Rats

There are two different common species of rats found in Britain, the Black Rat, and the Brown Rat.

Brown Rat, Rattus norvegicus

The Brown Rat generally nests outdoors in burrows dug under the floors of houses, sheds or other buildings, in banks, in piles of rubble or in rubbish heaps, compost heaps or refuse tips.

During the day rats usually stay in their burrows and come out a night to search for food.
They eat meats, fish, flour, seeds, grains, fruits, vegetables and anything a human will eat. They eat 30g of food per day and drink about 15ml water each day. A rat must have water daily to survive.

The brown rat is greyish-brown in colour but this varies from pure grey to pure black or any combination of this. They are large and stocky, measure 30-45 cm in length including the tail. They have a blunt nose, small close-set ears and a long naked tail. They weigh up to 650g. The rat dropping is 19mm long and oblong shaped.

Brown rats live in small, hierarchical family groups, including one or more dominant male. The dominant males territory extends up to about 100m and is explored daily, any intruders being ejected often after a fierce, sometimes fatal fight. They are neo-phobic (showing a fear of new objects) which makes them cautious and any new object in their territory takes them several days before they will accept it. Like mice, rats are colour blind and have poor eyesight. Their sense of smell and touch is however acute.

Rats can squeeze through a hole of 13mm diameter. Though not good climbers because of their bulk, the brown rat can climb up the inside and outside of pipes and jump as much as a metre vertically, drop 15cms without injury and can burrow down to depths of 1.2m.
Life Cycle

Brown rats are capable of mating at three months. Females come into heat every 4 or 5 days. Females have an average of 3 - 7 litters per year with 6 - 12 pups per litter. Their eyes open at 6 days and they are fully furred by 15 days. After giving birth the female goes back into heat in 24 hours. Adults live for approximately one year. Brown rats have 6 pairs of nipples.

Signs of Rats in and around your structure.

Droppings, which are soft when fresh, along well-travelled pathways, in feeding areas and near the rodent's shelter.

Tracks, including footprints and tail marks, on dusty surfaces, in mud and snow.
Urine along travelled paths or in feeding areas. Both wet and dry rodent urine will glow under ultraviolet light (black light).

Smudge or rub marks on beams, rafters, walls, pipes and other fixtures.
Gnawing marks on doors or ledges, in corners, in wall material, on stored material or on other surfaces.

Noises in the walls caused by gnawing, climbing, clawing, squeaks and fighting, particularly at night when rodents are most active.

Life span: Typically up to 18 months in the wild, but domestic rats live an average of three years.

Statistics: Head and body length18cm, Weight 200-400g.

Physical Description: Brown rats have coarse brown (occasionally black) fur, with a pale underside. They have a long tail, which is sparsely haired.

Distribution: Although originally native to east Asia and Japan, brown rats are now distributed world-wide. They are found all over Britain except for exposed mountain regions and some small offshore islands.

Habitat: Brown rats are highly adaptable and can be found in a variety of habitats, typically near human habituation.

Diet: Brown rats are omnivorous but prefer starch and protein-rich foods, such as cereals. Their diet includes meat, fish, vegetables, weeds, earthworms, crustaceans, nuts and fruit. They sometimes cache food for later.

Rats memorise specific pathways and use the same routes habitually. Rats are cautious and if their food is in a exposed place where it cannot be consumed quickly they will usually carry or drag it to a hiding place. Rats have a very well developed sense of taste enabling them to detect certain compounds, including poisons, at very low concentrations. Rats are omnivorous, eating nearly any type of food, including dead and dying members of their own species. Rats teeth grow up to 12.5 cm per year

As their alternative name suggests, they were commonly found on ships, resulting in their distribution throughout the world.

Life span - Up to 18 months.

Body length - 10-24cm, Weight: 150-200g.

Physical Description - Black rats are very similar in appearance to brown rats, but they are slimmer, with relatively larger ears and a longer tail. Despite their name, they are typically grey brown, with a pale grey underside, but they may be completely black.

Distribution: Although native to Asia, black rats have spread all over the world. They have largely been replaced by the brown rat in Britain.

Habitat: Black rats are highly adaptable and can be found in a variety of habitats, typically near human habituation.

Diet: They are omnivorous, but are more partial to fruit than brown rats are.
Behaviour. Black rats live in male dominated groups. Fights are common, often initiated by the females. They are predominantly nocturnal, but they will sometimes forage for food in the day. As with brown rats, they have good auditory and olfactory senses, but black rats have better eyesight.

Reproduction: Most breeding activity occurs from March to November, and they produce 3-5 litters a year. Females give birth to 7-8 young after a gestation period of 23-24 days. They are weaned after 3-4 weeks.

Conservation status - Black rats are now one of the rarest mammals in the UK, but persist mainly around port towns, such as Liverpool, London, the Shiant Islands (Inner Hebrides) and Lundy island. They are subject to persistent pest control due to the damage they cause and the numerous diseases they spread, including bubonic plague, typhus and rabies.