbivores (feeding only on vegetation). They feed on a variety of aquatic plants (especially water lilies) and the shoots, twigs, leaves, roots, and bark of woody plants. The bark, particularly the inner bark of trees and shrubs, are important foods, especially in winter. Aspen, birch, alder, and willow are particularly favored foods.
Beavers are Beneficial:
Since European settlement, more than half of the wetlands in the lower 48 states have been lost. By damming streams and forming shallow ponds, beavers create wetlands. These wetlands provide habitat for a tremendous diversity of plants, invertebrates, and wildlife. People benefit too. Wetlands control downstream flooding by storing and slowly releasing floodwater. They also improve water quality by removing or transforming excess nutrients, trapping silt, binding and removing toxic chemicals, and filtering out sediment.
Resolving Beaver Conflicts
There are a number of options for resolving a conflict with beaver:
- Tolerance - People who learn to tolerate a certain amount of beaver influence on their land generally find that co-existing with beavers provides far more benefits than perceived harm.
- Exclosures - Fencing can proved a long-term solution, while preserving the beneficial aspects of beavers. The most effective way to protect specific trees and shrubs is to construct exclosures around them. These exclosures should be constructed of heavy-gauge fencing, be a minimum of 4 feet tall, and be flush with the ground. To protect larger areas, such as orchards or nurseries, standard fencing is usually sufficient since beavers are poor climbers, rarely burrow under fences, and generally don't chew fencing unless it is wrapped tightly around trees or shrubs.
The following three options require permits or a trapping license. To find out how to obtain the proper permits to conduct the following activities, please read our "Beavers and the Law: A citizen's guide to addressing beaver complaints". If you are not trapping the beaver during the regulated trapping season, you will need to consult with your local Board of Health and, depending on the option you choose, your local Conservation Commission.
- Breaching and removing the dam - Dam breaching is an immediate, but short-term solution to flooding problems caused by beaver. Cued by the sound of escaping water, beavers will usually rebuild the damaged dam quickly, sometimes overnight.
- Water Level Control Devices (WLCD) - Sometime referred to as "beaver pipes" WLCDs can regulate water at desirable levels behind dams. By successfully installing an effective WLCD, the life of a beaver wetland, and its associated benefits, can be prolonged. Booklet on water flow devices
- Lethal removal -Removal of problem beaver can be a quick way to alleviate beaver problems when done by an experienced trapper. Beavers can be trapped during the open season (November 1-April 15) by a licensed trapper using permissible traps (i.e. box or cage-type traps). By removing beaver during the regulated trapping season they can be used as a natural resource. An Emergency Permit is needed to trap beavers with restricted traps (i.e. body-gripping traps, "Conibear" traps) and to trap beaver outside the regulated trapping season.
It is against state law to capture and release beaver into another area. Often people want to capture problem animals and release them someplace else. However, moving wildlife is harmful to both people and wildlife populations and is against the law. This law has been in effect for many years, protecting both people and wildlife.
Beavers are an important natural resource in Massachusetts. They are
classified as a furbearer species, for which an established regulated
season and management program exists. If you are experiencing problems
with, or have questions regarding beaver, contact your nearest MassWildlife