If you own a pond or live on a lake in Louisville, you enjoy the water views and the wildlife. But there is one aquatic visitor that can destroy your shoreline and drain your wallet: the Muskrat.

Muskrats are semi-aquatic rodents. They look like small beavers (about 2-4 pounds) but with a thin, rat-like tail instead of a flat paddle. While they don’t cut down trees like beavers, their digging habits make them a serious threat to man-made ponds, dams, and retaining walls.

The Burrowing Threat

Muskrats do not build dams. Instead, they dig. They create dens by burrowing into the steep banks of ponds, streams, and drainage ditches.

A muskrat den entrance is always underwater (usually 6-12 inches below the surface). From there, the tunnel slopes upward into the bank to a dry nesting chamber above the water line.

The Damage:

1. Bank Collapse: Muskrats honeycomb the shoreline with tunnels. This undermines the structural integrity of the bank. When you walk near the edge, the ground can suddenly collapse under your feet. This is a major safety hazard for people, livestock, and mowing equipment.
2. Erosion: As the tunnels collapse, soil washes into the pond. This leads to rapid shoreline erosion, making your pond shallower and muddier.
3. Pond Draining: This is the catastrophic scenario. If a muskrat burrows into a man-made dam or levee, they can dig all the way through to the other side. This breach allows water to leak out uncontrollably, potentially draining the pond and causing downstream flooding.

Other Nuisance Behaviors

• Chewing: Like all rodents, muskrats must chew. They often target the electrical wiring of pond fountains, aerators, and dock lights.
• Vegetation: They eat aquatic plants like cattails and lilies. While this can clear a pond, they can also decimate ornamental water gardens.
• Floating Docks: They love to nest in the Styrofoam billets under floating docks, chewing out cavities that ruin the flotation.

Signs of Muskrats

• Muddy Water: Persistent cloudiness in the water near the banks (from digging).
• Floating Vegetation: Cut cattails or reeds floating on the surface.
• Runs: distinct trails or channels worn into the mud in shallow water.
• Sightings: Seeing a small brown head swimming across the pond, especially at dawn or dusk.

Control and Prevention

1. Trapping Trapping is the most effective way to control a muskrat population. Because they reproduce rapidly (2-3 litters a year), you must be aggressive. We use underwater colony traps or body-grip traps placed directly in their underwater runs or den entrances.

2. Habitat Modification (Rip-Rap) To prevent future burrowing, you need to “armor” the shoreline.

• Rip-Rap Stone: Lining the bank with rocks (rip-rap) makes it impossible for them to dig. The stone should extend at least 2 feet below the water surface and 1 foot above.
• Slope Management: Muskrats prefer steep banks. Grading the shoreline to a gentle slope (3:1 ratio) makes it less attractive for denning.

3. Wire Mesh For dams and levees, burying heavy-gauge wire mesh along the face of the dam can prevent burrowing.

If you see signs of bank collapse or suspect muskrats are compromising your pond dam, don’t wait for a breach. Call Critter Removal of Louisville for a professional assessment and trapping program.