( Francach) Rats are rodents - furry mammals, with sharp front teeth designed for gnawing. They are bigger than mice and have longer tails. There are more than 100 kinds of rats. They are great swimmers and fast runners. They can wiggle through small holes. Most rats live in warm, tropical countries. The Norway (Common) rat and the Black rat live in almost every part of the world. They eat anything and live almost everywhere. They are most likely to be seen in sewers, rubbish dumps, farms and river banks.

A pair of rats may live only a year. But at the end of that time they may have produced almost one hundred offspring and thousands of descendants. Rats destroy up to one fifth of the world's crops each year. They can carry many diseases including rabies and bubonic plague. They are mostly nocturnal and spend the day in their systems of tunnels under the ground.

By Stephen Phillips and Barry Naughton

Index of mammals