An interesting observation that shows just how essential the ability to hear is to living species on the earth is that while researchers have discovered many types of reptiles, amphibians, fishes, and mammals who were blind, they have been unable to locate any species that is naturally deaf. However, doesn’t necessarily require ears to hear. Sounds waves – vibrations in the air – can be detected in a variety of ways. Vertebrates have ears. But, invertebrate animals possess other sensory organs to pick up on sounds.
Insects, for example, have tympanal organs that work as well as ears, and in fact give them far better hearing than humans; as an example, a species of fly that is a parasite to crickets can locate its prey at some distance 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. 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.
Even though fish don’t have ears (they perceive sounds using lateral lines that run horizontally along their bodies), they can detect sounds that humans would not be able to hear. 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.
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 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.
Bats and dolphins actually extend their hearing abilities using echolocation, a form of sonar in which they emit tiny clicks or chirps and then “see” the objects they bounce off of when the sounds return to them. Echolocation is extremely precise. It only takes one chirp to determine an objects’ size and location. Scientists have proven that by using echolocation dolphins can detect objects the size of a small coin from over 70 meters away. A bat can detect an insect 30 feet away in complete darkness.
Looking at the animal world is a great reminder of how vitally important hearing is.