guinea pig brawl time

i have two guinea pigs; their names are poof and opie.
i take no responsibility for their names, you can blame my girlfriend.
poof is fat.
opie is not fat.

because of this discrepancy in size, opie (skinny) acts as if it's perfectly within his rights to bully poof (fat).

skinny opie has two "attack moves" that he uses against his fat piggie brother.
these are the "rear hump"
and the "flying bottom strike"
(which entails him jerking to the side and tossing his backside into poof,
causing little damage to body
but significant damage to pride).

i have separated them by dividing their cage.

poof needs to lose weight.