Norway rat

Norway rats are burrowers and strong swimmers, living in colonies with complex social lives. They explore cautiously, avoid new objects at first, and learn quickly from each other what is safe to eat.

Laboratory studies of the same species have shown rats freeing trapped companions and making ultrasonic calls during play that researchers have compared to laughter.

Norway rats have shaped human history, as carriers of disease and as the laboratory rat, one of the most important animals in medical research.

Their intelligence, social learning and adaptability are exactly what have let them live alongside people on every continent except Antarctica. Alberta, in Canada, is a rare exception: it has kept itself free of established rats since the 1950s by constant vigilance at its borders.

Breeding — all year where food and shelter allow
Gestation — about 21 to 23 days
Litter — usually six to twelve young
Eyes open — at about two weeks old
Weaning — at about three to four weeks old
Maturity — at about two to three months old
Lifespan — usually a year or less in the wild

• Sealing openings, securing rubbish and removing food sources prevents rats more lastingly than killing them.
• Rats can carry diseases such as leptospirosis; wear gloves to clean up after them.
• Rodent poisons move up the food chain and kill owls, hawks, foxes, cats and dogs.
• Glue traps cause slow, painful deaths.

• Norway rats come from Norway. They came from Asia; the name is an old mistake.
• Rats are dirty animals. Rats groom constantly; the dirt is in the places people leave for them.
• Poison is a clean solution. Poisoned rats are eaten by owls, hawks and pets, which are poisoned in turn.

• Black rat
• House mouse
• Eastern woodrat
• Hispid cotton rat