A fact that shows how essential hearing is to living species on the earth is that while scientists have discovered various kinds of reptiles, amphibians, fishes, and mammals who were sightless, they have been unable to find any naturally deaf species. However, doesn’t necessarily take ears to hear. Sounds waves – vibrations in the air – can be detected in multiple ways. Vertebrates have ears. But, invertebrates have developed other types of sensory organs to identify sounds.

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. In some species, tiny hairs take the place of ears; in spiders and cockroaches these hairs are on the legs, while in caterpillars they are along the surface of 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. The dolphin is believed to have the best hearing among animals. Dolphins have no ears. Instead they have external ear drums on the outside of their body. In addition to having better hearing than humans, many animals can detect a much wider range of frequencies. They can hear sounds that are we are incapable 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. Birds, especially owls, have excellent hearing. Owls are particularly skilled at detecting the precise location of a sound – and detecting it very quickly. They can pin-point the origin of a mouse scurrying in under 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. 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. Bats can hear insects flying up to 30 feet away, in total darkness, and then catch them in mid-air…now that is hearing.

The animal world provides some excellent example to remind ourselves how important the sense of hearing is.

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