Wild vampire bats in Brazil that are believed to exclusively feed on bird blood have started to feed on human blood by night.
Better Adapted At Processing Bird Blood
The hairy-legged vampire bat, Diphylla ecaudata, which lives in northeast Brazil typically targets large birds to feed on at night time.
The bats primarily feed on birds because they have evolved to be better at processing bird blood, which is characterized by high levels of fat, than at digesting the thicker and high-protein blood of mammals. The nocturnal animals would suck a spoonful of blood from one animal as meal.
Earlier experiments have shown that many of the bats would opt to fast and starve to death when only pig and goat blood was available.
Enrico Bernard, from the Federal University of Pernambuco in Recife, Brazil, and colleagues, however, have found evidence suggesting that the bats have started to eat something that is outside of their traditional diet.
Traces Of Human Blood In Fecal Samples
Bernard and colleagues analyzed fecal samples from a colony of the hairy-legged vampires that live in Catimbau National Park in northeast Brazil. The researchers found that of the 15 samples that they managed to get DNA from, three had traces of blood from humans, suggesting that the animals have started to suck on human blood.
Domesticated Chickens As Alternative To Large Wild Birds
The researchers also found that most of the samples had traces of chicken blood. Chickens are commonly kept on farms and these domesticated birds became a tempting alternative for the large wild birds that are declining in numbers. The traces of chicken blood in the samples suggest that the bats are exploiting new resources in a bid to adapt to their changing environment.
Humans To Blame For Changes In Feeding Behavior Of Vampire Bats
The researchers said that human activities are likely to blame for the changes in the bats' diet. Humans increasingly inhabit the forests and bring domestic animals with them. As a result, birds such as the guans and tinamous, whose bloods are the favored food of the vampire bats are driven out of the area.
"The record of humans as prey and the absence of blood from native species may reflect a low availability of wild birds in the study site, reinforcing the impact of human activities on local ecological processes," the researchers wrote in their study, which was published in Acta Chiropterologica.
Changing Feeding Behavior Of Vampire Bats May Pose Health Risk
The changing feeding behavior of the bats though raises health concern since the flying animals are known to transmit rabies in Brazil. In 2005, outbreaks killed 23 people in northern Brazil in just two months.
Daniel Becker from University of Georgia in Athens who studies vampire bats in agricultural areas think it is necessary to investigate the infectious diseases that are carried by the species especially that bats have been known to carry hantavirus. The virus can cause respiratory disease in humans and can be potentially deadly.
