 In the Wild
In the wild Guinea Pigs live in groups usually consisting of one dominant sexually mature male and several females. As younger males in the group become sexually mature the males threaten each other by hissing and rattling their teeth and fights occur. Weaker males are driven from the group, and usually take with them a female to start their own group elsewhere. The females in the group develop a dominance hierarchy.
Guinea Pigs live in burrows and feed at night on vegetation. They have a scent gland on the rump which lays a scent marking their territory and acts to warn others to stay away. When excited Guinea Pigs run in circles or may stampede.
In Captivity
Guinea Pigs are sociable and will appreciate the company of others. However, sexually mature boars are intolerant of each other if there are Sows (females) around and fighting is likely to occur. However, Boars will live together provided they have sufficient room and no Sows are nearby. Sows will live together happily in a single sex group or with a single boar. | 
