Circus Animals

Should animals serve to entertain us?
Seeing as circus creatures are treated badly many times, but still experience acts of kindness by trainers when they are rewarded for achieving a performance. Even if a circus owner is nice, should we still have animals entertain us? They are bound by rules of entertainment and will no doubt be punished if they attack a human being in the audience or observer. What makes these animals want to attack? Do they understand the idea of freedom? If elephants are smarter than other animals, should we treat them better versus other animals? In our human society, we usually treat people who are more talented better by paying them more and rewarding them more. Therefore, should we do the same for animals to apply fairness?