Rats are rodents that belong to the Rattus genus of the family Muridae. These are the most dominant species on earth. There are several species of rats in the world. Most rodents are herbivorous, but some are omnivorous. In general, there are two basic types of rats. They are black or roof rats and Norway or brown rats. Both are thought to have originated in Asia and are now widely distributed throughout the world.

The brown rat, which is also known as the Norway rat, house rat, gray rat, barn rat, and wharf rat, is one of the best-known and is the larger of the two. Their scientific name is Rattus norvegicus. They are mostly grayish-brown, with a lighter colored stomach. A fully-grown brown rat is 18 to 26 cm long and weighs between 400 and 600 gm. They have a tail shorter than its body and their nose and muzzle are blunt. They prefer moist conditions and nest in deep burrows.

Roof rats (Rattus Rattus) are also called black rats and ship rats. They are usually black, slender, 16-21 cm long and weigh about 80-300 gram. Their tail is longer than the head and body and their nose and muzzle are pointed. As the name suggest, roof rats are climbers. Their paws enable them to climb and build nests in upper parts of dwellings, attics, rafters and crossbeams of buildings.

These rats breed when they are three to four months of age. They breed 1 to 13 times a year and produce 1 to 22 in a litter. Black rats and brown rats eat about the same things. Their diet typically includes seeds, nuts, grains, vegetables, fruits, cereals, meats and invertebrates. They consume about one-third of their weight in food every 24 hours.

They carry lethal diseases, damage structures and contaminate food. Some of the diseases potentially fatal to man that spread through rats are Weil's disease, plague, salmonella food poisoning and toxoplasmosis.