Sugar-free. Gluten-free. Paleo. Keto. Low FODMAP. Of all the diet trends in the world, none is more extreme than the high-iron, low-fat, low-carb diet of the vampire bat, the only mammal in existence that can survive on blood alone — and now we know how!

According to a study released in Science Advances on March 25, vampire bats have been gradually ditching genes over the past million years, causing them to develop a range of behaviors and physical characteristics that make it possible for them to survive on a diet that nightmares are made of.

What’s Lost Cannot Be Found

When comparing the genomes of the vampire bat to 26 other bat species, genomicist Michael Hiller of the Max Planck Institute in Germany and his colleagues found that the parasitic species had lost genes over time.

Of these lost or inactive genes, three were previously reported in the species and are associated with taste receptors in other animals, leading the researchers to believe the bats can drink so much blood because they can’t really taste it.

The other 10 missing genes are newly identified in the bats, but based on how they function in other animals, researchers believe their absence has contributed to the vampire bats maintaining a bloody diet as they have been found in animals to help control insulin levels, convert sugar, and break down solid food.

One of the genes is known to inhibit iron intake in other animals, but without it, the bats can hit the bloody bar hard. Even though they measure only 3 inches long and weigh about the same as a single AA battery, vampire bats typically consume 800 times more iron than the average human!

Lapping it Up

Unlike their namesake monsters, vampire bats don’t want to suck your blood — they lick it up instead! Native to South and Central America, the three blood-thirsty vampire bat species swoop around searching for livestock to feed on, puncturing the animals before letting the blood pool so they can lap it up.

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Though it was once believed that the bizarre bats preferred the taste of bird, pig, and goat blood, in 2017, researchers at the Federal University of Pernambuco in Brazil studied the feces of their local bat population only to find that over 20% of the guano included traces of human blood!

Despite the fact that they’re not out to drain the life out of your body, it’s still best to sleep with one eye open if you find yourself in the company of a vampire bat, as they can spread disease. These sneaky suckers hunt in the night and are likely to get you while you’re sleeping, coming through holes in roofs or biting people camping in the rainforest — and you can guarantee they’ve got friends!

Blood Donations Are Key to Their Survival

Since blood is extremely low in calories and nutrients, it takes a decent amount to keep these tiny bats thriving. A single vampire bat can guzzle down as much as 1.4 times their own weight every time they eat!

Pregnant Vampire Bat

This vampire bat is technically pregnant, but we imagine this is how one would feel after eating 1.4 times its body weight in blood.

Despite being out for blood, vampire bats are sociable creatures and form long-term bonds with their fellow bats in the wild. Since they are susceptible to starvation, they have no problem spreading the blood with their friends via regurgitation, though they are more likely to do so with bats who have donated to them before. Sharing is caring, after all!

By Meghan Yani, contributor for


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