Description of House Mouse
(Mus domesticus)

Habitat
The house mouse has been identified from pre-Roman Iron Age deposits and is believed to have arrived in Britain around the 10th century BC. It is likely that it was once a wild species somewhere on the borders of the USSR and Iran, and gradually spread with the practice of agriculture. Its small size makes it an easy animal to transport hidden in goods and materials.

It is common in a wide range of urban and rural buildings all over Britain. Mainly a house dweller, it lives very little out of doors where it does not compete well with small external mammals like wood mice. It is not found in sewers.

House mice are variable in colour from grey / dark grey to almost black. Softly furred with a tail that is about the same length as the head and body. The under belly may be slightly paler than the fur above but not usually markedly so.

In Europe two subspecies are recognised, Mus (musculus) domesticus , the Western European house mouse usually found in the United Kingdom and Mus (musculus) musculus the Eastern European house mouse. A third form Mus (musculus) castaneus is found in Southeast Asia. The two European forms are very difficult to tell apart visually and exact distributions are not clear.

House mice avoid wet or damp conditions and prefer dry environments. House mice do not like getting wet because their small size makes it more difficult for them to keep warm and retain body heat if they do so. They are able to cope with cold conditions if the environment is dry and if they have access to nesting material to make warm nests. They have been found living in deep freezes, for instance, where they develop longer and thicker fur to keep warm and feed selectively off high energy foods. This adaptability is one reason for their worldwide success.

Extremely adaptable, the House mouse is probably, after man, the most numerous mammal on earth. They are well adapted at living with humans and exploiting the environments that humans create. They are therefore almost always found living in close association with humans.

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Biology
Average weight - 15 - 18g (Less than 23g)

Combined head & body length - 70 - 90 mm

Tail length - 60 - 90 mm

Sexually mature - 5 - 6 weeks

Gestation period - 19 - 21 days

Average litter size - 5 - 8

Weaning period - 21 - 23 days

Average lifespan - 6 months - 2 years

Importance
The House mouse is considered one of the most prominent pests in the UK. In addition, it is highly dangerous to humans, due to spreading salmonellosis, hantavirus and numerous other diseases including leptospirosis. Hence why this animal is dispatched and controlled.

Control
Good hygiene, proofing, preventative measures, pest management and monitoring.

Distribution and Habitat

The social behaviour of the house mouse is not rigidly fixed into species-specific patterns but is instead adaptable to the environmental conditions, such as the availability of food and space. This adaptability allows house mice to inhabit diverse areas ranging from sandy dunes to apartment buildings.

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House mice have two forms of social behaviour, the expression of which depends on the environmental context. House mice in buildings and other urbanized areas with close proximity to humans are known as commensal. Commensal mice populations often have an excessive food source resulting in high population densities and small home ranges. This causes a switch from territorial behaviour to a hierarchy of individuals.

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When populations have an excess of food, there is less female-female aggression, which usually occurs to gain access to food or to prevent infanticide. Male-male aggression occurs in commensal populations, mainly to defend female mates and protect a small territory. The high level of male-male aggression, with a low female-female aggression level is common in polygamous populations. 

 

The social unit of commensal house mouse populations generally consists of one male and two or more females, usually related. These groups breed cooperatively, with the females communally nursing. This cooperative breeding and rearing by related females helps increase reproductive success. When no related females are present, breeding groups can form from non-related females.

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In open areas such as shrubs and fields, the house mouse population is known as non-commensal. These populations are often limited by water or food supply and have large territories. Female-female aggression in the non-commensal house mouse populations is much higher, reaching a level generally attributed to free-ranging species. Male aggression is also higher in noncommensal populations. In commensal populations, males come into contact with other males quite frequently due to high population densities and aggression must be mediated or the risk of injury becomes too great.

