Brazilian vampire bats are now feasting on human victims in the night. Historically, these hairy-legged vampire bats don’t go anywhere near people, dinner-wise at least. Even more unusual is the fact that their bodies aren’t supposed to be adapted to process mammalian blood.
The bats, D. ecaudata, normally drink the fat-rich blood of birds. Human blood is rich in protein, which makes it a poor meal for the little hairy suckers. In fact, so reluctant are bats to eat the wrong kind of blood that they would rather starve to death than drink wild-pig blood, says the New Scientist.
The bats were studied by a team from the Federal University of Pernambuco in Recife, Brazil, led by Enrico Bernard. They studied hairy-legged vampire bats that in a cave in the Caatinga dry forests in northeastern Brazil. The team identified the makeup of the bats’ meals by examining the DNA in the bats’ feces. They found mostly human and chicken blood.
“Blood-feeding is one of the most specialized foraging habits,” writes Bernard, “as it demands extreme morphological, physiological, and behavioral adaptations.” The bats are highly adapted to their task, which explains why they are such fussy eaters, making even the pickiest three-year-old look like a hungry dog. The bats have sharp incisors and canines to punch holes in their prey, saliva that stops the blood from coagulating, and a digestion system that removes water from the blood for more efficient processing. They can’t store fat, they can’t survive more than two days without a meal, and they feed only once per night.
What, then, made the bats start drinking human blood? Because the bats are so specialized, when their ecosystem goes out of balance, they get desperate. The wild birds that form the bats’ usual diet are reduced in numbers, and the Caatinga region has been invaded by humans, who are subsistence farmers or goat ranchers. That is, the most plentiful sources of food now in the region are people and goats, and apparently, people taste better.
The hairy-legged vampire bats aren’t the only species to feed on humans, not even in the Caatinga region, but this is the first time that such specialized bats have adapted to a new human diet. So, if you’re planning on a visit to the area, you might want to toss some crosses, and some garlic into your luggage along with your mosquito repellent.