Bats' Power of Echolocation Allows Them to Rule at Night
The power of both echolocation and vision has given bats an evolutionary edge over other nocturnal bird species making them the rulers of night, Tel Aviv University researchers revealed in a press statement.
According to the researchers, bats use their normal vision to see where they're going and their echolocation ability to catch smaller insects that other nocturnal birds can't see at night.
"Imagine driving down the highway: Everything is clear in the distance, but objects are a blur when you pass them," said Dr. Arjan Boonman from Tel Aviv University's Department of Zoology in the statement. "Well, echolocation gives bats the unique ability to home in on small objects - mostly insects - while flying at high speeds."
Bats do most of their feeding at dusk because there is enough light and insects are more active. They use their vision for hunting during this time because it provides more information about their prey. This led researchers to wonder why bats developed echolocation abilities if they already had vision. To answer this question, researchers conducted a test to see at what distance these senses were able to detect objects.
To estimate the range of ultrasonic bat echolocation, the researchers played taped calls of two species of bats in a soundproof room and recorded the way the sound bounced off four dead insects - a moth, an ant, a lacewing, and a mosquito. Since vision is hard to simulate, researchers used the data of two previous studies and calculated the distance at which bats would be able to see the same insects in medium to low light.
The results showed that echolocation was twice as effective as vision in detecting objects in medium to low light. Echolocation can detect objects at a distance of 40 meters compared to 20 meters by vision.
Echolocation gives bats an added advantage over other nocturnal birds allowing them to catch insects more accurately during feeding time. Even after peak hunting hours, when the night fades, bats can continue feeding unlike other birds that are blinded.
One drawback of echolocation is that it is poor at detecting larger objects at a distance. This is where vision out-performs the sound-based sense.
"We believe that bats are constantly integrating two streams of information - one from vision and one from echolocation - to create a single image of the world," said Dr. Yossi Yovel, also of TAU's Sagol School of Neuroscience. "This image has a higher definition than the one created by vision alone.
Currently, there are more than 1,000 species of bats, compared with just 80 species of non-echolocating nocturnal birds. Bats account for 20 percent of all classified mammal species on earth today.