Guinea Pigs: Solitary or Social,

First and foremost when considering a Guinea Pig for a pet, be prepared to consider Guinea Pigs in the plural form. In nature, Guinea Pigs live in family groups consisting of one male and up to nine females, and they are very social with each other. For a Guinea Pig in captivity to be happy, they should always have at least one companion.
There are a few simple rules to follow in order to avoid problems when pairing Guinea Pigs with companions. Don’t keep Pigs with other animals: though commonly kept with Rabbits, Guinea Pigs are often injured by them in attempts to mate or by being kicked in close quarters. Keeping both sexes together is not recommended unless the male is neutered. Unaltered males kept individually or with females only are less adaptable to being kept with other males, as they will begin to compete for dominance around five to seven months of age.
Keeping small groups of two or more females tends to lead to the most positive experience both for pets and owner. Guinea Pigs do tend to be rather skittish and will become nervous around loud noises and sudden movements, making them better pets for households without children or children over the age of six. While very social with each other, every Guinea Pig has his or her own individual personality, and some do not warm up to humans. However with some patience and caring, most Guinea Pigs will learn to enjoy their human companions.