The house mouse is believed to of arrived in Britain around the 10th century B.C. and remains have been found in Iron Age deposits. The house mouse probably spread from Russia moving west with the onset of agriculture and farming practices.
The house mouse is common through out Britain and is found houses and farm buildings where it will live for part or all of the year.
It is not found in sewers.

Mice have the same characteristics as the rat when it comes to the structure of the skull. You will notice that the House mouse has a notch in the upper incisor. Occasionally the wood mouse may be seen in or around your property, they can look very similar. The distinguishing factor being that they do not have this notch.

The house mouse requires only a 6-7mm gap anywhere around to property to gain access. Once in and given the right conditions they will quickly set themselves up with a nest site. They are prolific breeders, from birth they reach sexual maturity at around 35 days and the average pregnancy lasting no more than 19 days. Litters containing 6-8 young and around 8 litters a year make them worthy of more than just a passing interest when it comes to control. Saying that, if there is a good food source up to 16 young can be achieved.
 
Nest sites are usually set up in secluded dark places out of the way and where they won't readily be disturbed. Material for the nest will commonly include such things as paper, cottons, insulation and a variety of packaging material.

The mouse requires around 3gms of food a day and 1.5mls of fluid, although they can survive on the fluid extracted form the foods they eat. You may first notice that a mouse is present after finding droppings generally in or around the food areas. They are omnivorous, basically they’ll eat anything. Your bars of soap or candles under the sink will be most welcome but the favourite foods being cereal and cereal products. The main problem with mice is’nt that they’ll eat you out of house and home but more overly the damage and contamination through gnawing and soiling of products with their droppings and urine.

The Norway rat: (The rat). The typical life cycle of the rat from start to finish is around 11 - 13 months and once born is weaned around 21 – 28 days (The female will be already pregnant about 7 days prior to the finishing of the previous litter weaning period).
At 8 – 12 weeks they will reach sexual maturity.

The rat has a pair of incisors and three pairs of molars top and bottom. They do not have canine or pre molars. The space between the incisors and molars is called the diastema. The incisors are basically tools. Made of enamel and dentine. The enamel, which appears orange and on the front of the teeth is extremely hard, where as the dentine is much softer and as such wears away much more easily. As the rat closes its mouth the top incisors come down over the front of the lower set. This in turn wears away the dentine at the rear of the upper set so creating a very sharp chisel-like upper set ideal for gnawing. Rat’s incisor teeth will grow continually through out its life and if left unchecked will grow between 4 and 6” in length. Was this to happen, the rat would die, hence the need to gnaw and subsequently cause damage.

Rats are very intelligent animals. There ability to adapt, survive and proliferate in a given environment is truly remarkable.

They are partially sighted colour-blind, predominately relying on other senses. They have an acute sense of hearing and smell. Around the head and body are ‘guard hairs’. These are extremely sensitive to touch and vibration. It is also believed that they have one very special sense for survival, which is psychological and as such is being researched by man. It is where the brain logs muscle spasm when moving from one place to another. Now let's assume that the rat is under threat whilst on route. Without thinking the sub-conscious brain can take over from the conscious and get the rat to the next place or the last place of safety without tripping or fumbling about and placing it in more danger. Rats have very defined runs, probably for this very reason.

Rat burrows and harbourage (places of safety) are multi functional. They will rest up, raise young or escape from predators such as stoats, foxes dogs and cats.
If you have a rat/s inside your property they are getting in somehow. So you will be looking for holes that are about 75-100mm across and usually found close to the building or close by in shrubbery. If you have a climbing plant going up the outside of your property that reaches the soffits/facia check in these areas for holes into the loft spaces. Garage doors that do not fit properly is another area to check, certainly if it is an integral garage. Pipe work entering the building, damaged air bricks, open brickwork etc: are all common proofing problems.
If holes are found, get a piece of chicken wire and scrunch it up into a tight sausage shape the size of the hole and ram it in tight. If however you do inadvertently trap the rat inside, remove the wire for a few hours and do the same again. You will know as it will be scuttling about and will be clearly heard at night.

