Lots of herpers out for amphibian migration (Shelburne Pond, Shelburne)

Release Call!!

At long last! Big night! Last week was a bust, but last night was a great night for amphibian movement. With a steady rain beating down on my windshield, I drove down to Pond Rd on the south end of Shelburne Pond and the place was hopping (bad pun) with both people and amphibians. I moved about 15 male wood frogs, 5 females, 15 peepers and 3 salamanders. Oh, and 1 earthworm. There were probably as many people out helping the wee ones across the road.

Female wood frog during amphibian migration (Shelburne Pond, Shelburne)

Without a doubt the highlight was getting to hear the release call of the male wood frog. I wrote recently about the sexual dimorphism between male and female wood frogs. With a heavily skewed ratio of about 9 males to 1 female, competition is pretty intense. One unfortunate side effect is that there’s a quite a fair amount of misjudgment on the part of males. If you’re a male wood frog, I suppose it’s better to err on the side of erring and mount anything that moves in the chances that it might be a female. Wood frogs also migrate and mate significantly earlier than most frogs, so there’s a good chance that what they’re mounting is a wood frog, just not that it’s necessarily female.

Male wood frog during ampbhian migration (Shelburne Pond, Shelburne)

Males have a handy card to play when mounted: a release call. The call, more of a strained and angry warning croak, signifies that they’re a male and that the mounting male is wasting both of their time. I was showing a mom and her son a male wood frog and noting the engorged thumbs when it started making the release call! I wound up getting a short video of it making the sound. Enjoy!

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