There are two species of rat in Britain, Rattus Norvegicus which is commonly known as the Brown Rat or Common Rat. The Rattus Rattus, known as the Black Rat or Ship Rat is now rarely found in the UK.
The Brown Rat is the larger of the rats in Britain, often weighing over half a kilo and measuring about 23cm, without counting the tail. It has a blunt muzzle, small hair-covered ears and a tail that is shorter than its body. The Black Rat weighs half as much and is shorter. It has a pointed muzzle, large, almost hairless ears, a more slender body and a long thin tail that is longer than its body.
Rats have well developed senses of smell taste and touch. They have an acute sense of hearing, frequently using ultrasound to communicate, and are particularly sensitive to any sudden noise. Both species breed rapidly and become sexually mature in about three months. Each female may produce from 3 to 12 litters of between six and eight young in a year. Rats need to gnaw to keep their constantly growing incisor teeth worn down. They damage woodwork, plastic, bricks and lead pipes, and will strip insulation from electrical cables.
Brown Rats live in any situation that provides food, water and shelter. In homes, they will live in roof spaces, wall cavities or under floorboards. In gardens, they will burrow into grassy banks or under sheds. Brown Rats are often found living in sewer systems. Black Rats are rare and are occasionally found in shipping ports.
Rats feed mostly at night and an average rat will eat 50g of food a day. Preferred foods are cereal products, although rats are omnivorous and will eat almost anything that humans eat.