male fighting

Question
Hi Jules. We got two sows about 3 weeks ago, we bought them when they were 9 weeks old. This last week when we've brought them inside for a play and a cuddle they been snarling and hissing at each other. It started with one of them started to hump the other one, and this was not welcomed. In the cage we haven't seen them fight yet, but they do seem to "tippy toe" around each other. Will this end in a big fight or do you think they will sort themselves out and live happily ever after?

Answer
Hi Britt,

This is normal behavior that your girls are doing. They are just now at the age where they're trying to find out who'll be alpha or the leader of the group.

Guinea Pigs are herd animals, so they have 2 leaders normally a male and female, but when in a same sex group they only have one leader.

That is what your Guinea Pigs are doing, they are going through their dominance behavior. It'll settle down in awhile, depending on how stubborn they both are. Keep an eye on them though to make sure it doesn't escalate to serious aggression fighting.

Here is a list of things to expect from them both as they go through their dominance behavior and also a list of aggressive signs to watch out for.  

Safe, non-combative, dominance behavior

Rumblestrutting
Butt sniffing
Butt nudging
Chasing
Butt dragging (they are leaving their scent)
Mounting (any which way: rear mount, head mount, side mount, flying leap mount!)
Nose face-offs (higher in the air wins, one must lower their nose to be subservient to the other)
Teeth chattering: a little (signal of dominance)
Raised hackles (hair on the back of the neck and along the spine)

Posturing for possible attack, battle for dominance is
escalating

Teeth chattering: sustained (signal of anger, aggression, warning)
Nips, light bites, may result in little tufts of fur in their teeth
Wide yawn, but this is no yawn, they are showing their teeth
Snorting (like a strong puff or hiss)

These behaviors may sound serious and they should be monitored VERY CLOSELY, BUT do NOT separate the pigs exhibiting this behavior, yet. This is when the average pet owner loses it and pulls the pig out. Most of the time, this behavior will continue for a while until one backs down.

Fighting with intent to harm

Bite attacks are no longer warning nips, they are lunges with intent to harm.
Combination of raised hackles, loud and angry teeth chattering, rumblestrutting in place with the head staying in one position while facing the other guinea pig doing the same thing. Usually a signal of a biting attack. But they may back down before they engage.
Both pigs rear up on their haunches, face to face. This is a clear, brief signal of their intent to launch full attacks at each other. Separate if possible before the attack.
Full battle. The pigs are locked together in a vicious ball of fur. This is very serious. Separate immediately, but be careful. Throw a towel over them and use a dustpan or something other than your hand to separate them. Unintended bites from their very sharp incisors can cause serious damage.

When showing the signs of intent to harm, it is now that pet owners need to separate them. As this can end in serious injury.

It'll settle down soon and they should live happily ever after, sometimes it is just difficult to sit by and watch especially if they where getting along fine before they reached the age of sexual maturity. But things will settle down just give it some time, again it'll all depend on how stubborn they both are.

Take care now and I hope this helps,
               Jules