Breeding & Mating
Guinea pigs reach sexual maturity at around 10 weeks of age. When the female is receptive she may mount others in the cage. When approached by a male she will arch her back and lift her hindquarters. If she is not ready to breed she will reject the male by spraying him with urine, lunging at him, rearing up, swatting at his face and showing her teeth.
Pregnancy & Litter Size
Pregnancy lasts from 63-70 days. The average litter size is two to four babies (pups). A pregnant female will display a distended abdomen and increase her food and water intake to double and sometimes triple her normal amount. Do not make changes to a pregnant females cage, it may stress her and she will stop eating and drinking.
Guinea pigs make no preparation for the labor and birthing process. Labor lasts about 10-30 minutes with 5-10 minutes between each birth. The female gives birth by sitting up and hunching over or squatting. The mother will clean the pups on her own and the placenta and membranes are eaten by the mother or other guinea pigs in the cage.
Babies are adorable miniature versions of their mother. The pups are born with hair, eyes wide open, a full set of teeth and the ability to run around. They will rely on their parents for warmth and food until they are weaned at 14-21 days of age. Cavies are not protective of their young, males do not participate in rearing the pups, and females pay little attention to them. Unlike other rodents, they rarely eat their young. Female pups must be separated from their father by the time they are 21 days old to prevent breeding. Regular handling of the pups is tolerated by the parents and encouraged. It is important in helping them socialize as pets. Once weaned, the babies can be treated just like adults.
To sex your guinea pig hold him belly up with his back supported. Find the anus and look directly above it. A male will appear to have a slit just above the anal opening and the testes in adults can easily be seen. A female will have a skin fold in a Y shape above the anal opening and will also have an external urethral opening.