Were you aware that scientists have yet to find a vertebrate species on Earth which cannot hear? That is in contrast to a considerable number of fishes, amphibians, reptiles and mammals that are sightless. However, doesn’t necessarily require ears to hear. Sounds waves – which are nothing more than vibrations in the air – can be detected in a variety of ways. Vertebrates have ears. But, invertebrates have developed other types of 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. 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. Many animals not only hear better than we do, they hear more sounds, easily detecting sounds in frequency ranges far below or above the frequencies that we humans can hear. 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. 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.
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. A dolphin is able to detect a coin at a distance of 70 yards always. 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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