Bats’ hunting signals revealed
22 Sep 2015 by Evoluted New Media
By using images derived from echolocation, researchers have discovered that bats use the changes in sound profile to locate prey.
Scientists at Queen Mary University of London (QMUL) used acoustic tomography and found that bats not only detect echo-acoustic changes but also learn the layout of their habitat, down to the surface of individual leaves and stones.
“We constructed a brand new technique for tomographic imaging which allows us to perceive more accurately which cues are most important to the bat,” said research associate Dr Marc Holderied.
In the study, published in the journal eLife, the team used the new imaging technique to observe how bats catch their prey. To create this technique they combined measurements of the duration and amplitude of echoes with objects profile and acoustic changes cast by insects.
After applying the novel acoustic tomography the scientists converted echoes into visual representations to compare these cues to traditional echo measurements. They found that insects can interrupt the bats’ well-known environment by creating an ‘acoustic shadow’, sending a strong signal to the hunting bat. They believe that most bats hunt by detecting the movement of insects using echolocation.
Research leader Dr Elizabeth Clare from QMUL said: “Using information like X-rays to build pictures is well established in medicine with the use of CT scans and ultrasound, but no-one has ever before attempted to create images from sounds generated in ecology.”
Also, the researchers found that bats find it easier to detect insects on flat surfaces and hardest to detect prey on rough bark. They refer to this phenomenon as ‘acoustic camouflage’, employed by hunted prey to elude the elite hunters.
“Our findings also suggest a new phenomenon of acoustic camouflage, where insects are harder to discern on rough surfaces such as bark, and bats compensate for this by focusing their attention on the simpler, mirror-like surfaces in their patch,” said Dr Clare.
