Bat prevent them from spending too much time in unfamiliar places, and decrease predation. In some species, pregnant individuals may not use torpor. The smallest bat is Kitti's hog-nosed bat ("Craseonycteris thonglongyai"), which is long with a wingspan and weighs . It is also arguably the smallest extant species of mammal, next to the Etruscan shrew. The largest bats are a few species of "Pteropus" megabats and the giant golden-crowned flying fox, ("Acerodon jubatus"), which can weigh with a wingspan of . Larger bats tend to use lower frequencies and smaller bats higher for echolocation; high-frequency echolocation is better at detecting
Robert Galambos generate and hear sounds an octave higher than can be heard by humans and other animals. Experiments they conducted used methods developed by Hallowell Davis to monitor the brains of bats and their hearing responses as they navigated their way past wires suspended from a laboratory ceiling. They showed how bats used echolocation to accurately avoid obstacles, which they were unable to do if their mouths or ears were kept shut. Griffin coined the term "echolocation" in 1944 to describe the phenomenon, which many physiologists of the day could not believe was possible. Using electrodes implanted in the brains of