I had the opportunity last week to watch the bats return to the Bamberger Ranch Preserve’s chiroptorium. The morning return isn’t as dramatic as the evening emergence, but it’s still something to see. Realizing that, for the first time, I had a device that could capture high definition (720p) video, I propped up my iPhone 4 on the fence at the mouth of the chiroptorium and let it record for about 16 minutes. I’ve edited that recording down to two minutes in the following video. It is best seen at 720p - at lower resolution, the distant bats in the descending stream aren’t visible.
As the bats swooped down and maneuvered aggressively into the cave mouth, they produced a sound that I can best describe as a rapid vibration. My guess is that the trailing edges of their wing membranes vibrate violently during those maneuvers. (Much like the end of a piece of fabric held out of the window of a fast-moving car.) Unfortunately, that sound seems to represent some sort of pathological case for the iPhone 4’s audio capture system, and, as you’ll hear in the movie, it is distorted into something that sounds very much like static. That’s disappointing, but slightly better than no sound at all, I think. So, apologies about the static. It’s not an accurate reproduction of the sound produced by the bats, but its presence and intensity does correlate with the number of bats passing the camera at any given moment, so it has some value.
It is, of course, better to experience this first-hand, but one needs special permission to do so. Being fortunate enough to have that permission, it seems the least I can do to try and share some of that unusual experience. Enjoy.