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The Search for the Silent Frog

Posted by Jonathan Twining on Aug 15, 2016 11:20:37 AM

IMG_5449.jpgHave you ever been the first to discover something?  Seen something that few if any people have ever seen? Felt that tremendous burst of exhilaration as you realized you were part of something that has never been done before?  Finished first in a big race, or won a championship of some sort?

I had that kind of experience this summer. It happened on June 10, and I was in a pre-montane rainforest in Tinamaste, Costa Rica. I was part of a team comprised of Dr. John Cossel of Northwest Nazarene University and three students. Our research was in frog bioacoustics: the study of how frogs make, transmit, and receive sound, as well as the effects of the sound on the behavior of the frog. Frogs make sounds (or calls) for a variety of reasons. Among these are advertisement calls, which serve two purposes: (1) to attract a mate, and (2) to establish territorial boundaries with other males.  It is these types of calls that we were attempting to record for three target species, one of which had not been recorded previously in the scientific literature. I cannot yet reveal the name of this frog or make public a documentary I created about our team's quest to find this frog until Dr. Cossel's work is published But I can tell you that this frog is a canopy-dwelling tree frog that does not spend much time near the forest floor, and happens to live at an elevation that has been heavily deforested; thus its status as a Near Threatened species.

To find our target species, we had to be prepared for a variety of conditions. First of all, when studying most reptiles and amphibians (herpetology), it was a foregone conclusion that we would be working after dark, often until after midnight. Since we were there during the wet season, it rained almost every afternoon and into the evening hours. And third, it was imperative that we keep a constant lookout for where we were stepping and where we were putting our hands, because the Costa Rica rainforest has venomous snakes and spiders, as well as thorny palms and ants with painful bites, like army ants and bullet ants.  

To locate and record our three target species, we needed some special equipment.  We used Tascam audio recorders and Sennheiser shotgun microphones to pick up and record the frog sounds.  These had to be kept dry, so an umbrella and dry bag was essential.  In addition, we had Kestrel weather meters to record the weather conditions at the time of observation, and a GPS to record the frog’s coordinates.  All information was recorded in a field journal just like I use in my biology and environmental science labs.

IMG_5388.jpgOn our third night in Costa Rica, after a steady rain in the afternoon, we headed down the trail in pursuit of the previously unrecorded frog and our other target species. We heard several calls, and Dr. Cossel quickly narrowed down our search to an individual that seemed to be calling closer to the forest floor.  As a team we split up and triangulated on the frog’s position … and there it was. We could see the frog and the leaf of a plant about 1 meter off the ground.  We quickly switched to red lights and waited … and waited … and waited.  Finally, the frog called, and you could feel the excitement in the entire team, knowing that we were recording the call of this frog for the first time.  We waited and watched for over two hours, recording two bouts of calls from the frog.  When it seemed like he would call no more, we captured the frog so that he could be measured, weighed, photographed, and returned to the wild.  Throughout the rest of the week, we observed and recorded a number of other species of frogs, including an endangered species, Legler's tree frog, which you can see an image of below, along with an image of me holding one of our more common target species, Craugastor stejnegerianus.

I hope that one day you can feel the kind of excitement, wonder, and adrenaline rush that we all felt at the moment we found and recorded that frog.  Maybe you will have that opportunity when you study at Eastern Nazarene College … perhaps on a trip to Hawaii or Costa Rica like this one.  I hope we can share that kind of experience together.

For more information about studying biology or environmental science at Eastern Nazarene College, or our travel courses, please feel free to contact Prof. Twining at 617-745-3552, or by email at jonathan.Twining@enc.edu.

Written by Jonathan Twining

Jonathan Twining teaches the ecology and environmental science courses for the Biology Department and is the advisor for the Animal Caretakers Team (ACT). Twining worked for a number of years as an environmental scientist and project manager with consulting firms in Rhode Island and Massachusetts. He has been very active in the greater community, partnering ENC students with organizations like the Quincy DPW, Wildlands Trust of Southeastern Massachusetts, Massachusetts Audubon, the South Shore Natural Science Center, and the Department of Conservation and Recreation. His passion and primary research interest is the ecology and conservation of vernal pool habitats. He has written numerous articles for NCM Magazine, and has been a speaker in local congregations about the care of creation (environmental stewardship).

Topics: ENC Faculty, Academics, Environmental Science, Biology