Chupacabra Goat Sucker

Chupacabra is like a vampire, they suck the fluids out of the animal. They attack goats, chickens, pigs, all the, all the little livestock. The government got a hold of them, did some manipulation with genetics and unleashed them in Puerto Rico. I think it's just something that hasn't really been seen on earth before. How come there were no witnesses? Why not?