Rattus norvegicus; the Brown Rat
This rat species, the largest of the two inhabiting the UK, was thought to have arrived in the 18th century on ships that came from Russia. Today the population is approximately 6,790,000 with an unknown population trend. They live in colonies that are divided into clans; these groups have a patriarchal hierarchy with certain males staying closest to the best food sources. Their burrows may be used for generations just like the setts of badgers (Meles meles) and the two are known to share their underground home especially if near rubbish tips, although badgers do eat the rat pups sometimes (adults are usually too difficult to catch).
The brown rat is a very intelligent and agile rodent, eating a wide range of food depending upon where it resides; crops are preferred in the countryside and food waste (almost any food waste) in urban areas. It is considered a pest especially in urban areas and regularly killed as a result, though its reputation as an unclean animal is perhaps undeserved as it apparently spends a lot of time cleaning itself.
The brown rat is a very intelligent and agile rodent, eating a wide range of food depending upon where it resides; crops are preferred in the countryside and food waste (almost any food waste) in urban areas. It is considered a pest especially in urban areas and regularly killed as a result, though its reputation as an unclean animal is perhaps undeserved as it apparently spends a lot of time cleaning itself.