The muskrat (Ondatra zibethicus) is a common, medium-sized, semi-aquatic rodent found throughout the wetlands and waterways of North America. Muskrats are generally solitary and timid creatures that instinctively avoid human contact, preferring to flee or dive underwater when disturbed. While not inherently aggressive, the danger relates to defensive behaviors, disease transmission, and the significant damage their activities inflict on man-made structures.
Direct Physical Threats
Muskrats are not predatory toward humans or domesticated animals, but they will defend themselves vigorously if cornered, threatened, or protecting their young. Any physical encounter stems from a defensive reaction rather than an unprovoked attack. They possess large, sharp incisor teeth and strong claws, which they readily use to bite or scratch in self-defense.
A bite carries the risk of a painful wound and secondary bacterial infection. Pets, especially dogs, are more likely to experience a defensive confrontation near the water’s edge or a burrow entrance. It is important to maintain a safe distance and never attempt to handle one, as this is the most common cause of defensive injury.
Potential Health Risks
The potential for muskrats to carry and transmit various pathogens that affect human health is a significant concern. Like many rodents, muskrats act as reservoirs for several zoonotic diseases transferable to people.
The most notable is Tularemia, sometimes called “rabbit fever,” which spreads through contact with an infected animal or contaminated water. Infection can cause flu-like symptoms, fever, and infected sores, requiring prompt treatment.
Muskrats also carry Leptospirosis, a bacterial disease affecting the kidneys, transmitted through contact with water or soil contaminated by infected urine. Additionally, they can be infected with protozoan parasites such as Giardia and Cryptosporidium. These parasites cause gastrointestinal illness when water sources are contaminated by muskrat feces. Caution is necessary around waterways where muskrats are present. Protective gear, such as rubber gloves, should always be worn if handling a deceased muskrat or an area where they have been active.
Structural Hazards
While the direct threat to humans is low, muskrats pose a costly threat to property, particularly structures associated with water management. Their habit of burrowing into earthen banks to create dens is the primary source of structural damage. Muskrats dig extensive tunnel systems into the banks of ponds, dams, dikes, and levees, with entrances typically located below the waterline.
These tunnels weaken the embankment’s structural integrity over time. This destabilization accelerates erosion, which can lead to cave-ins, collapse, leaks, or localized flooding. Muskrats may also gnaw on materials like pond liners or the foam flotation blocks used in boat docks. Property owners must remain vigilant for signs of muskrat activity, as damage from extensive burrowing can become expensive to repair.