Breeding

This section is intended to provide you with basic information on guinea pig mating, pregnancies, birth and babies. In that sense, we are using the word "breeding" to mean guinea pig reproduction, and not raising guinea pigs and breeding them to achieve certain breeds, varieties or show stock. It is not my intent to teach people how to raise and breed guinea pigs, but rather familiarize you with guinea pig pregnancies and babies, in case you choose to mate your pets.

If you are interested in raising guinea pigs, you should consider joining your local cavy breeder's club, and talk with experienced breeders before starting. It is also recommended that you make sure that your area is not already overflowing with guinea pig breeders, as you shouldn't contribute to a guinea pig population that may already be bursting at the seams.

Ground rules for breeding

It's best to not breed your guinea pigs unless you are willing to keep all of the babies yourself, or you have found some responsible people who would like one or more of the your offsprings as a pet. Given the rapid breeding rate of guinea pigs, animal shelters constantly receive unwanted guinea pigs from irresponsible owners who allow their guinea pigs to breed over and over. Many of these animals are put to sleep, since owners can not be found for all of them. Several guinea pig "rescue" operations around the country do their best to find homes for all of these cavies, but it's simply not possible to find new owners for all of them. Pet stores aren't much better, as many stores mistreat their animals, or fail to give them proper care. You don't want to bring guinea pigs into a situation where they will be unwanted or abused.

That being said, females should not be bred until they weigh at least 500 g (just over 1 pound), which usually works out to 4 to 5 months of age. Younger sows can be too small to successfully deliver their babies, and may not have matured enough to properly care for their young. Also, no older female should have a first litter; somewhere between 9 and 12 months of age, the hip bones of a childless sow can start to fuse together. A litter after this happens will require a caesarean section, which is an extremely risky surgery that could threaten the life of the sow and her babies. If you are going to breed your sow, you should probably arrange for her first litter between the ages of 5 and 9 months. Otherwise, you might want to consider having your sow spayed for her own safety after nine months, if there is ever any chance that she may get pregnant.

For health reasons, many breeders will recommend that you not mate your boars until they are eight months old.

Mating

Male guinea pigs can mate at any time and, in fact, are very easily aroused: the mere scent of a female is enough to engage their instincts. However, females can only mate when they are in season. The vagina of a sow is actually blocked by a mucus plug when she is not in season. A sow's estrus cycle is typically 18 days, and when she goes into heat, this mucus plug clears so that she can accept the male. During this time, which can last for up to 24 hours, she and the male will mate several times.

When the male is aroused, which is pretty much several times an hour, he will lower his head and start walking around the females with slow, deliberate steps. He will make a rumbling sound as he does this, and wag his bottom from side to side. Sometimes, he will perch his front legs on something (like the side of the cage or a brick or whatever is handy), so that he can "dance" like this in order to attract the attention of the female. As he gets close to the female's behind, he may sniff her bottom and then try to mount; sometimes, if sufficiently aroused, hey may mount the female from the sides or the front, and might even try to mount another male (if present). In fact, if mixed with another species, such as rabbits, the male may even try to mount them, too.

As the male starts his mating dance, the females may start to squeak with anxiety, becoming louder as the male approaches. If the female is not ready to accept mating, either because she is not in season or she doesn't want to mate, and the male tries to advance, she may snap at him, bite at him or just run away. If the male is particularly persistent, she will let out a small spray of urine, usually in his face, to deter him.

If, however, she is in season, she may respond in kind. In fact, some females will even advertise their readiness to mate even if the male is not aroused. The female will lower her head and rumble just like the male does, and will raise her bottom slightly into the air. She may even wag her bottom slightly to attract the male's attention. The male may circle her a few times before positioning himself behind her to mount. Copulation lasts only a few seconds. They may mate several times each hour, sometimes as frequently as a few minutes apart.

Pregnancy

The gestation period for guinea pigs is typically between 60 and 70 days. Longer gestation times tend towards smaller litters, whereas shorter times tend towards large litters. The average litter size is 2 to 4, though they can carry as many as 8 or as few as 1.

During her pregnancy, your sow's vitamin C requirement will double, at least, to 20 mg/day. She may also demand more pellets and fresh vegetables, to aid in lactation and in providing for her developing babies. This, and a little bit of sugar (from fruits or clear fruit juice) will help prevent toxemia, which is an ailment that is most commonly seen in pregnant sows.

