Bat's Vision and Echolocation Empower Them to Be Top Nocturnal Predators

Not only are bats creatures of the night, when they take flight they are dominant hunters in the sky, with more than 1,000 species of the echolocating nocturnal mammals flying around the world, compared to just 80 species of non-echolocating nocturnal birds. Researchers from Tel Aviv University, suggest bats dominate the nighttime hunting because of an evolutionary edge provided by having both normal vision and echolocation abilities that allow them to hunt food most other predators can't see.

"Imagine driving down the highway: Everything is clear in the distance, but objects are a blur when you pass them," said Arjan Boonman of TAU's Department of Zoology."Well, echolocation gives bats the unique ability to home in on small objects -- mostly insects -- while flying at high speeds."

But one puzzling aspect of bats on the hunt is how they utilize both vision and echolocation to track down prey.

To determine an answer to their question, the research team compared the distances at which a bat's vision and echolocation are able to detect various sized objects in a variety of lighting levels. In a soundproof room, the team recorded the way the bat's echolocation noise bounced off the carcasses of four types of dead bug.

They found that echolocation was twice as effective as vision in detecting the insects in medium to low light. Bats' night vision was only effective no more than 20 feet away, while the echolocation was effective up to 40 feet away.

Echolocation gives bats a huge advantage, the researchers said, because they can track insects from farther away with greater accuracy at peak feeding time. Then, once darkness falls, bats are able to keep on hunting when their competitors are blinded by the night.

However, the team found that echolocation is poor at detecting large objects at a distance. Here, vision out-preforms echolocation, being able to spot large objects in the fields at distances several orders of magnitude greater than echolocation.

"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 Yossi Yovel of TAU's Sagol School of Neuroscience. "This image has a higher definition than the one created by vision alone."

Yovel and Boonman published their work in the journal Frontiers of Physiology.