How vampire bats survive on an 'extreme' diet of just blood

If you want to know howvampire bats can survive on a diet that as everyone knows consists exclusively of blood, the answer is simple. It's intheir genes.

Scientists on Monday said they have mapped for the firsttime the complete genome of a vampire bat, finding that thisflying mammal boasts numerous genetic traits that help it thriveon an exotic food source that offers nutritional disadvantagesand exposes it to blood-borne pathogens.

The researchers compared the genome of the common vampirebat, scientific name Desmodus rotundus, to genomes ofbatspecies that eat nectar, fruit, insects and meat. They alsoexamined microbial DNA from its droppings.

This bat and the world's two other vampire bat species, thehairy-legged vampire bat and the white-winged vampire bat, arethe only mammals that eat just blood.

The common vampire bat, a nocturnal cave-dweller with a7-inch (18-cm) wingspan, inhabits parts of Mexico, CentralAmerica and South America. It feeds on the blood of livestock such as cattle and horses. It lands near prey under cover ofdarkness, walks on the ground, then feeds on the sleeping animalusing razor-sharp teeth to pierce the skin and a lengthy tongueto lap up flowing blood.

"We decided to study this species because it has an'extreme' diet, in the sense that it requires many adaptationsin the organism to live on that," said study lead author Lisandra Zepeda, a University of Copenhagen doctoral studentwhile doing the research published in the journal Nature Ecology & Evolution. "Blood is a challenging dietary source since itprovides very low levels of vitamins and carbs, and a lot ofproteins, salts and waste products."

They pinpointed genome elements that augment the bat'simmune response and viral defense to cope with pathogens lurkingin blood. They also identified genes involved in the metabolismof vitamins and fats that could help the bat deal with theunique nutritional aspects of its blood diet.

To some people, vampire bats are creatures of dread,associated with fictional vampires like Dracula.

"Yeah, they're messed-up creatures, or amazing creatures,whatever you want to call them," Zepeda said. "My personal
feelings about them is that it's too bad people demonize themlike that. We should be amazed by them, not scared. They'reactually quite cute: abstract beauty. Sure, you don't want themto bite your cows if you're a farmer, but they were there waybefore you."