It is not necessary to remove the male during the pregnancy, though it is generally a good idea to do so in the last week before birth, since the female will come into season again within an hour after having her litter. Sometimes, however, the male can be considered a stressor in the final days of pregnancy, and you may need to separate them if he and the sow are not getting along. If you have multiple, pregnant sows housed together, then it is extremely important that they be separated during their gestation. The birth of one sow's litter can actually induce labor in the other sow, which can lead to a premature birth even if they were impregnated at roughly the same time.

Last, it is important that you make sure your sow's stress level stays low. Stress can cause abortions, premature births and stillbirths in guinea pigs, so don't make any radical changes in her environment throughout this time.

If your sow becomes ill, you should see a competent vet immediately. Treating a pregnant sow is always dangerous business, since her babies may not be able to withstand the shock of certain medications. A vet that is experienced in treating guinea pigs should be aware of what is, and is not, safe to do while she is in-pig.

Birth

Early into the second month of her term, the sow will start to become noticeably plump. As the babies grow in size, you will actually be able to feel their bodies and even estimate how large of a litter she will have. When the babies start kicking and moving inside her womb, she is roughly three weeks away from giving birth, give or take a few days.

You won't get many warning signs as the birth day approaches. Although some sows become noticeably "bitchy" in the last week, this is not true of all females. In short, there's really no way to predict when she will go into labor. Fortunately, you do not need to do anything for her to prepare for the babies, other than make sure she has plenty of soft bedding to nest in.

Most births tend to take place around dawn or dusk, which is when guinea pigs are most active. If you are fortunate enough to be present for the birth, you can watch quietly without disrupting the process. If the male is still with her, and he hasn't been neutered, then you should remove him immediately, as the sow will come into season within an hour after birth. Babies are typically born five minutes apart, and the entire litter should deliver within a half-hour. If it goes on any longer than this, it could mean that she is having trouble giving birth, and you will need to get her to a vet right away.

With each contraction, the mother will push the babies out, one at a time. When they emerge, she will reach down and, with her teeth, break the sack that covers the baby when it's in her womb. It is very important that she do this, or the baby will suffocate. After the entire litter has been delivered, she will pass the placenta, part or all of which is then eaten. There is very little "mess" left over after a guinea pig birth; all that will be seen are a few spots of blood here and there on the bedding.

The mother will then lick the babies clean. If the father is present, he may assist in this duty. Afterwards, she will direct the babies to a corner of the hutch, where they will huddle beneath her for warmth.

As mentioned above, within an hour after birth, the sow will come into season and will be ready for mating. You should never allow a sow to become pregnant so soon after giving birth, as it is extremely hard on her body to go from labor straight into pregnancy again. Most breeders recommend waiting at least two months to allow the sow to get back to her normal weight.

Caring for young cavies

Young cavies are almost fully independent of their mother at birth, requiring only her milk and her warmth. They are born with hair, teeth, claws and open eyes. They will begin to run around on their own within hours, and will start eating solid foods within a day. Every two hours, they will line up under their mother to nurse; though sows only have two teats, there is no fighting at the milk line since the babies can munch on hay, pellets and even drink from the water bottle, if it's in reach.

Like other animals that are born precocial, guinea pigs form their social bonds shortly after birth. It is important that they have human contact during this time to socialize and bond them to people. Unlike many other small mammals, the mother will not reject the babies if they are handled by humans, so the more you hold, pet and interact with them, the more they will grow up friendly towards, and less afraid of, humans.

The babies will continue to nurse for anywhere from three to four weeks. During this time, they will follow both the mother and father around the cage. During exercise time, the guinea pig family will tend to form a "guinea pig train", with the father or mother at the head, the other parent at the end and the babies in the middle. This lineup helps ensure that no young ones get lost while moving about. They will chirp and grunt to each other often, and if a baby does get separated from the group, he or she will squeal loudly until one of the parents comes over to lead him or her back to the family.

As they start to wean during the third week, they will nurse less often from the mother, and will begin to be more independent. By four weeks of age, all the babies should be completely weaned, and no longer require milk from their mother. At this point, you should start separating the males from the family. Males can become fertile at any point after weaning, and will be capable of mating with their mother. Females can come into season any time after one month of age, usually at 5 weeks, and can then be mated by their brothers or their father. Hence, separation of virile males and females is extremely important to prevent uncontrolled inbreeding.

After they have weaned, you may safely give away pets to new homes. For the first day or two, the baby will probably be somewhat frightened of its new environment, having lost the security of it's family and it's familiar hutch. Time, and lots of love and attention from the new owners, will be needed for the baby to adjust to it's new surroundings.

