Under the Cantarana Boardwalk

When it rains, there are frogs. When it doesn’t rain, the frogs hide. We are at La Selva in the midst of a bizarrely rain-less rainy season. While El Nino brings heavy rains to other parts of the world, global weather patterns withhold Costa Rica’s agua de vida. Unfortunately for us, this means that we must diligently scan the ground in order to find the normally abundant frogs. We’ve been lucky enough to spy some of these treasures.

This daring little punk, a green and black poion dart frog (Dendrobates auratus), was tromping across the paved trail as we whizzed towards him on our less-than-functional rented bikes. I slammed my brakes on, forgetting that my friend Signe, who was riding behind me, had brakes that took about twice the normal time to stop and only then in a pulsing rhythm. Luckily, I grabbed the back of her seat as she was about to zoom past me and right over this little guy, saving both her and the frog. Close inspection followed.

This next one is anything but cute (although it tries very, very hard). The smokey jungle frog (Leptodactylus pentadactylus) is about 6+ inches tall, and possesses an incredibly unintimidating defense that makes you wonder how natural selection hasn’t yet weeded it out of existence. When you pick it up (as my friend May is doing in this picture), it screams (loudly) like a crying child, and turns its’ head from side to side with pleading eyes. It is not scary, it is just pathetic. You may also note the ‘breasts’ on this male, used for clasping the female during copulation. Hmmm… Listen to the call (note: this is not the defensive cry) here.

My friends May and John did their independent student project with the strawberry poison-dart frog (Oophaga pumilio). They presented the frogs with both correct and incorrect visual and auditory cues to determine how the territorial males respond to intruding males. Pictured here, a real O. pumilio actually attacks a model frog of correct visual cue (similar coloration) and correct auditory cues (the tape recorder here is playing the males’ call). Needless to say, my friends had a great time with this project and got a lot of hilarious pictures of the males wrestling with the human equivalent of a life-size blow-up doll screaming ‘I’m in your house, I’m in your house.”

My other friends were working with the red-eye tree frogs here (Agalychnis callidryas), to determine if there is a different in the parasite load between mating males and non-mating males. To do this, they would go out in the swamp at night (while fording off venomous snakes), collect all the males their encountered, including those mating with females (see below), clip their smallest back toe, smear the blood on a glass slide, and then count the infected blood cells under a microscope. While this all sounds complicated when written out, in practice it meant that they got to handle a lot of these gorgeous frogs. They do an excellent job of making themselves look like leaves; when they close their eyes they are extremely hard to find.

This is an ‘amplexed’ (mating) pair of red-eye tree frogs (same as above). The male is the smaller one riding on top of the female. When a female is ready to mate (determined by her swelling body which contains eggs), the male will hop on for a piggy back ride. He will stay on for up to twelve hours. When the female lays her eggs the male deposits sperm on top of them and then the two part. You would think that it would be difficult to find these frogs mating, but my friends found three to four pairs a night, searching from 10pm until two or three in the morning.

After two weeks at La Selva, it finally rained. I don’t mean a light shower. It rained torrentially for over two hours, filling the previously dry ‘swamp’ with water. And, with water comes frogs. The night after the rain, we bundled up in our rainboots and rain gear and headed to the boardwalk that extends through the swamp. On the walk towards the swamp, the chorus of frog songs grew from a gentle distant humming to a deafening roar. This explains the name of this swamp in particular: “Cantarana” means singing frog. Frogs were everywhere. On the boardwalk, in the trees, in the grass. How many frogs can you count in this picture?