Last year I purchased a pair of hydrophones so that I could make underwater recordings. I never used them in the field until last night, when I decided to throw them into our backyard pond to see how the peeps of Spring Peepers would sound. Standing along the edge of the pond, I threw the two microphones about ten feet out into the pond, placing them about ten feet apart for a stereo effect, and then monitoring over headphones.
To my complete surprise and disbelief, there was quite a bit more going on than just the peeping of the peepers. which is all I could hear above water. There were loud snoring sounds, and a variety of chucking and stuttering calls. How could this be … none of these sounds were audible to me if I took off the headphones and listened to only the airborne sounds:
Underwater snores and croaks of Pickerel Frogs, made with hydrophones. 10pm, 19 April 2015, near Ithaca, New York. © Lang Elliott.
Luckily, I recognized the patterns. Apparently, they are the snores and croaks of Pickerel Frogs, Rana [Lithobates] palustris, which are somewhat common in my area, though I’ve never seen or heard them in our backyard pond. Pickerel Frogs are recognized by the two rows of square spots on their backs, They are known to call underwater, though I always presumed they did this only when frightened, when caused to submerge. In this case, ALL of their calling seemed to be underwater. I’ve heard plenty of Pickerel Frog snore in airborne situations here in upstate New York, usually during the month May, and they are very easy to hear. But last night, the calling seemed to be entirely underwater. Is this unusual? Or does it happen most of the time?
Below are typical above-water recordings for comparison. While the sounds recorded underwater seem more high-pitched and “tinny” than above-water calls, the snoring pattern is unmistakable, as are the occasional croaks or grunts. I’ll have to do a thorough search in the daylight to see if I can find a Pickerel Frog or two along the edge of the pond!
Typical “above water” snores and croaks of Pickerel Frogs. © Lang Elliott.
Surely, I have this figured out, unless there’s some strange aquatic insect that snores and croaks like a frog … maybe a Giant Waterbug having a really bad dream?