Muskrat control to improve water quality

Muskrats can have a negative impact on water quality in farm dugouts. Damage caused by muskrats is primarily due to their burrowing habits. Burrowing into the sides of a dugout can cause dugout leakage and bank erosion. Burrowing and harvesting of plants for food also causes increased amounts of disturbed sediments in the water. When the sediments become disturbed, turbidity increases and nutrients are released into the water.

Turbidity reduces the clarity of the water and can clog treatment filters. Increased nutrients in the water can also lead to unwanted algae blooms.

Muskrats are often carriers of disease-causing organisms such as Giardia and Cryptosporidium (both of which are intestinal parasites). Drinking water with Giardia can lead to giardiasis, an illness commonly referred to as "Beaver Fever". It can cause severe diarrhea in humans. Cryptosporidiosis or "crypto" is caused by the organism Cryptosporidium. Bloody diarrhea, serious blood infections or even death can occur in people due to a crypto illness.

Since muskrats can carry parasites that will infect humans, it is important to keep them out of domestic dugouts. It is also important to understand what makes a muskrat behave the way it does. Knowing the background on muskrat habits will make it easier to deal with them.

Muskrat biology

Muskrats (Ondatra zibethicus) are a medium-sized semi-aquatic rodent native to North America, and can be found in all Canadian provinces and parts of the Territories. They are short stocky animals with long, flattened, scaly tails.

The muskrat is found in wetlands and is a very successful animal over a wide range of climates and habitats. Muskrats are semi-aquatic animals that prefer still or slow-moving water. They are excellent swimmers and can stay underwater for up to 15 minutes.

Muskrats are active year-round. While they are most active at night, they may also move around during daylight hours. They live in either tunneled burrows or in crude houses constructed of aquatic plants. Their home range is usually within 180 metres of the burrow, although they will travel many miles over land in search of new habitat.

Muskrats are primarily vegetarians. They are able to close their lips behind their front teeth which prevent them from swallowing water while they feed on the roots and stems of most aquatic plants, such as cattails and rushes. They will also eat grasses, grains, legumes, garden crops and apples if the food sources are within 180 metres (m) of the water.

Over winter when plant material is scarce, muskrats may feed on other aquatic organisms such as snails and clams. They have been known to eat dead animal matter.

Muskrats have high reproductive rates. They breed from February to August and will give birth from March to September, usually peaking in May. Females are capable of giving birth at one year of age and can have two to four litters per year.

Gestation length is only 20-30 days and average litter size is six. Young muskrats are weaned at about eight weeks of age and will move to colonize a new location shortly after that. This may be a different spot in the same dugout, or at a new dugout altogether. Life span is three to four years.

Controlling muskrats in dugouts

There are two strategies available to control muskrats in dugouts. The first approach is to make the dugout uninhabitable for muskrats. The second approach is to eradicate the animals.

Habitat modification

Muskrats may be discouraged from entering or staying in a dugout if it looks uninhabitable. Removing food sources is a good first step. Remove as many rooted aquatic plants as possible and compost them at least 180 m away from the dugout. Ensure that the dugout edges are sown with short-grass species or cut to no more than 10 centimetres (cm) in height.

Burrowing can be made more difficult by placing rip-rap along the edges of the dugout. Rip-rap can consist of rocks or any other material that can be used to prevent burrowing. The material used should be about five cm in size. Apply it so that it is at least 15 cm deep. Place it in a layer that runs from 30 cm above to 90 cm below the water's edge.

A layer of one or 2.5 to 5.0 cm mesh chicken wire can also be used. Anchor the wire every few feet to prevent lifting. Chicken wire will eventually have to be replaced as it corrodes.

Ducks Unlimited has had good success with their muskrat exclusion fence. It consists of a sturdy, mesh screening held up with T-bar. The T-bar is pounded into the ground at regular intervals. At a point about one-third from the top, the bar is torch-heated and angled away from the water. Screening is then fastened to the bars and trenched about 15 cm into the soil at the bottom. Total fence height is about 90 cm.

Eradication of existing muskrats

Landowners can destroy muskrats when they damage personal property. It is important to contact local wildlife officers regarding regulations and permits required for such activity.

Since muskrats are classified as furbearers, it is illegal for landowners to sell the pelts of destroyed animals unless they are registered trappers and the animal has been killed in a regulated season.

If a landowner hires a second party to destroy a problem animal, that person must be a registered trapper. The trapper must have written permission from the landowner in order to trap on private land.

Contact the local wildlife office for instructions on the sale of muskrat pelts. If the intention is to sell the pelt, ensure permission is granted before killing the animal.

In all cases, the trap used should be a Conibear No.120 or a live trap. The Conibear trap may be set on land or underwater. Setting a Conibear trap can be extremely dangerous and it is best to seek help. Any live trap should be checked within 24 hours of being set.

Poisoning is not recommended. The risk of having the bait taken by a non-target animal (for example, a family pet) is high. Because of this, poisoning is not an acceptable control measure. If permission is in place to sell the pelt it is illegal in all provinces to kill furbearing animals with poison.

Eradication of the muskrat is an option. However, if the dugout looked good to the animal to begin with, others will soon take the place of the one that was removed. Making the dugout unappealing and/or preventing muskrats from making a dugout their home is the most feasible option.