I agree that the people that hoard animals are usually mentally ill.
I've seen some of this on Animal Precinct and Animal Cops. It's just so sad because they usually have to put all of the animals to sleep since they're either very sick or extremely feral. BTW one of the people that was doing this was a man. He had taken in a pregnant stray cat and before he knew it he had about 300 cats. He couldn't even live in his house any more so he had moved into his shed in the back yard. The investigators think that he had serious mental problems. Needless to say all of the cats had to be put to sleep.