Complications

Not every pregnancy goes smoothly. If you have problems with your sow or her litter, you should see a veterinarian that is experienced in the treatment of guinea pigs. The information provided below is for your reference only, and is not meant to be a substitute for a visit to a competent vet.

Young sows

Sows should not be bred until they weigh at least 500 g. However, many female guinea pigs that are purchased from pet stores are housed with males, and are already pregnant before they come home. Hence, it is rather common for a young sow to give birth before she has completely matured.

Sow fails to break the membranes on newborns

While in the mother's womb, that babies are enveloped in a membrane (or sack) and are protected by fluid. When the babies are born, the mother is supposed to reach down with her teeth and break the sack. If she does not do this, the babies will suffocate; often times, people may think her babies were stillborn, when in fact she did not break the sack in time. If you are lucky enough to be present during the birth, you can save any babies that are not released from their sacks.

Break the membrane over the nose, open the mouth and blow several breaths, in rapid succession into the babies throat. Move the legs to get circulation (and the heart) going, and the lungs. If the baby gasps, you may be able to save it. Keep it warm in your hands and continue to blow down it's throat until you can find a towel or cloth for drying it's body (rub gently!).

Once it starts to squeak, you are on the road to recovery. Keep it warm, but do not give it anything to drink. Cover the baby with a towel and place it near a source of heat, such as a warm water bottle, or insulate it well so it will retain it's body heat and not catch a chill. After about an hour or so, when the baby is able to stand on it's own, you can reintroduce it to it's mother. Because she hasn't cleaned the baby, she won't recognize it; put it under her body, and watch her very carefully to make sure she will accept it. If she rejects the baby, you may try again later, but if she continues to reject it then you will have to treat it as an orphaned cavy.

Premature termination of labor

If the sow is having an especially difficult labor, and can not deliver one or more of her babies, labor may terminate before they are all born. If you suspect that this is happening or might happen, then you should get her to a vet right away. If labor terminates with unborn babies in her womb, they will need to be surgically removed. The babies will die inside her and will poison her as they decompose if they are not removed immediately.

Rejected babies

Some sows may, on rare occasions reject one of their litter. She will refuse to nurse it, and will constantly move away from it if you try to introduce it to her. In these cases, you will have to treat the baby as an orphaned cavy.

Terrified mothers

Some sows are actually terrified of their own litter, even if they have partially cleaned the babies. In these cases, the mother will shriek wildly and run away from the babies, who will of course, try to follow her around the cage to be nursed and frighten her more. If left this way, the babies could die from chills.

In these cases, you should remove the babies and sow from the hutch, and introduce the babies to her one at a time. Hold the sow and let her smell each of her babies, then place her in a small space such as a box. Introduce the babies, one at a time, to the mother, even though she will probably start shrieking again. After the first has been introduced, wait and watch to see if she will settle down, and sense what the baby is. If she accepts the baby, you may slowly introduce the rest. If she continues to be afraid of them, then you will have to raise them as orphaned cavies.

Insufficient milk for the litter

If the sow is too young, or if the litter is large, she may not be able to produce enough milk to nurse all of her babies. If this is the case, you can either locate another lactating sow (with a litter under 10 days old) that the babies can suckle from, or you can assist the mother by feeding the babies a formula substitute for their mother's milk.

Orphaned cavies

If babies are rejected, or the mother dies during or shortly after labor, you will need to make arrangements to raise the babies. If you are fortunate enough to have another sow that has just given birth within the last one or two days, you can opt to try and raise the guinea pigs with her as a foster mother. To do this, remove all but one of the mother's litter, and rub your orphaned litter against these babies so that they will pick up their scent. Then introduce the orphans to their foster mother; she will sniff them, and then accept or reject them. If they are rejected, you'll have to hand-raise them.

If you have to hand-raise the babies, they will need a milk substitute formula every two hours during the daytime. If you feed them late at night before going to bed, and keep them very warm, they should be fine until the next morning. After each feeding, be sure to wash their mouths to remove any spilled milk, as guinea pigs are miserable if their coat gets sticky. You will need to feed them this way for the first four days.

You will also need to wipe the anus and genital organs of each cavy with a clean, damp cloth to induce urination and the passing of feces. If the father is present with the babies, he may actually perform this duty for you by licking them, but you should watch closely to make sure he is doing so.

After the fourth day, they will need to learn how to eat solid foods. Again, if the father is present, they may learn from him through observation, and may in fact have already picked it up. If not, any young cavy placed with the babies can teach them this activity; the babies will learn from imitation how to pick up pellets and fresh greens and put them into their mouths.

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