MUNICH, Germany, June 19 (UPI) -- German scientists say they've discovered vampire bats -- the only mammals to feed exclusively on blood -- recognize prey by the sound of its breathing.

In a study conducted by Udo Groeger and Lutz Wiegrebe at Ludwig Maximilians-University in Munich, two vampire bats were taught to associate recordings of different humans breathing with different cattle blood dispensers, providing food rewards. They were then played short clips of people breathing and had to associate them with the correct individual by going to the correct dispenser.

The vampire bats were able to spontaneously associate the clips with the particular individuals, regardless of whether the individual was recorded breathing at rest or breathing while under physical strain. Human participants were also able to recognize some clips, but they were unable to recognize the sounds of breathing recorded under physical strain.

The study appears in the open access journal BMC Biology.