Chinchillas are sociable animals, and it is best to keep them with company. A lonely chinchilla can become very depressed, engaging in stress behaviours such as fur-pulling. Though they do need to be introduced carefully a good rescue or breeder will be able to advise on the process and help match your chinchilla with a suitable friend. If same-sex company isn't available, male chinchillas can be neutered to enable them to live safely with the opposite sex, and this is a safer process than spaying a female.
Chinchillas are friendly animals, but easily stressed. They are rarely aggressive but will run and hide if disturbed by quick motions or sounds. It is important to limit any free-range time to avoid them becoming overheated or stressed, as they are prone to fitting. They are excellent jumpers, so must be handled with care to avoid them jumping from heights. Care should also be taken with free-ranging, as your Chinchilla will be able to find that fallen cushion that is only a short hop to a sofa, and will find and chew any exposed leads or wood, or forgotten food they shouldn't eat, in a space you don't expect them to fit into.
Chinchillas do sleep a lot of the day and must have enough nesting areas and spaces to ensure that they can each have their own space to sleep in. It is vital that you provide this to reduce any bickering, though you may still find them all piled up in a pile together sometimes. Chinchillas enjoy nests, hides and hammocks and must have cooling ledges and dustbaths available to help them regulate their temperature. Dustbaths are also essential to allow them to clean their fur.
Chinchillas can be very vocal, with a wide range of sounds. Alarm calls may indicate distress or excitment, such as a low barking sound. Higher pitched screams are more distressed and should be investigated. A low teeth grinding sound may indicate they feel safe or happy, such as when eating a favourite treat. A more urgent and continuous teeth chittering can often be a sign of anger. You can usually tell from a Chinchilla's body language, whether they are relaxed or stiff in posture, what a sound may mean for an individual.