How can I tell which of my two chinchillas is the aggressor when I'm...

[Brad B]

...trying to introduce them? I have two chinchillas: one is a male just under a year old that I've had for several months with his brother, but his brother was killed by a cat a few weeks ago, and the other is a male that is just over two years old who has been living by himself, and I just got him, hoping to provide a friend for my existing chinchilla.

I'm trying to use the cage within a cage method, where I put them both in a large, empty cage and watch them very closely. Then if one misbehaves and acts hostile towards the other, I put the aggressor in a small cage within the large cage for 30 minutes to an hour. Then I put them both back in the large cage and repeat.

When they are together, the younger, first chinchilla tends to sit in one of the corners, and the older, second chinchilla tends to investigate the cage. When the second chinchilla goes to investigate the first chinchilla, sometimes they will both stand up and chatter softly, sometimes they will sniff noses and the rest of their bodies, but then the first chinchilla will squawk or make a noise like its not pleased.

When the first chinchilla makes that noise, I can't tell if he's also trying to bite the second chinchilla, or if he's reacting to being bitten by the second chinchilla, or if he's just expressing discomfort. I always immediately separate them, since my hand is about 4 inches away from them. Since they are close together, and can move quickly, and I can't see where their mouths are very well, I can't tell if there are any biting attempts occurring, or who is being the aggressor. I haven't seen any blood yet.

I currently have them in two separate cages (normal sized ones) out of view of each other.

I need to know who is being unfriendly so I can put them in the smaller cage so he will learn that his behavior is not acceptable, but I'm not sure who is being unfriendly. Any tips?
This is the site I got the introduction method from, though frankly now I'm horribly concerned about them biting the fingers off each other: http://www.chincare.com/HealthLifestyle/Introductions.htm#cwacintros

 

[felixeatsmeowmix]

Put them in two separate cages next to each other so they can get used to each other and smell each other. That way they they won't be able to fight. When putting them in the same cage, whoever lived in the cage before will most likely be territorial. What worked with mine was putting them both in a cage that neither one has been in for a while so they don't have the territory issue.