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

Explanation

The notice outside a cage in the zoo at Lusaka, Zambia reads that “The world‟s most dangerous animal.” And inside the cage there is no animal but a mirror where one can see his image. It is a sarcastic way of making man realize how they are responsible for the destruction of so many species which has resulted in the depletion of resources and deterioration of environment. Man is responsible for this and his own survival is threatened.