Article by Russell Tofts

Other Names

Wild Cavy; Brazilian Guinea Pig; Cobaia.

Introduction

The genus Cavia (the typical cavies) contains eight species, including the Domestic Guinea Pig (Cavia porcellus). Although Wild Cavies do bear a superficial resemblance to Guinea Pigs, their behaviour is very different. They are nervous animals and do not enjoy being handled (although they can become quite trusting in time), are quite good at climbing and can even run up wire netting if startled. The Brazilian Cavy is popularly thought to be the ancestor of the Domestic Guinea Pig, largely on the basis of anatomical similarities, in particular the crest of hair on its neck. This theory has been reinforced by crossbreeding and biochemical studies. Results are not conclusive, however, and it remains equally likely (or, in my opinion, even more likely) that other species of cavy are implicated. There are two other possible contenders; these are Cavia fulgida (the Shiny Cavy) and C. tschudii (the Montane Cavy). It is equally possible that the Guinea Pig may have derived from either of these species, or perhaps even from a hybrid of all three. Let's just say the jury is still out!

Distribution

Widely distributed in South America, being found in central Ecuador, Colombia, Venezuela, southern Surinam, eastern and southern Brazil, Paraguay, Uruguay, north-eastern and east-central Argentina.

Natural Habitat

Open grasslands, swamps, forest edges, and rocky outcrops. They are sometimes found at elevations of up to 4,200 metres.

Social Structure

In the wild this species generally lives in extended family groups of five to ten individuals, but in favourable habitats many groups may choose to live close together giving the impression of large numbers living together. A maximum population density of 38 animals per hectare has been recorded. The average territory size for males (boars) is around 1,387 square metres and 1,173 square metres for females (sows). Since prime habitat is often bisected by swathes of unsuitable country, making dispersal of young animals difficult, wild populations are not infrequently inbred to some extent. Fortunately, this is not normally a problem with this species, although it is not something that should be encouraged in a captive situation where out-breeding should always be the goal.

In captivity they are best kept in pairs or trios of one male to two females. Never should they be kept on their own, as single animals are lonely and morose. Larger colonies are possible, but extra vigilance must be maintained to ensure subordinate members are not bullied. Both sexes have a strict linear hierarchy. Too many males results in fighting and serious injury. In particular, ear-lobes are nibbled and fur is pulled. If the victimised animal is left in the colony, its back may be flayed and ultimately it will be killed. If the alpha male loses a fight, he becomes withdrawn and passive and sometimes dies.

Natural Predators

Wild Cavies have many enemies but chief among them must be the Geoffroy's Cat (Felis geoffroyi).

Behaviour

Terrestrial, but can climb reasonably well if necessary. Crepuscular and nocturnal, they do have short bouts of activity at other times too. In cold weather they have been known to feed throughout the day. Like many other small mammals, Wild Cavies are accomplished swimmers. It is unlikely that they swim from choice but necessity, as when their territory is flooded, during which time they have been seen swimming several kilometres to dry land.

Home ranges are stable, centred around clumps of vegetation that are used for both food and shelter. Wild Cavies follow well- defined tracts through the grass. They take refuge beneath vegetation and brush piles or occupy the burrows (usually abandoned ones but not always) of other rodents such as viscachas and tuco-tucos. Wild Cavies may also excavate their own burrows from time to time. Cavies are naturally timid.

Vocalisation

Bubbly squeaks of excitement, particularly at feeding time or from the males when courting; "chirps" of anxiety especially in response to an unidentified sound or potential threat such as the silhouette of a bird-of-prey overhead; and a warning "tooth-chatter", usually directed at a rival.

Accommodation

Some form of enclosed pen either inside or outside. One immediately thinks of rabbit hutches, but these are usually too small. A conventional hutch combined with a large grassy pen, to which the animals have access at all times, is a preferable solution. Building the pen oneself is a relatively straightforward undertaking and allows the design to be more flexible. It should be constructed from 2" x 1.5" timber and 16 gauge wire mesh. The optimum gauge size for the wire mesh is 1" X 0.5". Any larger and there is a possibility that new-born young can become stuck. If the run is built outside, remember that Wild Cavies can climb to a certain extent and are likely to scale the fence if panicked, so the construction must have a roof of some description. Cover the roof and some of the sides to ensure the ground remains dry, as these animals cannot tolerate damp conditions. Ironically, although Wild Cavies are crepuscular, they do enjoy sunbathing from time to time, and so the cage should have a sunny aspect but with facility for the cavies to be able to escape from full sunlight whenever they wish. Remember, too, that they can burrow; therefore the ground must be level and the floor of the pen should be either concrete or wire mesh with a covering of top soil and sand. Protect exposed edges of the timber frame with metal. Wild Cavies are hardy creatures and additional heat is not usually necessary providing they have access to dry, draught- and frost-proof indoor quarters raised slightly off the ground, perhaps on a course of bricks. You can, if you prefer, bring the animals into a garage or similar outbuilding during the winter months where they will be warmer , but make sure they have adequate lighting and the garage is not used to park motor vehicles or to store hazardous chemicals, with all the attendant danger of fumes.

