History: Guinea pigs are rodents (related to chinchillas and porcupines)that originated from the Andes Mountains region of South America. They were probably first domesticated by the Indians of Peru, who used them for food and as sacrificial offerings to their gods. In the 16th century, Dutch explorers introduced guinea pigs to Europe, and selective breeding and captive rearing began in earnest.
Guinea pigs are very popular pets because of their availability, docile temperaments, tendency not to bite or scratch when handled, and relatively clean habits.

They are not long-lived, which can be disconcerting to owners (especially children). Many parents, however, believe that having their children experience the relatively short period of companionship and subsequent death is a meaningful way to expose children to the “ups and downs” of life.

In their natural habitat, guinea pigs live in open, grassy areas. They seek shelter in naturally protected areas or burrows deserted by other animals. Guinea pigs are sociable animals and tend to live in groups.

They are strictly herbivorous (plant-eating) and do most of their foraging for grasses, roots, fruits and seeds in the late afternoon and early evening. For many years guinea pigs have been used in biomedical research laboratories. Consequently, their medical problems have been traditionally approached on a group basis, rather than on an individual basis. As a result, very little practical information exists on the medical care and treatment of individual pet guinea pigs. Even less information is available to owners on the responsible home care of guinea pigs and recognition of their medical problems.

BREEDING:

The single most important breeding consideration is that female guinea pigs should be first bred before 7 months of age. If the first breeding is delayed beyond this time, serious (sometimes life threatening) problems with delivery are encountered. Females should be first bred between 3 and 7 months of age. Males should be 3-4 months old at their first breeding.

The guinea pig’s heat cycle lasts 16 days. The period during which the female is receptive to the male and will allow breeding lasts about 8 hours. Female guinea pigs can come back into heat 6-15 hours after giving birth. This is called a “postpartum estrus”, which means that they can be nursing a litter and pregnant at the same time!

Pregnancy lasts an average of 63-68 days. The larger the litter, the shorter the term of pregnancy and vice versa. The duration of pregnancy for guinea pigs is unusually long when compared with that of other rodents. Pregnant sows (females) exhibit a grossly enlarged abdomen during the latter stages of pregnancy. It is not uncommon for their body weight to double during pregnancy. The time of delivery may be difficult to determine because of the relatively long gestation period and because pregnant sows do not build nests. However, the week before a sow is about to deliver a litter, a slowly widening separation of the pelvis develops just in front of the external genitalia. This separation reaches slightly more than 1 inch in the hours just before delivery.

This separation of the pelvis does not develop in females that are bred for the first time after 7 months of age, creating an impossible and tragic situation. Delivery of the young is not possible and a cesarean section must usually be performed to save the life of the sow and her babies. An uncomplicated delivery usually requires about 1/2 hour, with an average of 5 minutes between delivery of each baby. Litter sizes range from 1 to 6 young, with an average of 3-4. Litters resulting from the first breeding are usually very small. Abortions and still- births are common with guinea pigs throughout their breeding lives.

The young are born relatively mature. They are unusually large and fully furred, and can walk about. They also have teeth and open eyes at this time. Even though newborn guinea pigs can eat solid food and drink water from a container, they should be allowed to nurse their mother for at least 2 weeks.

HOUSING:

Proper housing is a major factor in the maintenance of healthy guinea pigs. The well- being of the animals must be a primary consideration. Guinea pigs can be housed within enclosures made of wire, stainless steel, durable plastic, or glass. The last 3 materials are preferred because they resist corrosion. Wood and similar materials should not be used in construction of enclosures because they are difficult to clean and cannot withstand gnawing. The construction and design of the enclosure must prevent escape. The enclosure also must be free of sharp edges and other potential hazards. The enclosure must be roomy enough to allow normal activities and breeding, if the latter is desired. One reference recommends at least 100 square inches of floor area per adult, whereas breeders should be allowed 180 square inches per animal. The enclosure can be open at the top, provided that its sides are at least 7-8 inches high.

Male guinea pigs (especially breeding males) require enclosures with side at least 10 inches high. Males tend to be more rambunctious. Guinea pigs can be housed on wire mesh (suitable for housing rats) but it is not recommended. Though wire mesh allows urine and most fecal pellets to drop through, thereby keeping the bedding and the residents cleaner, guinea pigs housed for long periods on wire tend to develop serious injuries to the bottoms of their feet (see section on Foot Pad Infections).

Furthermore, a leg may be broken if it becomes entangled in the mesh. This is most often a problem with guinea pigs that have not been reared on wire mesh, and occurs soon after they have been introduced onto it. Enclosures that provide solid flooring and an adequate supply of a preferred bedding are best for pet guinea pigs. They should be easy to clean, well lighted, and adequately ventilated (see Vital Statistics for preferred temperature and relative humidity ranges).

Bedding must be clean, nontoxic, absorbent, relatively dust-free and easy to replace. Shredded paper, wood shavings, and processed corn cob are preferred bedding materials. Sawdust should be avoided because it tends to collect within the external genitalia of males, forming an impaction. Rarely does this impaction interfere with urination, but it may inhibit successful breeding.

Guinea pigs seem most comfortable when they are spared exposure to excessive noise, needless excitement and confusion, and other stresses. Sudden environmental changes should also be prevented. Guinea pigs have 2 types of reactions when startled by a loud noise or sudden movement or when placed in a strange environment. They may “freeze” completely motionless (for up to 20 minutes), or they may panic. Panic involves erratic running and leaping, often accompanied by shrill squealing. Groups of guinea pigs may stampede in a circle, often trampling the younger residents within the enclosure.

