The Biology of Mus domesticus (The House Mouse)

The house mouse, known scientifically as Mus domesticus, is one of the most widespread mammals globally, largely due to its close association with human activity. This small rodent has followed human migration and commerce routes, establishing populations on nearly every continent. Its adaptability has allowed it to thrive in a vast range of environments created or modified by people. As a result, it is a familiar creature in urban, suburban, and rural settings alike.

What Does a House Mouse Look Like?

The house mouse is a small, slender rodent easily recognized by its distinct physical features. An adult typically measures between 6 and 10 centimeters in length, with a tail that is roughly the same length as its body. Their weight generally falls between 15 and 30 grams. The fur is short and varies in color from a light greyish-brown to a darker brown, often with a lighter, buff-colored belly.

The tail of a house mouse appears nearly hairless and has a scaly texture. It possesses large, rounded ears and a pointed snout with long, sensitive whiskers. These whiskers, or vibrissae, are a part of its tactile sense, compensating for its relatively poor long-distance vision. The senses of smell and hearing, however, are highly developed and are used for detecting food and avoiding predators.

Where Do House Mice Live?

The habitat of Mus domesticus is intrinsically linked to human presence, a relationship known as commensalism. These mice are most commonly found living inside or around human structures, including houses, apartment buildings, farms, and commercial warehouses. Their ability to find harborage in wall voids, cluttered storage areas, and other undisturbed spaces makes human dwellings ideal shelters.

While strongly preferring human-modified environments, house mice can also survive outdoors, particularly in fields adjacent to buildings. In these settings, they may occupy shallow burrows or take advantage of natural cover. Their remarkable adaptability allows them to exist in a wide array of climates, from temperate to tropical regions, though they may face competition from other small mammal species in truly wild areas.

House Mouse Behavior and Eating Habits

House mice are primarily nocturnal, meaning their activity peaks during the night. They may become active during daylight hours if a location is free from disturbance or if food resources are scarce. These rodents are known for their agility; they are excellent climbers, can jump surprising heights, and are capable of squeezing through openings as small as a dime. This allows them to navigate complex indoor environments with ease.

Their social structure can vary depending on resource availability. In stable environments with ample food, they may form territorial groups, often consisting of a dominant male, several females, and their offspring. These groups defend their territory from outsiders. They construct nests from soft, shredded materials like paper, fabric, or insulation, located in hidden, protected locations close to a food source.

As omnivores, house mice are opportunistic feeders with a varied diet. They primarily consume seeds and grains but will readily eat fruits, nuts, and even small insects. In a household setting, they are attracted to cereals, pet food, and other stored goods. They have a characteristic habit of nibbling on many different food items within their territory, sampling a wide range of potential meals rather than consuming a large amount from a single source.

The House Mouse and Humans

The relationship between house mice and humans is often one of conflict, leading to their classification as pests. Their presence in homes and businesses can lead to property damage, as their constant gnawing can harm wooden structures, electrical wiring, and insulation. This gnawing behavior is not for food but is a necessary action to keep their continuously growing incisor teeth worn down.

Mice can also pose health concerns through the contamination of food and surfaces. Their droppings, urine, and hair can spoil stored food products and introduce pathogens into the human environment. Diseases can be transmitted through these contaminants, with salmonellosis being one example.

Observing the signs of an infestation is the first step in managing their presence. Common indicators include:

• Finding small, dark droppings in cabinets or along walls.
• Discovering gnaw marks on food packaging or structures.
• Hearing scratching or scurrying sounds within walls or ceilings, especially at night.
• A distinct musky odor may also become apparent in areas with a significant mouse population.