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Common Rat


   (Rattus norvegicus)


It is often said that there are as many rats in cities as people. In fact, rats are opportunistic survivors and often live in the closest proximity to humans where they can easily find food and shelter. The Common, Brown and Norway rat are well established pest species in the UK. The Black rat (Ship rat) once widespread has become rare and confined to ports. Rats are considered pest because they spread harmful diseases, contaminate human food and damage people’s property.

Appearance: The body of an adult rat is about 20 – 30 cm (8 – 12 in) long; its tail has a length of 13 – 23 cm (5 – 9 in). Rats weigh between 100 to 500 g (3.5 – 18 oz). The colour of their furs can vary significantly, but most frequently it is brownish grey on the back and grey on the belly. The rat has a blunt snout, stocky body as well as claws and small, furry ears. Sometimes, rats are confused with mice, although the latter are much smaller and have tails much longer than the whole body.

Infestation: Rats readily infest both domestic and commercial premises searching for food, water and shelter. They dig extended tunnel systems around buildings, in hedgerows as well as in rubbish and compost heaps. Rats invade human dwellings by exploiting poor design, construction and maintenance of buildings. To sneak into a house rodents use open, broken or poor fitting windows and doors, openings around pipes and conduits, cavities, gaps and holes in walls or woodwork, broken drains and sewer pipes as well as other spaces and ducts. The animals can jump quite high as well as are good swimmers and climbers, so they are able to overcome even very difficult obstacles. Under favourable conditions – food surplus and warm temperature, an uncontrolled population of rats grows rapidly, since each female rat can have up to 7 litters consisting of 8-12 young a year.

Habitat: Rats live in hierarchical groups both outdoors and indoors. They are widespread in rural and urban environments. Some figures show that there are over 80 million rats in the United Kingdom. It often happens that the rodents seek shelter in warm locations to breed and to find food. In doing so they invade residential, office and industrial buildings, restaurants, pubs, hotels, hospitals, schools, shops, warehouses, sheds and granaries. The animals make use of various burrows, tunnels, ducts and other hidden places in a building to rear young, to rest and to escape from enemies. Rats eat of types of food, but they prefer cereals and have a strong need for water. Living in human dwellings the rodents consume people food such as dairy and floury products, fruit, vegetables or meat.

Detection: Rats are more active at night, but they may be spotted while scavenging for food, water or shelter during the day. The rodents are very sensitive to any sudden noise and very cautious of new objects. Their senses of taste and smell are highly developed. All in all rats are extremely shy and well aware of their environment, so it is quite difficult to sight a live animal even if it is out of its hiding place. Nevertheless, it is quite easy to detect the pest itself, since rats leave typical signs of their presence that can be seen both inside and outside of the premises. These include above all tooth marks on building materials, plaster work, woodwork, furniture, skirting board, food packaging and foodstuffs. Gnawing is a part of rodents’ natural behaviour; hence they nibble to keep their teeth in good condition, to get at food or to build their nests. As a result there are always a lot of small pieces of debris, cuttings, scraps of paper, bits of fabric and gnawed food leftovers in buildings infested by rats. Rat droppings are another evident trace of possible infestation. The droppings usually found in groups are black and spindle shaped, with an average length of 1.5 – 2 cm (0.6 – 0.8 in). Rats build burrows with holes of about 8 – 10 m (3 – 4 in) as entrances. These holes can be detected in the ground around buildings, in floors, walls or the base of doors. Rats regularly move along the same run, where they leave smear marks of grease, dirt and natural oils from their furs. Outdoors these runways resemble tiny paths of about 5 – 7 cm (1.87 – 2.76 in) in width where vegetation has become flattened. Sometimes rat footprints are visible on dusty or sandy surfaces. Apart from that, urine stains, hairs or musty odour of the rodents clearly indicate a heavy rat infestation. It happens that squeaks and nibble of rats can be well heard at night.

Health hazards and damage to property: Rats transmit a lot of dangerous diseases such as leptospirosis (Weil’s disease), salmonellosis (food poisoning), rat bite fever, crypto, tapeworm and rabies. Humans usually get infected from the food and water contaminated by rats’ urine or mucous secretions. Apart from spreading diseases rats damage growing crops and stored food as well as building fabric. The rodents spoil much more food than they can eat by contaminating it with their droppings, urine and hairs. Rats gnaw woodwork and building materials, electrical and telephone cables, pipes as well as other fittings and fixtures, causing substantial damage to private and public property.

Hygiene and tidiness: High standards of hygiene and housekeeping with suitable protective measures are essential to prevent rat infestation. Premises should be frequently checked for conditions that may be welcoming to rats. It is important to have buildings properly and regularly maintained. All gaps, holes and other openings going through walls should be sealed up. Defective drainage and broken pipes have to be quickly repaired and manholes firmly secured. Building surroundings should be frequently and properly cleaned, since heaps of rubbish and compost, piles of timber, overgrown gardens and dense foliage provide a favourable environment for rats to build nests and to breed undisturbed. Boxes, bins and containers with food or household waste ought to be protected with lids and bird feeders or places with pet food regularly checked. No excessive food for birds or pets should be left outdoors. Apart from that keeping living and working areas clean, removing food residues as well as keeping food in closed and rodent proof containers are fundamental measures to curb the pest.

Professional pest control service: If a rat infestation has been already established, only a professional pest control service is able to effectively eradicate the overall population of the rodents in a property. Remedial steps to keep the premises and its surroundings clean and tidy can help to reduce the existing infestation, but they are insufficient to completely eliminate it. Rodenticides and traps have to be implemented in the places where rats live and run. Rodenticides are effective if ingested by a rat, so they are usually combined with the food baits appealing to the rodents such as cereals or grains. Professional pest controllers take into account the behaviour of rats when laying baits. They use special bait boxes or stations to ensure that no humans or domestic animal come into contact with the poison.

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