A panic reaction scatters bedding and food, fouling the food and water containers. Visual security (a place into which they can retreat when frightened) should always be provided. Rectangular enclosures containing barriers also reduce the tendency to stampede and circle.

FOOD AND WATER:

Food and water must be readily available at all times. Commercially available pelleted chows provide all of the essential nutrients, as long as the pellets are fresh and wholesome when offered. Some guinea pig owners are tempted to feed rabbit pellets, assuming that they are roughly equivalent to guinea pig pellets, but this is not so. Unlike most mammals (including rabbits), guinea pigs require a high level of the vitamin, folic acid. Unlike rabbits, guinea pigs cannot manufacture their own vitamin C and must, therefore, receive it from an outside source. Interestingly, people and our primate relatives share this dependence on vitamin C from the food we consume. Pellets milled for guinea pigs take these special requirements into consideration and are appropriately fortified with these 2 nutrients, among many other essential ones. Guinea pig chows generally contain 18-20% protein, 16% fiber and about 1 gram of vitamin C per kilogram of ration. Even when the fresh pellets are properly stored in a cool, dry place, about half of the vitamin C content is degraded and lost within 6 weeks of manufacture.

Therefore, the diet should be supplemented with vitamin C as follows: 250 milligrams of ascorbic acid (vitamin C) should be added to about 1 qt of drinking water, made up fresh every 12 hours, or a single guinea pig should be offered one handful of kale or cabbage or one-quarter of an orange daily. We recommend both adding vitamin C and also feeding the above food to insure adequate vitamin C intake. A piece of chewable children’s vitamin C may also be administered as many pigs will eat them readily.

Researchers are not in agreement on the advisability of adding other items to the balanced ration (pelleted chows). We recommend that fresh greens, hay (timothy) and small amounts of fruit be offered daily with several precautions: These items should not exceed 10- 15% of the daily diet. Furthermore, the fresh items must be thoroughly washed to avoid pesticide residues and possible bacterial contamination.

All foods should be provided in heavy ceramic crocks that resist tipping over. The sides of the crocks should be high enough to keep bedding and fecal pellets out of the food, or the crocks should be elevated slightly above the bedding. Water is most easily made available and kept free from contamination by providing it in one or more water bottles equipped with “sipper” tubes. Guinea pigs tend to contaminate and clog their water bottles more than other pet rodents by chewing on the end of the sipper tube and “backwashing” food particles into it. For this reason, all food and water containers should be cleaned and disinfected daily.

Guinea pigs tend to be creatures of habit and do not tolerate changes in the presentation, taste, odor, texture or form of their food and water. Pet owners should avoid making radical changes in the food and water containers. Any changes in the food itself should be made gradually. Failure to do so usually results in the guinea pigs’ refusing food and water, which can lead to disease.

HANDLING AND RESTRAINT:

Guinea pigs rarely violently struggle when they are being picked up but often make a “squeal of protest”, which sounds pig-like to many people. Nevertheless, great care should be taken not to injure them when picking them up. The guinea pig should be approached with 2 hands. One is placed under the guinea pig’s chest and abdomen, and the other supports its hindquarters. Adults and those that are pregnant should receive gentle, but firm, and total support.

One of the most desirable features of guinea pigs as pets is that they rarely bite when being handled or restrained. One reference indicates that only 1 in 400 will bite under these circumstances.

HUMAN ALLERGIES TO GUINEA PIG DANDER:

Certain people are allergic to the hair and/or dander of guinea pigs. People working with guinea pigs in laboratory situations are more likely to develop such allergies because of their continual association with them. Signs include itchy eyes, sneezing, runny nose, persistent cough, shortness of breath, wheezing, a skin rash, and anaphylactic shock (a true medical emergency). Owners of pet guinea pigs may also be susceptible, and a medical doctor should be consulted about suspected allergy problems if a guinea pig is kept as a pet in the household. Guinea pig owners with such a suspected allergy may want to consult an allergist.

HYGIENE:

The frequency with which the enclosure is cleaned depends on its design, the materials out of which it is made, and the number of guinea pigs that reside within it. As a general rule of thumb, the enclosure and all cage “furniture” should be cleaned and disinfected once weekly.

Food and water containers should be cleaned and disinfected once daily. More than one set of containers should be maintained, and the soiled set should be washed in a dishwasher, if possible. Vigorous scrubbing of the enclosure and “furniture” with hot water and soap and a thorough rinse should be followed by use of a disinfectant (Roccal-D: Winthrop or dilute chlorhexaderm). Vinegar is often required to remove the scale deposited by the crystalline urine of guinea pigs.

VITAL STATISTICS:

Scientific name: Cavia porcellus Potential life span: 6-8 years Desirable environmental temperature range: 65-75F Desirable relative humidity range: 40-70% (50% is considered ideal) Recommended age at 1st breeding male: 3-4 months female: 3-7 months (not after 7 months) Length of estrous : 16 days (heat) cycle Length of estrus (period) 8 hours during which female is receptive to male for copulation) Gestation (pregnancy) period: averages 63-68 days Average litter size: 3-4 young (range, 1-6) Age at weaning: 2-3 weeks

CLUBS AND ORGANIZATIONS: (These references may no longer be correct) A wealth of additional useful information may be obtained by joining one or more of the organizations listed below. All of these groups publish newsletters or bulletins. American Cavy Breeders Association c/o Linda Mowers 933 Krieger Road Webster, NY 14580

California State Rabbit and Cavy Breeders Association c/o Sonny Harper 20041 Clark Street Orange, CA 92669 (714) 538-0821

San Gabriel Valley Cavy Breeders Association President: Marolyn Briese City Farmer Caviary 11142 Tarawa Drive Los Alamitos, CA 90720 (213) 431-1571