Hearing in Cockroaches, Insects, Dolphins and More

An interesting observation that shows just how essential hearing is to living species on the earth is that while researchers have identified various kinds of reptiles, amphibians, fishes, and mammals who were blind, they have been unable to locate any naturally deaf species. That said, the ability to hear does not necessarily call for ears. Only vertebrate animals have ears, whereas invertebrates use various other sense organs to perceive the vibrations we know as sound waves.

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. 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. A marine mammal, dolphins have no ears, but have eardrums on the outside of their bodies that give them the best sense of hearing among animals, over 14 times better than human hearing.

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. 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. 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. 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.

A quick look around the animal world is a great way to remind ourselves how vital hearing is.