I don't think its right to hold an animal in a little confided place why would you even think about even doing that but now you Can let them go because they will die on there own. Because they have been in the same place and have not had to catch there own food. They should not catch anymore.
Besides animals won't know how to find food by themselves which they will need to survive and in captivity they only feed the animals when they can still teach them to find food to survive but they only care about the people that come to see the animals instead of them
I think that animals can be kept in captivity to a cirtan point. More than not animals are abused all over and that is what needs to stop, but they can be kept in a cage in my opinion with the following requirements
*a cage that is 3-4x there size
*grooming every day( or every other depending on the animal)
*fresh food and water and food and water should be at least 1/2 full all of the time
* no negitive attention
And * no risk of death because of an animal test