What Size Are Rats?
WouterThe size of a rat depends on two factors: its species and age. Adult rats are usually larger than babies, and male rats are heavier than females. The size of the rat’s tail also affects its appearance. Although the tail may seem hairless, it is actually covered with short, fine hairs.
Rats range in size from four to five inches long, and their tails can be nearly as long as the body. The Integrated Taxonomic Information System lists more than 60 species of rat. The largest species is the Bosavi woolly rat, which was discovered in Papua New Guinea in 2009. Its body length is about five inches (12 centimeters) and weighs about 3.3 pounds (1.5 kilograms). Another species that is relatively small is the Osgood’s Vietnamese rat, which ranges from five to seven inches (12 to 17 cm) long.
Rats can live for approximately three to four years. Female rats begin breeding at three or four months old, and can breed continuously if there is plenty of food. Rats typically have five litters per year. The average litter size is between six and eleven rats, but it can reach 22. The young rats are blind and hairless, and reach full development within two to three weeks.
A young rat has a blunt face and a large tail. These characteristics give young rats a clumsy appearance, while adults are angular and proportionate in size.
