How Do Bugs, Dolphins and Other Species Hear?

Did you know that researchers have yet to find a vertebrate species on Earth that is deaf? That’s unlike a considerable variety of amphibians, fishes, reptiles and mammals that are sightless. However, hearing doesn’t specifically call for ears. Only vertebrates have ears, whereas invertebrates utilize other types of sense organs in order to perceive the vibrations we know as audio waves.

Insects have tiny tympanal organs that can provide them with far more acute hearing than humans; for example, the female cricket fly can pinpoint the exact location of the cricket it parasitizes just by hearing its song. Hair can also be used to detect sounds. In spiders, cockroaches and caterpillars, tiny hair cells play the role of ears. The spiders and cockroaches have the hairs on their legs, while the caterpillar has them along its body. Some animals have two ways of processing sound vibrations. For example, an elephant has extremely large ears, but it also takes in sound information via its feet. Elephant feet are sensitive to the very low frequency calls of other elephants and also the rumble of thunder many miles away.

Sound travels both faster and farther through water than it does through the air, and even though fish don’t have ears, they can effectively detect sounds using lateral lines that run horizontally on the sides of their bodies. A marine mammal, dolphins have no ears, but have eardrums on the outside of their bodies that give them the best sense of hearing among animals, over 14 times better than human hearing.

Not only do many animals have better quality hearing than humans, they can hear more sounds, detecting frequency ranges that are much higher and lower than the range that humans are capable of hearing. Cats are recognized as having the most acute hearing among domesticated animals. They can hear sounds at lower and higher frequencies than humans can. A normal human range is 64 to 23,000 HZ. A normal cat range is 45 to 64,000 HZ. Birds also have acute hearing, especially owls, whose hearing is not only far better than ours, but more precise in its ability to locate the source of the sound. An owl can pinpoint the exact location of a scurrying mouse in less than 0.01 seconds.

Some species, such as bats and dolphins, extend their hearing abilities by using a form of sonar called echolocation, in which they emit ultrasonic chirps or clicks, and then interpret the sound waves as they return from objects the waves strike. Echolocation is extremely precise. It only takes one chirp to determine an objects’ size and location. Dolphins can use echolocation to detect objects the size of a small coin over 70 meters away. And if you want a real display of hearing, bats can not only hear insects flying 30 feet away from them, they can then pursue and catch them in mid-air, all in total darkness.

Looking at the animal world is a great reminder of how vitally important hearing is.