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Rats & Mice

 

 Advice to Householders - Rats & Mice

Characteristics

 
House mouseHouse Mouse:- Brownish grey in colour, the body is 80-100mm long, the tail is 80-100 mm long, it weighs between 14 & 20gms, has a slender and small build, has a pointed nose, large hairy ears and pink feet. The droppings are small spindle shaped or irregular.
 
RatCommon Rat:- Brownish grey with grey belly fur, 200-270mm in length with the tail 165-205 mm in length, weighs between 200 & 500gms, has a large and thickset build, a blunt nose, short thick opaque finely haired ears, and grey feet. The droppings are banana or sausage shaped
 
Ship Rat:- this can be grey, black, brown or tawny and may have white belly fur, its body is 145-200mm in length and its tail is 250mm long, it has a slender and streamlined build, a pointed nose, its ears are large, thin, translucent and almost hairless with pink feet. The droppings are ellipsoid or spindle shaped.
 

Behaviour

 
Rats are intelligent and social animals. They live in colonies, which may be several hundred strong and can jump, swim, climb and prefer to move under the cover of darkness. They have a strong tendency to burrow, especially into soil or under secure coverings such as piles of rocks. They are frequently found living near water, by drains, along ditches, streams and sewers. Occasionally they live inside buildings in spaces between walls, in lofts or beneath piles of rubbish. Due to their agility they can squeeze through small openings and it is very difficult to keep them out.
 
Their wide-ranging habitat means that they are never far away from human activities and will infest anywhere that has a suitable food supply for them. An infestation can build up rapidly without you knowing about it as they are more active at night. If you do see a rat during the day then there is a sizeable colony present.
 
Rats establish runways which are regularly used to travel from their nest to a food and water supply which give rise to signs as to where to bait by finding droppings, grease smears, footprints and signs of gnawing. But they do not like new things and as a result may not take from the bait stations straight away, they need to get used to something new being there.
 
Mice, on the other hand are inquisitive creatures and lots of small bait stations will attract their attention providing it tastes good. Mice can be more of a problem than rats as they do live indoors, they are therefore likely to cause more damage to food stuffs and cabling through their constant gnawing. They also can get through very small gaps and build their nests in areas that are difficult to get to.
 

Signs of Infestations

Often the first sign of rodents is finding droppings.  Rat droppings are approximately 1cm long and rod shaped, whilst mice droppings are similar in size to a grain of rice.  Other evidence include footprints in dust, gnawing of packages and furniture, nesting sites, smear marks.

Health Risks

Rats and mice carry diseases including salmonella, Leptospirosis, Weil's disease, Murine typhus, Viruses, parasites, Brucellosis, Aujeszky's disease and foot & mouth disease.

 
Whilst disease transmission to man from rats is a potential problem, it is a greater risk in farm animals. Rats are a major hazard to livestock production especially pigs, calves and poultry. Control must be a top priority.
 

Life Cycle

 
A healthy female can produce up to five litters a year each of 8-10 young. Gestation is 21 days and offspring can reach maturity in 8-12 weeks. As many as 30% of the females in a colony can be pregnant at any one time.
 
Mice follow a very similar pattern except that they reach sexual maturity after only 42 days thus can increase the size of their colony much quicker than the rat.
 

Methods of Control

a) Trapping - it is best to use a large number of traps for a more successful treatment.  Place traps in the area of the infestation, at an angle.  Suggested bait to be placed on traps are small pieces of fruit e.g. strawberry, chocolate, peanut butter, or cereal.
 
b) Rodenticides;- The only effective way to deal with an infestation in the first place is by using these to kill off the population. Different types of bait are available and they have differing degrees of success on each of the three species.
 
When treating mice lots of small bait feeding stations are necessary as mice are curious and move from food source to food source. However if the bait is not palatable to them, or they have access to a better food source then they will become 'bait shy' and not take the bait, which obviously leads to greater problems.
 
Rats on the other hand have to get used to anything new and will not feed from a bait station until they have got used to it being it there. Therefore it does take a little bit longer to start treating a rat infestation with the use of bait. It is therefore essential that once again any alternative food source is denied.
 
Lack of success in controlling an infestation is usually down to poor application of the baits. Once this has been corrected if there are still not takes form the bait then bait resistance must be considered and further advice sought from MAFF (Ministry of Agriculture, Fisheries and Food).
 
TAKE CARE WHEN PLACING ANY POISON OR TRAPS.  ALWAYS LAY THE POISON IN A SAFE POSITION.  FOLLOW MANUFACTURERS INSTRUCTIONS AND ENSURE CHILDREN AND ANIMALS CANNOT GET ACCESS TO THE POISON OR TRAPS.
 
c) Hygiene/management:- It is essential that basic housekeeping is good. All food sources should be removed and refuse kept in covered containers, preferably rodent proof ones. Sources of water such as dripping taps and leaky pipes must also be removed. Proofing of the building is essential to prevent rodents re-entering the premises . Blocking up holes where service pipes enter the premises, any holes behind kitchen cupboards, ensuring no gaps between floors and floorboards ensure that doors fit properly or have bristle strips fitted to them or steel plates etc. Air vents should be covered with a metal mesh, which will prevent rodents getting in but still allow air through. Ensure that any holes under the eaves etc are filled. Any drain breaks also need to be repaired to prevent rats from the sewers getting into your private drains.

Any holes that may allow rats or mice to gain entry to the property should be sealed up.

Poisoned rodents will usually attempt to return to their nesting area to die.  If this happens, a smell may occur, which can last a few days.  The small can be masked with air fresheners or rodent deodorant.

If you want further information, please contact Environmental Health Department on 876543 or email on  envhealth@barrowbc.gov.uk
 
Please be advised that we are not responsible for any injury or damage caused where persons carry out treatment themselves.  Ensure you follow the manufacturers instructions carefully when using any product. Keep any insecticide away from children and animals and ensure it is stored safely.