BIOLOGY AND BEHAVIOR
The range of the muskrat extends across most of North America. The muskrat spends its life in aquatic habitats and is well adapted for swimming. Its large hind feet are partially webbed and its laterally flattened tail is almost as long as its body. The muskrat has a stocky appearance, with small eyes and very short rounded ears. Its front feet are smaller than its hind feet and adapted primarily for digging and feeding.
The overall length of adult muskrats is usually from 18 to 24 inches. Large males however will sometimes be more than 30 inches long, 10 to 12 inches of which is the laterally flattened tail. The average weight of adult muskrats is 1.5 to more than 4 pounds. The color of the belly fur is generally light grey to silver to tan, and the remaining fur varies from dark tan to reddish brown, dark brown, and black.
Muskrats can live where water and food are available year round. In shallow water areas with plentiful vegetation, they use plant materials to build houses, generally conical in shape. Elsewhere they prefer bank dens and in many habitats they build both bank dens and houses of vegetation.
Muskrats are mainly herbivores. They will eat almost any aquatic vegetation as well as some field crops grown adjacent to suitable habitat. Although primarily herbivores, muskrats will also feed on crayfish, mussels, turtles, frogs, and fish.
Muskrats generally have a small home range and are rather territorial. During breeding season some dispersal is common. Dispersal of males, along with young that are just reaching sexual maturity begins in the spring. The availability and accessibility of food impact population levels.
Both male and female muskrats become more aggressive during the breeding season in defending their territory. Litters may contain as many as 15 young. But generally average between 4 and 8. Young may be produced any month of the year.
Muskrats are host to large numbers of endoparasites and exctoparasites. They serve as carriers of a number of diseases, including tularemia, hemorrhagic diseases, leptospirosis, ring worm disease, and pseudotuberculosis. Most common exctoparasites are mites and ticks. Endoparasistes are predominately nematodes, cestodes, and trematodes.
Burrowing activity is a source of the greatest damage caused by muskrats. They damage pond dams, floating styrofoam marinas, docks and boat houses, and lakeshores. In water fowl marshes, muskrat population eruptions can result in the virtual elimination of aquatic vegetation in large areas. In aquaculture reservoirs, muskrats cause damage by burrowing into levees or pond banks.
BIOLOGY AND BEHAVIOR
The Norway rat is the common domestic rat in Utah. It has course hair, close set ears, and its muzzle is blunt. The tail is dark on top and light on the underneath side. The tail is shorter than the combined length of the head and body.
The fur is grey brown on back and grey white on the belly. The adults weight between 0.12 and 0.20 ounces and the combined length of the head and body is 7.5 to 10 inches long. The tail length is between 6 and 8.5 inches. The feces are capsule shaped and about 0.75 inch long.
Norway rats can be found in warehouses, farm buildings, houses, sewers, rubbish, dumps, wood piles, and building foundations. They are good climbers and they can jump 24 inches vertically. The Norway rat has relatively poor vision but keen sense of smell, touch, taste, and hearing. Long whiskers on the snout serve the sense of touch. Their home is often 100 to 200 feet.
Norway rats and other domestic rodents are mainly nocturnal, but they may go about in undisturbed places during the day. They feed on virtually anything edible. Norway rats are unable to vomit, they must drink water to survive.
Rats urinate often, creating stains and offensive odors. A single rodent will produce about 25,000 feces droppings in a year. They also do damage to electrical wiring by chewing off the insulation. It is estimated that 25% of fires are caused by rats. Rats burrow holes in yards and chew entry points of homes and buildings.
Rat bites and scratches can result in disease and rat-bite fever. Rat urine is responsible for the spread of leptospirosis, which can result in liver and kidney damage. It can also be contracted through handling or inhalation of scat. Complications include renal and liver failure, as well as cardiovascular problems.