|
|
|
|
November 1998
To me, one of the most intriguing images is that of beavers in a lodge on
a winter-frozen pond. There the
beavers have cover from snow, rain and wind.
The floor of the interior chamber is above the water level and covered
with wood chips. Given their warm
pelts and the constant air temperature in the lodge, it’s a cozy scene.
The weatherproof lodges are made from logs, branches and mud, and have a
twenty-five foot diameter. They rise about seven feet above the water’s
surface. There are usually two entrances, located beneath the water’s surface.
If the riverbanks are high enough, instead of building lodges they may excavate
dens in the bank, with the entrance below water.
Lodges and bank dens are used for raising young and for winter shelter.
In autumn beavers feed heavily on twigs, bark and cambium, the layer just
below the bark where plants store nutrients at that time of year. They don’t
hibernate and, for their winter food supply, gather and store small trees and
branches underwater near the lodge entrances.
The constant cool temperature of the water acts like a refrigerator to
preserve the food’s nutritional value.
In winter when the water freezes over completely, beavers rarely visit
the shore. They stay in the lodge
or swim about below the ice. If
they must get ashore, they dig canals in the pond bed from the lodge to the
bank, tunnel into the bank below the ice and burrow up through the soil and snow
to forage for food.
Spring is a busy time for them, when they eat the greening
vegetation on land and repair the winter’s damage to the lodge and dams. Adult
beavers usually pair for life and have one litter each year.
The kits, as many as eight, are born in mid-May or early June.
They stay in the family unit for two years before leaving to establish
their own territories. All family members help look after the kits and bring
them solid food while they are being weaned from the mother, a period of three
months. The adult male has a strong
paternal sense. If a kit falls into a floor entrance before it is ready to swim,
the father is often the one to rescue it with a nudge back to the safety of the
lodge chamber.
Beavers are the largest rodents in North America.
A fairly recent ancestor of the beaver, living about two million years
ago, was a giant species the size of an American black bear. The giant
beaver’s brain size was no larger than our beaver’s.
Nowadays, an adult beaver may weigh from twenty-seven to sixty-seven
pounds, but some exceed one hundred pounds. Because of the quality of their
pelts, beavers were nearly exterminated from the United States by unregulated
fur harvests in the 1800s. Their
populations have recovered and stabilized as a result of trapping restrictions
and reintroduction into suitable habitat.
Beavers are present in all of Maine.
They feed at night, preferring aspens, poplars, willows, alders and
birches less than fifteen years old. They may be active in daytime in remote
areas. In spring and summer they
eat herbaceous plants such as sedges, pond lily roots and bulrushes instead of
their winter diet of bark.
By instinct, beavers dam flowing water and raise water levels to make a
good habitat for themselves. They
use slowly flowing brooks, streams or rivers that usually are bordered by
woodlands. The locations selected have enough favored trees and shrubs for an
adequate food supply. Logs and
branches are sources of food and building material.
To build a dam, beavers make a foundation of mud and stones across the
river or stream. They collect these
materials from the riverbed with their forepaws.
They fix small branches in the foundation and add logs, more mud and
stones to raise up the barrier. The
same dams and lodges are maintained by many generations of beavers.
By regulating water flow, the dams create ponds of sufficient depth for
the beavers’ lodges. The deep water is a protection from predators such as
bobcats and coyotes.
The wetlands that beavers create are ideal habitat for many wetland
wildlife species. The diversity of plants at the water’s edge provides
excellent cover and sources of food.
There is a great cycle of nature that beavers initiate when they build
their dams. The dams expand streamside wetlands or create ponds and wetlands
where none exist. The long period
of high water kills trees and other vegetation.
When the beavers’ food supply is gone, they move to a new location.
With the dam abandoned the water table drops. Old beaver ponds, called
beaver meadows, have fertile soils because of the decayed organic matter,
sediment and nutrients deposited over the years. The forest returns with natural
plant succession, replenished. Once
again, beavers come to settle the area, and the forest-and-pond cycle necessary
to sustain this habitat is continued. Beavers
are like industrious peasants. By
their labor, they enrich the land and provide for many beside themselves.
By Nancy Coverstone (ncstone@umext.maine.edu), University of Maine Extension Educator in Androscoggin and Sagadahoc Counties
Return to Wild About Nature Table of Contents
Putting knowledge to work with the people of Maine
A Member of the University of Maine System
Last Modified:
08/13/06
These pages are currently being maintained from the
Communications Office Office, University of Maine Cooperative Extension.
Send comments, suggestions or inquiries to www-questions@umext.maine.edu
COUNTY OFFICES | PROGRAMS | RESOURCES | PUBLICATIONS | WHAT'S NEWS | UMAINE EXTENSION HOME | UMAINE
Information in this web site is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned in this web site. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.
