While we at Ecostudies Institute primarily work on birds, I had the opportunity to attend a week-long workshop about the other group of fascinating, flying creatures: Bats! Many of the same technical challenges of monitoring bird also aggravate and perplex bat biologists. Their flight, for example, makes them difficult to catch or track.
I was lucky enough to attend a training in Spokane taught by Cori Lausen and focusing on how to deploy acoustic equipment and identify specific bat calls. While most bird enthusiasts can walk outside and easily hear and identify an American Robin, bat biologists have to get creative hear bats.
Bats vocalize at “ultrasonic” frequencies, which means the calls they make are higher than what the human ear can detect. Interestingly, young girls have the best hearing of any humans and can hear up to 20 khz. To put this in perspective, most American bats broadcast from 16 khz up to 100 khz.
When we think of bats vocalizing, we usually think of echolocation. Bats use echolocation to navigate and find food in the dark by producing “screams” at particular pitches. These screams bounce off prey or obstacles and return to the bat as echoes. From these echoes, bats can determine the size, shape and distance of the object.
The old joke “blind as a bat” does not apply here. Although they operate in almost complete darkness, bats can use echolocation to detect tiny mosquitoes or swerve out of the way of individual leaves with breath-taking dexterity.
Bats can do this by producing sound up to 140 decibels! For comparison, humans feel pain from sound at 120 decibels. Bats in the Pacific Northwest are able to produce such loud “screams” without damaging their sensitive ears by temporarily disconnecting their ears, rendering them deaf while they vocalize. This gives a whole new meaning to the phrase “selective hearing”!