Angry guinea pig?

[BillyThePig]

Hi everyone, I've had two guinea pigs for 2 years and 1. My older guinea pig all of sudden has started picking on the younger one. He's for the most part a very friendly guinea pig and has never fought really hard. He hasn't been hurting him, just pushing him back into one of the houses and going nose-to-nose with the other. I was wondering if anyone had a reason for why he's doing this? I remember him doing this last year around the same time.

 

[Siikibam]

It may be he’s just asserting his dominance. How is the other piggy behaving? And how long has this behaviour been going on? Boars can still have hormone spikes past their teenage months.

Make sure the cage is big enough (minimum 150x60cm), there is two of everything and all hides have two exits. Hopefully he will settle down soon. Have a read of the guides below as well.
Dominance Behaviours In Guinea Pigs
A Comprehensive Guide to Guinea Pig Boars