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The brown rat

Latin: Rattus norvegicus.

Brown rat eating
Brown rat eating

The brown rat is found all over the world. It originated in East Asia, from where it has spread, partly on foot and partly by sea on ships. It arrived relatively late into Europe. We first hear about “wandering rats” ravaging the continent in the early 1700s. The brown rat has great adaptability and it quickly drove away the black rat, which until then was the most common species in houses.

An adult brown rat is about 45 cm long. Of these, 20 cm is tail. The weight is usually 200 – 250 g. The colour varies somewhat, but the upper surface is usually dark brown or noble. The underside varies from whitish to grey. The brown rats thrive on the most diverse locations, but are primarily found in stables, warehouses and homes. In towns and cities, they often live in waste water pipes. Rat invasions in urban property are almost always due to sewer rats that come up through a break in a pipe. The rat is practically omnivorous. It prefers cereal products, but it also eats meat and may occasionally arise as a predator that eats chickens and other small animals. An adult rat eats an amount of feed that corresponds to 1/10 of its own body weight a day. Some of the places in the world where people have little access to food, the rats eat more than half of the stored food. In our latitudes rats’ main demerits are the gnawing of packaging and products, as well as contamination of food. There is no doubt that rats (and mice) are responsible for a large part of the food poisoning caused by Salmonella bacteria.

The brown rat breed all year round. One pair of rats that are doing well in a granary or stable can in the course of a year produce 800 rats. Rats live in herds and they recognise each other by smell. The rats are shy animals that are primarily active during the dark hours. They are suspicious of new objects and do not cross open areas, but move along walls.

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Henri Mourier
Biologist at Statens Skadedyrslaboratorium
Author of:
"Pests in House and Home"
"Bed Bugs - Bites, Stings and Itches"
"Food Pests"
"Husets dyreliv" (Insects Around the House - Only danish)
"Skadedyr i træ" (Timber Pests - Only danish)
"Stuefluen" (Common Housefly - Only danish)
Latest posts by Henri Mourier (see all)
    Food Pests
    Introduction
    An old problem
    Competition for food
    Pests can ruin stored goods
    Why not just eat the insects
    Some insects are unhealthy to eat
    Allergy to pests
    Transmission of infectious diseases
    Where do pests come from?
    Synanthrope species
    (1) The house dust mite and the sugar mite
    (2) The firebrat and the silverfish
    (3) The German cockroach and the forest cockroach
    (4) The rust-red flour beetle and the confused flour beetle
    (5) The merchant grain beetle and the saw-toothed grain beetle
    (6) The cigarette beetle and the drugstore beetle
    (7) The rice weevil and the granary weevil
    (8) The pharaoh ant and the common black ant
    History of the dark flour beetle
    Pests in bird’s nests
    Mould fauna
    The Look and Behaviour of pests
    Insect appearance
    Internal
    Insect development
    Insect senses
    Behaviour
    Water and Moisture
    Temperature
    What insects live off and live in
    The Air
    Mites
    Bug Indentification
    The various species
    Mites
    The flour mite
    The sugar mite
    The common house mite
    The Lardoglyphus zacheri
    The prune mite
    The cheese mite
    The house dust mite
    The Cheyletus eruditus
    Silverfish
    The Silverfish
    The firebrat
    Cockroaches
    The German cockroach
    The Oriental cockroach
    The brown-banded cockroach
    The American cockroach
    The extermination of cockroaches
    Crickets
    Earwigs
    Booklice
    Butterflies
    The Mediterranean flour moth
    The warehouse moth
    Tropical warehouse moth
    The brown house moth
    The Indian meal moth
    Grain beetles
    The saw-toothed grain beetle
    The merchant grain beetle
    The rust-red grain beetle
    Flour beetles
    The yellow mealworm beetle
    The lesser mealworm beetle
    The dark flour beetle
    The confused flour beetle
    The rust-red flour beetle
    The bolting cloth beetle
    Furniture beetles
    The drugstore beetle
    The cigarette beetle
    Bostrychidae
    The lesser grain borer
    True weevils snout beetles
    The granary weevil
    The rice weevil
    The corn weevil
    Bean weevils
    The common bean weevil
    The coffee bean weevil
    Skin beetles
    The bacon beetle
    The dermestid beetle
    The leather beetle
    The khapra beetle
    The reesa vespulae
    Chequered beetles
    The red-legged ham beetle
    The red-breasted copra beetle
    The black-legged ham beetle
    Spider beetles
    The Australian spider beetle
    The white-marked spider beetle
    The golden spider beetle
    The smooth spider beetle
    Plaster beetles
    Flies
    The common house fly
    The lesser house fly
    Blowflies
    The grey flesh fly
    The cheese skipper
    Fruit flies
    Hymenoptera
    The common black ant
    The pharaoh ant
    Wasps
    Birds
    The domestic pigeon
    The house sparrow
    Prevention and control of birds
    Rodents
    The house mouse
    The yellow-necked mouse
    Mouse prevention
    Mouse control
    The brown rat
    The black rat
    Rat prevention
    Rat control
    Imaginary pests
    Niches of food pests
    A: The Waste Niche
    B: The seed niche
    C: The dead plant niche
    D: The sugary excrement niche
    E: The carrion niche
    Prevention and Control, Integrated Control
    A. Inspection of the company and its environment
    The environment
    The premises
    Examination of raw materials and food on site
    Sampling
    Laboratory methods for detection of pests in food
    B. Statement of the problem
    C. Prevention and control
    1. Proper organisation of the company
    2. Proper operation
    3. Exclusion, proofing buildings
    4. Packaging
    5. Non-chemical control measures
    6. Chemical control
    D: Effective monitoring and communication
    Practical information
    Index

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