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~distinguish the sex of a beaver,
<br /> Unless the female is lactating, is to
<br /> ~l~eel for the presence of a baculum
<br />~="~ ~ ~ne in the penis) in males and
<br /> i~ absence in females.
<br />
<br />Rang
<br />Beavers are found throughout
<br />North America, except for the arc-
<br />tic tundra, most of peninsular
<br />Florida and the southwestern
<br />desert areas (Figure 4). The species
<br />is locally abundant throughout the
<br />Great Plains wherever aquatic
<br />habitats are found, e.g., streams,
<br />lakes, farm ponds, wetlands and
<br />Iow Iyin$ lands or swamps and
<br />along flood-prone creek and river
<br />bottoms.
<br />
<br />Habitat
<br />
<br />Beaver habitat is almost anywhere
<br />there is a year-round source of
<br />water, e.g., streams, lakes, farm
<br />ponds, swamps and wetland areas.
<br />Personal observations have located
<br />beaver in highway roadside ditch-
<br />es drainage ditches, canals, mine
<br />, oxbows, railroad dumps,
<br />drains from sewage disposal ponds,
<br />and below natural springs or arte-
<br />sian wells. In areas beavers move
<br />into they seem to be stimulated by
<br />running water. They will quickly
<br />begin building dams to modify the
<br />
<br />environment more to their liking.
<br />Some of the surrounding timber is
<br />cut down or girdled by beavers to
<br />form dams. Subsequent flooding of
<br />growing timber causes it to die,
<br />and aquatic vegetation soon begins
<br />growing. Other pioneer species,
<br />e.g., willow, sweetgum and button-
<br />bush, soon are' 8rowing around the.
<br />edge of the flooded area adding to
<br />the available food supply. The
<br />beaver thus helps create its own
<br />habitat.
<br />
<br />Food .Habi,ts?
<br />
<br />Beavers prefer certain trees and
<br />woody species depending on avail-
<br />ability, such as populus species,
<br />e.g.', aspen and cottonwood, and
<br />willow, sweetsum, blackgum, and
<br />pine. However, they can and will
<br />eat the leaves, twigs and bark of
<br />most species of woOdy plants
<br />which grow near the water, as well
<br />as a wide variety of herbaceous
<br />and aquatic plants. Beavers often
<br />will travel 100 yards (90 m) or more
<br />from the pond or stream to get to
<br />corn fields, soybean fields and
<br />other growing crops, where they
<br />generally cut the plant off at the
<br />8round and drag the entire plant
<br />back tothe water. Adding insult to
<br />injury, they not only eat part of
<br />these plants, they often use the re-
<br />mainder as construction material in
<br />the dam.
<br />
<br /> General Biology,
<br /> Reproduction and
<br /> Behavior
<br />Beavers are active for approximate-
<br />ly 12 hours each night except for
<br />the coldest of winter nights. The
<br />phrase "busy as a beaver" is ap-
<br />propriate. However, it is not Un-
<br />common to see beavers during'
<br />daylight hours, particularly in
<br />larger reservoirs. Because of the
<br />valvular ears and nose and other
<br />physical adaptations, they can re-
<br />main underwater for over 15
<br />minutes when necessary.
<br />
<br />After a gestation period of about
<br />128 days, the female beaver
<br />generally gives birth to three or '
<br />four kittens between March and
<br />June, and nurses them for from iix
<br />weeks to three months, The kittens
<br />are born fully furred with their
<br />eyes partially opened and the in-
<br />cisors erupted through the gums.
<br />They generally become sexually
<br />mature by the age of 1 1/2 years.
<br />
<br />BeaverS'have a relatively long life
<br />span, with individuals known to.
<br />have lived to 21 years. Most,
<br />however, do not live beyond 10
<br />years. The beaver is unparalleled at
<br />dam building and can build dams
<br />on fast-moving streams as well as
<br />slow-moving ones. They also build
<br />
<br />Figure 5. Cross section of a beaver lodge.
<br />
<br />B-3
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