Muskrat (CR 1/2)
Alignment: Always neutral
Initiative: +2 (Dex)
AC: 20 (+2 size, +2 Dex, +0 natural), touch 14, flat-footed 12
Hit Dice: 1/2d8 (2 hp)
Fort +0, Ref +2, Will +1
Speed: 10 ft., swim 15
Space: 2-1/2 ft./0 ft.
Base Attack -2; Grapple -12
Attack: bite +2 melee
Full Attack: Bite +2 melee
Damage: 1 pt damage
Abilities: Str 2, Dex 15, Con 10, Int 2, Wis 12, Cha 6
Special Qualities: Semi-aquatic, cold tolerant
Feats: Expert Swimmer
Skills: Swim 10*
Climate/Terrain: Temperate and cold marshes
Organization: Family (2 adults and 1d8 young)
The muskrat is a medium-sized semi-aquatic rodent. The muskrat is found in wetlands and is a very successful animal over a wide range of climates and habitats. It plays an important role in nature and is a resource of food and fur for humans.
An adult muskrat is about 16 to 24 inches long, almost half of that tail, and weighs from 1.5 to 4 lb. That is about four times the weight of the brown rat, though an adult muskrat is only slightly longer. Muskrats are much smaller than beavers, with whom they often share their habitat.
Muskrats are covered with short, thick fur which is medium to dark brown or black in color with the belly a bit lighter but as the age increases it turns a partly gray in color. The fur has two layers, which helps protect them from the cold water. They have long tails which are covered with scales rather than hair and are flattened vertically to aid them in swimming. When they walk on land the tail drags on the ground, which makes their tracks easy to recognize.
Muskrats spend much of their time in the water and are well suited for their semi-aquatic life, both in and out of water. Muskrats can swim under water for 12 to 17 minutes. Their bodies, like those of seals and whales, are less sensitive to the buildup of carbon dioxide than those of most other mammals. They can close off their ears to keep the water out. Their hind feet are semi-webbed, although in swimming the tail is their main means of propulsion.
Muskrats normally live in family groups consisting of a male and female pair and their young. During the spring they often fight with other muskrats over territory and potential mates. Many are injured or killed in these fights. Muskrat families build nests to protect themselves and the young from cold and predators. In streams, ponds or lakes, muskrats burrow into the bank with an underwater entrance. These entrances are 6 to 8 inches wide. In marshes, lodges are constructed from vegetation and mud. These lodges are up to three feet in height. In snowy areas they keep the openings to their lodges closed by plugging them with vegetation which they replace every day. Some muskrat lodges are swept away in spring floods and have to be replaced each year. Muskrats also build feeding platforms in wetlands. Muskrats help maintain open areas in marshes, which helps to provide habitat for aquatic birds.
Muskrats are most active at night or near dawn and dusk. They feed on cattails and other aquatic vegetation. They do not store food for the winter, but sometimes eat the insides of their lodges. Plant materials make up about 95 percent of their diets, but they also eat small animals such as freshwater mussels, frogs, crayfish, fish, and small turtles. Muskrats follow trails that they make in swamps and ponds. When the water freezes, muskrats continue to follow their trails under the ice.
Muskrats provide an important food resource for many other animals including mink, foxes, coyotes, wolves, lynx, bears, eagles, snakes, alligators, and large owls and hawks. Otters, snapping turtles, and large fish such as pike prey on baby muskrats. Caribou and elk sometimes feed on the vegetation which makes up muskrat lodges during the winter when other food is scarce for them.
Muskrats, like most rodents, are prolific breeders. Females can have 2 to 3 litters a year of 6 to 8 young each. The babies are born small and hairless and weigh only about 0.8 oz. In southern environments young muskrats mature in 6 months, while in colder northern environments it takes about a year. Muskrat populations appear to go through a regular pattern of rise and dramatic decline spread over a 6 to 10 year period. Some other rodents, including famously the muskrat's close relatives the lemmings, go through the same type of population changes.