Rats and Mice

Rats

Description

The most common species in the UK is the Brown Rat, also known as the ‘common’ or ‘sewer’ rat.  The brown rat has a blunt nose, small furry ears and is generally a brownish-grey colour on top and slightly lighter underneath.  On average, they will live between 6-18 months, in that time reproducing up to 7 times.  Each litter can consist of between 6-14 young.  The brown rat ranges from 25-45cm in length (including the tail).  Their eyesight is generally poor, but they have excellent hearing.

Brown rats are omnivorous - they will eat almost anything – and can consume about 30g of food per day, which is about 1/10th of their average body weight.

Distribution

Rats are a worldwide pest, they are very adaptable and known to spread life threatening diseases as well as causing structural damage in the areas they infest.

Significance

Rats have been known to cause major structural damage to residential and commercial properties as well as to services such as power supplies.  Rats have also been known to spread the following diseases:

• Listeria and Pasteurella, which cause food poisoning and stomach bugs
• Leptospira, which causes flu-like symptoms
• Worms, which can lead to general ill health
• Cryptosporidia and Taxoplasma, which cause diarrhoea.

What to look out for

Rats can live indoors and outdoors so evidence can be found in either location.  However they are more likely to be found outside or in buildings such as garages or sheds.  If rats do enter your house, they are more likely to be found in cavity walls, lofts and basement areas, and under suspended wooden floors.  If you suspect you have rats, indoors or out, look out for the following:

• Rat droppings, which are about 1-2cm long and look like dark brown jelly beans.  These are distinctly different from mice droppings, which are much smaller and look like small, dark brown grains of rice.
• Droppings in and around the edges of garden sheds, compost heaps, pet hutches and bird tables. (Rats will use the same area in general as a toilet area so there droppings will not be so widespread as mice). On average a rat will leave about 40 droppings a day.
• Rats are thirsty creatures and will drink on average 150ml of water a day and so will always requrie access to fresh water.
• Burrows (rats are burrowing animals) that can be found in gardens, near rubbish, sources of food and compost heaps, which provide rats with ideal harbourage.
• Smears along surfaces where you suspect rats have been running.  They are habitual animals, and will follow specific paths.  These smears are normally caused by the build-up of grease from their fur.
• Rats secrete urine as they move and eat, so be aware of any unusual smells.
• Gnawing damage to containers, pipes or structures.
• Flattened vegetation and/or worn earth.
• Damage to packets of food, electrical cables, gas and water pipes, woodwork and shredded paper which is used for nesting.

Mice

Description

The main type of mouse in Britain which can become pests are the common house mouse.

The adult house mouse may weigh up to 50 grams, usually has brown fur on its back and is grey underneath, its ears are fairly large in relation to its body and its feet are small.  The tail is the same length as the head and body but is much thinner than the tail of a young rat.

Distribution

Mice are widely distributed throughout urban areas and in farm buildings.  

The house mouse is a more common domestic pest which will nest in partitions, floors and behind wall boarding.  Mice are most active at night and will range over a very small area if food is plentiful.  They are less dependent on water than rats and will normally obtain sufficient moisture from their food.

Significance

Mice are not welcome guests.  They are responsible for the spread of many diseases.  They eat food which may be intended for human consumption and contaminate much more with their urine, droppings and fur.  Mice will also cause structural damage to property by gnawing through woodwork, wires, pipes and household items. Mice are also more destructive and dangerous than rats and can cause more serious problems such as chewing through electrical cables.

Life cycle

The life expectancy of mice is around one year during which time a female may breed up to six times.  The average size of a litter is six.

Breeding occurs throughout the year but especially in the spring and autumn. The average litter of a pair of rats is between 4 to 16 babies and they can breed up to 7 or 8 times a year which could result in over 2000 new problems.

Control

You will need professional help in controlling colonies of mice.  They are particularly difficult to control because of the rate at which they breed and are able to colonise new areas.

If you have a Rat or Mouse promlem you should call as immediately on the number below. Never try to treat this problem yourself.