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Did you know that researchers have yet to find a vertebrate species that is deaf? That is unlike a substantial number of amphibians, fishes, reptiles and mammals that are blind. But, it doesn’t require ears to hear. Sounds waves – vibrations in the air – can be perceived in a variety of ways. Vertebrates have ears. But, invertebrate animals possess other sensory organs to identify sounds.

In the case of insects, they have extremely sensitive tympanal organs which offer excellent hearing capabilities. Certain fly species can locate their prey exclusively via its song from a substantial distance. 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.

Fish are interesting too. Fish don’t have ears, but are able to perceive sounds underwater using lateral lines that run horizontally along the length 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. Cats have the most acute hearing among animals we have domesticated as pets; while humans can only hear sounds between 64 and 23,000 Hz, cats can hear sounds between 45 and 64,000 Hz. Owls also have phenomenal hearing, both in terms of acuity and reaction time; they can detect 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. This echolocation is so precise that with a single chirp, a dolphin or bat can tell the exact location, direction, size, and even the physical nature of objects in its environment. 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.

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