Okay, I’m doing an experiment with gerbils pertaining to their reaction to isolation. When we first got them they were all in the same cage, and got along. After isolating one, he became depressed (eating and sleeping more) as I expected. After attempting to take the gerbil out of isolation and rejoin him with the rest, he was attacked. I should have seen it coming. I read on another website that covering them in talcom powder would erase their scent, and they could live together again. Sounds strange, but plausable, so I tried it, and it’s working so far. My question is whether or not they’ll try to kill each other again when the talc powder rubs off.
Probably by then they’ll be used to contact again.
Why do you want to torment Gerbils?
It seems a rather cruel experiment, with an obvious outcome, as you said.
Anyway: as a kid I used to breed Gerbils, for sale to pet shops, and they will fight if introduced as strangers, the secret is to separate the newcomer from the rest by a chickenwire partition for a few days so the others get used to its presence and scent.
They can also be real killers as mothers, who will sometimes if disturbed or stressed, kill and eat their babies even when quite grown up.
They seem to especially like eating their brains and leaving the skull and scalp.
I belive there is a species of killer carniverous desert mouse that also hunts in this way.
I would be fascinated to find out how to train them to kill/eat each other- could you imagine a snake getting eated by a mouse?! 
Found out more about the KILLER MOUSE it’s called Onychomys Leucogaster and apparently it’s capable of attacking prey 3 times it’s own size!
It gives out a cry before attacking says http://animaldiversity.ummz.umich.edu/accounts/onychomys/o._leucogaster.html
also howls like a wolf (pint sized!) at http://www.nsrl.ttv.edu/tmot1/onycleuc.htm
I’d love to seem my big tom cat meet one of these!
Make that last ref. http://www.nsrl.ttu.edu/tmot1/onycleuc.htm
If I remember the old TV programme it likes to eat the brains of other rodents as they are the bit with the most protein.
The mouse from Hell!
Perhaps we should be parachuting a few hundred of these into Sadam’s palace.
The poor things would starve to death!
Oops, Sorry. I succumbed to kneejerk patriotic jingoism. Please disregard.