Guinea pigs are (as you probably know) not really pigs. They are also not from Guinea or New Guinea. They are rodents, originally from South and Central America, and are more accurately called "cavies". Guinea pigs were originally raised for food.
There are three main types or breeds of guinea pigs: English, which have short, smooth hair; Abyssinian, which have longer, wiry hair in swirls; and Peruvian, which have long, silky hair.
The average life span of a guinea pig is 4-8 years.
A sow is pregnant for 60 - 72 days, and can have up to 10 babies. Average litter size is 3 or 4.
Babies are born well-developed and can eat solid food the day they are born, though it is best to allow them to nurse for at least a week.
Guinea pigs are mature enough to have babies of their own at 2 - 4 months old, so the young should be separated from their parents (or neutered) at 3 - 4 weeks old.
Cavies should be kept in a clean cage, with at least one square foot (12" x 12") of floor space for each pig. Recycled paper, cob, pine or aspen shavings, or wood pellets are appropriate bedding.
Cat litter, sand, and cedar shavings are not good choices for bedding.
Guinea pigs drink and urinate a lot for their size - cages must be cleaned and bedding changed on a regular basis.
Solid floors are preferable to a wire mesh floor; mesh may be easier to clean, but your pet may get toes caught through the mesh and break or cut them.
Most guinea pigs prefer to have a "hide box" that they can sleep in or run to when they are scared. Cardboard boxes, plastic "igloos" or wood boxes are all good choices, but your guinea pig will probably chew on a cardboard or wood box, so you may have to replace it periodically.
The cage should not be placed in direct sunlight as cavies are prone to overheating.
Rabbit food is not a good diet for guinea pigs; they need more Vitamin C than rabbits do, so it is important to feed them a good quality guinea pig food. Food kept in a sealed container or in the fridge will stay fresh longer than food left open. Vitamins will break down in the food without changing its appearance. Even if the food looks OK, if it's more than a few months old you should buy new food.
Free-choice grass hay or fresh grass should be offered. This should provide the bulk of the diet, as the long fiber is very important for dental and intestinal health.
Use caution when switching from hay to fresh grass; too much fresh grass at one time can lead to serious stomach upset and diarrhea.
Most guinea pigs enjoy a variety of vegetables in their diet, with fruit as treats. A few leaves of cabbage or kale, or a slice of orange or apple are good choices. Other treats your cavy might like are parsley, beet greens, spinach, green pepper, broccoli, tomato, or kiwi fruit. Remember that fruit is a treat, and contains a lot of sugar. A large amount of fruit on a regular basis is a recipe for a very fat pet.
Be careful when changing a pig's diet or adding new foods - too sudden a change can cause severe diarrhea, and many guinea pigs will not eat unfamiliar food.
Guinea pigs are usually quite social, and can be kept in groups, as long as adequate space is provided for them. Intact males kept in close quarters will often fight; if you have multiple males, consider separating them or having then neutered. And remember that they will reproduce quickly, so don't mix males and females unless you want (and are prepared to take care of) babies. The most common pet situation is 2 - 4 females kept together without males, or with neutered males.
Make sure that older or more dominant cavies are not chasing less dominant individuals away from food. Providing multiple bowls or separating at feeding time will help ensure that all pets get enough to eat.
Sometimes more aggressive guinea pigs will chew on, or "barber" other pigs, leaving bald spots where they've pulled all the hair. These pigs should be separated, for the safety of the picked-on individual(s).
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