thank you, I will definitely check out the links.The vibrating is called "rumblestrutting" (rumbling while wiggling the bum). It is mild dominance behaviour for both genders although you often see it on a daily basis with some boars while only occasionally with sows, mainly during introductions or when they have a strong season.
With boars, it usually translates as "Look what a strapping lad I am!" When my various neutered boars do their motorized waggle dance with their neighbours (especially any new boars on the block), I call this a "boar haka". It is there to establish and reinforce their little territory; if sows were present, it was to impress them enough to choose him as their mate - in guinea pig society it is the girls' that choose which boar they want to live with, not the other way round.
There can be times when boars seem to only have two words in their vocabulary, rumblestrutting and food wheeking...
Boars generally hit the teenage hormones are around 4 months old. That is usually the time when the rumbling etc. goes up another gear or two.
You may find the first part of the first link and the list of dominance behaviour in the other thread helpful:
Boars: Bullying, Fighting, Fall-outs And What Next?
Dominance Behaviours In Guinea Pigs
Thank you, They are already in two different cages due to not knowing if Tiberius is a boy or girl.Hi CharleneN, this rumbling sound is called 'Rumble Strutting' and it's a very normal behaviour for Guinea Pigs, especially males. Tiberius is showing Septimius that he is the boss, it's a dominance behaviour. You don't need to do anything about this or be worried about it unless they begin to fight and draw blood, or if constant rumbling strutting is making one Guinea Pig stressed and depressed and having a negative impact on his quality of life. If they have been recently introduced they will rumble strut until they have established the dominance hierarchy, once this phase has been completed, the rumbling will stop or decrease, some pairs can continue to do this though, it depends, as long as nothing comes of it they will be fine. If any of these things arise then it's best to separate them.
What makes you think he may be a she? You can always post pics of his/her parts so others can weigh in on gender.
Septimius my other guinea pig every time they are together he starts to hump Tiberius and that made me think he may be a she. I looked at the sexing thing on this sight and my mom just helped me confirm actually that he is a boy. so it's good. I was just confused
Thank you, it has helped me so far.
I'm glad he's the sex you expected! Boys (and girls) will hump each other as a dominance display, to figure out whose boss. It's isn't necessarily about breeding, it's a 'sorting out who is the boss' behavior for both genders.
They're together right now and are getting along just fine, when septimius was trying to take a nap tiber jumped on him and started a little fuss but they ended up taking a nap together. Very cute
lol. I think it means that they are happy. or a boy thinks a boy is a girl vice versa 
