how to tell aggression from a guinea pig

Question
my guinea pig got a friend maybe like a month or a little bit more than that, anyways, somtimes i will here a squeal every now and then also seeing the baby piggy running to a different side of the cage. i will watch them for about a minute or so and i will see my older piggy walking around(as though she is trying to look BIG and TALLER than my other piggy as she walks toward her)     is that a sign of aggression or that she just simply wants to be left alone?
as i am typing this, i just witnessed my older piggy repeat this routine again.  

Answer
Hi Becca,

It sounds like normal behaviour. It's probably rumblestrutting, where they rumble a little and "swagger" rather than walk, and they sway their butt from side to side. It's a guinea pigs' way of telling other piggies who is boss.

More dominance behaviours include:

Nipping
Chasing
Butt-sniffing
Mounting
Nose-offs

Best Wishes,

- Laura
www.cavy-care.com