Brown rat
As a brown rat you would know every pipe, gap and bin behind the city’s façade – and treat anything new on your route with deep suspicion.
The city’s underground tenant
The brown rat, Rattus norvegicus, also called the Norway or sewer rat, originated in northern China and Mongolia and spread across Europe mainly in the 18th century, largely displacing the black rat in many towns. Today it lives wherever humans store food: sewers, cellars, farms, railway embankments, riverbanks and the soil under bins. Adults weigh roughly 250–500 g, with a scaly tail somewhat shorter than the body.
You would see poorly in colour but have excellent hearing, including ultrasound, a keen sense of smell and sensitive whiskers that map tunnels in the dark. You can squeeze through a gap about the width of a thumb, swim well and climb rough walls.
Cautious, clever, social
Rats live in colonies with dominance hierarchies, digging burrow systems with several exits. You are mostly active at night and eat almost anything: grain, meat, rubbish, insects, snails. A key survival skill is neophobia, a wariness of new objects and foods. You would taste a small amount of an unfamiliar food and wait; if you felt ill, you would avoid it for good. Young rats learn what is safe partly by smelling the breath of colony members.
Rats also play, especially when young, and laboratory research has recorded ultrasonic chirps during play and when they are tickled by researchers.
Fast lives
A female can breed from about two to three months old, with litters of typically six to twelve pups roughly every month in good conditions. Yet few rats grow old. Owls, cats, foxes, dogs, poison baits, traps, cold and fighting mean most wild rats die within a year. In laboratories, where Rattus norvegicus is one of the most important research animals, they live about two to three years.
