On the ever-popular Myth #1: Male Guinea Pigs Can't Live Together post, Frances asked:
i have a male guinea that is about 4 years old. i want to get him a friend but i'm afraid he might be too old. i have introduced him once to another male and he was very "dominant" with him, if you know what i mean. anyhow, do you have any suggestions. i have thought about taking him to a pet store to see if they would let me socialize him with another male to see if they would get along. would that be a good or bad thing?
The answer? It depends on the pig.
Guinea pigs are, by nature, social animals for whom communal living with members of their own species is not only instinctual, it's critical to their physical and emotional well-being. So, no, attempting to find this boar a roommate is not a bad thing.
But, as I've written before, everything about guinea pigs comes down to individual personality -- so categorical statements about what will or won't work are virtually impossible. Observation by owners, breeders, and rescues over the last decades (including the writings of Peter Gurney) gives enough anecdotal information to help owners make well-informed gambles, but there are no guarantees.
Age won't be a deterrent to introducing a first roommate to an older guinea pig of either sex -- so long as the older guinea pig is open to having a roommate. Age might be a challenging variable, but I won't say it's an absolute. An older guinea pig might decide it doesn't want a roommate (ever), or it might surprise itself by liking the idea of a live-in buddy...especially when the perfect one arrives. Even a guinea pig that isn't displaying overt signs of depression still could be experiencing loneliness at some level and, thus, would be receptive to company.
I will say that going to a rescue might yield a better chance at matching success than going elsewhere, because the rescue workers know the temperaments of their guinea pigs and can identify the ones who are likely to mesh the best with your pig's temperament. Once you've found some candidates, it comes down to handling the introductions properly, and listening to what your guinea pig tells you through body language and other behaviors (e.g., eating peacefully together, curling up in a corner together, teeth chattering, huffing, stomping, excessive domination, nipping, charging, etc.).
As a final note, you're not likely to find a pet store that will let you bring your pig onto the premises and try introducing him/her to different candidates. Generally, it's come in, pick out a critter, take it home, and live with the decision (whether your pig accepts the roommate or not). Also, it's really not recommended since the health of the pet store pigs can be a bit of a question mark. The young guinea pigs brought into the stores from the breeders often experience an enormous amount of stress that can affect their immune systems and make them susceptible to things like upper respiratory infections, which are contagious. (Think about it: at eight weeks old, these pigs lose contact with their mothers, sometimes their siblings, and their first home, and are taken to a new, brightly lit, noisy living environment with new roommates that disappear each day and don't come back. Wouldn't that stress you out?)
We're not disqualifying pet store pigs, and we know that some people don't have guinea pig rescues in their area or other avenues for the adoption option. But if you do get a pet store pig, you should plan on keeping side-by-side cages for 21 days to allow for a quarantine period, giving the pigs time to get to know each other, and being prepared for the possibility that they won't get along. The pet store won't take the critter back, so you'll either have pigs in side-by-side cages permanently or will need to rehome the new pig with a good family.
Finding your guinea pig a roommate can prove to be far easier than you anticipated, or every bit as challenging as you feared. But if you succeed, even if it was a difficult and drawn-out process, you'll be well-rewarded by the sight of your piggy blissfully napping with its new buddy.