You need to be careful whenever you introduce two chinchillas (of any sex). If you are lucky, they will get along fine from the start. Often times however, even the tamest chin will not immediately get along with another.
I like to divide a cage in half for my introductions. I had one cage specially made that comes with a divider. (See the Cages/Setup page for a picture). This way they are close to each other but cannot get at each other. Note that if the wire dividing them has too large of openings, they may still be able to bite each other. I once had a toe bitten off of one this way.
Each night I let them run around with each other until the fighting gets too bad. Then I put them back in their cage and try again the next night. Usually after a week they are fine. If you put 2 cages side by side, I find that it can take longer, but will usually work. Some people like to put them together and give them a dust bath. This may also help.
Note: There is no guarantee that 2 chins will get along, but in 8+ years, I have had very few instances of this. Just be careful or you could end up with a DEAD animal.
I breed mine in pairs or one male with 2 females. I do not use collars. It can be a little trickier when introducing 3 together. The younger the better in this case. I have had it successful by getting the 2 females along, and then adding the male. I have also had a major war this way. I also have tried adding a female to an existing pair, with similar results. Every case is different, and sometimes it is better to just leave an existing pair alone and be happy they are doing well.
Although this varies by breeder, I typically wait until females are 8 months of age before breeding them. If they are small females, I wait a little longer. Some breeders will breed at a younger age, but since they are still growing, I believe it is best to wait. Patience is one of the hardest things and most important things to breeding chinchillas.
Cages for Breeding
I have seen baby chinchillas get out of a cage with 1" x 1" openings. I recommend getting 1/2" x 1" openings, as babies cannot get out of this size opening. You should be prepared ahead of time, and not have to run out after the babies escape. Many pet stores will not have a cage of this size. I get mine made from a company called Da-Mars in South Beloit, IL. Their phone number is 1-800-95-BUNNY (I am not associated with this company in any way other than being a customer).
I also recommend that if you have a multi-layer cage, you shut off the higher levels. Babies can climb the day they are born, and a long fall may kill them.
I like to use cages with solid bottoms and pine shavings so the babies do not get their feet caught in the wire bottom. I also believe it is warmer than the wire bottom cage. I know many people that use wire bottom cages w/o a problem.
Most deliveries go smoothly, and no intervention is required. Unless you want to breed the female back right away (not recommended - this can be tough on the female), the male should be removed for 1 week, as the female goes into heat the day she delivers. After a week, the male can be returned, and usually there are no problems, but always be careful when re-introducing them. I remove the babies and let the parents get re-acquainted and then put the babies back in.
Although deliveries typically do go well, anything can happen. I have lost females and had dead babies. Anyone who plans on breeding must be prepared for this and able to accept it.
Now that the 111 day gestation period is over and you have your bundle of joy(s), what's next? The average litter is 2 babies, and having 1-3 is normal. I have heard of larger litters. When you have 3 babies in a litter, sometimes the babies will fight over milk. The teeth on these babies are very sharp, and they can actually kill each other with their fighting. If they get bit on their nose, it can scab over and they will be unable to breathe. If you see fighting, you will need to rotate the babies to avoid the fighting. You can rotate every 2-4 hours. Although I don't like leaving them longer, I have left them alone for 8 hours w/o a problem.
If I do leave them for an extended period, I supplement them by feeding them a mixture of Gerber's Mixed Dry Baby Cereal with Vitamin D milk. I heat it to luke-warm, or feed cold. This can also be given if one does not seem to be nursing well. It may take some practice, but you can usually tell if a baby's stomach is full by feeling its tummy. Yogurt can also be fed but I find they gain weight faster with the other mixture. If you do hand feed, use an eye dropper, but be careful not to force it down their throat, as that could kill them. The baby will probably squirm at first, so you may want to try holding them in a wash cloth. Get a little on their tongue, and they will usually take over from there. They will usually push the dropper away when they are full.
You will notice that after 1-2 weeks, some babies will start eating alfalfa or pellets on their own. They will however continue nursing for many weeks. I leave mine in with the mother for 7-8 weeks. I know others who remove the babies sooner. I only do this if the mother seems to be out of milk or having some other problem.
Female chins will typically accept babies from other litters. If a female dies, another nursing mother may take on the babies. I have also done this when a female has 3, and another has 1. As usual, be careful and watch for any sign that the other female may reject the baby.
For more information on breeding, check out the breeding section of the ChinNet Chinchilla FAQ.