Vampire bats use infrared sensors to help them find veins when hunting their prey, according to new research.
A nerve channel sensitive to heat on the bats' faces enables them to detect infrared radiation given off by warm-blooded animals, and use the information to detect "hot spots" on their bodies where veins are close to the surface.
In other bats this channel is "tuned" to temperatures above 43C but in vampire bats it activates at 30C, meaning it can detect infrared radiation, according to a study in the Nature journal.
They are the only known vertebrates apart from three species of snake – pythons, boas and pit vipers – which have this capability.
Humans have similar molecules on nerve fibres in their tongues, skin and eyes which sense pain when they come into contact with capsaicin, a chemical in chilli peppers.
But vampire bats have evolved to turn the nerves into a sensor for heat rather than pain.
Dr David Julius, one of the researchers from the University of California, San Francisco, said: "Vampire bats feed on blood, and it's useful for them to have an infrared detector to be able to find the circulation."
They use their special sense to find the best spot to bite before releasing chemicals into the wound to prevent the blood from clotting, and drinking it with the help of grooves on their tongues.