Guinea pigs - fighting?

I've got two male guinea pigs who are brothers and have always been together. They're now nearly three years old.

They recently got moved into a bigger hutch. We've also got a young (three month old) dward lop who is in a different hutch. I put them all in the run together for a short supervised play yesterday and they didn't take much notice of each other, except for a bit of a sniff.

I've gone out to check on them and change their water etc this evening, and one of the guinea pigs has got some blood around his face and the other has got some on his fur. I've been watching them for the last twenty minutes or so and the one who has the blood around his face keeps jumping on the other one, not really sure if he's fighting or getting frisky!

They are quite large guinea pigs and I'm worried they could cause each other quite a bit of harm.

Does anyone have any idea what might have happened, why now after all this time and what I can do sort the problem?
Answers:
When you moved the guinea pigs into a bigger hutch, you changed the dynamic between the boys. In the old hutch, someone was "alpha male" and that was the status quo -- he ruled the roost. Even in a harmonious pair that, to humans, appears to be a match between equals, there's a nuance in the relationship between pigs that established and maintains the hierarchy. It's abundantly clear to them who's boss...it's not always clear to us humans.

However, the new hutch is neutral territory. When you moved the boys into the hutch, someone in that pair decided "Huh...okay...new digs, new boss." Problem is, whoever was the boss in the old digs is not going to easily give up his "alpha male" status...and now they're working it out.

The presence of a new friend (the rabbit) may or may not have exacerbated the situation (if one of the pigs is calling "mine" on everything he sees right now) -- but he's not the cause.

I'd keep an eye on your guinea pigs for a day or two (and clean and treat any wounds). If the problem escalates, you'll have to separate them.

(P.S. If you end up having to separate them, and think you're going to get them each a live-in girlfriend, *get each male neutered by a vet who specializes in exotic animals*. Vets who specialize in the treatment of exotics -- guinea pigs, rabbits, ferrets, chins, etc. -- tend to promote this expertise very conspicuously on their Web sites and in their yellow pages ads.)

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perhaps he woz after his red wings if you're gona let them fight i'll have a fiver on the rabbit

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I would imagine that the presence of a third animal even though it was a different sort has changed the pecking order and the guinea pigs were sorting out who was the boss. I wouldnt put them all together again and hopefully it wont happen again.

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they might be wanting to mate and thts y they are fighting try sperating thm and or buy 2 females and seperate them thn they wont be lonly but u will end up with babys

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I'm surprised that you actually haven't had a problem with this before now. I used to keep loads of guinea pigs..and always had to separate the males as they always fought. With guinea pigs, 2 girls can be kept together fine, but 2 males will always fight each other. Guinea pigs don't get lonely on their own, so i think it would be very wise to purchase a new hutch and keep them separate. You could face the hutches opposite each other so they can see each other, if you're worried that they'd get lonely. Possibly, they may of even had little fights in the hutch, that you may not of noticed before. I put two brother hamsters together once.boy, did i nearly lose a finger separating them! Good luck!