Glass frogs!

Posted on November 21, 2010 by Tim 1 Comment

You wait but no more calls. A minute turns to two. You grow impatient then hear another, just over there. But now you have to wade into the stream. Carefully navigating stream banks, boulders, and rocks you walk up the stream with your gear in thigh deep water hoping not to go all the way in. You walk closer to where you think the new frog called. And wait. Only to hear the frog you just left call. Then silence except for the patter of rain on leaves. The impatient hunter will walk back and forth between the two teasing frogs until frustration (and the frog) wins. If you are good and wait them out they’ll call again.

Hyalinobatrachium colymbiphyllum from the Pacific coast of Costa Rica showing spectacular eyes.

But they know you are there and they are going to have fun with you. Because now, six frogs simultaneously let out a chirp-chirp call that has you spinning around trying to locate them. The high pitch doesn’t help. Many times I thought I had one zeroed in only to realize he was several meters above me. No chance I can reach up there, unless…smack!…another raindrop in the eye. Glass frogs truly require patience and dedication. Give it some time, and with species that are willing to come down low enough for you to reach, you will narrow down a calling frog to a small segment of a tree or bush. You know he’s less than a meter in front of you. You look and look. You examine every single leaf out of a few hundred. Chirp-chirp. Then you look at each leaf again. Just as you convince yourself you scared him away: chirp-chirp. Then finally, you see him sitting proudly on top of a leaf, clear as can be just a foot from your face. At first you are excited to see him but then you start thinking how much of an idiot you are for missing him sitting there all along.

Sachatamia albomaculata on a leaf from the Pacific slope of Costa Rica.

The tricky part is trying to catch him because if he leaps you most likely are going to have to start all over. Using lights in forests at night means things disappear easily once they leave your beam of photons and a hunted frog is a wily frog. But now it’s easier. Slowly cruising around you’ll see another frog, then another; each male calling from his leafy perch. Or even from under it. Those annoying raindrops in your eyes can be a tough hit for some of these dainty frogs so many use the undersides of the leaves for calling or egg laying. Their special fingers and limbs are amazingly well suited for this lifestyle.

A pair of Teratohyla pulverata in amplexus (mating). You can see the unlaid green eggs through the skin inside the female. This pair were hopping around in a tree in the Osa peninsula of Costa Rica.

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