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Both commensal and noncommensal house mouse males aggressively defend their territory and act to exclude all intruders. Males mark their territory by scent marking with urine. In marked territories, intruders showed significantly lower aggression than the territory residents. House mice show a male-biased dispersal; males generally leave their birth sites and migrate to form new territories whereas females generally stay and are opportunistic breeders rather than seasonal

Biology

House mice usually run, walk, or stand on all fours, but when eating, fighting, or orienting themselves, they rear up on their hind legs with additional support from the tail – a behaviour known as "tripoding". Mice are good jumpers, climbers, and swimmers, and are generally considered to be thigmotactic, i.e. usually attempt to maintain contact with vertical surfaces.

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Mice are mostly crepuscular or nocturnal; they are averse to bright lights. The average sleep time of a captive house mouse is reported to be 12.5 hours per day. They live in a wide variety of hidden places near food sources, and construct nests from various soft materials. Mice are territorial, and one dominant male usually lives together with several females and young.

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Dominant males respect each other's territories and normally enter another's territory only if it is vacant. If two or more males are housed together in a cage, they often become aggressive unless they have been raised together from birth.

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House mice primarily feed on plant matter, but are omnivorous.[citation needed] They eat their own faeces to acquire nutrients produced by bacteria in their intestines. House mice, like most other rodents, do not vomit.

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Mice are generally afraid of rats which often kill and eat them, a behaviour known as muricide. Despite this, free-living populations of rats and mice do exist together in forest areas in New Zealand, North America, and elsewhere. House mice are generally poor competitors and in most areas cannot survive away from human settlements in areas where other small mammals, such as wood mice, are present. However, in some areas (such as Australia), mice are able to coexist with other small rodent species.

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Senses and Communication

 

Vision
The visual apparatus of mice is basically similar to that of humans but differs in that they are dichromats and have only two types of cone cells whereas humans are trichromats and have three. This means that mice do not perceive some of the colours in the human visual spectrum.

However, the ventral area of the mouse retina has a much greater density of ultraviolet-sensitive cones than other areas of the retina, although the biological significance of this structure is unknown. In 2007, mice genetically engineered to produce the third type of cone were shown to be able to distinguish a range of colours similar to that perceived by tetrachromats.

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Olfaction
House mice also rely on pheromones for social communication, some of which are produced by the preputial glands of both sexes. The tear fluid and urine of male mice also contains pheromones, such as major urinary proteins. Mice detect pheromones mainly with the vomeronasal organ (Jacobson's organ), located at the bottom of the nose.

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The urine of house mice, especially that of males, has a characteristic strong odour. At least 10 different compounds, such as alkanes, alcohols, etc., are detectable in the urine. Among them, five compounds are specific to males, namely 3-cyclohexene-1-methanol, aminotriazole (3-amino-s-triazole), 4-ethyl phenol, 3-ethyl-2,7-dimethyl octane and 1-iodoundecane.

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Odours from adult males or from pregnant or lactating females can speed up or retard sexual maturation in juvenile females and synchronise reproductive cycles in mature females (i.e. the Whitten effect). Odours of unfamiliar male mice may terminate pregnancies, i.e. the Bruce effect.

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Tactile
Mice can sense surfaces and air movements with their whiskers which are also used during thigmotaxis. If mice are blind from birth, super-normal growth of the vibrissae occurs presumably as a compensatory response. Conversely, if the vibrissae are absent, the use of vision is intensified.

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Lifecyle and Reproduction

Female house mice have an estrous cycle about four to six days long, with estrus itself lasting less than a day. If several females are held together under crowded conditions, they will often not have an estrus at all. If they are then exposed to male urine, they will come into estrus after 72 hours.

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Male house mice court females by emitting characteristic ultrasonic calls in the 30 kHz –110 kHz range. The calls are most frequent during courtship when the male is sniffing and following the female; however, the calls continue after mating has begun, at which time the calls are coincident with mounting behaviour. Males can be induced to emit these calls by female pheromones. The vocalizations appear to differ between individuals and have been compared to bird songs because of their complexity. While females have the capability to produce ultrasonic calls, they typically do not do so during mating behaviour.

