Mice

Mice

Appearance
The House Mouse has grey/brown fur and is slightly lighter on its underside.  The average weight is about 15 grams.  It has along tail, which is about 80% of the length of its head, and body, which is 70-90 mm long.  The House Mouse has large ears and a pointed snout.

Life Cycle
The life cycle of mice are very similar to rats.  Mice colonies typically develop from a pair or a single pregnant female.  Rodents can breed even more efficiently than rabbits and size able infestations can develop very quickly.  Conditions that suit a rapid population increase are a good supply of food and water, suitable temperatures and an undisturbed cover.  With these ideal conditions breeding will continue throughout the year.

Mice are capable of reproducing from the young age of three months.  Pair bonds are not formed and mating is carried out on an opportunistic and promiscuous basis.  Mating is brief and can take place with a number of males.  After mating and conception there is a relatively short period of pregnancy (gestation) 17-20 days.  The average size of the House Mouse litter is between 5-6.  The weaning period is 3 weeks.

Unlike most mammals mice do not have to wait until the original litter is weaned and the female has stopped giving milk before coming back into oestrus.  This means that the female mouse may be willing to mate and can conceive again soon after the original litter is born.

Mice may give birth every 24-28 days and this can give rise to rapidly increasing populations.  At very high densities reproduction rates decrease to take account of the reducing availability of resources and the increasing competition within the population.  Mice have a life span of up to 2 years.

Diet
They feed on practically everything, but prefer to eat cereals and insects.

How to spot a mouse infestation
As rodents interact they leave signs of their activity that help to signal their presence, indicate the size and extent of the infestation.

The most reliable way to tell if there is an infestation present is with an actual sighting of the identified pest.  If mice are seen frequently during the day this may indicate that a large infestation is present.

House mice produce a stale odour, which is very distinctive.  It can be readily recognized when an infestation has been present for a while in a covered area.

Mice droppings are much smaller than other rodent droppings.  They are 3-7 mm in length and may often be spindle shaped, they will produce about 80 a day.  It is possible to identify an active infestation as the dropping are soft and shiny, as apposed to hard and dull if they have been there for some time.  Note that bat droppings look very similar to mouse droppings, however they usually crumble very easily and mainly contain insect fragments.  Bats are legally protected so it is essential that correct identification is made.

Damage to goods
Unfortunately, often the first sign of rodent activity is the discovery of partially eaten, spilled or hoarded food, damaged packaging material and other signs of gnawing.  Damage is a frequent consequence of indoor mouse infestations, gnawing of electric cables and wires in the loft area is a common problem.  A House Mouse can be distinguished as their incisor teeth marks are about 1 mm wide.

Why are mice pests?
Rodents are of particular health importance because of their close association with human settlements, their worldwide distribution, and the link they can provide between man and other carriers of infection.

The most important of these is the ability to transmit diseases to man and his livestock and the economic damage they may cause to foodstuffs and structures.  Rodents whether being seen or heard can be very distressing and causing abhorrence and fear to some.

Rats and mice damage both growing crops and food stored.  The scale of these loses are enormous.  One estimate claimed that 5% of food production worldwide was lost due to rodent activity.  Even in Britain the loss is considerable and cannot be tolerated.  On these facts alone rodent control is justified.

Salmonellosis
Another disease of particular significance in this country is salmonellosis caused by bacteria of the salmonella group.  It ranks as one of the most wide spread animal-borne diseases.  Infection in humans commonly occurs from the contamination of food and drink with rodent excreta, or as a result of passive transmission of the bacteria by rodents.  Salmonellosis is a type of food poisoning and symptoms can include acute gastro-enteritis accompanied by headache, fever and vomiting.

Other diseases
Parasites carried by rodents include ringworm, mites, nematodes, tapeworm, ticks and fleas.  There are also a number of diseases that can be transmitted to animals including foot and mouth in cattle and sheep.