Did you know that researchers have yet to discover a vertebrate species on Earth which cannot hear? That is unlike a considerable number of amphibians, fishes, reptiles and mammals that are blind. But, doesn’t necessarily take ears to hear. Sounds waves – which are nothing more than vibrations in the air – can be perceived in multiple ways. Vertebrate animals have ears. But, invertebrates possess other sensory organs to pick up on 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. One species known for its acute hearing is the elephant. Elephants have large ears, but they can also hear through their feet. This form of hearing is so acute that elephants can detect the sound of thunderstorms or the low-frequency call of other elephants coming from 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 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. 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. A bat can detect an insect 30 feet away in complete darkness.
A quick look around the animal world is a great way to remind ourselves how vital hearing is.