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Muskrat
Muskrats have large, robust bodies, with a total body length of
twelve and a half inches. The tail is flat and scaly and is nine and
a half inches in length. Muskrats have dense fur that traps air
underneath for insulation and buoyancy. Their heads are very large
and their ears are almost invisible underneath the fur. The whiskers
are medium size. Muskrats have short legs and big feet; the back
feet are slightly webbed for swimming. Adult muskrats have glossy
upperparts that are dark brown, darker in winter and paler in the
summer. Muskrats are found in wet environments, favoring locations
with four to six feet of water. While muskrats are found in ponds,
lakes, and swamps, their favorite locations are marshes, where the
water level stays constant. Marshes provide the best vegetation for
muskrats. They find shelter in bank burrows and their distinctive
nests. Bank burrows are tunnels excavated in a bank. The nests of
the muskrats are formed by piles of vegetation placed on top of a
good base, for example a tree stump, generally in 15 to 40 inches of
water.
Reproduction
Southern muskrat populations can breed year round while northern
populations only breed in the warmer months (March to August). The
gestation period is 29 - 30 days and the litter size averages around
6, with northern populations having larger litters. Young are born
in a grass lined nest. When born, the muskrat has short dark fur,
closed eyes, and weighs around 22 grams. They are able to swim at 10
days and by 21 days can eat green vegetation. In 30 days muskrats
gain their independence and will reach adult size in 200 days.
Young are cared for and nursed by their mothers in the nest until
they are about 2 weeks old, when they begin to swim and eat
vegetation. They are fully weaned by 3 to 4 weeks old and leave
their mother's home range after their first winter, usually when
they are less than a year old.
Although muskrats have been known to live to 10 years old in
captivity, they probably live about 3 years in the wild.
Behavior
Muskrats are arranged in large family groups and live in definite
territories. If the conditions are overcrowded, the females will
kick their offspring out of the group. Muskrats continue to live in
large groups even when fighting and cannibalism occur in high rates.
Muskrats are active at all times of the day but most active from
mid-afternoon until just after dusk. Muskrats are good swimmers and
can stay underwater for 12 - 17 minutes. Muskrats, however, move
relatively slowly on land. Muskrats communicate by musk, which also
is used as a warning for intruders. They are capable of vocalizing
by squeaks and squeals. Muskrats have poorly developed senses of
sight, hearing, and smell. They are affected by quick changes in
temperature, and dry, hot weather is especially bad for them. Their
homes and burrows protect them from the elements. Muskrats also have
a special adaptation called regional heterothermia, which regulates
the flow of blood to the feet and tail, allowing these structures to
be cooler than the body core.
Muskrats communicate by a secretion from their glands called musk.
This scent also serves to warn intruders. They are capable of
vocalizing by squeaks and squeals. Muskrats have poorly developed
senses of sight, hearing, and smell.
Food Habits
Muskrats are mainly vegetarians but will eat animals as well.
Muskrats consume about one-third of their weight every day. Their
digestive system is designed for green vegetation. In the summer
they eat the roots of aquatic plants. In the winter, they swim under
the surface ice to get to the plants. Muskrats also eat agricultural
crops.
In captivity they should be offered a complete diet of rodent lab blocks, and rat or mouse
mix, with bits of fruit or veggies regularly. Cheerios or wheat
bread are great treats, in small quantities. Do NOT feed chocolate,
fried foods, salted foods, candy or junk food! They may enjoy
crickets and mealworms if they are captive bred, never feed wild
insects as they may carry parasites. Vitamins, like Nutri-Cal are a good addition to their diet, and added calcium
during nursing and growth due to demands on their systems at those
times, but take care not to overdo it. Water bottles should be used
to proved constant, clean water. Ceramic or stoneware food dishes
work well for keeping seeds or fresh foods off the floor, and a wire
mesh hopper that allows them to eat the lab blocks through without
extra waste.
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