Guinea pigs have the longest gestation period of rodents commonly kept as pets. Pregnancy of a female guinea pig (sow) lasts 63 to 68 days, or about nine weeks. Unlike hamsters, gerbils and rats, baby guinea pigs (piglets) are born with open eyes, erupted teeth and a furry coat. Although they will nurse for as long as three weeks, piglets begin eating adult commercial guinea pig food within a few hours of birth.
Breeding Guinea Pigs
Guinea pigs are social animals who do well living in same-sex pairs of approximately the same age. Housing a male and female together will quickly result in pregnancy, as sows enter estrus every 16 days. During estrus she might exhibit increased appetite, mount cage mates, lift her rear when touched, and growl. If these behaviors cease, it is a good indication she is pregnant. If you are intentionally breeding guinea pigs, it is advisable for a sow to have her first litter at 3 to 7 months of age. A significantly earlier or later start to breeding can result in pregnancy complications.
Sows are pregnant for an average of eight to nine weeks. You are likely to notice weight gain during this time, particularly in the abdomen. Some sows double their weight during gestation. If you regularly handle your guinea pig, you might be able to see and feel the fetuses moving inside her when she is close to the end of her pregnancy. Remove the male from the cage before birth, as sows become fertile again soon after delivery, and males as young as 5 weeks are able to mate.
The average size of a guinea pig litter is two to four piglets, though as many as seven or eight are possible. A sow tends to give birth overnight, with delivery taking approximately 30 minutes. Each piglet is born in its own amniotic sac, which the mother will strip away and eat. Babies will begin nursing right away. But they'll quickly transition to adult food, so stock the cage with plenty of dry food and water.
Guinea pigs mature rapidly. They can be fully weaned from their mother at 3 weeks of age. Separate the piglets into same-sex groups to avoid unintentional breeding. Even siblings from the same litter will mate with one another if left together through sexual maturity.
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