When the rain falls down, the frogs come out

The extreme change in habitat and climate that one experiences after traveling for just a few hours in Costa Rica never ceases to amaze me.  Whereas the dry forest of Palo Verde was bone-dry and scorching hot, Monteverde’s cloud forest is chilly and perpetually raining, thanks to a combination of altitude, topography, and the rain shadow effect.  Clouds moving up one side of the mountain cool and condense at the top and drop lots of rain, making that side of the mountain very wet.  Then the clouds, cool and void of moisture, sink down the other side of the mountain, warming as they descend and making that side very dry (thus, the mountain has cast a “shadow” of dryness).  Our biological station in the Bosque Eterno de los Niños sits near the top of the “dry” side—the Pacific Slope—but the intense winds push rain from the “wet” side up and over the top of the mountain, giving our cloud forest 5000mm precipitation annually (for reference, that’s about four to five times the amount in Boston, New York, or Washington, D.C.).

Monteverde is home to plenty of birds and mammals, but in all the wetness they tend to be less active and difficult to spot.  Instead, a different taxon is more comfortable in this moist environment: amphibians.  Since many amphibians are nocturnal predators, the best way to see them is by going on a night hike!  Huddled in raincoats, our class ventured out into the woods with our flashlights guiding the way.

Looking for frogs in the cloud forest is not an easy task.  Many frogs exhibit incredible mimicry of leaves, bark, and various substrates.  The easiest way to find them is by looking for movement when and where you step.  If you’re up for more of a challenge, look closely on and under each leaf you pass, and sooner or later one of those brownish blobs that you thought was a clump of wet moss or dirt will turn out to be a frog, sitting perfectly immobile as it waits for unsuspecting prey to crawl or fly by.

We encountered several species of ground toads on our walk; the males are rather flat and round and look like a wet conglomerate of sandy pebbles until you get a closer look.  The females are several times larger and much easier to spot from a distance.

ground toad (Rachel Moon)

Male ground toad (Photo credit: Rachel Moon)

 

By far our most impressive find was the rufous-eyed stream frog, which sports typical “tropical frog” characteristics like bright coloration, slick skin, and large toe pads for gripping to trees.

rufous eyed stream frog (Rachel Moon(

Rufous-eyed stream frog (Photo credit: Rachel Moon)

 

Not only are night hikes great for spotting frogs and toads, but you are able to see things that you would never consider looking for during the day.  On the walk back to the station, our professor stopped and instructed everyone to turn off their flashlights and look around.  For a few minutes we struggled to see into the dark forest, no one daring to move an inch for fear of toppling into the stream below the trail.  Suddenly someone spotted specks of light on the ground.  It looked as if as if a bunch of lightening bugs had been crushed over top of a leaf—in fact, we were looking at a bioluminescent fungus.  The fungus-covered leaf passed from one person to the next, a mass of sparkling, yellow-green jewels suspended in blackness.

When we emerged from the forest back at the station, we were greeted with another fantastic bioluminescent display as dozens of click beetles circled the trees.  We watched for a while, letting them come up close to our faces and then dart away quickly, until the chilly rain began to make us numb and we retreated into our warm beds with the image of the beetles still dancing in our minds.

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