Rats are some of the most serious rodent pests in the world. They can carry diseases such asleptospirosis, salmonellaand campylobacter and cause structural damage to buildings by gnawing and burrowing. It can be found both indoors and outdoors and, once colonised indoors, will even use cavity walls to move around the premises and to create an undisturbed breeding environment. The most common rat found in the UK is the brown or norway rat (Rattus novegicus). The black rat associated with the black death is now rare and usually only found at ports.
The brown rat is generally brownish-grey in colour, with a paler greyish belly. An adult may weigh on average 340g.
The brown rat is a burrowing animal, and will live indoors, outdoors and in sewers. When brown rats are found in buildings it is usually due to holes in the fabric of the building and/or defective drainage. Rats will also emerge from any unblocked sewer, which includes dry toilet bowls.