Mice

Introduction

Using these notes

These notes:

    • have been written to be consistent with community, industry and research and teaching based animal welfare legislation
    • apply to all schools in NSW, government and non-government
    • contain standards (in a red box at the beginning of each section) and guidelines. The standards must be met by schools, in accordance with the requirements of the Animal Research Authority. The guidelines are the desirable practices to achieve desirable animal welfare outcomes
    • reflect available scientific knowledge, current practice and community expectations.

Each section of these notes lists any approved activities, with their approved categories, that are applicable to mice. A complete list of the approved activities for all species can be found in Approved activities.

Category 4 and 5 activities may be undertaken by students only if prior written approval from the SACEC has been obtained using Application form 1.

Before a teacher demonstrates a category 5 activity to students, the teacher must have written certification from the SACEC. Certification is sought using Application form 4.

 

Varietal range differences

There are over 330 known species of mice. There is a huge variety of fur colour combinations and several different fur types such as longhaired or curly haired

In Australia, mice are kept purely as pets with no production output. In other countries people show their mice however this is not very common in Australia. Mice are common children’s pets, especially in inner city areas where keeping larger animals is not possible. They are also used in laboratories for research and scientific work. Mice are suitable animals for schools with space restrictions, primary schools and inner city schools that cannot have farm animals.

Schools that wish to keep mice should select individual animals suitable for classroom pets that have had previous handling and do not show signs of aggression or extreme stress when being handled.

 

Physical characteristics

Size: Approximate length from snout to base of tail is 7-9 cm. Approximate length of tail is 7–9 cm. Overall length is 14–18 cm.
Weight: Adult is approximately 20–40g.
Age at adult size: 10–12 weeks.
Average life span: 18–24 months.
Weight at birth: 1–1.5g.
Gestation period: 19–21 days.
Number of offspring: 8–12.
Range of breeding ages: 2.5–12 months recommended.
Healthy characteristics:
    • Temperature: 37°–38°C
    • Heart rate: 600 beats per minute
    • Respiration rate: 160 per minute (can be up to 230 per minute)

 

Vision

Being nocturnal animals, mice have the ability to see in the dark however this also means that they have very little, if any, colour vision. Mice will also dislike bright lights and will always seek out a darker environment. Mice have poor depth perception but the positioning of the eyes on their head, allows them to observe movement overhead. This is a very important feature for survival as mice are ground dwelling prey animals that are usually attacked by larger predators from above. For this reason, handlers should never approach a mouse with their hand from above, the handler should always move their hand towards the mouse from ground level.

The mouse’s sense of touch, smell and taste makes up for its limited vision. Its whiskers, which flick back and forth rapidly, sense its immediate surroundings, brushing against objects and giving the mouse a detailed picture of its surroundings. The mouse’s acute sense of smell allows them to identify one another, distinguishing between males and females and identifying possible dangers or threats. Taste is also a means of identification for mice. Smelling items usually leads to tasting them, and if appropriate, eating them. Usually the young will eat what their mother has been eating while lactating, which allows young mice to be able to identify safe appropriate foods from early on and ensures survival.

 

Hearing

Mice have very sensitive hearing, far superior to humans, allowing them to identify approaching predators or danger and flee quickly or find a hiding place.

 

Behavioural characteristics

Healthy mice are alert, active and inquisitive animals. Mice are exceptionally agile animals and enjoy running, jumping, climbing and standing on their hind legs while in their cage. Individual animal behaviour will depend upon the conditions that they are kept in and how many mice are kept together. The size and type of the cage will also influence the behaviour of mice, as well as the environmental enrichment that is provided. Mice should never be kept in isolation, as they are naturally adapted to living in groups for social enrichment, protection, warmth and comfort. Adult male mice should not be housed together, even if littermates, as they are very territorial and will fight.

To avoid unwanted pregnancies, mice should always be kept in single sex groups, which should be established shortly after breeding. Mice are extremely rapid reproducers, giving birth multiple times every year. Female mice also experience oestrus within 24 hours of parturition so can potentially breed at least 10 times per year if continually kept with a male. Breeding should only be allowed if surplus animals are wanted and there is adequate space, care, handlers and financial means to care for them sufficiently. A plan for the disposal of unneeded surplus animals should always be in place prior to breeding. Selling or giving animals to appropriate homes or other schools is allowed however if killing animals is the only way of disposing of surplus animals, breeding is not allowed.

Mice are nocturnal animals and are always more active at night. They usually feed at night and during the daytime it is normal for them to huddle together in groups to sleep and gain body warmth from one another. A healthy mouse will always sleep in a foetal position. If a mouse is sleeping in an extended position, this may be a sign of illness. Cannibalism is rare but does occur and is usually indicative of inadequate diet, maintenance or stress factors.

Mice are generally not aggressive animals however if they feel frightened or threatened, they may bite. Some strains of mice however are particularly aggressive and these animals should not be used in the classroom. During the breeding period, it is normal for the male mouse to nibble the female’s head or body and to examine her rear end prior to copulation. Mice are suitable pets for primary schools and inner city schools where space and facilities are limited. Having these small animals in the classroom allows students to experience caring for and observing an animal’s behaviour as well as becoming aware of the responsibilities involved in owning animals. While mice will get accustomed to handling and grooming by handlers over time if they are handled appropriately, it must be considered that mice are very small prey animals and will always find being handled by a human very threatening and stressful. Handling should always be carried out in a careful, calm manner and the animals’ privacy must be respected, allowing them plenty of time to be in their enclosure without excessive handling or observation. Animals should never be handled for extended periods of time repeatedly throughout the day. If animals show signs of stress, handling should cease.

Cage mice enjoy participating in all behaviours that they would participate in the wild, including fossicking for foods and other items, running, jumping, socialising, exploring and resting with other mice. It is very important to provide mice with an environment that can enable them to participate in these activities.