Nature’s sonar system, echolocation, happens when an animal emits a sound wave that bounces off an object and returns an echo that provides information about the object’s distance and size.
More than a thousand species echolocate, including most bats, all toothed whales, and small mammals. Many are nocturnal, burrowing, and oceanic animals that rely on echolocation to find food in an environment with little to no light. Animals have several methods of echolocation, from the twitching of their throats to the flapping of their wings.
Nocturnal oilbirds and some swifts, some of which hunt in dark cave environments, “produce short clicks with their syrinx, the vocal organ of birds,” said Kate Allen, a postdoctoral fellow in the Department of Psychological and Brain Studies at John Hopkins University. by email.
Some people can also echolocate by clicking their tongue, a behavior only shared by a few other animals, including tenrecs, a shrew-like animal from Madagascar and the Vietnamese pygmy dormouse, which is basically blind.
Bat signals
Bats are the ultimate echolocation poster animal, using their built-in sonar to chase fast flying prey at night.
Most bats, like the tiny Daubenton bat, contract their laryngeal muscles to make sounds that are out of human hearing – the tapped equivalent of a scream, Allen says. (Related: When it comes to echolocation, some bats just fly it.)
Bat calls vary wildly between species, which allows them to distinguish their voices from other nearby bats. Their calls are also specific to a particular environment and prey: the European bat “whispers” in the presence of moths to avoid detection.
However, some moths have developed their own defenses against echolocating bats. The tiger moth flexes the tymbal organ on either side of its thorax to produce clicks, which block the bat’s sonar and keep predators at bay.
As expert echolocators, some bats can target objects as small as 0.007 inches, about the width of a human hair. Because insects are always on the move, bats have to click continuously and sometimes make 190 calls per second. Even with such a difficult quarry, the predators can still eat half their weight in insects every night.
Leaf-nosed bats make echolocation calls through their large, intricately folded noses, focusing sounds that bounce back. Some species can also quickly change their ear shape to accurately pick up incoming signals.
A few fruit bats, like the South Asian little dawn bat, even click by flapping their wings, a recent discovery.
Watch a bat use echolocation in total darkness
A slow motion video shows a Macroglossus fruit bat zero in on a perch during an experiment.
Ocean sound waves
Echolocation is a logical strategy in the ocean, where sound travels five times faster than in the air.
Dolphins and other toothed whales, such as the beluga, echolocate through a specialized organ, the dorsal bursae, located at the top of their heads, close to the blowhole. (Learn how whales have a “sonar beam” to target prey.)
A fat deposit in this area called the melon lowers the impedance or resistance to sound waves between the dolphin’s body and the water, making the sound clearer, says Wu-Jung Lee, a senior oceanographer at the University of Washington Applied Physics Laboratory .
Another fat deposit, stretching from a whale’s lower jaw to its ear, brightens the echo returned from prey, such as fish or squid.
A favorite prey of orcas, harbor porpoises make extremely fast, high-frequency echolocation clicks that their predators cannot hear, which can keep them incognito.
Most echolocation sounds from marine mammals are too high for humans to hear, with the exception of sperm whales, killer whales, and some dolphin species, Lee added.
Navigate by sound
In addition to hunting or self-defense, some animals echolocate to navigate their habitats.
Large brown bats, for example, which are widespread across America, use their sonar to navigate noisy environments, such as forests buzzing with other animal sounds.
Amazon river dolphins can also echolocate to move around tree branches and other obstacles caused by seasonal flooding, Lee says.
Most people who echolocate are blind or partially sighted and use the skill to perform their daily activities. Some click, with their tongue or with an object, such as a stick, and then navigate through the resulting echo. Brain scans of echolocated people show which part of the brain processes vision during this process. (Read how blind people use sonar.)
“Brains don’t like undeveloped real estate,” says Allen, so “it’s metabolically too expensive to maintain” echolocation in people who don’t need it.
Still, humans are remarkably flexible, and research shows that with patience we can learn to echolocate ourselves.