In the wild, chinchillas live in herds of 100+ so it's understandable that they love company!
When kept in pairs or groups, they spend a lot of their time grooming each other as well as themselves, they also have several different 'calls' that they make - some are 'warning' calls and 'don't come near me' sounds, along with various noises of 'communication' to each other, and of course, mother's with their kits and their own identifiable sounds

If chinchilla breeding is required, the pair should be introduced to one another no earlier than 8-9 months of age. if you introduce them before this age, the female could become pregnant which would be detrimental to her health and cause a lot of stress. it may also prove to be a very difficult birth for such a young animal.

If you already have a chinchilla and would like to purchase a companion for it, there are a few things that you should think about first. 

The first tip for introducing the chinchillas is to push their two cages together.  Place the cages about 2” apart, so that the chins can see and smell one another, but cannot bite each other’s toes.  Sometimes, one of the chins will bang on the cage mesh, obviously very annoyed that a stranger is in its vicinity, but hopefully within a few days this should stop and they should be able to tolerate each other

Once they begin to lose the urge to spit or show any aggression to one another, the chinchillas can be introduced.  I find that the best place to do this is on a carpet in a small room.  I use my kitchen or hallway.  I place a sand bath in the middle of the room and ask someone else to come into the room with me – just in case we have to separate the pair!  Sometimes, everything goes smoothly and the chinchillas tend to become friends almost immediately, but on other occasions the female will rear up and spray the male with urine and take several chunks of fur out of his coat!  If things become a little ‘nasty’ separate the chinchillas and try again a few days later.  Unfortunately, there are a few chinchillas that will never accept a mate.

Chinchillas can also be introduced to one another in a cage, but the cage should be one that neither of them has lived in – or claimed territorial rights over.   Once confined to a cage the hostility may be more severe than out on mutual territory – like the carpet!  Lots of boxes, tubes etc should be available, in case one of the chinchillas feels the need to escape from the other one.  During the first few minutes the chinchillas may be so busy exploring the new cage that they may not feel the need to bicker or fall out.  But keep watching and never leave them alone.

Some breeders put the pair of chinchillas into a very tiny cage.  This mesh cage is so small and low that the chinchillas cannot really move about – or chase one another!  After several hours the chinchillas are let out into a larger cage and seem to be friends.  I am not sure whether I like this idea – but I know a breeder who does this and things tend to go well for him.

In the wild a female chinchilla would be able to run from a male if she did not feel ready to mate.  But if the pair is to be introduced in a cage – things can turn a little nasty.  If the pair do not get along on the first introduction, then it is best to separate them, leave their cages side by side and try them again a week or so later.

 I would recommend that you purchase two young chinchillas.  If they are of opposite sexes they can be housed separately but kept side by side until the female is 8-9 months.  They can come out and run around together during their daily free run, but make sure that someone watches them at all times 
It only takes a minute!
If you do not wish to breed your chinchillas it may be a good idea for you to purchase two young sisters, two young brothers, a Mum and daughter or a Father and son.  They will not have to go through the ‘introductory ordeal’ and should get along very well.  The only problem that may arise is if you bring a female into your home once the two males have reached sexual maturity.  They may bicker/fight when they can smell the female in season and things can become very serious.

If a pair of chinchillas have been living happily together for several months/years, problems can still arise if they are separated for any reason. on June 19th 1998 my first pair of standard grey chinchillas gave birth to a daughter. As the weeks went by, I realised that they had mated again as Rosie was expanding rapidly. I decided that I had to get basil castrated as I couldn't face the idea of re-homing babies to people that I did not know (after a while you run out of family and friend who want your baby chinchillas!) I booked Basil in with a very good Vet in my area and the operation went well.
The following day I put basil back into the cage with Rosie and was not prepared for what happened next! Rosie f;ew at poor basil, bit mouthfuls of his fur out, sprayed him with urine and was obviously not happy to see him. I can only assume that he came home from the surgery smelling 'different'. it was either this or the fact that Rosie was expecting again, so it could of been her hormones! I tried several ways of getting the pair back together but everything failed. Rosie was just not interested. I could not believe how horrible she was to poor basil, when only a few days earlier they were the best of friends and inseperable>
I had to wait until the next kits were born and weaned before trying to put Rosie and basil together again
(one male and one female were born on October 9th 1998)
 It took a few days, but Rosie was less aggressive and eventually she let Basil stay with her without pulling his fur out!  It was lovely to come down one morning and see them cuddled up together again.  I always tell people to take the female along to the Vet when the male is being castrated now …. In the hope that this problem may be avoided.  If the female has the smell of the surgery too – she often does not attack the male when they are returned to their own cage at home.  My Vet only separates the pair for the operation and will return the male to the female as soon as 'he' has come around from the anaesthetic.  Although there is always a risk with a small animal having an anaesthetic, I think that castration is well worth it.  The majority of castrations are a success and the pair can live the rest of their lives together without bringing many babies into this world.  Think about it – it may be the best thing to do.