Biology Reference
In-Depth Information
cies, including ash and birch. Beavers normally eschew the bark of evergreens as food, but will turn to
it if forced to by a shortage of better foods.
When winter draws near, the beavers cut quantities of tree branches and shrubs and bury the butt
ends in the mud next to their lodge. As soon as the pond becomes icebound, the beavers retire to the
safety of their lodge; when they want food, they swim out, cut sections of branches, bring them back
to the lodge, and munch off the bark. The peeled sticks are carried outside to float up under the ice;
otherwise their debris would soon fill the lodge. Although bark represents their primary winter food
supply, beavers also supplement their diet with the thick, tuberous rootstocks of pond lilies, at least in
those ponds where these plants grow.
Like a number of other wild creatures, beavers mate for life, but that doesn't mean what most people
seem to think it does. The common perception of lifetime mating in the wild is that the death of one
partner relegates the survivor to a single existence for the remainder of its life. That's not the case at
all. Like many humans, a wild animal that normally mates for life will, after the death of its mate, seek
another.
As previously noted, beavers live in a colony that consists exclusively of a single beaver family.
Each colony begins with a mated pair of young beavers. After the pair have constructed dam and lodge,
and laid down a winter's food supply, they breed during the winter. After a gestation of about ninety
days, the young, called kits, are born in the spring. There are usually three to five kits in a litter, and
occasionally more.
The young remain with the parents through the winter, and the following spring the colony is en-
larged by a second litter of kits. The colony now contains the parents plus the offspring from two suc-
cessive years. All of the beavers in a colony share the work of maintaining the dam and lodge, and
cutting and storing the winter food supply.
Although a number of myths have grown up concerning beavers, the phrase “busy as a beaver” most
assuredly isn't one of them. Beavers labor intensively during the warm months, preparing for the long
winter to come. Constant diligence and great effort are required to ensure an adequate and secure hab-
itat, as well as an ample winter food supply. Only when the pond finally becomes icebound can the
beavers relax and enjoy the fruits of their labors.
Big changes occur during the colony's third spring. As another litter of kits is born, the young of
two years before either leave the colony voluntarily or are driven out by their parents. These “dispos-
sessed” beavers must now seek new territory, find mates, and begin new colonies. Stark evidence of
this springtime diaspora is often visible in the form of dead beavers killed by automobiles as they try to
cross highways.
Thereafter, for the life of the colony, a new set of kits will be born each spring, and the two-year-olds
will either set out on their own or be driven out. Although this system may seem harsh, it's necessary
for the colony's survival. Without this annual dispersal, a beaver colony would soon become impos-
sibly overpopulated, to the detriment of all.
