Naturespeak A naturalist's view of the world

March 18, 2009

“Croaking Voyces”

Filed under: Uncategorized — wykes @ 9:26 pm

It’s hard to ignore Chorus Frogs. They are easy to overlook, but impossible to underhear. The breeding season for these diminutive frogs has begun in earnest and the males are now filling the air with their creaking calls. I was there for what I believe to be the opening salvo for this yearly ritual. I located the songsters in a flooded roadside ditch in southern Monroe County and recorded some of their voice talents (here).

Chorus Frogs are tiny members of a group known as the New World Tree Frogs – barely reaching an inch and a quarter in length. They possess small toe pads as proof of their lineage but they rarely, if ever, climb trees. Instead they secret themselves away under the leaf litter for most of the year and only put in a public appearance during the brief breeding period. One of the identifying features of a Chorus Frog is the presence of a dark face mask and a series of three broken lines running down the tan colored back. The combination of micro size and subtle coloration makes them difficult to spot against  a backdrop of wet brown vegetation (see the calling male above). Their voice, however, is more than enough to key you in to their presence.

When I say that these frogs fill the air with sound, I really mean it.  True to their name, they sing as a group. When in full chorus, there is little room for any other sound in the aural space. The distant moan of a train whistle was about all I could hear above the fray. This particular group of frogs, perhaps a few dozen in number, were prompted  to begin their ancient rite of passage by the mild afternoon sun.   With small patches of ice still clinging to the shaded portions of the water surface, males and females alike, gathered at the temporary spring pool in obeyance to a deep instinctive drive. The sonic nails driven by Chorus Frogs are decisive blows in constructing winter’s coffin. When these soggy gathering spots explode into bustling singles bars, the action continues non-stop for weeks until Spring is well on the way.

The early activity at these ponds goes on throughout the day and into the night. Things begin to taper off into evening/cloudy day affairs as the season wanes into late April and ceases altogether by middle May.

The males do all the singing. By pumping a single mouthful of air back and forth over their vocal chords (see here in this video clip) they make a sound akin to rubbing one’s fingers along the teeth of a stiff comb. Once a female is lured to the vicinity, the crooner immediately grabs onto his potential mate and locks his arms around her body immediately behind her front legs. His duty is then to hold onto her for dear life for the next few hours. This behavior is called “amplexing”  (see the amorous pair below and here).

Eventually the female begins to lay packets of jelly covered eggs (20-300 per cluster) and the male fertilizes them as they are released. Once she is done laying her quota of up to 1500 eggs, a process normally taking less than an hour, the male releases her without even leaving his e-mail address.  The idea is, of course, for the guy to pick up another date and repeat the process. In at least one major study, however, only some 17% of any gathering of males are able to mate with a female and they do so only once. This means that most of the males are croaking blanks most of the time, but you can’t blame them for trying!

Edward Topsell in his 1658 treatise on reptiles and amphibians called “The History of Serpents” somewhat accurately explained what goes on in the world of frogs.  “When with their croaking voyces,” he writes, ” the male provoketh the female to carnal copulation, which he performeth by covering her back.”  He then attempted to explain that mating was performed under the cover of the night because of the natural understanding of the “modesty and shamefullness of this action.” Obviously, Topsell never encountered a mid-day orgy of Chorus Frogs.

4 Comments »

  1. Hi Gerry, I too heard chorus frogs in southeast Ann Arbor on March 17, as well as a whole chorus of chorus frogs, with a few spring peepers (and highway noise) thrown in. The second recording actually sounded way louder in real life, louder than the first. My friend Pete made the recordings.

    Comment by Monica — March 19, 2009 @ 11:27 am

  2. I came from Monica’s blog. I am going to try to do FrogWatch this season. It’s too early in western NY, but we have wetland woods and lots of ponds near my house, so I really want to see what I can hear. I had to laugh at your amplexing photos as I had a pair of SA clawed frogs that I inherited from my daughter when she left for grad school. The male got a grip on her and didn’t let go for days. She used to get annoyed and try to get him off, but he was determined.. Poor frog, his mate died last summer..probably of exhaustion…Michelle

    Comment by ramblingwoods — March 19, 2009 @ 11:40 pm

  3. Michelle.
    Good luck with your frogging this season. The real trick is to try and figure out how many individuals of a given species are calling at any given time. I find that peepers and chorus frog calls have a ventriloquistic effect which seems to defy the human ability to pinpoint them! At any rate, you’ll have a ribbeting experience.

    Comment by Gerry Wykes — March 21, 2009 @ 1:20 pm

  4. Many thanks for sharing this information. I’d like it in even more details though, do e-mail me about it.

    Comment by Naida Mackson — March 14, 2010 @ 3:15 pm

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