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Following copulation, female mice will normally develop a mating plug which prevents further copulation. The plug is not necessary for pregnancy initiation, as this will also occur without the plug. The presence or absence of the plug will not affect litter size either. This plug stays in place for some 24 hours. The gestation period is about 19–21 days, and they give birth to a litter of 5–8 young. One female can have 5 to 10 litters per year, so the mouse population can increase very quickly. Breeding occurs throughout the year.

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The pups are born blind and without fur or ears. The ears are fully developed by the fourth day, fur begins to appear at about six days and the eyes open around 13 days after birth; the pups are weaned at around 21 days. Females reach sexual maturity at about six weeks of age and males at about eight weeks, but both can copulate as early as five weeks.

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Appearance and Other British Mouse Species

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As it is much smaller the house mouse should not be confused with the two rat species. Indeed, a newly weaned Norway rat will weigh more than an adult mouse. The young rat will also have a larger head and larger feet in proportion to its general body size, and its tail will be noticeably thicker.

The house mouse may, however, be confused with three other species of mouse found in Britain, the wood mouse or long-tailed field mouse (Apodemus sylvaticus) , the yellow-necked field mouse (Apodemus flavicolIis) and the harvest mouse (Micromys minutus) . Both species of Apodemus look most like the House Mouse but prefer to live out of doors.

Wood mice enter houses, but can more commonly be found in sheds, garages and outhouses. There is however increasing evidence that there is more wood mouse activity in domestic houses than is generally realised. Wood mice tend to cover trays of bait and fill bait boxes with insulation and other materials when baits are laid.

 

Wood mouse droppings are also slightly larger and rounder than house mouse droppings. Significant wood mouse activity can also be found in external bait boxes, particularly in the absence of Norway rat activity and it is this access to rodenticides that causes concern about food chain contamination through wood mice being eaten by predators after they have been feeding on external rodenticide baits.

 

(No rodenticides are to be applied or used against the Wood mouse, Field mouse or Yellow-necked mouse)

The tail skin of the house mouse does not as readily slip off as it does with Wood Mice.
There are distinguishing features of the house mouse and the wood mouse. The measurements given for these two species show that the house mouse is generally smaller. The yellow-necked field mouse is about one and a half times the size of the wood mouse. One infallible aid to identification is the characteristic notch in the upper incisors of the house mouse.

The harvest mouse is very small (6-8 g), rather blunt-nosed and small-eared. It is yellowish brown in colour and has a moderately long tail with a prehensile tip. It lives in fields and hedgerows and makes nests among the stalks of cereals, grasses, reeds and sedges and is rarely encountered during rodent control operations.
 

Mice pose a huge threat to both domestic and commercial properties so it is advised to act quickly if you have, or suspect you have a problem with mice. Contact us today on 01282 777549 or email us at info@atlasenviro.co.uk. Our comprehensive site surveys at commercial premises are conducted free of charge and are carried out discreetly at a time both suitable and convenient in accordance with your working hours.

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We will inspect all locations of the site in both internal and external locations, providing a full photographic digital report of our findings and survey results followed by our recommendations and next course of action to take.

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Here at Atlas Environmental Services Ltd we are specialists when it comes to dealing with mice, our team of expert technicians have the skills and abilities to permanently eradicate and exclude these unwanted pest species from your property in Burnley or Lancashire and to prevent any further reoccurrence of ingress.

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Here are some signs to look out for regarding the ingress of mice:

• Sightings

• Smell

• Droppings

• Urine and Urination Pillars

• Hairs

• Runs

• Footprints

• Smears

• Harbourage and Nests

• Damage to Goods and Structures

 

Commercial sites normally always require regular servicing and inspections, in which these are conducted from our trained team of specialist technicians at 6 weekly interval visits to coincide with the breeding cycle  of rodents, and to ensure your premises remain free from pest related issues and in good order.

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Proofing work and preventative installations are always carried out from ourselves where required - This is always highlighted to our clients and actioned whilst on site!

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We are Burnley and Lancashire's leading pest control and pest management service provider - We currently look after approximately 200 commercial sites across the North West region and visit many domestic properties on a daily and regular basis!

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Our policy still remains the same - " Your Site - Remains Our Priority! "

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