Guinea Pig behaviour

Question
I have three brothers (not neutered) about 8 months old. Leadership seems to have changed suddenly and the former top pig now excludes himself from the others, settling for long periods as far away as possible. From being the alpha male he now appears withdrawn and disinterested.
I am feeding him separately which he eats.
My concern is that he may be lying out in the open all night, rather than join the others in their sleeping section, although I can't be sure.
The new leader expresses dominant signals and chases his predecessor around if he gets the chance but I can't see any bite injuries on either of them,
Thanks

Answer
I would suggest putting some kind of shelter at the other end of the living quarters to allow the dethroned prince a place of his own to get shelter and peace. Watch his weight for signs of his not being able to get sufficient food to maintain his body weight.

As long as he is indifferent to his brother's takeover he should get along well. It sounds like you're saying they have an outside cage or living arrangement, which is fine but they each need a shelter to allow them to sleep comfortably and safely.

At the first sign of injury you should separate the one who is taking the beating. They are all sexually mature males now, and as such they are running on an overdose of testosterone. Being unneutered their personalities can take sudden changes. So be aware that you may need to arrange different circumstances to protect each of them from harm.