In G.S Pest Control we use various methods of control. All pest control officers hold diplomas in pest control from the Royal Society of Health and The British Pest Control Association. These we regard as basic requirements for our officers and as such regular courses and seminars are attended to keep at the cutting edge of the techniques and legislation.

Home/property owners should employ self-help methods in the first instance.   
Rats require three basic elements to survive:

1. Food
2. Water
3. Harbourage

If you were to take away anyone of these elements the rat would not survive.

Harbourage and water. Well we can do very little about these two elements ,short of turning our properties into barren wastelands akin to desert conditions.

However we can do an awful lot when it comes to food. As previously explained the rat is a Commensal Rodent meaning living at the table of man. So, rubbish sacks left out, pet food being fed to pets outside, rabbits guinea pigs, caged birds outside along with a menagerie of other caged pets together with the feeding of the birds, all encourage the rat to take more than a passing interest in your property.
It should be borne in mind that whether it be discarded food waste or feed for your animals, they are all far more palatable than rodenticides that will be laid on your behalf. Sometimes people take offence when pointed out to them that the hygiene surrounding the aforementioned issues are highlighted as a root cause.
Feeding of birds must stop immediately when a rat is spotted on your property.

 It is helpful to speak with your neighbours as well. Often, and invariably due to the stigma and misperception that it's due to your house being dirty, people don’t necessarily like to take this approach. Often getting the reply that it’s everybody else’s problem and not mine. It’s everybody’s problem within the area. Rats can have a feeding radius from harbourage sites of 800 mtrs and have been known to travel 3.5km for a good food source, although in urban areas you would average probably no more than 100 mtrs. If a pest control officer comes to your property and as a result has to speak to a neighbour then they take it that someone is causing trouble. But if you make the first approach it can alleviate this and we find that everybody takes an interest in the welfare of each other and together sort out the problem.

Clear up and proof against food from caged pets outside dropping onto the ground below. If it does inadvertently drop out, clear it up. Bowls of food left out for dogs and cats must be taken away and cleaned once the animal has finished feeding, not left out. It would not be the first time a dog in the district has contracted leptospirosis. The year 2002-2003 6 cases came to the authorities' attention. For information on proofing and or best practice contact a pest control officer who will be happy to assist you.

Compost bins are another area that comes to our attention regularly. If you have a compost bin, or are thinking of starting composting, it is very easy to proof. Lay 10mm chicken wire (as used on the front of rabbit cages) on the ground first. Place the bin on top and bring the wire up around the sides and secure. This will stop the rat burrowing underneath and coming up inside but will let the worms, which are so important to composting.

You may not see an immediate cessation in the activity. This is for three main reasons.

1. If poisons are laid then it will take 7-10 days to kill the rat.

2. Rats are neophobic. This means that they do not react well to something new in their environment (bait boxes etc.) therefore they will treat it with caution for two or three days. They will come into it eventually but it is with extreme caution.

3. If you have not tackled the hygiene issues highlighted previously they will ignore in the best part any baits for food that is much more palatable

The poisons used are anticoagulants and basically deplete the vitamin k1 in the body.
Rats cannot generally find enough vitamin k1 in the wild. Therefore they recycle a certain amount within their bodies naturally. This is stored within the liver. K1 is used as the capsule that holds the blood cell together. The molecular structure of the poisons that are used is very close to that of k1 and is ingested into the liver and are accepted into the areas that k1 are held. Once there they stop any further re-cycled k1 from entering and as a result the re-cycled k1 will be discarded from the body by natural means. As the capsule of the blood cell can no longer maintain the level of k1 it requires to stay together it becomes thinner and subsequently ruptures. The rat during this time becomes ill and very lethargic, ultimately falling asleep and from which it doesn’t wake up.