I am not sure where you got your quote but it is rather amusing.
The cock represents greed perhaps because he has quite a few wives in the chicken coop.
The snake represents anger perhaps because it can be quite vicious when provoked.
The pig represents stupidity perhaps because he is more concerned about eating and is so blissfully ignorant of his imminent demise. Such is the nature of ignorance as described by the Buddha: we are blissfully ignorant about the great matter of life and death.
That is why we keep revolving in the Wheel of Reincarnation. We are in great suffering and do not know how to end it. We often experience great pain during Birth, Aging, Sickness, and Death. That is why the Buddha’s first teaching was of the Four Noble Truths, to help us end suffering and attain liberation and bliss.