Before inserting its razor sharp teeth into an unsuspecting animal each night, a vampire bat must find the best place to bite — an area that will keep the blood flowing. But how does it know where to bite when blood pulsing through another creature’s body isn’t outwardly visible?

Vampire bats (Desmodus rotundus) have a highly specialized neural system in their noses that help them target where to suck the blood from animals they feed on, according to research by UC-San Francisco scientists.

Think of it as infrared night vision, where a bat senses heat emitted from areas of an animal’s body where there’s more blood flow.

No wonder these bats survive on blood alone, sometimes drinking half their body weight of the stuff in one sitting. Vampire bats also take advantage of anticoagulant chemicals in their saliva that keep the blood flowing once feeding starts.

For years, researchers knew something in the bats’ noses helped them achieve this, but it wasn’t until now that the mechanism became clear. Vampire bats have a molecule called TRPV1 that regulates a bundle of nerve cells in their faces. In humans, TRPV1 is activated when we eat certain spicy foods such as hot chili peppers or to sense intense thermal stimuli like getting sunburnt.

Since the molecule plays a role in types of burning and pain sensation in humans, scientists want to learn more about how it functions to better develop drugs that target it.

To take a better look at how the process works, the team gathered tissue samples from deceased vampire bats from Venezuela, discovering the bats benefit from a genetic phenomenon called RNA splicing that allows genes to produce multiple proteins with different functions. In vampire bats, splicing has resulted in a form of TRPV1 that helped them target where to bite prey, which was likely a favorable trait that helped them survive.

Though other animals have the same genes that produce TRPV1, they do so differently, and the process isn’t as pronounced as in vampire bats. After comparing the genes responsible for thermal sensing to those of other mammals, scientists found that vampire bats were more similar to horses, dogs, cows, moles and dolphins, and more distant to humans, rodents, monkeys and flying lemurs, challenging the idea that bats are closer to our side of the mammal family tree.

Occurring only in Central and South America (sorry, Romania), vampire bats are the only known mammals to have this type of infrared sensing. Other animals such as pit viper snakes can “view” the world through heat as well.

Photo by Dr. Pascual Soriano/Universidad de los Andes