As if flying around in the dark swooping and diving to catch insects was not tricky enough, bats also listen for their fellow hunters.
A study has revealed how these winged mammals recognize other bats’ voices. They are able to differentiate the ultrasonic “echolocation” calls that other bats make as they navigate. In the journal PloS Computational Biology, the scientists report that the bats have an internal reference call to which they compare others.
Yossi Yovel from the Weizmann Institute of Science, Isreal, and hiscolleagues in Germany recorded the echolationcalls of five greater mouse-eared bats
The bats use these brief bursts of sound in sonar navigation – bouncing sound waves off their surroundings to find their way and locate prey.
Dr. Yovel’s team tested the bats’ ability to identify the othes by playing the recorded to them.”Each bat was assigned two others it had to distinguish between”, Dr. Yovel explained. “So we trained bat A on a platform, playing a sound from bat B on one side and from bat C on the other. He had crawl to where the ‘correct’ sound was coming from”. Each of the subjects was taught that a call from just one of the other bats was correct. So during this training exercise, if bat made the right choice, and crawled towards the sound of bat B, it was rewared with it’s favourite food – a mealworm.
“The in the next stage – the test – we rewarded them no matter what choice they made, and they still chose correctly more than 80% of the time”, said Dr. Yovel. “So we knew the bats were able to distinguish individuals. But it wasn’t clear what they’re using to distinguish one from the other.
“If you think of this in comparison with humans, it’s like being able to recognize a person just by listening to the same one syllable yell in different voices. “The bats learnt the voice by listening to hundreds of very short ‘yells’, but were then able to recognize an individual based on one single yell.”
Modelling sound. In the second part of the study, Dr. Yovel’s team designed a computer model to mimic the way in which the bats compared with different sounds. “The model takes all the calls the bat thought were A, and all the calls it thought were B, and tries to understand what differences it is using to match them up,” said Dr. Yovel.
“Our analysis showed that each bat as a typical distribution in the frequencies it emits, probably a result of the differences in each animal’s vocal chords.” He thinks the bats may have an internal “prototype” – a sort of reference sound against which they can compare these subtle differences.
This could explain how bats remain in a group when flying at high speeds in darkness, and how they avoid interference between each others’ echolocation calls. – Victoria Gill; BBC
Sign up for our Vakacha Bird Watching Tour Package and experience a bat cave in the outskirts of Lusaka, which is just about 30 minutes drive. You will spend the whole day at the bat cave in the bush viewing the bats and other birds(unforgettable memories of the bats, excellent pictures, great adventure in the wilderness just a few kilometres from the capital).
