I’ve always been fascinated by bats darting through the evening sky, snatching insects mid-flight. Every time we go fishing in Northern California, they’re there, silent shadows against the fading light.

One trip from a few years ago, I decided to record them. Armed with night vision and a bat detector, I set out to capture their hidden world.

A bat detector picks up the high-frequency sounds bats use for echolocation and converts them into sounds we can hear. I used the Belfry Bat Detector. It’s a solid little unit that gets the job done.

Here’s a video showing how it works.