On Frogs and Their Nostrils

Had I of titled this blog “On Green Frogs and their Manner of Calling” I would have instantly turned away those of you who are looking for light summer reading. It would have sounded far too scientific and, well, far too boring for a good beach read.  Now, the subject of frog nostrils is much more intriguing. The mere fact that frogs have nostrils might be shocking enough to prompt the reader to continue on. O.K., so it’s not that intriguing. I take it that anyone reading this blog is not looking for a light summer read but a deep fascinating insightful look into the world of nature and how she works. What better way to do so than to delve deep into a frog’s nose. O.K., so that’s not true either. So what of it? The frog and his nose is the subject that needs exploring – even if it is in a shallow and superficial way.

The shallows rimming the edge of Dollar Lake are choked with all manner of submerged aquatic plants and floating lilies. Towards dusk, these places begin to resound with the clucking calls of the resident male Green Frogs. The silent sunset scene pictured above lacks the necessary amphibian sound track. These large frogs, second in size only to the portly Bullfrogs, can put out a hefty burp of a call but it fails to carry far. It is has a hollow quality that dissipates like a smoke ring. The calls are random and widely spaced, so they never become irritating to the human ear. I’m sure they are music to the feminine Greens, however.

One especially talkative fellow was located a few feet from my dock and I was prompted to watch him with great interest. Normally watching a stoic green frog is like watching paint dry since they will remain motionless for hours at a time. This one was in a calling mode and performed his task while floating half-submerged on the surface.  His sequence was basically the same each time. The first noise out was the trademark “plunk” – a sound likened to plucking a loose banjo string. This was followed by a series of rolling “bulla-rup bulla-rup” vocalizations terminated by a final terse “tuck”. The last note had the quality of knocking on wood. Watch the video here and you’ll see and hear what I mean (note the competing notes of another green frog nearby).

Green Frogs have paired vocal sacs. Each time a rumble or a cluck is produced, the yellow throat pouch expands forward and around the sides under the ear drums. Air is forced between lung and throat and the whole body is involved in the thrust. The internal pressure even pushes out the ear drums a bit.  Up until now, I had assumed that a single gulp of air was alternately sucked and blown through the vocal chords during this process, but in looking at the video and examining my photos I discovered something interesting (perhaps even fascinating) was happening. During the actual noise production, the frog closed his nostrils and opened them to inhale between notes. Like any good singer, he has mastered the art of breath spacing.

This is not something that would be noticeable without film evidence. Take another look at the video sequence and compare the two calling photos. In the first photo (above and detail here) the frog is inhaling and the tiny nostrils are wide open. In the second photo (below) the frog is in mid-call and the nostrils are pinched shut.

That, my friend is the singular purpose of this blog. If you seek more, you’ll need to haul out a worn copy of the “Biology of the Amphibia” and take it to the beach for a good long read.

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One thought on “On Frogs and Their Nostrils

  1. That is so cool! I do a toad & frog survey in Ann Arbor, but it’s at night and by sound–so I never see the cuties. Also, I’m only familiar with the plunk, so it was cool to hear and SEE the other sounds. And of course to learn about nostrils. Is this true for other MI frog/toad species, too?

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