Dams: Beavers build dams for two
good reasons, food and protection. They begin by cutting larger trees and placing them
with the branches facing upstream. The branches catch other debris in addition to the
sticks and mud placed there by the beaver. Some dams can be quite large, others very
small. Sometimes, beavers will build a series of dams down a stream.
Beavers are strict vegetarians, and the aquatic vegetation that grows in
ponds supplies summer food. The favorite plants of the beaver are duckweed, pickerel weed,
cattails, and spatterdock. Since beavers are slow moving on land, they are much safer
swimming in the beaver pond they create by building a dam.
trees: Beavers have many uses for the trees that they cut down. They cut the trees by
standing on their hind legs, using their tails for balance. A ring is chewed around the
tree using the upper incisors. Like most rodents, beavers teeth grow continuously
throughout their lives. The large incisors have a special coating of enamel, which wears
away more slowly than the rest of the tooth. This gives the beaver a sharp biting edge. A
beavers chewing force is 176 pounds per square inch, compared to mans 88
During the winter, beavers subsists on the inner
layer of bark, the cambium. The rest of the wood is not wasted. It is used for dam and
lodge maintenance and expansion.
The favorite trees of beaver are willows, aspens, cottonwoods and
alders.They also eat birches, oaks and maples and highbush blueberries. Some trees they do
not like, such as hemlocks and pines, are usually girdled and left standing. These dead
trees serve as homes to many forest creatures
There is no limit as to the size of the tree that beavers may cut. They will use small
saplings that are taken in one bite, or larger trees which then have to be cut into
sections to move. They seem to prefer trees that are three to four inches in diameter. If
you find a tree that was felled by a beaver, look for the wood chips on the ground. Newly
cut trees are blonde in color, those that are approximately a year old appear a silvery
gray, and those that were cut over three years ago are gray and commonly have turkey
tails, a type of mushroom, growing on them.
beavers run out of resources (trees) near the pond, they will dig canals to nearby areas
with better habitat. This way they do not have to leave the water.
Winter Caches: Look for branches sticking up outside of the lodge when ice
forms. This is the winter food supply that was collected during fall. They cut down
surplus food, and anchor it into the bottom of the pond with mud. Beavers do not have to
go far from the lodge and waste energy breaking through the ice to get food.
Scent Mounds (or Castor piles): How a beaver marks
territory. The piles are started by placing mud and leaves in a clump in a prominent area
near the pond, and then a yellowish substance is deposited on the top if it. This
substance is called castoreum and is secreted from a scent gland near the tail. If
you find a scent mound, smell it. This is a sure sign that there are beavers in the area.
Beavers walk the same path over and over again, and drag their tails behind them,
wiping out any tracks that may be left in the mud. The well worn trails are seen coming in
and out of the water. By looking carefully at these, you may come across a track. The
beaver has five toes on both front and hind feet, and large nails that leave deep
impressions. The back feet are webbed.
Scat: Beavers normally defecate in the water, so look for scat when
the ponds dry up in the summer or where the water is shallow and clear. Scat is
very hard to find. Winter scat resembles little balls of sawdust.
Mating occurs in January and February and 2-6 kits are
born in April or May. A beaver family works together building and gathering food. The
family is made up of the parents, the young from the previous year, and the current kits.
At the end of their second year, they young are forced to leave the lodge. They often move
downstream, creating a chain of beaver ponds following a watercourse.
In 1764, beavers were trapped out of Massachusetts. Today, there are
upwards of 54,000 beaver, (compared to the 26,000 in 1996) Beavers have reached nuisance
levels in some areas. With very few natural predators the number of beaver is only going
to increase in the bay state.