Two male guinea pigs are fighting...what could help?

Question
I had Radar for around a year when I first got Bruce, who
was around 2 months old at the time. I put Bruce through
the suggested quarantine period (3 weeks), and their first
introduction went well. After another introduction, I
figured they were ready to go into their 2x4 C&C cage.

Things went fine for the first few weeks, (except for a wee
bit of territory problems in the first hour or so, but that
was easily worked out) but after a while, some teeth-
chattering has started. They will chatter for somewhere
between 3 and 10 seconds, then one of them will scurry
away. I'm just hoping to fix the problem, so they won't be
as stressed and can go on with their happy lives.

Radar and Bruce both come from pet stores, HOWEVER, Radar
lived with five other guinea pigs in a gigantic cage with
plenty of food and housing, and yet when he came home, he
was shy and timid. He may have been mishandled by the
workers there.

Bruce came from a small, family owned-and-operated pet
store in my small town. He lived in a smaller, regular
sized pet store cage with another guinea pig, with plenty
of food but no house or shelter of any kind. The owners
were caring, and Bruce was energetic when he came home, not
shy at all.

My diagnosis is that they have very clashing personalities,
and the age difference could also be a problem. They both
have houses, they share a food dish, and they share a water
bottle. They have hay most of the time, but I must admit
that I need to be better about that. I've only just decided
that they will be litter-trained soon (hopefully...), and
they currently have fleece bedding.

Thanks, so much! Hopefully you'll help make my guinea pigs'
lives a little brighter. You're a great person!

Answer
Jason,
The one that is doing the most teeth chattering is probably because he's saying 'I'm going to be the boss around here!' and the one that starts after is saying the same thing! Usually, in these cases you don't have to worry much as Bruce(which I believe is the young one) may be going through maturity and is trying to establish dominance over Radar who was probably the dominant one when Bruce was small.

Don't worry too much as long as they're not biting each other and drawing blood, usually owners separate them as soon as they see them nip or teeth chattering accompanied with yawning and swaying side to side, let them figure it out. You can tell if they're fighting when they have tuffs of hair in the teeth and they're pretty much in a vicious ball of fur and at that stage, separate them by getting 2 towels and covering them and use a dustpan or cardboard as accidental bites are nasty and can cause some serious damage (this has happened to me before and I had a bleeding finger! I had to separate them, although this was couple years ago). My advice is that if they really do draw blood, separate them into different cages but close to each other and they can communicate and try to establish dominance from there, if they start biting cage bars and you see blood on the bars, they're biting too hard, thus you should introduce them slowly on neutral territory as much as you can!

You seem like a great owner! I wish you luck with your piggies Radar and Bruce!

--Cerian, hope this helped! Feel free to ask anymore questions or concerns