As well as being staples of horror movies since forever, vampire bats are evolutionary marvels. Now scientists are slowly starting to decode exactly how these animals survive by feasting on blood.
Feeding exclusively on blood requires a high degree of specialization. Not only have the bats evolved the tools for the trade – teeth that let them pierce the skin of their meal and shave away any hairs or feathers beforehand, and the ability to distinguish individuals from their breathing patterns alone – but also the capability to live off blood itself.
Blood is not a good food source. While it might be high in protein, it is low in pretty much all other essential nutrients, like carbohydrates and vitamins. In addition to that, such large volumes of liquid – vampire bats can drink up to half their weight in blood every night – also puts monumental strain on their kidneys and bladder. As if that wasn’t enough, blood also tends to be full of deadly bacteria and viruses.
Yet despite all this, three species of bat have managed to overcome these issues and are now the only mammals known to dine exclusively on the red stuff. How exactly they have managed to evolve this feat is still something of a mystery, something that the authors of this latest study has attempted to solve by delving into not only their genome, but also their microbiome, publishing their results in Nature Ecology & Evolution.
They found that the common vampire bat has key differences in the genes related to immunity and food metabolism compared to the 1,200 other species of bats that have diets filled with fruit, meat, or insects. This includes certain bits of DNA, known as transposable elements, which are able to shift their position on the chromosome, being concentrated in the region that dictates immunity, as well as differences in genes that process high levels of iron and nitrogen.
These genetic adaptations are coupled with a highly distinctive gut microbiome. By studying the poop of the bats, they were able to identify up to 280 different bacteria that make up the ecosystem in the bats’ intestines, many of which would cause sickness if found in most other mammals.
“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],” study author Dr Marie Zepeda Mendoza, told the BBC.
They think that these changes at both the genetic level and that of the microbiome might have worked in conjunction to allow the animals to make their shift towards feeding exclusively on blood. One suggestion is that perhaps the animals moved from feeding on insects to focusing on blood-sucking parasites such as ticks, before going fully sanguivorous some 4 million years ago.