MICE

Rodents are a superb example of nature's ability to diversify and come up with the ultimate machine for the task.

A mouse (plural: mice) is a small mammal belonging to the order of rodents, characteristically having a pointed snout, small rounded ears, and a long naked or almost hairless tail. The best known mouse species is the common house mouse (Mus musculus). It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles. They are known to invade homes for food and occasionally shelter.

The American white-footed mouse (Peromyscus leucopus) and the deer mouse (Peromyscus maniculatus), as well as other common species of mouse-like rodents around the world, also sometimes live in houses. These, however, are in other genera.

Cats, wild dogs, foxes, birds of prey, snakes and even certain kinds of arthropods have been known to prey heavily upon mice. Nevertheless, because of its remarkable adaptability to almost any environment, the mouse is one of the most successful mammalian genera living on Earth today.

Mice can at times be vermin, damaging and eating crops, causing structural damage and spreading diseases through their parasites and feces. In North America, breathing dust that has come in contact with mouse excrement has been linked to hantavirus, which may lead to Hantavirus Pulmonary Syndrome (HPS).

Primarily nocturnal animals, mice compensate for their poor eyesight with a keen sense of hearing, and rely especially on their sense of smell to locate food and avoid predators.

Mice and rats are the most commonly used animals for laboratory tests.

Mice build intricate burrows in the wild. These burrows typically have long entrances and are equipped with escape tunnels/routes. There is some evidence from a new study that indicates that the architectural design of a burrow is a result of what is pre-written in a mouse's DNA.

LABORATORY MICE

Mice are common experimental animals in biology and psychology primarily because they are mammals, and also because they share a high degree of homology with humans. They are the most commonly used mammalian model organism, more common than rats. The mouse genome has been sequenced, and virtually all mouse genes have human homologs. They can also be manipulated in ways that would be considered unethical to do with humans. A knockout mouse is a genetically engineered mouse that has had one or more of its genes made inoperable through a gene knockout.

There are other reasons why mice are used in laboratory research. Mice are small, inexpensive, easily maintained, and can reproduce quickly. Several generations of mice can be observed in a relatively short period of time. Mice are generally very docile if raised from birth and given sufficient human contact. However, certain strains have been known to be quite temperamental. Mice and rats have the same organs in the same places, just of different size.

REPRODUCTION

Breeding onset is at about 50 days of age in both females and males, although females may have their first estrus at 25–40 days. Mice are polyestrous and breed year round; ovulation is spontaneous. The duration of the estrous cycle is 4–5 days and estrus itself lasts about 12 hours, occurring in the evening. Vaginal smears are useful in timed matings to determine the stage of the estrous cycle. Mating is usually nocturnal and may be confirmed by the presence of a copulatory plug in the vagina up to 24 hours post-copulation. The presence of sperm on a vaginal smear is also a reliable indicator of mating.

Female mice housed together tend to go into anestrus and do not cycle. If exposed to a male mouse or the pheromones of a male mouse, most of the females will go into estrus in about 72 hours. This synchronization of the estrous cycle is known as the Whitten effect. The exposure of a recently bred mouse to the pheromones of a strange male mouse may prevent implantation (or pseudopregnancy), a phenomenon known as the Bruce effect.

The average gestation period is 20 days. A fertile postpartum estrus occurs 14–24 hours following parturition, and simultaneous lactation and gestation prolongs gestation 3–10 days owing to delayed implantation. The average litter size is 10–12 during optimum production, but is highly strain-dependent. As a general rule, inbred mice tend to have longer gestation periods and smaller litters than outbred and hybrid mice. The young are called pups and weigh 0.5–1.5 g (0.018–0.053 oz) at birth, are hairless, and have closed eyelids and ears. Cannibalism is uncommon, but females should not be disturbed during parturition and for at least 2 days postpartum. Pups are weaned at 3 weeks of age; weaning weight is 10–12 g (0.35–0.42 oz). If the postpartum estrus is not utilized, the female resumes cycling 2–5 days post-weaning.

Newborn male mice are distinguished from newborn females by noting the greater anogenital distance and larger genital papilla in the male. This is best accomplished by lifting the tails of littermates and comparing perineums.

PETS

Many people buy mice as companion pets. They can be playful, loving and can grow used to being handled. Like pet rats, pet mice should not be left unsupervised outside as they have many natural predators, including (but not limited to) birds, lizards, cats, and dogs. Male mice tend to have a stronger odor than the females. However, mice are careful groomers and as pets they never need bathing. Well looked-after mice can make ideal pets. Some common mouse care products are:

Cage – Usually a hamster or gerbil cage, but special mouse cages are now available.

Food – Special pelleted and seed-based food is available. Mice can generally eat most rodent food (for rats, mice, hamsters, gerbils, etc.)

Bedding – Usually made of hardwood pulp, such as aspen, sometimes from shredded, uninked paper or recycled virgin wood pulp. Using corn husk bedding is avoided because it promotes Aspergillis fungus, and can grow mold once it gets wet, which is rough on their feet.

NUTRITIONAL REQUIREMENT

In nature, mice are largely herbivores, consuming any kind of fruit or grain from plants. However, mice adapt well to urban areas and are known for eating almost all types of food scraps. In captivity, mice are commonly fed commercial pelleted mouse diet. These diets are nutritionally complete, but they still need a large variety of vegetables. Food intake is approximately 15 g (0.53 oz) per 100 g (3.5 oz) of body weight per day; water intake is approximately 15 ml (0.53 imp fl oz; 0.51 US fl oz) per 100 g of body weight per day.

AIRPORT SECURITY

Israeli scientists have tested mice as a new form of airport security detector. It consists of three concealed cartridges, each containing eight specially trained mice. If they sense traces of explosives or drugs, they will trigger the alarm. According to the New Scientist, the mice work four-hour shifts and are more accurate than using dogs or x-ray machines.

FIELD MICE

The true field mouse is a long tailed Field Mouse or Wood Mouse. it is one of our most endearing animals in the UK. It is also a vital food source for many of the UK’s carnivorous creatures, and for humans a major pest. 

They have brown fur with large eyes and ears for their size. They grow to about 10cm long and weigh 30 grams or so full grown.

The Wood Mouse lives just about anywhere there is food and shelter. It traditionally roams fields, hedgerows, forests and grass lands where it can find plenty of food. They are omnivorous and will eat a range of seeds, berries, invertebrates, worms, carrion and other similar food. They have a short life in the wild because many other animals prey on them. They live longer in captivity. 

They can reproduce frequently around every 25 days. They give birth to between 4 and 7 mice which are soon out on their own after 4 weeks or so.

They are generally nocturnal animals with superb hearing and vision (hence the large eyes and ears), because of this they are a vital source of food for other larger nocturnal hunters such as owls,

An original painting in acrylics on paper - 'Field Mice' taking advantage of the ripening wheat

RODENTS:

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