The brown rat (Rattus norvegicus) is thought to have been introduced into the UK amongst goods imported during the 18th century from eastern Russia or China and has since spread rapidly across the whole country.
They have drab, shaggy grey-brown fur and a long scaly tail, which is nearly as long as their head and body combined. They live in large colonies and the most powerful, aggressive males choose the best territories, nearest to their food source. They identify each other by smell and will fight off rival packs or their members. They are creatures of habit and tend to use the same passageways to get from one place to another, leaving clear signs of their passage, hence the phrase ‘rat run’. They are highly intelligent and adaptable creatures and can swim and climb with great agility, so if a population grows to pest proportions, they can be very difficult to eradicate. They are typically associated with farms, rubbish tips, sewers, urban waterways and warehouses but they will also live in hedgerows and cereal crops. They are commonly found in compost heaps, under garden sheds and wherever poultry or wildfowl are kept. They dig burrows in banks, leaving heaps of earth nearby. They are very common and are widely distributed throughout the UK’s towns and countryside where they thrive alongside man.
They breed throughout the year and females can have up to 5 litters per year. Six to eleven blind, helpless young are born per litter and become independent within just three weeks. Young brown rats are grey and are often confused with adult mice. They are omnivorous and will eat almost anything from grain, fruit, eggs, young poultry and animal fat, to whatever they find in rubbish tips and refuse areas. They will even eat soap and candle wax. A cereal diet with some animal matter is preferred. Food is not stored but is often taken to a safe place to be eaten. It is claimed that as much as 20% of the world’s food supply is either destroyed or eaten by rats.
Brown rats are capable of carrying and transmitting a number of diseases to both livestock and humans including Salmonellosis, Tuberculosis, Cryptosporidiosis, Escherichia coli, Leptospirosis (Weil’s disease), Lymphatic choriomeningitis, Murine typhus and Foot-and-mouth disease. Parasites carried by rats include nematodes, mites, tapeworms, fleas and ticks. Cats, foxes and birds of prey hunt very young rats but the adults are often too fierce for predators to catch. Rats are often killed on the roads by cars and are regularly poisoned by man due to their serious pest status.