The House Mouse (Mus musculus) is a small rodent. As a wild animal the house mouse mainly lives associated with humans, causing damage to crops and stored food.
House mice have an adult body length (nose to base of tail) of 7.5–10 cm (3.0–3.9 in) and a tail length of 5–10 cm (2.0–3.9 in). The weight is typically 10–25 g (0.4–0.9 oz). They vary in colour from white to grey, and light brown to black. They have short hair and a light belly. The ears and tail have little hair. The hind feet are short, only 15–19 mm (0.59–0.75 in) long; the normal gait is a run with a stride of about 4.5 cm (1.8 in), though they can jump up to 45 cm (18 in). The droppings are blackish, about 3 mm (0.12 in) long, and have a strong musty smell. The voice is a high-pitched squeak.
House mice thrive under a variety of conditions: they are found in and around homes and commercial structures as well as in open fields and agricultural lands. House mice consume and contaminate food meant for humans, pets, livestock, or other animals. In addition, they often cause considerable damage to structures and property. They can transmit pathogens that cause diseases such as salmonellosis, a form of food poisoning.
Young males and females are not easily distinguished: females have a significantly smaller distance between their anus and genital opening. Females have 5 pairs of mammary glands and nipples; males have no nipples. When sexually mature, the most striking and obvious difference is the presence of testicles on the males. These are large compared to the rest of the body and can be retracted into the body. In addition to the regular pea-size thymus organ in the chest, house mice have a second functional pinhead-size thymus organ in the neck next to the trachea.
House mice usually run, walk or stand on all fours; but when eating, fighting or orienting themselves, they stand only on the hind legs, supported by the tail. When running the horizontal tail serves for balance; the end stands up vertically, unless the mouse is frightened. Mice are good jumpers, climbers, and swimmers.
Mice are mostly active during dusk or night; they do not like bright lights. They have an instinctual fear of so-called "black lighting" and strobe lighting, which leads to a common method of controlling mice in the home. They live in a wide variety of hidden places that are 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. Dominant males respect each other's territory and normally enter another's territory only if it is vacant. If two or more males are held together in a cage, they will often turn aggressive unless they have been raised together from birth.
House mice primarily feed on plant matter, but they will also accept meat and dairy products. Although they are generally known to like fruits, they are repelled by the scent of many varieties of artificial fruit scent, for example strawberry or vanilla-scented candles. The reason for this is unknown, although it dates back to antiquity when Roman Senators used candles scented with strawberry oils to keep mice out of their sleeping chambers. They will drink water but require little of it, relying mainly on the moisture present in their food. They will eat their droppings to acquire nutrients produced by bacteria in their intestines. House mice, like other rodents, do not vomit.
Senses and communicationEdit
As primarily nocturnal animals, house mice have little or no colour vision. They have a sharp sense of hearing and can perceive ultrasound, possibly up to 100 kHz. They communicate both in the human audible range with squeaks (for long-distance warnings), and in the ultrasound range (for short-distance communication).
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.
The urine of house mice, especially that of males, has a characteristic strong odor. At least ten different compounds such as alkanes, alcohols, etc. are detectable in the urine.
Mice can sense surfaces and air movements with their whiskers.
Recent research has shown that mice have a special 'fear instinct', which includes a sudden burst of adrenalin when even the smell or sound of certain predators are detected, even if the mouse has never previously encountered predators before. The experiment was made by placing cat unrine in a cage of captive mice (info from BBC Wildlife Magazine).
Life cycle and reproductionEdit
Female house mice have an estrous cycle that is 4–6 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 become estrous after 72 hours.
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 be different in different individuals and have been compared to birdsongs because of their complexity. While females have the capability to produce ultrasonic calls, they typically do not do so during mating behaviour.
Following copulation, female mice will normally develop a vaginal plug which prevents further copulation. 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 3-14 young (average 6-8). One female can have some 5-10 litters per year, so their population can increase very quickly. Breeding occurs throughout the year (however, animals living in the wild don't reproduce in the colder months, even though they don't hibernate). The newborn are blind and without fur. Fur starts to grow some three days after birth and the eyes open one to two weeks after birth. Females reach sexual maturity at about 6 weeks and males at about 8 weeks, but both can breed as early as five weeks.
House mice usually live under a year in the wild. This is due to a high level of predation and exposure to harsh environments. In protected environments, however, they often live two to three years.