I noticed that animals do get bounty on their heads the same as people (not sure if that's how it supposed to be) and even when they're dead you can still carry them to the prison and jail them (they appear to be standing in the cage even when they're dead) and get money for that.
I am not sure if "bounty on animals" thing is a bug but the fact that they're standing when they're dead is clearly a bug.
Hope it helps
Ps. I freaking love you for making a game like that!
Ps2. Apologies for any mistakes in my writing. I still learn english :p