[Gpdd] [BEHAVIOUR] Guinea pig eating cagemate's poop

[Sarah]

I am new to owning guinea pigs so please bear with me.  

I recently adopted a female 2 year old Abyssinian who has taken to chasing the 
other guinea pigs around their cage (we have four piggies in total, three 
females, one neutered male), sniffing at their bums, taking poops from them. 
 Sometimes she is trying to pull the poops out while they are being produced! 
 She focuses particularly on our neutered male.  He is not impressed by this. 
 She seems to enjoy sneaking up on them while eating and they jump in surprise 
with a little nose poking their in backside.  

Is this behaviour normal?