Although the species is believed to be native to India and possibly other Indo-Malayan countries, it has been introduced through human travel overseas to all continents. (Rattus rattus) is found on all continents of the earth. They are serious pests to farmers as they eat a wide range of agricultural crops. The black rat also has a scraggly coat of black fur, and is slightly smaller than the brown (Norway) rat.īlack rats are generalist omnivores. This included an unusual green tinted variety. In England during the 1920s, several variations were bred and shown alongside domesticated brown rats. It is usually black to light brown in color with a lighter underside. Despite its name, the black rat exhibits several color forms. SHIP RAT (BLACK RAT or ROOF RAT) DESCRIPTIONĪ typical adult black rat is 12.75 to 18.25 cm (5.02-7.19 in) long, not including a 15 to 22 cm (5.9-8.7 in) tail, and weighs 75 to 230 Grams, depending on its subspecies. The parasite has a long history with the brown rat, and there are indications that the parasite has evolved to alter an infected rat’s perception to cat predation, making it more susceptible to predation and increasing the likelihood of transmission. This species can also serve as a reservoir for Toxoplasma gondii, the parasite that causes toxoplasmosis, though the disease usually spreads from rats to humans when domestic cats feed on infected brown rats. The average female rat has 4 to 6 litters per year and may successfully wean 20 or more offspring annually. These seasonal trends are most pronounced in more severe climates. Breeding often peaks in spring and fall, with reproductive activity declining during the heat of summer and often stopping completely in winter, depending on habitat.

They become completely independent at about 3 to 4 weeks and reach reproductive maturity at 3 months of age.įemales may come into heat every 4 or 5 days, and they may mate within a day or two after a litter is born. They can eat solid food at 2 1/2 to 3 weeks. Newborn rats are hairless and their eyes are closed, but they grow rapidly. Litters of 6 to 12 young are born 21 to 23 days after conception. Nests may be lined with shredded paper, cloth, or other fibrous material. Norway rats usually construct nests in below-ground burrows or at ground level. Their sense of taste is excellent, and they can detect some contaminants in their food at levels as low as 0.5 parts per million. Rats use their keen sense of smell to locate food items and to recognize other rats. Therefore, for safety reasons, baits can be dyed distinctive colors without causing avoidance by rats, as long as the dye does not have an objectionable taste or odor. Rats have poor eyesight, relying more on their hearing and their excellent senses of smell, taste, and touch. Some individuals may be active during daylight hours when rat populations are high. They usually become active about dusk, when they begin to seek food and water. In the United Kingdom, brown rats are an important reservoir for Coxiella burnetii, the bacterium that causes Q fever, with seroprevalence for the bacteria found to be as high as 53% in some wild populations.

Similar to other rodents, brown rats may carry a number of pathogens, which can result in disease, including Weil’s disease, rat bite fever, cryptosporidiosis, viral hemorrhagic fever, Q fever and hantavirus pulmonary syndrome. In fact it is common for breeding wild brown rats to weigh (sometimes considerably) less than 300 g (11 oz) Stories of rats attaining sizes as big as cats are exaggerations, or misidentifications of other rodents, such as the coypu and muskrat. Exceptionally large individuals can reportedly reach 900 to 1,000 g (32 to 35 oz) but are not expected outside of domestic specimens. Adult body weight averages 350 g (12 oz) in males and about 250 g (9 oz) in females. The length is commonly in the range of 20 to 25 cm (8 to 10 in), with the tail a further 18 to 25 cm (7 to 10 in), thus being roughly the same length as the body. The brown rat is a rather large true murid and can weigh twice as much as a black rat and many times more than a house mouse. The fur is coarse and usually brown or dark grey, while the underparts are lighter grey or brown.

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