Muskrats are 16-28 inches long, around half of that length comes from their tail. They weigh 1-4 lbs.
Signs of their presence:
Visual sighting of the animal
Houses: Muskrats will build houses from vegetation including cattails and small branches. The houses will look like a dome in the water.
Dens: Muskrats will dig into the banks of the pond
Smell: a musky smell
Noises: young will squeal when they want to get attention from their mother. Adults will make low squeals or snarl when cornered or threaten. When fighting they will chatter.
Tracks: Their hind foot has five long finger-like toes and their front foot has four long fingers. Similar to that of a raccoon their prints are smaller, approximately 2-3 inches long. Sometimes their tail will leave a mark in the mud as well.
Scat: often found near the water, their scat are elongated 3/8 to 5/8 inches long and ¼ inch in diameter. Their scat is clustered in a pile.
Evidence of their feeding: Muskrats will eat mussels and plants. An area in which there are less aquatic plants or opened mussel shells may indicate a muskrat.
Omnivores, but mainly consume a plant-based diet. They eat roots, stems, leaves, and fruits of aquatic vegetation. Once their plant food source is depleted they will eat insects, fish, amphibians, and in the winter: freshwater mussels.
Typical activity patterns:
Social style: live with their mate and young
Daily activity: more active at dust but feeding throughout the day. Remain active through winter, just stays under the ice if the pond freezes over.
Hibernator: No, muskrats remain active during the winter. Often foraging for food as they do not store food in their houses. They have been known to eat food stored by beavers.
Muskrats can be found throughout Oregon where there is water.
Muskrats can be found in ponds, marshes, and swamps. They do not like waters that are deep, instead they prefer shallower areas.
Territory and home range:
Muskrats have a small home range to about 100-120 feet in diameter, often sticking to the pond or swamp area they are in. They become very territorial during mating season.
Pair bonding style: Monogamous, both parents will raise the young.
Breeding Dates: March through August
Birthing Period: Gestation is about 28 days
Litter Size: 1-14 young per litter. Average 6-7. They can have up to three litters a year
Weaning Dates: Around 1 month old
Common nuisance situations:
Time of year: Spring.
What are they doing?
Most muskrat damage is caused by their burrowing.
They burrow into earthen dams, dikes, levees, and railway embankments, weakening their structures. They also burrow into the banks of ponds, canals, and irrigation and drainage ditches. Their tunnels may drain a small farm pond. They may damage floating docks, marinas, and boathouses.
Muskrats will cross yards. Some people are frightened of them, or mistake them for Norway rats.
Occasionally eat field crops. May cause substantial financial losses in states with major rice and aquaculture operations, because they eat rice, cut it down to use as building material for their lodges, and damage the field by burrowing through levees.
Damage aquaculture sites by burrowing into levees or pond banks.
Damage ornamental aquatic gardens by eating water lilies or cattails or other plants.
When their populations grow too high, they may “eat out” all of the aquatic plants in the area, reducing the quality of the habitat for other species, such as waterfowl.
They will eat small fish, possibly hurting the fish population in the future if one has a pond they are using to fish in
Disease risks: tularemia, hemorrhagic septicemia, leptospirosis, salmonellosis, ringworm, pseudotuberculosis. They are hosts for many ticks, mites, fleas, and various worms.
Legal status in Oregon:
Protected. Protected furbearing species with set trapping season.
To prevent damage,”overbuild” a dam or farm pond:
Normal water level should be at least 3 feet below the top of the dam.
Spillway should be wide enough to prevent the water level from rising more than about 6″ during heavy rainfall.
Inside face of dam (towards water) should be built at a 3:1 slope (three feet out for every foot of height)
Outer face of dam should be built at 2:1 slope.
Top of dam should be at least 8 feet wide, best if it’s 10–12 feet wide.
To solve an existing conflict, reduce their food sources (this may be necessary if there’s extensive damage):
Around a pond, mow grassy areas frequently.
Remove the aquatic plants that muskrats eat. They prefer starchy foods including cattails, pickerlweed, bulrush, smartweed, duck potato, horsetail, water lily, sedges, young willow trees, and rice, when grown as a flooded crop.
Reduce the slope of the bank, muskrats prefer to den in steep slopes. A ratio of 3:1 regarding horizontal to vertical rise is ideal to deterring muskrats.
Remove the following upland plants from around the pond (and replant with other species): bermuda grass, clover, johnsongrass, and orchard grass. Muskrats can survive entirely on those plants.
If muskrats are traveling from the pond to feed in fields or gardens, fence those areas. Muskrats will eat corn, soybeans, wheat, oats, grain sorghum, sugarcane, and ornamental flowers.
If you don’t want to remove plants from your pond, try to attract muskrat predators instead. Increase cover in and along the pond’s edge to attract mink, one of the main predators of muskrat.
Protect vulnerable ponds and dams:
Before attempting to modify a wetland environment permits may be needed.
Riprap the inside of the pond’s dam with rocks or cover it with vinyl-coated welded wire. Rocks should be flat and closely-fitted. The rock layer must be at least 8″ thick, extending 3 ft. below and 1 ft. above the normal water line.
“Draw down ponds” during the winter (requires a permit). Remove the muskrats, and make sure they’re gone. Reduce the water level to expose their burrows (this often means lowering the water from 1 1/2–3 ft). Then fill in any burrows and tamp down the soil. Cover them with rocks.
Trapping is often a critical part of a strategy to control muskrat damage. When possible, invite licensed trappers to remove muskrat during the legal season.
To avoid catching beaver, otter, mink, and birds:
Avoid trapping if there’s sign of otter nearby, if possible.
Use natural baits (in the spring, try muskrat musk. In the fall and winter, use sweet-smelling oils such as oil of sweetflag, spearmint, or anise; apples, parsnips, or carrots also work well). Do not use baits made from beaver or otter glands.
Use only small foothold or body-gripping traps, and anchor all traps so they’ll hold any live animal that may be accidentally caught. Put crossed hoops over a floating log set to discourage birds from landing on the log.
Use catchpoles to release any otters or beavers that are accidentally caught in the trap.
Don’t set traps in spillways, channels, large bank holes, or other natural funnels.
Cage traps, 8 × 8 × 24″
Leg-hold trap, #1 or 1 1/2, set in 1–2″ of water and anchored in at least 18″ of water.
set traps in active runs as close to the den’s entrance as possible.
if the water is less than 18″ deep, use a body-gripping trap (preferable) or a guarded foothold trap.
Set the traps on slides, near den entrances or channels muskrats frequent
Preferred killing methods:
foothold trap in a submersion set
shooting (practical if removing a few muskrat from a small pond)
Acceptable killing methods:
stunning and chest compression
stunning and cervical dislocation
Control strategies that don’t work particularly well, or aren’t legal in Oregon:
Conventional frightening techniques aren’t effective against muskrats.
For information on pesticides follow the link, https://www.oregon.gov/ODA/programs/Pesticides/RegulatoryIssues/Pages/RegulatoryIssuesCompliance.aspx