Norway Rat (also known as common rat, street rat, sewer rat, brown Norway rat, Norwegian rat) is found worldwide, largely in developed towns and cities where refused collects, drains and sewers. It is common in Britain and continues to increase its range.
Biology: If conditions are suitable a brown rat breeds through out the year producing upto five litters a year and the litter can number from 7 to 14. The gestation period is only 21 days. The maximum life span of a rat is upto three years. The estimated mortality rate of a rat is 95%.