• There are three species of rat and mouse that are the most common in homes and businesses due to their ability to adapt to the human environment. These are the brown rat (Rattus norvegicus, also called the common or Norway rat), the black rat (rattus rattus, also called the ship rat or roof rat) and the house mouse (Mus domesticus).

    Brown Rat

    The brown rat typically weighs about one pound. Their fur is coarse and usually brownish or reddish gray with white below on the belly. Brown Rats tend to live in close association with people. They may burrow to make nests under buildings and other structures. Although they can climb, they tend to inhabit the lower floors of multistory buildings. Brown rats eat nearly any type of foods. They prefer grains, meats, fish, nuts and some fruits.

    Brown Rats are primarily nocturnal. They usually become active about dusk, when they begin to seek food and water. Rats have poor eyesight and are considered color-blind; therefore baits can be dyed distinctive colors without causing avoidance by rats. Unlike mice, which rarely burrow, rats will dig under buildings, along fences, and under plants and debris. A female rat can have six litters of up to 12 young per year. These 70+ rats can start to breed by the time they are three months old. Rats can live up to 12 to 18 months.

    Evidence of Brown Rat Invasion
    Brown rat droppings are wide and dark brown in color. They are typically found in tapered, spindle shape – resembling a large grain of rice. Signs of presence also include gnawing marks, tracking, runways and burrows.

    Black Rat
    Also known as the “roof rat”, it is typically 6-12 ounces in size, much smaller than the brown rat. They are black to brownish gray in color with a tail length of 7-10 inches. If there is plenty of food and shelter, black rats will live in close proximity to humans, particularly in attics, ceilings or wall areas. These rats inhabit upper areas of buildings or homes often gnaw on wires found there, possibly leading to fires, outages and production down-time.

    Evidence of Black Rat Invasion
    An adult rat typically produces 40-50 droppings per day. These fecal pellets are usually dark-colored, ½ inch in length and pointed at both ends. Similar to the brown rat, you will also find gnawed marks on wooden structures such as corners, floor joists, and wall studs.

    House Mouse
    The house mouse weighs ½ ounce to 1 ounce and is typically a dusty gray color. Unlike the rat, a house mouse has excellent hearing, vision, smell and touch which enable them to be highly adaptable to homes and indoor buildings. They only need ¼” opening to be able to enter a building, so they often have plenty of options available to them.

    Evidence of House Mouse Invasion
    Mouse droppings are approximately 3-8mm in length and are often found scattered randomly during an infestation. Mouse droppings are granular in shape and black in color and can be found near nesting areas.

    Damage Prevention or Control
    Physical barriers can prevent rats from gaining entry to structures where food and shelter are available. “Ratproofing” is an important and often neglected aspect of rat control. It is a relatively permanent form of rodent control that prevents damage from occurring. To exclude rats, seal all holes large than ½ inch across.

    In addition to the above-mentioned techniques, sanitation plays an important role in controlling rat populations. In agricultural environments, proper sanitation cannot always eliminate rat populations, but it can often prevent rats from flourishing in large numbers. Sanitation involves good housekeeping, including proper storage and handling of food materials, feed, and edible garbage. Warehouses, granaries and grain mills, silos, port facilities, and similar structures may provide excellent habitat for rats. Pet foods are often a source of food for rats in and around homes. Keep all such materials stored in metal rodent-proof containers. Feed pets only what they will eat at a single time. See below for indoor and outdoor sanitation tips.

    Indoor Sanitation


    • Clean areas under stoves, refrigerators and dishwashers.
    • Keep counter tops clear of food.
    • Do not leave glasses of water out overnight.
    • Store dry food, pet food and birdseed in sealed containers.
    • Clean pet bowls at night.


    • Keep storage areas free of clutter.
    • Rodent-proof hard-to-access areas that tend to be neglected.
    • Store supplies or materials off the floor. Don't forget about maintaining the outdoors as well. Properly maintain your garden and store firewood away from your home for effective rodent control.


    Outdoor Sanitation

    • Properly maintain landscaping - trim any overgrown vegetation and shrubbery until ground underneath is visible.
    • Remove any debris - rock piles, old equipment etc.
    • Elevate lumber and firewood at least 18".
    • Store firewood away from the house.