By Elliott Thompson
Bay Area waterways are home to a unique genus of mammal, the muskrat, or Ondatra zibethicus. This prolific breeder is close in size to a small rabbit and loves the water almost as much as we do. It is semi-aquatic and is named for it’s musky smell and rat-like appearance, but is a rodent and not a “true” rat. Common muskrats have adapted in a number of ways to their aquatic environment, developing a rudder-like tail that is flattened side-to-side, partially webbed hind feet for efficient paddling, and fur that traps air for insulation and buoyancy. Because their fur has commercial importance, they were taken to Japan, South America, Scandinavia, and Russia, and there are now feral populations in some places where they were introduced.
Muskrats are the most common semi-aquatic animal in the area, and are known for their destruction of plants (as their primary source of food) and banks of waterways (where their habitats are built.) Despite this problem, these animals actually play an important role in some ecological systems. Here’s why: for shelter, muskrats will either dig tunnels or construct lodges, depending on what is around them. In areas with steep banks or dams, muskrats will sometimes dig tunnels that begin underwater and lead up above water level where the chamber can remain dry. No steep walls or dams? No problem, muskrats will build dome-shaped lodges out of nearby vegetation and mud. The eating and denning habits of muskrats can help create flat nesting areas for birds. Also, snakes, turtles, and many other animals use the tops of muskrat lodges as habitat. Net result: bad for plants, and the “good life” for other local wildlife.
Muskrats are omnivores, but they mainly enjoy a plant-based diet consisting of the roots, stem, leaves and fruits of aquatic vegetation, hence their destructive nature. But, as local plant food becomes scarce, muskrats expand their palate and will feed on small aquatic animals such as insects, fish and amphibians.
The classification name Ondatra is the Iroquois name for the muskrat and zibethicus means “musky-odored” in Latin, named for the strong musky odor adults emit to communicate with one another, especially during breeding season.
Historically, muskrats were trapped and considered valuable for their fur or pelts, and are some of the most trapped animals in history. The Iroquois were paid 25 cents per adult pelt (versus $4-5 for a beaver pelt.)
The muskrat is unique in a number of ways: they can swim both backwards and forwards. They also have extraordinary lung capacity. Muskrats have been observed swimming underwater for up to 17 minutes, surfacing for three seconds, and then going back underwater for another 10 minutes. They have fur mouth flaps behind their teeth to prevent water from getting in their mouth while chewing underwater. Muskrats are prolific breeders, producing up to 3 litters a year. Most of the time muskrats mate underwater. Muskrat kits are born hairless and blind, and are in litters of 4-8 kits, and up to 15 young at once in warmer months – muskrat love!
Next time you are close to the water and hear a splash, look for a small mammal in the water and watch for the distinctive slim tail behind. That’s your neighborhood muskrat.
