Wildlife Species Guide
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Habitat | Foods | Importance |
The beaver is North America's largest rodent.
Adults may be 4 feet long and weigh over 60 pounds. A beaver
is easy to identify because of its large size, its distinctive webbed
hind feet and its large flat tail that resembles the end of a canoe
paddle. The tail is nearly hairless and is a dull-black color. The
"splat" that the tail makes when slapped on the water is one of the
most distinctive of nature's sounds. The beaver's body fur is dark
brown on its back and sides, and a light brown on its chest and
belly. Its front feet are short and have heavy claws, and possess
good dexterity for feeding, grooming, digging and lodge construction.
Its hind legs are large and have fully webbed feet which
propel it through the water when it is swimming.
Like the muskrat's, the beaver's fur is virtually waterproof, and
provides the protection and buoyancy necessary for the animal's
extended underwater activities. The beaver's eyes are small in
proportion to its body size, allowing moderate vision both under
and above water. It has well-developed senses of smell and hearing,
and its nose and ears have valvular processes which close
tightly under water. There is a similar valvular process in its mouth
behind the incisor teeth, which allows the beaver to gnaw while
The beaver also possesses a specialized digestive system to help
it digest tree bark, and a special respiratory adaptation which gives
it the capability to remain submerged for nearly 20 minutes. These
specialized physiological and morphological adaptations serve
both positive and negative functions; they have made the beaver
well suited for a specific environment, but have also restricted it
to very narrow habitat tolerances.
The beaver has two chisel-like incisors in its upper and lower
jaws that grow constantly and are very effective tree cutting tools.
These teeth are both self-sharpening and ever-growing, which
means the beaver must use them continually to maintain their
proper length and sharpness.
Distribution and abundance
In the early and mid l870s, beavers ranged over most of North America,
but excessive commercial trapping and human encroachment on its habitat
resulted in the beaver being nearly wiped out in the eastern and the
southern parts of the country. Their numbers were also reduced in Nebraska,
and as a consequence, trapping seasons were closed during the
1940s. Fortunately, there is no shortage of beavers in Nebraska
today, and they can be found in virtually all areas of the state.
Habitat and home
In Nebraska, beavers are found along
streamcourses and rivers, small lakes and marshes. A beaver may
dig a tunnel and form a den in a high stream bank or river bank,
but in the standing water of lakes, marshes and backwaters, they
most often pile tree limbs and other debris together, making a
large, bulky, dome-shaped lodge. Beaver lodges are large structures
constructed of wood and mud with at least one exit in deep
water. Lodges contain a large bark-lined, above-water chamber
which serves as the colony's "activity center." Although lodges
are the most visible den sites, bank burrows are by far the most
common denning structure in Nebraska. Burrows are usually dug
from six to 20 feet into the bank before an above-water chamber
is excavated and lined with fresh, shredded bark. On rivers like
the Platte, where sandy soil prevents normal excavation, beavers
will use the structural support of trees or shrub root systems to
construct or maintain a den and burrow system. Over time, beavers
will reinforce bank dens with sticks and mud, forming conical
lodges called "half houses" at the water's edge.
The engineering skills possessed by beavers are well
known. They are particularly adept at building dams, and may
construct them across narrow, flowing waters, such as shallow
streams and the channels of larger rivers.
When a beaver cuts a tree, he usually-starts by gnawing a notch at
an easy-to-reach height, then goes to the opposite side of the tree
and gnaws another a few inches below the first. He continues
chewing the bark and wood away from between the two notches
until the tree falls. The only way the beaver can control where the
tree falls is by the position of the notches he chews in the tree's
trunk. In addition to building the dam and lodge, beavers often
form waterways so they can float food and building materials from
one area to another.
Beavers are primarily bark-eaters, and ingest the bark of
young twigs, and new growth of wood found between the outer
bark and the wood of tree branches and trunks. In spring and fall,
about half of the beaver's food is made up of woody vegetation.
In summer it eats little woody vegetation, but in winter it feeds on
it almost exclusively. It also eats corn and other row crops when
they are available, as well as various water plants.
As fall approaches, the beaver begins to actively cut trees and
shrubs for the colony's food cache. The quantity, quality and
availability of this under-ice food supply will determine the condition
and survival of the colony.
Beavers reproduce once a year, with mating activity beginning in January
when rivers and wetlands are covered with ice. A 107 to 110 day gestation
period follows, with an average of three to four young usually born in May.
At birth the kits (young beavers) are fully furred, have their eyes open and
incisor teeth visible. Kits are seldom seen until they are about one
month old, though they are able to swim at birth, and are capable
of being weaned in six to eight weeks. Although weaned within
three months, the young usually remain with the family unit or
colony for up to two years before leaving to establish a colony of
their own. Typically, these two-year-olds will disperse, pair, establish
territories, and raise their first litters at three years of age.
However, under favorable conditions, they will produce their first
litters at two years of age. The average lifespan of a beaver in the
wild is three to four years. However, it is not uncommon to find
eight-year-olds and rare individuals may reach or exceed 15 years
The huge market for beaver felt was one of the main incentives that
prompted the exploration and settlement of
the west. Today beavers have both positive and negative economic
values. The positive values center on the income generated by the
harvest of beaver for their meat and fur, and the related recreational value.
From 1942-86, nearly 400,000 beavers were taken by fur
harvesters in Nebraska. Harvest totals from 1981-89 indicate an
average annual harvest of 14,850 beavers valued at $255,000.
Beavers are also important in the management of river and wetland
habitats. Their construction of dams and the subsequent
formation of pools create habitat for a large number of highly
beneficial wildlife species.
Negative impacts from beavers center on damage to trees and
depredation to farm crops by cutting or flooding. Their burrowing
activity can also cause shoreline erosion and structural damage to
farm ponds, stock dams and dikes. These negative impacts are
minimized through population regulation.