More than 200 years ago, bats were totally baffling to scientists. Observers could tell that the furry mammals were expert fliers. They maneuvered silently through complete darkness with stunning precision. They even nabbed tiny bugs as they fly through the dark. The problem was, no one could figure out how they were doing it!
The other confusing thing that scientists noticed: when they placed wax in the bats' ears, the animals turned into complete klutzes. They bumbled through the air, colliding with walls and objects. Why would bats need their ears to navigate? They weren't making any sounds as far as the scientists could tell. 🤔
It wasn't until many years later that we got an answer to this question. When scientists developed technology to detect high-frequency sounds, they realized that bats weren't silent at all! Bats make chirps and other sounds as they fly, but in frequencies above what humans can hear. These sounds allow them to echolocate the same way our favorite rock-shaped buddy does in Project Hail Mary.
How does it work? Echolocation relies on sound waves bouncing off objects. Have you ever clapped in a large, empty room and heard the echo bouncing off the walls? It's the same principle. For example, bats emit sounds in the frequency range between 20kHz and 200kHz (our hearing limit is around 20kHz). When the sound reflects off objects and returns to the bats' ears, they produce a mental map of their environment. This is why bats with wax-filled ears kept crashing into things!
Other animals use echolocation to hunt or navigate, too. Sperm whales emit sounds to locate fish or giant squid. Dolphins send out a series of clicks and squeaks and sense the returning sound with their lower jaw.🐬Scientists are pretty sure nocturnal oilbirds and cave-dwelling swiftlets also use some form of echolocation.
Now that humans have a handle on how echolocation works, we use an artificial form of it called sonar on ships and submarines. Sonar equipment sends out sound waves and uses the echo to map the ocean floor and spot objects in the distance.
It turns out, detecting how waves reflect off objects works for more than just sound. "LIDAR" is a mapping technology that uses laser pulses. The light from the laser bounces back to sensors, which form a 3-D picture of the target area. With LIDAR, planes, helicopters, and drones can produce extremely accurate images of the terrain, even if plant life is covering the ground. Archaeologists can even use it to find ruins hidden from sight by trees!
These days, designers of self-driving cars and mobile robots incorporate LIDAR to help with navigation. All thanks to the hidden superpower of echolocating bats! 🦇
The graph below shows the frequency ranges of the sounds that dolphins and other toothed whales use for echolocating their prey. One fascinating fact: all the species of toothed whales in the world each make just one of four categories of sounds!
Here are some questions I think of when I look at this graph:
💡Humans cannot perceive sounds above about 20kHz. Which types of echolocation sounds can be detected, at least in part, by people?
💡Which sound type has the widest frequency range? How does that compare to the type with the smallest frequency range shown on the graph?
💡The types of sounds that toothed whales make depend on the sound-making structures in their bodies. Different structures produce different types of sounds. What does the graph suggest about the sound-making structures of sperm whales versus pygmy sperm whales? Explain.