Like other small rodents, guinea pigs (Cavia porcellus) mature at a fast rate. If you have more than one guinea pig, or cavy, keep them separated until you're certain of their genders. Your veterinarian can neuter a male cavy, but the abdominal surgery required for spaying a female is more complicated. Guinea pigs reach sexual maturity early, so once a cavy is weaned, there's the potential for breeding and pregnancy.
Newborn Guinea Pigs
In some ways, guinea pigs are mature at birth. Unlike most other mammals, they can eat solid food within hours of coming out of the womb. It's actually possible for a baby guinea pig to survive without nursing, although the animal's growth is generally stunted. Female guinea pigs nurse their pups until the babies are between 2 and 3 weeks old. At that point, the mother guinea pig goes into another estrus cycle and loses interest in her brood.
Guinea pigs reach sexual maturity between the ages of 3 and 4 months. Although they're capable of breeding at this time, it's best to wait until the ages of 5 to 6 months before allowing them to mate. One caveat: If you're planning to breed a female guinea pig, do so for the first time before she reaches the age of 8 months. After that, the bones in her pelvis start to fuse, so if she hasn't already given birth she's likely to have extreme difficulty delivering the babies. Both the mother and the litter might die.
Guinea Pig Size
At birth, guinea pigs can weigh between 1.5 and 4 ounces, with an average weight between 2.5 and 3.5 ounces. The larger the litter -- which can range from one to 13 offspring -- the smaller the average weight. When full grown, male guinea pigs weigh between 2 and 2.6 pounds, while females weigh between 1.5 and 2 pounds.
Guinea Pig Care
Expect your guinea pig to live between four and eight years, with five about the average. Good care helps your pet live longer. Make sure your guinea pig always has grass or timothy hay available. Not only does this fiber keep his gut moving, but it wears down his continuously growing teeth. He should always have access to fresh water. Since guinea pigs can't manufacture vitamin C on their own, supplementation is necessary. High-quality pellets designed for cavies have sufficient amounts of vitamin C, but you can also give your pet small amounts of fresh fruit and vegetables containing this vitamin every day. Spinach, kale and oranges are cavy favorites.
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