How Do Bugs, Dolphins and Other Species Hear?

Did you know that scientists have yet to find a vertebrate species on the earth that is deaf? That’s unlike a considerable number of amphibians, fishes, mammals and reptiles that are sightless. That said, the ability to hear doesn’t specifically require ears. Only vertebrates have ears, while invertebrates utilize other types of sense organs to perceive the vibrations we all know as sound 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. Elephants not only have large ears, they can also hear using their feet. They are particularly attuned to low-frequency sounds, and can detect the sound of thunderstorms or the deep-voiced call of other elephants many kilometers 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. Dolphins have external eardrums on the outsides of their bodies that are so sensitive that they have the best sense of hearing among animals, and are able to hear 14 times better than humans.

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. Among domesticated animals, cats have the sharpest hearing, and can hear frequencies between 45 Hz and 64,000 Hz (humans can hear frequencies between 64 Hz and 23,000 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.

Echolocation is an extension of hearing often considered it own sense since it functions like sonar. Bats and dolphins emit small click or chirps which bounce off of surrounding objects and return to them. They are essentially using sound waves as a tool to “see” their surroundings. Using echolocation, bats and dolphins can determine a great deal about objects they can’t even see, including the objects’ size, location, and even their physical nature. Scientists have proven that by using echolocation dolphins can detect objects the size of a small coin from 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.