Housing and husbandry: Guinea pig

The guinea pig (Cavia porcellus) is highly social and generally docile rodent that is most active during dusk and daylight hours (diurnal crepuscular) [1]. Guinea pigs make a range of distinctive vocalisations that can indicate their affective state (mood) [1, 2]. They are also notably neophobic (fearful of novelty) and can become stressed by unfamiliar people or objects [2].    

Guinea pigs are highly social animals, forming close-knit groups in the wild and in captivity, making social housing essential for their welfare [1, 2, 3]. Guinea pigs display low levels of aggression in comparison to other laboratory rodents. However, boars (male guinea pigs) will become highly aggressive towards one another when kept in visual or olfactory contact with sows (females) [4]. As such, separation into same sex groups at the weaning age of roughly three weeks is recommended [5].

Breeding groups should consist of one boar co-housed with one or more sows. Breeding males can be replaced by another boar without risk of aggression from the sows. Guinea pigs have an acute sense of smell and exposure to the scent of sow urine will provoke aggression between boars [6]. Care should be taken to remove scent from clothing when working between enclosures, or groups of boars should be tended to before sows. Additionally, suckling sows may become aggressive towards unknown sows that enter their enclosure. New females should not be introduced to a group when there are lactating females or suckling young present [7].

Guinea pigs are generally docile and easy to handle, however they can respond fearfully to unfamiliar humans. Avoid startling these rodents with sudden loud noises or unpredictable movements. Hand feeding guinea pigs can help to gain their trust.

Enclosure sizes

Minimum enclosure sizes for guinea pigs in EU research establishments are detailed in Table 1.5 of Annex VII to Directive 2010/63/EU. An adult animal over 700g in weight should be provided a minimum enclosure floor space of 2500cm² and enclosure height of 23cm, with groups sizes greater than two being provided an additional 900cm² of space per animal. Note that adult guinea pigs grow to roughly 30cm in length and require a minimum of 3cm additional horizontal space to perform their species characteristic stretching posture.

Lighting

Guinea pigs are typically most active in the early morning and evening [8], although their circadian rhythms are flexible and this activity can change in line with the feeding and cleaning routines of the animal unit they are housed in [6]. Lighting in guinea pig enclosures should be soft and follow a 12-hour day-night cycle.

Temperature

Guinea pigs are sensitive to extreme temperatures; they do not dissipate heat well, making them sensitive to heat stroke [1]. They should be housed within a temperature range of 15-21°C [9], preferably in an open floor pen to allow for good ventilation. Due to their relatively large size and weight (adult animals can reach weights in excess of 1kg), guinea pigs can develop pressure sores and pododermatitis (inflammation of the skin of the feet) if housed in cages with wire or mesh floors [10]. It is recommended that all animals are housed in enclosures with solid floors, covered with a layer of dust-free substrate such as wood chip or fleece.

Structuring enclosures

Guinea pigs are sensitive to the presence of unfamiliar or unseen persons in their vicinity [11]. To reduce stress, cages or pen walls should be made from a material that allows good visual contact with the surrounding environment (e.g. wire mesh or transparent plastic). Guinea pigs will recognise handlers and actively seek to interact with them [12].

Guinea pigs avoid open surfaces and housing them in an unsheltered environment will increase stress [11]. Guinea pig enclosures should contain at least one sheltered area large enough to hold all animals within the group. Ideally a pen will contain multiple shelters to allow the opportunity for animals to hide or isolate themselves from other members of their group. Guinea pigs do not create burrows in the wild. However, hay should be added to an enclosure, to allow animals to actively utilise it both for burrowing and as a supplement to their usual diet [5].

Summary of the key housing features

Guinea pig enclosures must:

1. Be large enough to provide enough space for exercise and normal social behaviour – see Table 1.5 of Annex VII to Directive 2010/63/EU.
2. Be designed with a minimum height of 23cm.
3. Be well ventilated with sides that permit observation of the out-of-pen environment.
4. Have solid floors covered with an adequate depth of an appropriate substrate (such as wood chip) for hygiene, comfort and to permit foraging.
5. Contain sheltered areas for resting, security and managing social interactions.
6. Be softly lit and subject to a light-dark cycle.
7. Kept at a temperature range of 15-21°C.

The most important environmental enrichment for guinea pigs is being part of a social group [2, 3, 6]. As a minimum, animals should be pair-housed and without exceptional justification, single housing of animals should not be permitted. If single housing is found to be necessary, the animal should remain within visual and olfactory contact with its cage mates and the period of isolation kept to an absolute minimum.

Guinea pigs are notably neophobic (fearful of novelty) and may stop eating as a response to the stress of new foods or structures in their enclosure. While it is important that these animals be provided with a diverse home environment, introducing new enrichments should be carried out carefully, gradually and with particular attention to the responses of the animals. It may be more appropriate to rearrange familiar items within the enclosure than introduce new objects [2].

Unless there is justification to the contrary, diets should be supplemented with fresh fruit and vegetables such as carrots or lettuce as a form of enrichment and, if given by hand, to help foster a positive animal-handler relationship.

Guinea pigs are unable to synthesise vitamin C in sufficient quantity to meet their nutritional requirements, and provision of fruit or vegetables is a simple way to meet this need [8]. Note that maintaining a consistent food selection from a young age is recommended as guinea pigs will typically refuse to eat unfamiliar food items [5]. Guinea pigs may respond to appearance of a favoured food item (or handler) with behaviours such as a high pitched ‘weeking’ vocalisation or a quick jumping motion referred to as ‘popcorning’ [6]. Both behaviours are associated with low anxiety and positive affect (mood) in guinea pigs and should be considered an indicator of good housing and husbandry [12].

Hay is a particularly important form of food enrichment for guinea pigs, supplementing their usual diet and encouraging natural foraging and grazing behaviours. Lack of forage material may result in stereotypies such as trichophagia (compulsive eating of hair) and as such hay should not be withheld without scientific justification [13]. The hay utilised should be of good quality and soft enough to prevent risk of eye damage to the animals.

Guinea pigs’ front teeth continue to grow throughout their lifetime. Provision of hard items to chew on is essential to preventing overgrowth. A hard-pelleted diet should be considered a minimum requirement to maintain tooth length, with preferable inclusion of wood blocks or chew sticks from a young age [5]. 

Summary of environmental enrichment options

Guinea pigs:

1. Must be socially housed and should be kept either in single sex groups or in stable breeding colonies.
2. Require objects to gnaw on (e.g. soft wood blocks, hard pellets, cardboard tubes) to prevent their teeth overgrowing.
3. Require soft hay as bedding and to supplement their usual diet, allowing enactment of natural foraging behaviour.
4. Should have their standard hard pellet diet supplemented with fresh fruit and vegetables as a form of enrichment and a source of vitamin C.

• Clemons DJ and Seeman JL (2018). The laboratory guinea pig, 2^nd edition. Taylor & Francis.
• Donnelly M (2015). Guinea pigs. In: Comfortable Quarters for Laboratory Animals (Eds. Liss C, Litwak K, Tilford D, Reinhardt V), 10^th edition. Animal Welfare Institute.
• Kaiser S (2010). The Guinea Pig. In: The UFAW Handbook on the Care and Management of Laboratory and Other Research Animals (Ed. Kirkwood RHJ), 8th edition. Wiley-Blackwell.
• Kleven GA (2021). Behavioral Biology of Guinea Pigs. In: Behavioral Biology of Laboratory Animals (Eds. Coleman K and Schapiro SJ), 1st edition. Taylor & Francis.
• NA3RsC (2022). Guinea pig housing and handling.