Rats

Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. “True rats” are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus. Many members of other rodent genera and families are also referred to as rats, and share many characteristics with true rats.
Rats are typically distinguished from mice by their size. Generally, when someone discovers a large muroid rodent, its common name includes the term rat, while if it is smaller, the name includes the term mouse. The muroid family is broad and complex, and the common terms rat and mouse are not taxonomically specific. Scientifically, the terms are not confined to members of the Rattus and Mus genera, for example, the pack rat and cotton mouse.

Rats as pests
Rats have long been considered deadly pests. Once considered a modern myth, the rat flood in India has now been verified. Indeed every fifty years, armies of bamboo rats descend upon rural areas and devour everything in their path.
Rats have long been held up as the chief villain in the spread of the Bubonic Plague,
however recent studies show that they alone could not account for the rapid spread of the disease through Europe in the Middle Ages.

Still, the Center for Disease Control does list nearly a dozen diseases
directly linked to rats. Most urban areas battle rat infestations. Rats in New York City are famous for their size and prevalence. The urban legend that the rat population in Manhattan equals that of its human population (a myth definitively refuted by Robert Sullivan in his book “Rats”) speaks volumes about New Yorkers’ awareness of the presence, and on occasion boldness and cleverness, of the rodents.

New York has specific regulations for getting rid of rats—multi-family residences and commercial businesses must use a specially trained and licensed exterminator.
Places to look for rat infestations are around pipes, behind walls and near garbage cans. Effective rat control requires municipal workers and individuals to work together.

Reproduction
Rats can reach sexual maturity at 5 weeks of age
Rats don’t have a breeding season, although very hot or cold temperatures will reduce breeding. Females of breeding age come into heat all year round, every 4 to 5 days