Contrary to the popular myth that bats are blind, not only can they see, but many bats possess a super sense that enables them to “see” with sound. Known as echolocation or biosonar, the basic way in which it works is that bats emit a series of high frequency shouts a second either through their mouths or noses.
These ultrasonic waves are way to high for people to hear but bats can hear them as they return, after they’ve bounced off whatever is in their environment at the time.
Did a wave return very quickly or did it take a longer time? Was it crisp or fuzzy? And how loud or quiet was it? The answers to these question will tell a bat how far away an object is, whether it’s solid or not and in this way, bats can build up a very accurate picture of their surroundings.
In fact, this ability is so sensitive that they can detect a strand of hair!
The mind boggles at just how they’re able to process all this information, fly, perform dazzling feats of agility and catch insects all at the same time! Speaking of insects, echolocation tends to be found mainly amongst insectivorous bats, which make up 70% of all known bat species.
However, there is a fruit bat, the Egyptian flying fox, that does echolocate, using a series of audible clicks. This ability gives it the advantage of being able to roost in caves, as it can navigate its way round them in the dark and roost in relative safety from predators.
Different bat species have signature patterns of echolocation that can be used by experienced bat workers to identify them. Often, there’ll be a frequency that a bat will echolocate the loudest at e.g. the Soprano pipistrelle is loudest at about 55 kHz. But a species will also use a range of different frequencies as well as vary the number of shouts it emits per second (the pulse interval) according to what situation it’s in.
So for instance when it’s closing in on a soon to be eaten insect, a bat will increase the number of shouts it emits per second. This increases the amount of information it gets back, which will boost its chances of catching it.
Bat detectors can be used to hear these high frequency sounds. It can be a lot of fun to watch bats as they dart about while listening to a soundtrack of clicks or warbles. One can get a certain amount of child-like glee from the comical buzzing sound that signifies a insect is going to be caught very soon.
This fantastic ability has enabled many bat species to increase the advantages of being a nocturnal mammal by being able to feed on the wing. Bat echolocation has inspired human inventions such as navigation systems that use sonar. And there’s also a growing number of blind people who have started to use echolocation that’s similar to the Egyptian fruit bat’s, to navigate their way round, which is pretty amazing.