Once an animal is established in captivity, it can be very harmful to native populations to release captive animals back into the wild.
You would have to know the exact origins of the animal to not cross wild genepools and introduce new genetics to an area.
Captive animals do get 'trained' in a sort of way. They are not 100% 'wild' once we start providing their food and water. My snakes expect food on a certain day of the week....they are conditioned to do so. What would happen if they were released in the wild?
It is difficult for a captive animal to establish itself in the wild. A captive release has to compete with established wild animals for resources. This is not as easy as some would believe. If they do establish themselves, they take resources away from originally wild populations.
Not to metion the possibility of introducing parasites and diseases into the wild population.....that could be nasty.