Guinea pig dominace

Question
Hello,
I have two male guinea pigs. (1) Dexter and (2) Kovu. I just got back from a 3 day trip in Portland and since i couldn't find anyone to watch my boys i took them with me. They never got along and i've had them for almost 6 months and when i took them i put them together in a pop up dog carer and added a play pen for more room. Dexter is the alpha pig and he and kovu got along great on the trip. When we got back i put them together in their 2x5 c&c cage and dexter has kept rumblestruting all night. Is this normal? will he continue this or will it get less and less as they spend more time together?
Thank you

Answer
Yes this is a natural response. Grown boars have one purpose in life, to reproduce.  That rumblestrutting is often seen when putting two boars together for the first time, or when reintroducing such as you have. Their environment was changed even if for a short time, so returning home it presented the same type situation as if they'd just met. Dexter sounds like behaving as if he's just found a new girlfriend.  Generally this will stop when he realizes (again) that it's not the case.

Sometimes what sounds like the "flirting" kind of rumblestrut is actually a precursor to a fight.  The hair on the attacker stands up and the growl gets a little more fierce. They sway their backside back and forth as a warning. That's a sign that there's trouble and blood may be drawn.  

Male pigs will get along if raised together, or if a baby is introduced to a senior boar.  But two seniors often have issues just because nature has given them that hormonal drive. Their instinct is to keep other males away from their territory. Sometimes they'll get along fine until they reach their sexual maturity, which is about six months.  

You may find that you'll have to divide the cage and keep them from making physical contact.