Article by J. Turner
The muskrat (Ondatra zibehticus) is a fairly large rodent which has adapted to life in and around water. Their name comes from their two musk (anal) scent glands, the odour used in communication, especially during breeding season. Muskrats are found in North American wetlands and waterways and are considered to be an important creature in their freshwater environments.
These animals have a round, portly body covered with rich waterproof fur made up of a short dense silky under coat and a longer, coarse glossy guard coat. Their fur covers small ears and provides buoyancy in the water. Fur colour ranges from a dark brown head to a light grey belly. Their feet are mostly hairless; the hind feet acting like paddles during swimming and described as semi-webbed, with the four longest toes of each foot having a fringe of specialized hairs along each side, giving the foot a paddle like effect in use. The front feet are used like hands to build lodges, hold food and dig burrows and channels. There are five toes on all feet, but the inner toes of front feet are small so rarely show in tracks. Full grown large adults can weigh from 1 – 2 kgs (2 – 5 lbs) and are up to 60 cm (24 in) long (including the tail). Their tail is slender, flattened vertically (to act as a rudder when swimming) and covered with scaly skin to protect it from damaging easily. The muskrat has special teeth that protrude ahead of the cheeks and lips, which can close behind them, permitting the animal to chew on stems and roots under water “with its mouth closed.” Its four front teeth are chisel-like (two upper and two lower incisors), each up to 2 cm long, used for cutting stems and roots of plants.
Muskrats typically live in freshwater marshes, marshy areas of lakes, slow-moving streams, dugouts, ponds, and watery areas controlled by beaver dams. The water must be deep enough to not freeze to the bottom during winter, but shallow enough to allow for the growth of aquatic vegetation. Areas with good food sources such as bulrushes, cattails, pondweeds, or sedges are preferred.
Muskrat homes are compact mounds of partially dried and decayed plant material scattered among cattails, reeds or bulrushes, looking much like dead heaps of plants. If these materials are not available, muskrats dig burrows in firm banks of mossy soil or clay. They still need quick access to deep water for escape from predators and food access in the winter. Their construction of open-water canals through reeds, and floating houses of aquatic vegetation, creates habitats for many species of waterfowl and aquatic plants which could not survive among dense areas of cattail and sedges.
After freeze up, muskrats chew through the ice, and push up plant matter to cover the hole with a dome to make a miniature lodge, which is used as a feeding station and resting place when searching for food underwater. They can remain underwater up to 15 minutes by reducing their heart rate and relaxing their muscles when submerged, thus reducing oxygen use by their body.
What’s unusual about the muskrat?
- They are more widely dispersed across North American (north to south, east to west) than any other mammal.
- They were introduced to Europe in 1905 and are now common there too.
- If normal plant food is not available, and animal food is abundant, they are known to become carnivorous (eating fish, frogs, clams)!
- Numbers decrease dramatically every 7 to 10 years. This is believed to be the result of cyclical health declines, deaths and reproductive failure.
- Muskrats appear to thrive even when harvested heavily for fur, impacted by agricultural draining of wetlands and increases in industrial activity! They can even adapt to brackish (salty) water. Hardy little creatures, aren’t they?
If you find an injured or orphaned muskrat, or other wild animal or bird, please contact the Calgary Wildlife Rehabilitation Society for further instructions.
