Mischievous Mammals: Are Muskrats, Beavers & Otters Harmful to Ponds?
As an ecologist, I field questions on topics ranging from the lifespan of a tadpole to the best way to defend koi against the ravages of a great blue heron. Of all the animals I am asked about, however, three mammals probably produce the most concern and curiosity: the muskrat, the beaver, and the otter.
Each of these aquatic animals plays a unique role in the environment, fulfilling a niche that contributes to its aquatic ecosystem, and all three animals are frequently found together, thanks largely to the services provided by the beaver. Beavers are perhaps the world’s first engineers, modifying their environment to suit their needs. Relying on deep water for safety, beavers have an innate drive to dam up moving water. When they see a stream, they want it to be a pond. As a result, they often create habitat for other aquatic wildlife, including fish, amphibians, waterfowl and, of course, muskrats and otters. In the wild, this makes them hugely beneficial as they provide so much habitat. In a man-made waterbody, however, where the water needs to be kept at its intended level, they can be extremely destructive. Also, their proclivity for felling trees both for timber and food can wreak havoc on expensive landscaping.
Muskrats, like most small rodents, serve as important prey for many predators, including mink, eagles, hawks and owls. They feed primarily on vegetation, though they do occasionally eat some shellfish, especially in the winter. In addition to ponds, muskrats will colonize any marsh, stream or river where adequate food can be found. Unfortunately, their burrows can cause tremendous damage to the shoreline. For some reason, they also like to chew through wiring, including the power cables of lake and pond fountains.
Otters are the only true predator of the trio, feeding primarily on fish but also settling for any other small animal they can catch in or near the water. Members of the weasel family, they are renowned for being playful and gregarious, and can be observed sliding on their bellies as if they were sledding. Otters are frequently found in and around ponds created by beavers, and have been known to kick beavers out of their lodge and take it as their own home. Unlike beavers and muskrats, otters are unlikely to cause structural damage to a pond or stormwater basin. The main issue they pose, however, is fish predation. Otters, like human anglers, like to catch and eat large trophy fish. If you value your sportfish, you should look for ways to limit the otter population in your waterbody.
For muskrats and beavers, prevention is far better than removal. Controlling shoreline vegetation like cattails and black willow seedlings will discourage muskrats, and removing woody vegetation from near the water will help to keep beavers from setting down roots. Otters, however, are not so easily discouraged. In the instance that any of these animals takes up permanent residence where they are not welcome, trapping or lethal control may be your only recourse. The options available for controlling muskrat, beaver or otter populations will vary based on the laws in your state and the individual situation. It’s recommended to consult with your community and your lake management professional to determine the best management plan for these incredible creatures.
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