Having guinea pigs is amazing; however, sometimes you end up with a solitary guinea pig. Solitary guinea pigs are not kept with other guinea pigs for a myriad of reasons. As the owner, you need to compensate for this lack of companionship.
Why You Might Have Solitary Guinea Pigs
One of the primary reasons for solitary guinea pigs is behavior. Guinea pigs who fight need to be separated, of course. Unfortunately, this happens often when male guinea pigs hit sexual maturity since their instincts tell them they need to compete for sows, even if there isn’t one around.
Another reason is folks only adopt one guinea pig sometimes. In particular, pet stores are notorious for doing this without letting new piggle owners know about the long-term effects.

Why Guinea Pigs Need Companions
A guinea pig is solitary if it cannot interact with other guinea pigs. A guinea pig is not solitary if it can interact with other guinea pigs, even if that interaction is through cage bars because they fight. Even having multiple cages in the same room allows the guinea pigs to interact.
Guinea pigs are social animals and evolved to live in herds. Typically, this herd consisted of a half dozen female guinea pigs and a single male. Obviously, mixing male and female guinea pigs in the same cage all the time is a bad idea. However, guinea pigs still do better in pairs and trios as a rule of thumb.

How You Can Help Your Solitary Guinea Pig
If you are keeping a solitary guinea pig, your attention is the key to helping the guinea pig thrive. In short, you will have to substitute your attention for the social interaction that the guinea pig would receive from living with other guinea pigs.
That means you need to pay attention to the piggle in question. Now, that looks different depending on your preferences. It could be extensive cuddling and grooming sessions a few times a day. It could be playing with your guinea pig on the floor. You could even read to your guinea pig if you want.
All of this interaction with you helps keep your guinea pig happy. If you cannot provide the necessary interaction level, consider enlisting a friend or family member to stop by during the day.

Enrichment Options
Enrichment is a code for things that stimulate your guinea pig’s brain, and you should consider enrichment even if you have multiple guinea pigs. Guinea pigs are prey animals as well as foragers, so take that into account.
One way to provide enrichment is changing up your guinea pig’s habitat so that they have new things to explore. Items like adding a cardboard box or some rocks you washed off can change the whole cage and send your guinea pig exploring for the entire day. You can also consider creating half and full levels for your guinea pig to negotiate.
Another option is food. Guinea pigs evolved to forage, so hiding treats, using food puzzle toys, and making them work to find treats are all fine ideas. Things like hiding pieces of spinach in different cage parts are great for guinea pigs.
Remember, when choosing an enrichment activity, make sure it is safe for the guinea pig to eat. Use untreated woods that you have verified as nontoxic, simple treats, and make sure to sanitize anything you found in nature.