The bats that live in the United States all come out at night. Night is a great time to be active because that is when many insects are out as well.
Plus feeding at night protects the bats because predators like hawks aren’t active then.
Yet, when it’s dark, eyes are not so useful. It is not true that bats can’t see, but seeing at night is not exactly easy. They use sound and its reflections to help them at night.
A bat creates a loud, high-frequency sound that it sends out into the night. That sound is too high for us to hear (from most bats).
That sound reflects back off of objects in the night. The bat hears that reflected sound and is able to figure out what is ahead of it.
Bats use their high-pitched sound to help find insects in the dark. That sound bounces back from a bug into the bats’ very sensitive ears.
They can tell where the insect is and how it is moving from this sound system, which is pretty remarkable. Think about it. A bat is moving fast, so is an insect, so the bat has to find its prey, track it and catch it, all in the dark!
Using sound and its echo to find where things are is called echolocation. It is like sonar of the air. A bat will fly with its mouth open so it can echolocate. That is why so many photos of bats show them with their mouths open (which looks bad, but does not represent the gentle nature of these animals).
Bat echolocation is so good that they can “see” details as small as a hair on your head. I find that pretty remarkable. They are “seeing” objects and space in front of them just through sound and its reflection. So think about the old wive’s tale that bats will get tangled in someone’s hair – that’s not going to happen because they sense hair just fine.
To get a good reflection of sound, the echolocation call has to be very loud, plus bats need sensitive ears to better hear the reflection. Yet that call is so loud that bats could get hearing problems because of it.
Bats have adapted to this challenge. Their ears and associated elements will disconnect the ear when calls are going out and reconnect as the calls return. This is done with split-second timing, too!
Bat sounds are mostly too high for our ears. They mostly start at frequencies above 20,000 hz and go as high as 120,000 hz. Our hearing typically tops out at about 18,000 hz (technically, people can hear from 20-20,000 hz, but once you become an adult, that becomes less and less likely at the high end). Sometimes very young kids will hear certain bat sounds – the ability to perceive high frequencies declines with humans as they age.
The night can be filled with bat sounds, but we will not hear them.
A qualification to hearing bats – many bats make a chirpy, chittering sound in their roost, especially large group roosts as they get ready to fly at night.