Black Rat

The Black Rat (Rattus rattus), also known as the Asian black rat, Ship Rat, Roof Rat or House Rat, is a common long-tailed rodent of the genus Rattus (Old World rodents) and the subfamily Murinae (murine rodents). The species originated in tropical Asia and spread through the Near East in Roman times before reaching Europe in the 8th century and spreading with Europeans across the world. Today it is again largely confined to warmer areas, having been supplanted by the Brown Rat (Rattus norvegicus) in cooler regions.

Despite its name it comes in several colour forms. Compared to the Brown Rat, it is a poorer swimmer, but more agile and a better climber, tending even to flee upwards. It is usually black to light brown in colour with a lighter underside. A typical rat will be 15 to 20 cm long with a further 20 cm of tail. It is nocturnal and omnivorous, with a preference for grains. In a suitable environment it will breed throughout the year, with a female producing three to six litters of up to ten young. Females may regulate their production of offspring during times when food is scarce, throwing as few as only one litter a year. R. rattus lives for about 2-3 years. Social groups of up to sixty can be formed.

R. rattus has been known to fall victim of a number of diseases, of which bubonic plague (via the rat flea), typhus, toxoplasmosis and trichinosis are the most well known.

In New Zealand, ship rats have an internationally unusual distribution and importance, in that they are utterly pervasive through native forests, scrublands, and urban parklands. This is typical only of oceanic islands which lack native mammals, especially rodents. Around most of the world, ship rats are found only in disturbed habitats near people, mainly near the coast. Ship rats are the most frequent predator of small forest birds, seeds, invertebrates, and perhaps lizards in New Zealand forests, and are key ecosystem changers. Controlling their abundance on usefully large areas of the New Zealand mainland is a crucial current challenge for conservation managers.