The vampire bats are the only mammals in the world that live on blood alone, and the unique challenges of that diet make them some of the most specialized, fascinating and downright weird animals that nature has to offer.
For many centuries now, the Bats are firmly rooted in Western vampire lore, as ugly blood drinking creatures though only three species, out of some 1100 in the order Chiroptera, actually have a taste for blood.
The common vampire feeds primarily on the blood of mammals —ranging from tapirs to horses to the occasional human—and seems to have a preference for livestock animals. The hairy-legged vampire, meanwhile, lives almost exclusively on bird blood, while the white-winged vampire is more versatile and drinks from both birds and mammals.
Evolution of Blood Drinking Habit
The bat can drink up to half its weight in blood a day unlike other relatives, which dine on fruit, nectar or insects. When the bats feed, they use their highly evolved teeth to shear away hair or feathers from a small spot and then cut into their victim’s flesh with their sharp incisors. Rather than actively suck the blood from the wound like their namesakes, the bats let the physics of capillary action do the work. They lap at the blood and specialized grooves on their lips, tongues, and/or roof or their mouths suction it up. A protein in the bats’ saliva called a plasminogen activator prevents the blood from clotting and keeps it flowing freely while they drink.
Blood is low in nutrients and can harbour deadly viruses. The researchers say the bat’s gut microbes are also distinct. They found evidence of more than 280 types of bacteria in the bat’s droppings that would have made most other mammals unwell.
“The data suggests that there is a close evolutionary relationship between the gut microbiome and the genome of the vampire bat for adaptation to sanguivory (feeding exclusively on blood),” said study author, Dr Marie Zepeda Mendoza of the University of Copenhagen in Denmark.
Vampire bats have key differences in genes involved in immunity and food metabolism compared with other bats. International researchers analysed both the genome of the vampire bat and its microbiome – the microorganisms that live inside the gut. They found that genome size was similar to that of other bats but the genome contained more “jumping genes” (DNA sequences that change position in the genome).
These were found in areas involved in immune response, viral defence, and both lipid and vitamin metabolism, suggesting they have played a key role in the evolution of the bat’s specialised diet. The microbiome of vampire bats is completely distinct from that of nectar-feeding, fruit-eating, and meat-eating bats, they say.
The researchers argue that microorganisms in the bat’s gut may also be involved in digestion, immunity and overall health, and have evolved alongside changes in the genome. “Adaptation to specialised diets often requires modifications at both genomic and microbiome levels,” they say in the journal, Nature Ecology and Evolution.