Take it slow!! First step is to be sure the Chins you are introducing are the same gender! Don't take it as fact from someone else as many have mis-sexed chinchillas! It's irresponsible to house male and female chins together as they will breed eventually. Here's a good page that shows how to position your chin to take the correct picture to help determine sex.
Just post your picture in the group and we'd be more than happy to help sex them.
If you are bringing in a new chinchilla to add to your existing herd, it's highly recommended that you keep them separate for a 30 day quarantine. This gives a chance for whatever contagious ailments your new chinchilla might be hiding to show itself so not to endanger your existing animals. Alternatively, you can get a veterinarian to do a look-see and give you a clean bill of health.
So now your new chinchilla is settled in and healthy. Start by putting the 2 cages close together so they can see and smell each other. You can swap cages as well, let them explore the scents of each other without physically letting them reach other.
Neutral Play Time
The next step is actually introducing them in a neutral play area... Somewhere neither has been before. It's normal for there to be some chasing and even some humping. Those are signs of dominance.
Be sure to break it up if it starts to be too much. Start out with short times, 5-10 minutes. Once it starts going well, you can let them into the normal play area for supervised play time.
After some time playing together successfully, the next step is to put them in a cage together. The cage should be cleaned thoroughly beforehand, removing any lingering scents - re-arrange it if it's been the home of one of them. The idea is that it should be "new" to both of them. Let them explore the new cage together. Don't leave them alone and together until they've taken a nap or eaten together. Then just keep an eye on them. There are other methods, but this is the safest and most likely to be successful method.
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