Monday, April 17, 2017

Frog Choruses in the Clouds

Monteverde is one of Costa Rica’s most visited regions. When I first visited over spring break I could definitely see Santa Elena was a touristy town. With zip lines, hanging bridges, and thrilling drops and swings, who wouldn’t want to spend a few days at this beautiful tropical cloud forest. I guess if you aren’t a huge fan of heights like me then not all of the thriller activities would peak you’re interest but there is still lots to do. Coming back for class was a completely different experience. Dropped off at the Santa Elena Cloud Forest Preserve we hiked for an hour down a muddy road to a trail that led to the San Gerardo biological station in el Bosque Eterno de los Niños that we would stay at for the next five nights. The station is only accessible by hiking or ATV but it is absolutely gorgeous. By just walking out of your room you could see Arenal volcano and lake Arenal as long as it wasn’t too cloudy, which it was most of the time, but hey that’s why it’s called a cloud forest. It always impressed me when you could look out at just see a wall of white cloud. From the deck that had this view we also saw many different birds including a large vulture posing for it’s photo shoot and a swallow kite carrying a snake off into the distance. The surrounding scenery the San Gerardo field station was great place to relax and learn about biology.
            The first couple of days we learned about gaps in the forest, seed dispersal, and pollination. When a tree falls in the forest it changes the dynamics in the undergrowth since the amount of light, temperature, and wind have all changed in what was originally in the trees shadow. It was interesting to see these changes that gives seedlings stuck in the shaded undergrowth their time to shine. My favorite part of this hike was going a little ways off the trail and lying down for about fifteen minutes while we stared up at the complex canopy above. Mau, our professor, asked us to imagine how we would grow if we were a tree seedling with the obstacles present at each of our chosen locations. Those who were closer to light gaps imagined an easier path to growth than others. I of course lay down under a huge heliconia leaf which would have impeded my “growth”. I had never viewed the forest in this way and it was an interesting change of perspective.
Later in our visit at Monteverde, Mark, a guest faculty, came to teach us about frogs, frog calls, and the recent frog decline. In the late 1980s there was a sudden crash in many of the frog populations not only in Costa Rica but around the world as well. Among these was the golden toad that lived in higher altitudes in Monteverde. It is believed to be extinct now since it hasn’t been seen since 1989. Several theories have been proposed for the worldwide decline of amphibians including ones related to forest fragmentation, pollution, pesticide use, climate change and its indirect effects, and disease. Today the most compelling evidence is for disease, particularly a fungus called Batrachochytrium dendrobatidis, or Chytrid. It’s hypothesized that the fungus was brought over to the Americas from Africa when some frogs were being transported to the U.S. for using as pregnancy tests and pets. There is evidence of Chytrid spreading in a disease like fashion down to Central America through human travel or other animals. Genetically, tests have shown that the Chytrid in Central America has also come recently from a common origin. There are also arguments for climate change as well and suggestions that climate change has helped the spread of Chytrid and other frog diseases. Some frog species appear to be recovering from the initial crash while others continue to decline. It was especially interesting to hear about how frogs may be adapting to the fungus in order to become resilient to it. These include sunbathing to kill the fungus since it thrives in moist environments and compounds that have been found in frog skin, which act as a defense to the fungus. I think the theories about the frog declines are interesting and something I will now keep an eye out for as evidence for the causes continue to be found. We went on a couple night hikes and found quite a few frogs among the leaf litter and on leaves, but I was definitely able to hear more frogs than I could see or catch. There are so many different frog calls that I hope to learn more about as we travel to La Selva which is also known for it’s frogs. I found out catching frogs is quite a skill as you have to be very sneaky and quiet because otherwise it is just two or three hops and they are gone.
Overall I felt like Monteverde was by far one of my favorite places that we have visited in Costa Rica. I will miss waking up to a view of clouds rolling over the forest, the great food, the ping-pong and puzzles we did in our free time, and of course the frog choruses that greet you as you walk the trails at night.

Hayley Stutzman
Macalester College

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