Part 3.4 Behaviour and environmental enrichment

This is Part 3.4 of the Code of Practice for the Housing and Care of Laboratory Mice, Rats, Guinea Pigs and Rabbits.

Typical behavioural repertoires of these species include foraging, burrowing, climbing, nesting and nest building, social grooming and play, habitat manipulation and exploration, rest and communication. Addressing these behavioural needs is complex but involves the appropriate use of a combination of the following broadly classified conditions:

1. physical enrichment (items added to the environment)
2. social enrichment
3. structural enrichment (such as, modifications to the enclosure design).

3.4.1 Behaviour

Minimum standards for behavioural requirements:

1. Animals must be able to perform a variety of natural activities consistent with species specific behaviour, including the opportunity for sufficient exercise within their enclosure.
2. Breeding animals must be provided with the opportunity to nest.
3. Animal behaviour must be monitored closely to detect early signs of ill health, abnormal stereotypy or unexpected adverse effects during experimental protocols.

General recommendations:

1. Experimental protocols involving the modification of animal behaviour should comply with The Australian Code.
2. Young animals involve themselves in more play and exercise which is important for their development. Adequate exercise is important for skeletal and muscular development and maintenance. Exercise should be enabled through the provision of adequately sized enclosures, group housing and sometimes play objects.

3.4.2 Environmental enrichment and complexity

The aim of enrichment is to provide variety and stimulation in an artificial environment to enable normal animal behaviour without compromising experimental outcomes.

Mice and rats

The provision of environmental enrichment for mice and rats should mimic natural habitat and behavioural requirements including in particular tunnelling, foraging, climbing, social groupings and nesting. This encourages more social, content and easy to handle animals, particularly for rats held singly for experimental requirements.

As mice and rats have relatively poor eyesight, they rely heavily on their sense of smell and create patterns of urine markings to compartmentalise their environment or for territorial purposes. Provision of appropriate bedding is essential for these species.

It should be noted that stereotypic wire-gnawing in mice has been shown to be a form of displaced behaviour reflecting a lack of appropriate shelter (not a lack of provisions for gnawing) and can be easily corrected with shelter provision.

Guinea pigs

Vocalisation appears to play an important part in guinea pig social and sexual behaviour. They instinctively spend less time in open spaces, to prevent advertising their presence, preferring to sit or lie against the solid walls of their enclosure. They are poor diggers, but enjoy burrowing for concealment and protection of young. Guinea pigs like to shuffle and run in the floor pens, and young often chase each other. Guinea pigs will chew and eat plastics and other materials, but this generally does not appear to cause harm.

Rabbits

The welfare of laboratory rabbits can undoubtedly be enhanced by enriching their environment and providing sufficient space for exercise, social interaction and play. The provision of environmental enrichment is particularly important for singly housed or caged rabbits, and the provision for adequate exercise is fundamental to normal skeletal and muscular development and maintenance of all laboratory rabbits.

Minimum standards for environmental enrichment and complexity:

1. Ways of improving the environmental complexity to encourage and facilitate the natural behaviours of animals must be introduced, particularly for singly housed animals.
2. Enrichment items must not only meet the animals' needs, but must also be practical and safe for the animals.

General recommendations:

1. Care must be taken to monitor the worth of the enrichment items. Increased environmental enrichment should not be viewed as a substitute for clinical observation and close monitoring of the welfare of laboratory animals.

2. Prejudgements and preconceptions about how animals will interact with enrichment devices or materials should be avoided. The introduction of novel devices should be trialled as appropriate.

3. In general, the environmental complexity of housing can be increased by providing:

Physical enrichment, for example:

• opportunity for the animals to retreat from light and modify their environment by the use bedding and nesting materials
• a varied diet or alternative means of accessing food, such as by foraging, provisions for gnawing
• materials for specific behaviours (retreat, withdrawal, play) and exercise (such as piping or tubes, tins to hide in, exercise wheels, items or play objects to move about).

Social enrichment for example:

• social companionship both with other animals (visual, audio and olfactory stimuli) and through human interactions. The transfer of some soiled nesting material into clean cages can reduce aggression following cleaning;

Structural enrichment for example:

• transparent cages or boxes, provision of shelves, sufficient height of enclosures for rats, provision of exercise pens or increasing floor area for rabbits.

4. Animals should be observed for social interaction and signs of stereotypic gnawing, noise-induced circling (mice), barbering, fighting or excessive repetitive behaviours which may be abnormal stereotypies or stress-related behaviours.

Species specific recommendations

Mice and rats

Specific examples of methods of providing environmental enrichment are:

• Food treats and foraging activities such as, hard shelled nuts, pumpkin seeds for rats, sunflower and sesame seeds for mice.
• Chewing, gnawing and shelter provisions such as, non-toxic gnawing blocks or wooden balls, golf balls cardboard rolls or tubes or boxes, old, clean plastic water bottles.
• Consideration should be given to priority implementation of environmental and exercise devices for aggressive groups of males or singly housed mice and rats (such as, exercise wheels for mice, PVC piping for rats). High top cages are mandatory for rats (see appendix 1) and are particularly important for singly housed rats to ensure that they are able to see out to gain social interaction.

Guinea pigs

Specific examples of methods of providing environmental enrichment for guinea pigs are:

• Food treats and foraging activities — a daily supplement of hay is considered as a basic form of enrichment and fibre provision; and
• Hiding and chewing — upturned cardboard or plastic boxes, plastic tubes, sterilised softwood sticks.

Rabbits:

1. Rabbits housed in cages should be provided with environmental enrichment.

2. Specific examples of methods of providing environmental enrichment for rabbits are:

• Varied food and other supplements for foraging, chewing, gnawing (and hiding and nest building) can be supplied to rabbits in cages or pens, such as daily provision of hay/straw, hay blocks, chew sticks, branches with leaves, small cardboard boxes, vegetables; and
• Ledges or compartments on which to sit or to retreat. Ideally ledges should be 20 to 30cm above the cage or pen floor, and accommodated by the necessary cage height. Ledges and nesting boxes (outside the cage) will also increase the space available to the rabbits.

3. Enrichment in floor pen systems can be readily achieved with the use of hay bales, PVC pipes, boxes and compartments for elevation and concealment.

4. Rabbits undergoing experimental procedures in confinement or isolation should be given periodic access to an exercise area wherever possible.