Welp I had to separate the two, Murray bit Guybrushes tail and it's a little bloody. he isn't bleeding all over or anything, but Murray did draw some blood. I've got him separated in the old tank that was used for Cell and I am going to call up the pet store and let them know what happened and ask if it is possible to bring Murray back and exchange him for the other cage mate.
Murray is considered a 'bully' at this point and as such could be dangerous for me to handle :\ if he bit Guybrush then he's likely to bite me as well and as bad as I feel giving him back there is no way I can safely try to tame him at this point and I need to keep Guybrush safe.
It's really strange since they where housed together at the store without any problems, where likely littermates, and coexisted perfectly fine for the first night we had them.
Guybrush is fine, and seems unharmed other then the nibble on his tail. He's up and about, active, alert and fairly tamed as it is but I'll be letting him settle in without Murray for a little while before I try to interact too much with him.
:\ I feel very unhappy about returning Murray, but he absolutely cannot be housed with another mouse at this point and will not be handled well. He's more suited to someone who isn't interested in trying to form a bond with him and won't be handling him often.
Hopefully his other cagemate will be a good match instead.
This is Guybrush, who had previously discovered a lovely sleeping spot of on top of the water bottle:
This is Murray, in his time out cage sleeping. He's pretty much just fallen right to sleep in the second cage and is not bothered by being alone: