El Chupacabra's Cousin Camazotz
Long before the birth of Christ, the indigenous people of Mexico and Central America were telling tales of a creature called Camazotz, or the "death bat." The Zapotec Indians of Oaxaca, Mexico, spawned a cult that worshiped an anthropomorphic bat-headed monster named Camazotz associated with night, death, blood, and sacrifice; the Quiché, a tribe of Maya, adopted the dark deity into their own pantheon, associating it with their god of fire, Zotzilaha Chamalcan.
According to Popol Vuh, a sacred Mayan book, Zotzilaha was not a god at all, but was instead a cavern known as "The House of Bats." The cavern was home to a dangerous bat-creature called a camazotz; one of whom famously decapitated the hero Hunahpú. It's possible that these myths and legends of vampiric camazotz helped inform today's stories of the bloodthirsty chupacabra, at least in Mexico and the southwestern United States, or even that they describe a previously unknown or hidden species responsible for the reported sightings in those areas; although most archaeologists blame the common vampire bat (Desmodus rotundus) for ancient belief in the death bat.