Adult and almost adult veiled chameleons (Chamaeleo calyptratus) can not be housed together. This species is a solitary animal and it will not allow members of its species to live within its own territory. Even males and females cannot be housed together. The chameleons will threaten each other with hissing and bright coloration, and will eventually fight and wound each other. This causes a lot of stress.
Baby veiled chameleons can be housed together without problems. They do not fight and do not have their own territory yet. Of course their terrarium should be large enough and they should have enough space to walk, climb and plants to hide behind. When a veiled chameleon becomes around 4 – 5 months old it should be moved to a terrarium of its own. When its around 8 months old it will reach sexual maturity, then it should definitely be housed alone.
You will find stores where older veiled chameleons are still housed together. This is done because of economics and space restrictions. For the chameleons this is not a good situation. They will get stressed. Luckily they are generally not that long in this situation, as the turnover in pet shops is usually pretty high. Pet shops are not a good example of how to house your pet Yemen chameleon.
In very large places, like a greenhouse or zoo, multiple chameleons can live in the same space as they can set up their own territory and send the other chameleons away to their own area. If every chameleon can set up its own territory, there will be no fighting.
How does it work when you want to breed chameleons?
Of course you will start to wonder: how can veiled chameleons breed when they cannot live together? When a female is sexually mature and ready to mate, she will allow a male in her territory. She will signal this with the colors on her skin. She can also signal with these colors that she is not willing to mate and is ready to fight the male. The male recognizes the colors and will respond appropriately. Breeders will thus allow a male chameleon to enter the females enclosure and see if he is welcome or not. When mating is done the male has to be brought back to its own terrarium.