Yeah I don't get why they felt like they HAD to nerf this. Seeing a little butterfly in someone's tower was kinda cool.
It's not like you could have very many animals in a tower to begin with, considering the width of the area is very short. The population limit would be insanely tiny in that case.
Also, seems the people who already had animals in their towers get to keep their animals. The rest of us who haven't managed to get a tower up and running yet won't get to have that same luxury.