Vampire bats are known to suck blood from animals. Now, the nocturnal animals have a new menu on its list - human blood!

Vampire bats typically prey on animals such as birds but this time it seems that it is not content with its former food and looked for a new menu. This behavior of bats sucking human has raised health concerns especially for the victims.

A team from the Federal University of Pernambuco in Recife, Brazil led by Enrico Bernard examined samples of 70 vampire bats' faeces from the hairy-legged species, D. ecaudata. These bats are usually found existing in Catimbau National Park in north-east Brazil.

Bernard's team discovered that three samples from the 15 samples where they were able to get DNA contain traces of human blood.

"We were quite surprised. This species isn't adapted to feed on the blood of mammals," Bernard said.

Generally, these vampire bats species aim at big birds during night-time, sucking the blood of about a spoonful from one animal. They were able to modify the fat which is the major ingredient of bird blood in contrast to the thicker mammal blood that is rich in protein, News Scientist reported.

The researchers are certain that human disturbance in the national park has driven the vampire bats to attempt on the blood of mammals.

According to the researcher's note published in Acta Chiropterologica, "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."

Mail Online reported that aside from traces of human blood found in the faeces samples, there are also traces of chicken blood. Researchers also believe that these type of vampire bats intrude through small holes in the roof or windows or just target people sleeping outside their home especially campers.

The species' new habit became a concern because it could spread disease since vampire bats are main transmitter of rabies. Besides, there are always outbreaks in Brazil. Previous studies discovered that they carry the hantavirus that could cause a fatal respiratory disease in humans. More information about how vampire bats bite humans will help evaluate the public health risk.