Norway Rats are one of two species of rats in British Columbia. They are usually brown or dark grey in colour, with lighter grey or brown underparts. The ears are smaller than in BC's other rat species, the Black Rat. The tail of the Black Rat is longer than its total body length, while the tail of the Norway Rat is shorter than the total body length (Rattus rattus), and this can help distinguish them.
The Norway Rat is usually active at night and is a good swimmer, but a poor climber (unlike the Black Rat, which is a good climber). It is an omnivore and will eat a variety of foods, although grains are significant in the diet. "Foraging behavior is often population-specific, and varies by environment and food source. [Norway] rats living near a hatchery in West Virginia catch fingerling fish. Some colonies along the banks of the Po river in Italy will dive for mollusks, a practice demonstrating social learning among members of this species. Rats on the island of Norderoog in the North Sea stalk and kill sparrows and ducks" (Wikipedia 2012).
Norway Rats excavate burrows and live in large hierarchical groups, either in burrows or subsurface places such as sewers and cellars (Wikipedia 2012).
This species is more aggressive than the Black Rat and will displace it.
The Norway Rat probably originated in Asia, Northern China and Mongolia, and is thought to have spread elsewhere in the Middle Ages, but did not reach North America until around 1750-1755 (Wikipedia 2012). In Canada it is found in all provinces except Alberta. In British Columbia, it is found in the Lower Fraser Valley, Vancouver Island, the Queen Charlotte Island, and on small islands along the coast. The precise date of arrival in BC is not known, but according to Nagorsen (2005), it was common in Vancouver by the 1880's. It did not arrive in the Queen Charlottes until the 1980's, where it displaced the Black Rat (Nagorsen 2005).
Carl and Guiget (1958) provide insight into this species arrival in BC: "The Norway Rat apparently arrived in British Columbia very early, probably with the first [sailing ships]. The Norway Rat is well established throughout the coastal sections and just about everywhere." Nagorsen (2005) indicates that although it was common in Vancouver by the 1880's, it did not arrive in the Queen Charlotte Islands (Haida Gwaii) until 1980.
The Norway rat is a vector of several human disease, including Weil's disease, rat bite fever, cryptosporidiosis, viral hemorrhagic fever, Q fever and hantavirus pulmonary syndrome. However, it does not carry bubonic plague, which is spread by Black Rats (Wikipedia 2012).