AS SEEN IN Community Assets, Written by Industry Expert Gavin Ferris, Ecologist, SOLitude Lake Management

The North American Beaver, Castor canadensis, is a truly remarkable animal. It is common knowledge that beavers build dams, and that the water held back by these dams provides them with protection from predators. What few people know is that their instinct to build these dams approaches the point of outright neurosis. When a beaver sees or hears water flowing, he is obsessed by a desire to make it not flow.

In the wild, this little quirk is highly admirable. Beaver ponds provide vital habitat for waterfowl, amphibians, reptiles, and numerous wetland plant species. As beavers were once nearly wiped out across the continent this valuable ecosystem service became all too rare, and many species suffered. Beavers are now becoming common again, and thankfully these key wetland habitats are reappearing throughout their range.

In a stormwater pond, however, this trait becomes a major character flaw. These ponds are carefully designed to allow water to flow at a specific rate to allow the ponds to be maintained at the correct water level. Any obstruction to the pond’s outflow hinders this operation, resulting in improper stormwater discharge. If allowed to persist, the inevitable flooding can lead to property damage.

By J. Wesley Allen, Environmental Scientist

The Muskrat and North American Beaver have adapted to the increasing number of stormwater ponds and facilities, and can cause huge headaches if not recognized and controlled.

Muskrats are small dark brown to black aquatic rodents (16-24 in., 1.3-4.4 lbs.) that live in ponds and wetlands throughout most of the United States and Canada, feeding on the aquatic vegetation found there. Muskrats are prolific breeders and can have two to three litters of up to eight young per litter every year. Muskrats were once trapped extensively for their fur, but reduction of trapping and predator numbers have allowed muskrat populations to remain strong, even with the loss of wetland habitat.

The muskrat has moved into many stormwater ponds, wetlands, and facilities. They can seriously damage these areas by burrowing into embankments, leading to massive erosion and even pond/facility failure. They can also eat installed and beneficial wetland plants. Because they breed prolifically, the population can quickly become destructive. They are active mainly at dawn or dusk, but burrows in the embankment near the water and disappearing aquatic vegetation are indicators of muskrats. There are very few preventative measures to keep muskrats from your pond, but keeping cattail populations under control can reduce the risk. Trapping is the best method to control muskrat populations.