The term “water rat” is a common label for several semi-aquatic rodents, primarily muskrats and nutria, that live near human infrastructure and natural waterways. These animals often raise concern regarding potential property damage and disease transmission. Clarifying the specific species involved and the nature of the risks they present is necessary to assess the danger these rodents pose to human health and property stability. This assessment details the specific health and structural hazards associated with their presence.
Identifying the Animals Known as Water Rats
The animals most frequently identified as “water rats” are the native muskrat, the invasive nutria, and sometimes the common Norway rat, which has adapted to living near water sources. Distinguishing these species is important for understanding potential risks, as their size and habits differ significantly. The muskrat (Ondatra zibethicus) is a medium-sized rodent, typically weighing between two and four pounds, characterized by a long, flattened tail that aids in swimming.
The nutria (Myocastor coypus), a larger, introduced species, often weighs between 10 and 20 pounds and possesses a long, round, sparsely haired tail. A tell-tale sign of the nutria is its large, bright orange-yellow incisor teeth. The Norway rat (Rattus norvegicus), smaller than both, is distinguished by its thin, scaly, non-flattened tail and smaller overall body size, generally weighing less than one pound.
Diseases and Health Risks
Semi-aquatic rodents can carry various pathogens, posing a health risk primarily through contaminating water sources and waste. Muskrats are known reservoirs for tularemia, a bacterial disease caused by Francisella tularensis. Transmission can occur through consuming contaminated water, handling infected animal tissue, or through an open cut.
Leptospirosis is another concern, a bacterial disease that muskrats and nutria can carry and shed through their urine into the water. Humans or livestock can become infected by contacting contaminated water or soil. Furthermore, these rodents can host various parasites, including blood flukes and nematodes, which cause conditions like “swimmer’s itch” upon exposure to contaminated water.
Physical Interaction and Structural Damage
Direct physical injury from these animals is uncommon, usually only occurring when a rodent is cornered or handled, leading to defensive bites or scratches. The more significant danger relates to their burrowing habits, which threaten the stability of water-retaining structures. Muskrats and nutria create extensive tunnel systems into the banks of ponds, dams, levees, and dikes.
This tunneling can severely weaken the structural integrity of these earthen works, potentially leading to breaches, erosion, and collapse, especially when the soil is saturated. Nutria are known for undermining water-retention levees in agricultural areas. Burrowing under buildings, roadbeds, or concrete slabs can also weaken foundations. Additionally, these rodents may gnaw on wooden structures and foam floats under boat docks, causing them to lean or sink.
Safe Practices and Avoidance
Reducing the attractiveness of an area is the most effective approach to managing semi-aquatic rodent presence and preventing damage. Eliminating accessible food sources is primary, which includes securing trash bins with tight-fitting lids and avoiding the feeding of wildlife. Removing sources of standing water, such as leaky pipes, and ensuring proper drainage can also discourage their presence.
When near water, avoid direct physical contact with the animals and never attempt to corner or handle them. If cleaning up droppings or handling a deceased animal, always wear rubber gloves to prevent disease transmission. If burrows threaten the stability of a dam, levee, or foundation, professional wildlife control services should be consulted to ensure humane and legal removal.