Scientists wire bats for sonar secrets

A tiny sensor weighing less than five percent of the bats' body weight is mounted on its back with surgical glue. This allows researchers to record communication and sonar and study its navigational capabilities, said Noam Tzvikel, who has been conducting research on fruit bats under the guidance of Dr. Yovel.

"We've got much smaller GPS than what we used to have so we can record where they have been for a few nights in sequence and not only one or two nights, we can do it for a whole week for example and more than that we also have an ultra sonic microphone on this GPS unit so we can also record the sounds that they make," said Tzvikel as he held up an antenna to track down one of the bats they wired up with the devices.

Bats make up twenty percent of all mammals, more than any other mammal group except rodents. The winged creatures are also known for their "sixth sense" or echolocation - sounds that they emit and then detect as returning echoes - allowing them to navigate, hunt prey and communicate with each other.

The ultrasonic "pings" allow bats to identify an object and its exact location by the sound reflected back from the object. They give bats the unique ability to measure time within hundreds of nanoseconds, while judging the approximate distance within less than a millimetre.

Using a GPS and ultra sonic microphone, the researchers can study those reflecting "pings". They hope their findings could pave the way to new and improved radar systems, which are essentially based on sonar similar to that seen in bats.

"We humans use radar and stuff like that that is based on sonar and we invented it only recently, the bats have it for thousands of years and I believe that we can learn a lot of stuff from them that we don't know for example, bats can distinguish between objects of in one millimetre of distance and they can do a lot of stuff that engineers nowadays, human engineers cannot understand yet," said Tzvikel during field work in a dark cave near the coastal city of Herzliya.

Dr.Yovel said the field of neuroecology will contribute to studies into how the bat's brain controls behaviour. But since most behavioural experiments in neuroscience are performed in a laboratory, in a highly controlled environment, it's difficult to study natural behaviour.

The brain responds differently in natural and non-natural situations, Dr. Yovel explained.

"We are trying to take neuroscience out to the field so we're monitoring bats outside in the field where they are flying in their natural behaviour, it's extremely noisy, it's not a controlled environment and to do this we are trying to develop highly controlled sensors that we can put on the bat and monitor for instance the sensory input coming in. So what we already have and started doing recently is we have a small GPS device that also include an ultra sonic microphone and we're putting these on fruit bats, which are relatively large bats and this allows us now to record a full night behaviour," he explained from a laboratory at Tel Aviv University where his team was conducting an experiment that could potentially bring advances in the fields of sonar, radar and robotics.

Equipped with state of the art recording and imaging systems, the acoustic room in the laboratory allows researchers to examine changes in the bat's nose structure, which reflects the focus, direction and width of the sonar beam.

"We're simultaneously recording, using video to do high resolution imaging of their nose leaf and recording with a very large microphone array to see if there's any change in the structure that correlates to changes in the beam. We hope to show, for the first time, that bats actively form their beams, or change this beam," said Dr. Yovel.

"Bats perform better than any human sonar they do so in several different aspects they use signal designs that radars don't use they have better resolution better accuracy and as I said before, they are autonomous machines so they are able to perform all of this on their own and of course we are always thinking of how we can take this now and implement this in the radar world, to create better sensors, either for radar, for sensor, for robotics or anything else," he said.

The research, Yovel says, could also contribute to understanding the limits and functioning of the brain.

"Another direction is of course more basic science so we are all interested to understand how the brain works. The bat brain is a mammalian brain it's just, you know, if people use rats to study humans, bats are as close to humans as rats, more or less, and we are trying to learn general things about the brain".

In the future, Dr. Yovel says, he is planning to build what he calls an "imprinted colony", an artificial bat-like environment simulating wilderness where bats will be equipped with sensory devices.

"Our plan which we are now trying to fulfil is to establish what I call an imprinted colony, so a colony of fruit bats that will be roosting in our facility in Tel Aviv university but will be every night free to forage outside, so essentially a wild colony. All of the bats in this colony will be mounted with GPS plus microphone sensors that I've just mentioned and then we will be able to ask questions," he said.

Dr. Yovel says he also hopes to mount cameras on the bats and even measure their brain activity for the first time ever with Functional Magnetic Resonance Imaging (fMRI).