A new study published in December in the journal Acta Chiropterologica and first reported in New Scientist finds that the bats have started to feed on human blood, something scientists didn’t even think was possible. As people have started to move into the Caatinga dry forests of northeastern Brazil, they’ve been cutting down trees and hunting the tinamou and guan birds these bats would normally drain for a meal.

So a group of researchers from the Universidade Federal de Pernambuco in Recife, Brazil, decided to test the bats’ feces to see what they’d been eating as their normal meal sources disappeared, thinking they may have decided to turn to the animals that humans bring with them. DNA analysis showed they’d been consuming chicken blood — not a big surprise. But it also showed that the bats had been preying on humans. “We were quite surprised,” Enrico Bernard, who led the study, told Sandrine Ceurstemont of New Scientist. “This species isn’t adapted to feed on the blood of mammals.”