My piggies

Question
Hello,  I got 4 male piggies when they were young. I have had them since June. They have always been housed together and always gotten along until a couple of days ago. They were all fighting each other (including mounting) and destroying there house and everything in it. One even had a bite that bled.  I separated them into pairs and they still fought each other so I housed them independently through the night. This morning I put  them back together and they started all over again. Three of them seem to start picking on one individual and then it turns into a free for all so I took him out and left the other 3 together and they have settled down. They are all supposed to be males, but now I'm wondering if one is a female and perhaps in heat. They have always been very sweet and I want to keep them together but I don't want them to hurt each other.  As far as I can tell, their genitals all look alike.  Your feedback is greatly appreciated.  THANKS!

Answer
The behavior you describe is typical of boars (male guinea pigs) reaching their sexual maturity. Even when raised from infants male animals begin to develop their hormones and the behavior that follows. Unless they are neutered this applies to just about all of the male species.

All herding animals (horses, cattle, zebras, elephants,hippos,dogs, cats, wolves,rabbits etc) are allowed to stay in the herd while they are young. A herd is governed by the alpha male. The exception to that is elephants. They are a herd of females and the alpha female is the boss. The alpha male is the only one allowed breeding rights. This is a behavior that controls inbreeding in wild herds.

As long as the young males behave and don't challenge the alpha male everything is happy. Once they start acting on their hormones a fight begins. If the alpha male wins the youngster is banished from the herd. If the young stud wins the old alpha is sent away.

These young boys are beginning to feel the effects of their hormones. At this age the hormones are raging and the boys don't know how to deal with it. The mounting behavior is both sexual and a dominance move. The problem is there are four boys all trying for the lead role. It's not going to work.

They will continue fighting until someone gets seriously injured or even killed. Guinea pig bites will quickly develop into an abscess and the infection is a serious one. This is not something you will be able to change as they are hard wired to do what they're doing.

The exception to this is when you have a very old boar who no longer wishes to be king and will allow the young male to think he's boss. I often use my old boars as nanny boars to the young males I've weaned. But the time still comes when they must be separated. If not, the old boar will be injured by the younger one because they are persistent and won't give up.

At their age the testicles should be quite visible so I doubt you have a female in the herd. If you do she's already pregnant. But even then the fighting will continue. It's hormonally driven and it's natural instinct.

The best thing to do for all of them is to separate them. They'll be fine side by side and can touch noses through the wire, but left together is a recipe for serious injury.