Another possibility is a bird aviary with attached indoor accommodation. It is not recommended that birds and Wild Cavies share, however, as whilst it is true that Wild Cavies will not directly injure birds, there is a risk of cross-infection and contamination of the cavies' food. The cavies, being at their most active phase in the late evening, early morning, and indeed throughout the night, can cause "night fright" (the birds are panicked by strange noises, erupt from their perches and, being unable to co-ordinate themselves in pitch darkness, invariably fly into the walls with catastrophic consequences).

Whichever method of housing is chosen, it must be impervious to rats and other potential predators. Not only will rats kill cavies, as well as transmitting disease, but cavies could escape through the rat holes. No matter how approachable - how apparently 'tame' - a Wild Cavy might appear to be, once it escapes it can be very difficult to recapture, as I have found to my cost.

Litter & Bedding

In an indoor location, I use clean wood-chips, hay and shredded paper, or a dry mixture of soil and sand. Chopped bark is aesthetically pleasing but not very absorbent. Hay is both a bedding and a food. It gets damp quickly, so must be renewed frequently. Don't make the mistake of piling clean, fresh hay on top of old. Cavies produce copious quantities of faeces and urine. The droppings are not the dry, inoffensive pellets of many other rodents, but wet and odoriferous. I would therefore suggest cleaning out the bed at least once a week or twice a week, and scrubbing the walls with hot soapy water.

I tend to avoid straw, after learning of at least two Domestic Cavies which were blinded in one eye by the sharp ends of straw. Finely chopped straw is perfectly acceptable, though, and provides a very soft and comfortable bed.

Accessories

A sleeping box is appreciated, as are a few ledges and branches set at gentle angles for climbing. Leave one or two branches on the floor for gnawing on. Rocks can be cemented together to provide facility for climbing and sunbathing. A sand bath filled with Chinchilla dust will help to ensure the fur is maintained in good condition.

Feeding

Most rodents are omnivorous (that is to say, they eat both plant and animal matter). The Wild Cavy is an exception, being strictly herbivorous. In its natural environment it eats large quantities of grasses, herbs and other plant matter. Its basic diet in captivity consists of a proprietary Guinea Pig food, such as Gertie Guinea Pig™, and Chinchilla pellets. Cavies consume about 125g of food per day. Avoid rabbit foods. Although these may look very similar and often contain the same ingredients, some incorporate a coccidiostat, added at time of manufacture as a prophylactic measure against a terrible scourge of rabbits called coccidiosis. Cavies, on the other hand, must not routinely receive any oral anti-bacterial medication, which would destroy the beneficial bacteria that live in the gut as an aid to digestion.

One other reason for feeding proprietary Guinea Pig mixture is that cavies are unusual in that they cannot synthesise vitamin C (ascorbic acid) and must receive it in their diet, and Guinea Pig mixes are specially formulated to contain it. This is not to say that additional vitamin C should not be added anyway, as it is an unstable, water-soluble vitamin that starts to oxidise as soon as the bag is opened. Cavies should receive at least 10 mg/kg/day, increasing to 30 mg/kg/day during pregnancy. Therefore it is essential to provide plenty of vegetables and other green food in the diet, including good quality hay (should be green, not too dusty, with a sweet, slightly musty aroma), coarse grass, garden 'weeds' such as groundsel, chicory, and dandelion. Make sure such plants are collected from a safe, i.e. unsprayed, area. Grass that has gone through a mower may be contaminated by oil. Cultivated food plants that can be provided include broccoli, Brussels sprouts, cabbage, carrots (which they love), cauliflower leaves (even more nutritious than cabbage), celery, corn-on-the-cob, cucumber (little nutrition as it is mostly water, but cavies enjoy the taste), mushrooms, parsley, parsnip, spinach, swede, Swiss chard, etc. Leeks are generally ignored. If possible, greenery should be offered in a wire basket to prevent soiling. Remove uneaten green food on cold winter nights if there is any danger of it becoming frozen.

I no longer feed lettuce. Although safe in moderation, in excess lettuce can "scour" the stomach. It also contains minute quantities of a toxin, "lactucarium".

Wild Cavies, like Degus, are susceptible to diabetes, being unable to convert sugar into energy. Consequently fruit, if fed at all, must be kept to a minimum. The only fruit I used to feed to my "herd" was apples, but they received only about half an apple a day. Whilst it is true that I never had an incidence of diabetes in any of my animals, I have since decided to err on the side of caution and withdrawn apple from the diet.

Non-preserved beetroot can be offered, although you might find the animals' urine has been turned slightly pink. As with all other animals, sudden alterations to the diet can cause digestive upsets, so any radical change must be introduced gradually to allow time for the digestive enzymes to adapt.

