Vampire bats are the only mammals that feed solely on blood—an odd and potentially dangerous diet. Blood is very low in vitamins and high in protein, making it difficult for the kidneys to digest. The bats’ snack of choice also threatens to expose them to deadly pathogens, and scientists have long wondered how the critters manage to live on blood and blood alone.
According to Veronique Greenwood of the New York Times, a new study has started to unpack the mystery surrounding vampire bats’ diet. A team of researchers, led by Marie Lisandra Zepeda Mendoza of the University of Copenhagen, used vampire bat droppings to analyze the blood-thirsty mammals’ DNA and microbiome. They found that vampire bats have evolved a unique relationship between their genome and gut bacteria, which helps them safely lap up smorgasbords of blood.
Many of the adaptations that facilitate vampire bats’ bloody feasts have been well studied, as Carrie Arnold of National Geographic points out. The bats have sharp teeth that allow them bite into flesh, their saliva contains an enzyme that stops blood from coagulating, and they have special facial nerves that help them sense the heat of their prey’s veins. Little research, however, has been done into vampire bats’ “hologenome”: the entire set of genes, including bacteria and other microbes that reside within an organism.
Mendoza and her team compared the DNA and microbiomes of three species of vampire bats to those of bats that subsist on insects, fruit or meat. The results of their study, which was published recently in the journal Nature Ecology & Evolution, revealed that vampire bats have a unique composition of gut bacteria. According to Helen Briggs of the BBC, researchers found 280 types of bacteria in the bat’s droppings that would make most other animals quite sick. Vampire bats’ gut microbes also performed different kinds of tasks, focusing on breaking down proteins and producing vitamins that the bats do not get from their diet.
Though the size of vampire bats’ genome is similar to that of their relatives, researchers found that vampire bats boast an unusual number of transposons, or “jumping genes,” which are able to change positions in the genome. As Briggs reports, these genes were primarily found in areas involved in metabolism, immune response and viral defense, which might explain why bats are not made sick by the blood that they drink.
The bats also seem to have special genes to resist some viruses. As Arnold reports, the bats can hold off a group of viruses found in blood that insert copies of their own DNA into their host's genome.
The study shows that there is “a close evolutionary relationship between the gut microbiome and the genome of the vampire bat,” Mendoza tells Briggs of the BBC. The data also suggests that analyzing both DNA and gut bacteria can be vital to understanding how animals with strange diets function.
But even with their new insights into vampire bats, researchers find the blood-sucking mammals somewhat mystifying. As Mendoza tells Briggs, "I usually call them 'messed-up creatures.'"