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The Rat

Description

Britain is home to two kinds of rat:

• Ship Rat (Rattus Rattus), also known as the black rat, which is rare in the UK and is not described further in this page.
• Common Rat (Rattus Norvegicus), also known as the brown or sewer rat, is the most abundant and widespread species found throughout the UK.

The adult common rat weighs 100-500 grams, measures about 24 cm (excluding tail) and has a brown back with grey fur underneath. Their tails are shorter than the head and body together. The house mouse, in comparison, weighs only 30 grams and is around 10 cm long (excluding tail), they have large ears in relation to their body with small feet and a tail which is longer than their body.

Lifestyle

Rats need shelter, food and water to survive.

• They are efficient burrowers and favour compost heaps and the ground underneath hedges and sheds, where they will dig shallow burrows and form nests with dry grass and leaves - in houses they will nest in wall cavities and beneath floor boards.
• They are good climbers and can climb vertical brick walls.
• They are good swimmers and at home in sewers where they have food, water and shelter.
• Their front teeth grow continuously. To keep teeth to a useful length they gnaw on hard objects all the time e.g. lead water pipes, brickwork, electric cables, wood etc.
• They are usually active at night but may also be alert in the day.
• They usually have well worn runs between their living area and source of food and water.
• Rats life expectancy is around one year, during which time a female will typically breed five times with an average litter of 8. Female rats will have their first litter at the age of 4 months.

Significance

Rats can be major hazard to health as they can spread many forms of disease - especially through their droppings and urine. Some of these diseases can be fatal to man, such as leptospirosis, although the incidence of such diseases is rare.

They may eat food which is intended for human consumption and their gnawing can cause structural damage to woodwork, water pipes, electric cables etc.

Signs of Infestation

• damage caused by gnawing - packaging will often show tooth marks which will indicate whether it is a rat or a mouse.
• holes made by the rats in doors and walls, and the entrances to nests, are about 80mm ( 3 inches) in diameter, and nests may be made in wall and floor cavities.
• rat runs - once the best route has been established, rats tend to use this "run" frequently and it will become soiled with the grease and dirt and be very apparent in even moderate infestations.
• smears and droppings - a good indication of the size of infestation and how long it has been there.
• footprints can be seen on soft or dusty surfaces.

Control

Remove food, water and harborage - the three main requirements for survival.

The infestation should be controlled using poison bait, which can be purchased from chemists, hardware shops and garden centres. To be effective, baits must be readily available for the rat, but should not be accessible to other animals or humans, and extra care is needed if there are children present - safety instructions on the packaging must be adhered to. It is also essential that all other food sources are removed in order to force the rats into eating the poison bait.

It will take several days before the rats will feed freely and when no more poison is being taken all baits should be removed. Rats that have taken bait will return to their nest and a dead rat may cause a smell - this should go off after a short while and it is not recommended that attempts are made to find the nest as this usually proves very difficult. Repair of damage caused may be required, and proofing of the premises from further access to the property is essential.

Rat traps (similar to mouse traps but larger) are not usually recommended as they are capable of injuring someone if set off by mistake. They also have the disadvantage that rats caught in the trap have to be disposed of.

|Pest Control Service

Elmbridge Borough Council provides a charged service for the treatment of premises infested with rats. To take advantage of this service, either:

• Complete and submit the |online form and we will contact you to arrange an appointment.
• Contact the |Environmental Health & Licensing Division

For further information read our |Rat Advice Leaflet (PDF format).