Chinchilla an aggressive biter?

[kwinto_katie]

My boyfriend rescued 2 male chinchillas in august. They are both brothers, not neutered, and about 4 years old. The one chinchilla Nibbles was beat up very badly by another chinchilla (not his brother) when he was young and has only one good eye and hardly any hair on his forehead. He is a sweety, loves to be held and cuddled, and most of all loves food. His brother Gizmo on the other hand hates to be handled and when you stick your hand in the cage will scream at you and lunge for your hand and if you don't move it quick enough you have a very deep bleeding bite. Gizmo has cycles of being friendly and loving and somewhat tolerant of being handled and picked up. Lately he has been doing well and hasn't bit my boyfriend for quite awhile. Yesterday however, Gizmo started chewing on a baseboard when he was out so my boyfriend said no and picked him up to put him back in his cage and Gizmo bit him REALLY hard on his finger blood was dripping all over the place but he didnt let Gizmo go and tried to get him to calm down before he put him back in his cage as he didnt want to reward bad behaviour. So Gizmo screamed and bit him again so hard on the thumb that it actually bruised the nail bed and indented the nail and also got the thumb pad really deep. Could these cycles of aggression be Gizmo's way of showing dominance or trying to? Would neutering help the situation? We were told that pushing your finger farther into his mouth would stop him biting but he bites without warning and is a bite and run kind of chinchilla there is no way to even go about doing that. Please help!

Gizmo is not at all food motivated so its hard to know what to do for a reward for good behaviour if by chance he is good. Sometimes he gets 1/4 of a raisin (but only occassionally as we don't want him to become diabetic)