To satisfy their need to gnaw, provide cavies with tree branches, cuttlefish bone, pumice stone, etc. Salt blocks can also be given. Clean drinking water must be available at all times. Wild Cavies drink about 100 ml per day. Mine have a choice of both a drinking bottle and an open water dish, although I have never known any of them use the bottle. Whether they would do so if the dish was not available must remain a subject for conjecture.

Handling

I would recommend handling as little as possible, as they are nervous, highly strung animals that succumb easily to stress. Subdued lighting will help quieten the animal if you do need to restrain it. The best method is to place one hand around the shoulders, whilst supporting the hindquarters with the other hand. I have never known Wild Cavies to bite. Rough handling will cause the fur to be shed, similar to the 'fur slip' of Chinchillas.

Sexing

Even at a young age, cavies can be sexed with confidence. In a young specimen the genital aperture appears as a dot in the male, and is Y-shaped in the female. In the slightly older animal it is possible to manipulate the genital area. By restraining the animal on its back and applying gentle pressure on either side of the genital opening will cause the penis of the male to protrude. In the mature boar, the scrotal sac is clearly visible.

Reproduction

Wild Cavies breed throughout the year if environmental conditions are favourable, but birth rates tend to peak in spring. Gestation 62 days (range: 60-70 days). Litter size 1-5 (average 2-3). The young are born furred, with their eyes open. They weigh around 60 grams at birth, but this can vary according to the size of the litter. They are mobile after just a few hours, able to eat solid food within the first day of life, and can survive without further nursing after just 5 days but usually continue to suckle for the first 3 weeks. Sexual maturity is attained in as little as 55-70 days for the females, and 84 days for the males, although between 4-5 months is more average. A female can produce a maximum of five litters annually.

Infant mortality appears to be quite high in this species, the bodies of the babies usually being discovered partially eaten. The reason for the high death rate within the crucial first 24 hours is unclear, as it is unlikely that the young are killed deliberately, although overcrowding and a surfeit of males probably play a part. The fact that the young are often found in a partially eaten state is probably incidental, many species consuming the bodies of other members of the colony that have died from natural causes, although one is at first surprised to find such cannibalistic behaviour in the normally vegetarian cavies. Until the young are mobile, there is a risk of their being accidentally trampled by the other adults in the group. Since the male, heavier and larger than the female, mounts her almost as soon as she has given birth, it is possible that occasionally, in his boisterousness, he inadvertently crushes the babies that get in his way.

Females are polyoestrous. The oestrus cycle lasts 20.5 days.. A postpartum oestrus occurs, but receptivity lasts for less than half a day. Males congregate around the female when the birth is imminent, with the alpha male aggressively guarding her from the younger, subordinate males. It is he who generally mates her first when she comes into season again immediately after giving birth. If, for whatever reason, he does not mate with her, the other males will seize their opportunity and will pursue and mate with her. This should not be allowed, as their persistent solicitations prevent her from attending to the needs of her new-born offspring, which is a significant cause of neonatal deaths within the first few hours. Another major cause of premature deaths is accidental trampling by other family members.

Health

Like Domestic Guinea Pigs, Wild Cavies are susceptible to mange, a condition caused by a microscopic mite that burrows beneath the skin, causing intense irritation and severe hair loss. In severe cases, the skin may become ulcerated as a result of the cavy continually scratching itself to relieve the persistent itching. It is usually transmitted by direct contact with an infected animal, but the condition can also lie dormant, suddenly flaring up when the animal is subjected to stress such as transfer to a new cage or even the stress associated with pregnancy and the rearing of young. It is curable and your veterinary surgeon should be able to prescribe appropriate treatment.

Once in a while very gently pull the hairs on the animal's rump, and should the hairs detach easily without any real effort, it may be an early indication that mites are present. At the first sign of hair loss, the infected animal should be separated from the colony and advice sought from a veterinary surgeon, preferable one with plenty of experience with small mammals. Infected stock should be fed and attended to only after you have finished dealing with all your other animals, and remember to wash your hands well afterwards. Mange cannot, of course, affect humans but it is a very infectious disease that can be inadvertently transmitted from cage to cage, and from individual to individual, quite easily. Sarcoptic mange, in particular, is so prevalent that I advocate treating cavies, both wild and domestic, prophylactically about once or twice a year with an anti-mite preparation such as Ivermectin (available under a number of brand names). New arrivals and individuals (even if they appear healthy) that are to be transferred to new owners should also be treated as a precautionary measure. Nowadays I treat the animals by applying a drop of Ivermectin to the nape of the neck, or it can be given orally (the latter method is less reliable owing to the difficulty of making sure that one drop, and one drop only, is given). Both methods are possibly slightly less effective than an injection but are safer, being less traumatic for the animal. Ivermectin (available under a number of brand names) remains the drug of choice, but it should be noted that this product is not licensed in the U.K. for use on rodents, although it is widely used by rodentologists and seems to be safe when applied as directed. Again, take your vet's advice.

As mentioned before, an abundance of males in the colony can lead to fighting. You will soon find that injuries are the commonest complaint these animals suffer from.

Life Span