What does the notice “The world’s most dangerous animal” at a cage in the zoo at Lusaka, Zambia, signify?

The notice placed at the cage in the zoo at Lusaka, Zambia read “The world’s most dangerous animal.” There is no animal in the cage. There is a mirror in it. One sees his own reflection in the zoo. It signifies that man himself is the most dangerous animal. He is responsible for the deterioration of ecology and environment.