Bats Speak Language All Their Own

Oct. 31, 2007 -- Bat calls serve to identify each individual in a group, but twin bat siblings sound so alike that researchers are starting to suspect the calls also carry information about familial relationships.

A new study on the matter, which has been accepted for publication in the journal Animal Behavior, adds to a growing body of evidence that bats are social, vocal creatures able to communicate with each other in complex and detailed ways.

Lead researcher Mirjam Knornschild and her team focused on the calls of Nyctalus noctula, a medium-sized, insect-eating bat from Europe. Only the pups emit the "isolation" calls that were the focus of the study, which are low in frequency and are often repeated in succession, not unlike the repetitive cries of human infants.

"Isolation calls of Nyctalus noctula convey the pups' wish to nurse, their current location and also their individual identity," Knornschild, a researcher at the University of Erlangen-Nuremberg's Institute for Biology, told Discovery News.

She and her colleagues recorded young twin bats from a colony of captive bats at the university. The parents of the twins sustained previous injuries in the wild that prevent them from flying, but otherwise they exhibit normal bat behavior.

The twins were separated from their mothers for a maximum of 15 minutes and placed in a sound-proof chamber, where the recordings were made. The researchers also recorded the isolation calls of other, unrelated pups. Recordings were conducted when all of the bats were 1, 3, 9, and finally, more than 19 days old.

The calls revealed that all baby bats have distinct cries, but twins sound alike. As bats get older, their isolation calls become even more distinctive, but twins retain their vocal connection.