Brown rat
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Rattus norvegicus
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The Brown Rat (Rattus norvegicus, also known as the Norway rat, Wharf rat, or Common rat) is a common long-tailed rodent of the genus Rattus, the family Muridae and the subfamily Murinae (Old World rodents).
The species originated in northern China but are now common in urban areas throughout the world, or indeed anywhere with a good food supply. The rat is a true omnivore. It will consume almost anything, but prefers grains, and eats up to a third of bodyweight a day. The rats are known to catch fish or small rodents. It is active usually at night and is a good swimmer, although a poor climber.
The fur is coarse and usually brown or dark grey, the underparts are lighter grey or brown. Length can be up to 40 cm, although 25 cm is more common, with the tail a further 15 cm or so, but less than half the body length. The adult body weight averages 300 g in males and 200 g in females. They have acute hearing and are sensitive to ultrasound. Average heart rate is 300-400 bpm, with a respiratory rate of around 100 per minute. Their vision is very poor and they are unable to detect colour and are blind to long-wave light.
The rat can breed throughout the year if conditions are suitable, a female producing up to eight litters a year. The gestation period is only 21-23 days and litters can number up to fourteen, although seven is common. They can live for up to three years, although most barely manage one - a mortality rate of 95% is estimated, together with predators, intraspecific conflict and cannibalism are major causes. They live in large hierarchical groups, either in burrows or subsurface places such as sewers and cellars.
Selective breeding of the Brown rat has produced the albino laboratory rat. Rats are also exelent pets and are also the focus of attention if shows of fancy rats. Rats are clean, social and intelligent pets.
It is a carrier of a number of diseases, including bubonic plague, Weil's disease, cryptosporidiosis, haemorrhagic fever (often HFRS), Q fever and hantavirus pulmonary syndrome. It is considered to be one of the most significant mammal pests.