Vampire Bats Smell & Find Blood With Heat-Detecting Noses

The vampire bat, Desmodus rotundus, must find a blood meal every 1-2 days to survive. Razor sharp teeth and infrared-sensing "pit organs" surrounding its nose help the bat achieve this goal. (Dr. Pascual Soriano)

Count Dracula used his piercing eyes to mesmerize his victims. Vampire bats, researchers say, rely on sensors nears their nose.

Researchers in California and Venezuela say they have figured out how vampire bats know exactly what spots to bite to draw the most blood: they have heat-detecting noses.

Vampire bats have sensitive nerves on their nose, called TRPV1, that guide them to the best spots on an animal’s skin – where their razor-sharp teeth could rupture a vein and suck the blood. The study, by researchers from at the University of California, San Francisco and Instituto Venezolano de Investigaciones Científicas in Caracas, Venezuela, investigated wild vampire bats in South America.

"Vampire bats feed on blood, and it's useful for them to have an infrared detector to be able to find the circulation," said David Julius, the Morris Herzstein Chair in Molecular Biology & Medicine at UCSF, who led the research.

Vampire bats, which are nocturnal and feed solely on blood, are common in South America.

The finding, published this week in the journal Nature, illustrates how a small change to a genome of a species can allow the vampire bat to detect infrared heat from their prey, allowing them to find and feed on blood.

It also allows researchers to learn more about pain because their receptors are similar to human ones that sense heat and pain. Figuring out how the bats adapt to these sensors could be useful in finding ways to treat chronic pain.

"There is a double-edged sword with pain," Julius said. "Pain is necessary as a warning system to let us know when we are in danger of injury but, at the same time, pain can outlive its usefulness as a warning system when it fails to resolve and becomes chronic and debilitating."

Rodent-like Features

Vampire bats look like rats with wings, though they are evolutionarily grouped with horses, dogs, cows, and dolphins. They sneak up on sleeping prey, usually animals like birds and cows though sometimes humans, with a swooping gallop and leap.

They are the only known mammals that survive on blood, and need it every day to stay alive. Their teeth stay razor sharp, and can sink their teeth into an animal without waking them. Within minutes, they can drink half its body weight in blood.

But the bat must find the right spot to bite to draw the most blood – they have to tear into a vein that pumps a lot of blood – and for years researchers couldn’t figure out how they found it.

The UCSF researchers worked with scientists in South America, who took samples from vampire bat’s nose tissue. They found that TRPV1, their sensitive receptors, was able to detect heat. In their study, they said a special molecule emerged in the noses of the bats, helping them find the hottest and bloodies spots on the body.

Very few other animals possess this “sixth” sense, though pythons and boas are able to detect blood heat as well.