It is a common misconception that male guinea pigs cannot be kept together. Because of this myth many boars spend their whole life in solitude never seeing or interacting with another guinea pig. Baby boars are often re-homed alone, only weeks old, and start a lonely journey of life all alone.
Guinea pigs are incredibly sociable animals, and in the wild would live in groups (admittedly not groups of males!). Therefore it is important that if you are going to keep a boar that you do not keep him alone and that he has a companion. Whether this be another boar, or if he is neutered he can live with a female or group of females.
A lot of people have had bad experiences of keeping a pair of boars together or have heard of other people who have had problems when keeping boars. Some boars don’t get on and do fall out, but this is the minority, and usually a personality clash.
This means that adopters are often reluctant to adopt pairs of boars. This means that handsome and loving boars end up getting overlooked in rescue and have difficulty finding homes.
If problems are going to happen you would usually see them when the guinea pigs hit adolescence at between 4 – 8 months old. At this age they begin to work out a hierarchy and an increase in squabbling and dominance behaviour is often seen. It can also occur in times of stress, a change of environment, or if there is simply not enough space for them. With enough space, mental stimulation, and patience, often the boys can work it out, and settle together. In some cases they can’t, and if they start hurting each other, to the extent they draw blood they would need separating. If this happens, you should look to find your boars new companions, it does not mean that they will not get on with another boar.
In general boars should be kept in no more than a pair, if you start adding more, this can upset the balance of the hierarchy. If you have a well bonded pair of males don’t upset the status quo!
If you are keeping boars they need to have plenty of space, exercise, mental stimulation, and keep them away from female guinea pigs!
If you already have an adult male the best bonding is with a baby male, and this bonding seldom fails. A lot of the males who come into rescue alone are bonded with a baby male, this works very well.
Alternatively neutering you male can enable him to live with a female, these pairings work very well, and you end up with a very happy couple (usually).
CAUTION: It is very difficult to bond two adult boars, and if put together they will fight. Rare circumstances happen when two mature boars will accept each other, but this is not often. Do not attempt to bond two adult boars unless you are very experienced, as they could fatally injure each other.
It is well worth reading the following webpage if you are planning to bond your guinea pig with another.