A Song in the Darkness: Audio Loggers and Panama’s Imperiled Amphibians

Authored by Mark Vassallo, Detroit Zoological Society (DZS) Amphibian Department Supervisor.

The cloud forest of central Panama is a unique and mysterious place, full of rare creatures and plants that call these moisture-laden peaks home. At night, the jungle writhes with life as the nocturnal world takes over the mountainsides. In this veil of darkness and nestled in the elevations of these dense jungles, some of the earth’s rarest amphibian species reside. Many of these species are yet to be described by science, and others are considered to be extinct.  As I gazed up at the gathering rain clouds on the volcanic peaks of El Valle, I could not help but wonder which of these potentially extinct amphibians could still be out there.

I have been traveling to El Valle, Panama for the last seven years to work with the El Valle Amphibian Conservation Center (EVACC). This organization is run by Edgardo Griffith and Heidi Ross, a husband-and-wife biologist team, who have dedicated their lives to the conservation of Panama’s most endangered amphibians. Usually during these trips, I am undertaking projects involving the installation of life support and infrastructure or helping troubleshoot specific husbandry issues that arise in one of the modified shipping containers in which EVACC houses seven species of Panama’s rare and endangered amphibians, including the iconic Panamanian golden frog (Atelopus Zeteki). 

A Warzewitsch’s frog was identified in the area.

While those types of jobs are on the docket for this trip, we also have an important task to complete that will bring us into the upper reaches of the cloud forest in the hopes to hear a sound that could mean some hope for the imperiled amphibians of Panama. The sounds we are hoping to hear are the calls of thought-to-be-extinct amphibians, including Raab’s tree frogs (Ecnomiohyla rabborum), large and highly unique arboreal frogs who lays their eggs in tree cavities and can glide through the air to evade predators. In the last year, EVACC has begun the process of deploying audio loggers in some of the area’s hard-to-reach elevations to listen for the calls of amphibians like the Rabb’s tree frog that are widely thought to be potentially extinct. 

The audio loggers are sturdy boxes that contain a microphone, batteries and SD cards accompanied by a digital screen. The idea is that these listening devices, which are programmed to turn on during the dusk and nighttime hours, will pick up the call of one of these rare frogs. If a call from one of these frogs is detected on the logger recording, this would give the biologists at EVACC a very good lead on the areas where intensive surveys could take place to potentially locate this species.

Armed with some GPS coordinates, batteries, fresh SD cards and rough information about the audio logger’s location from a member of the last group who placed it, we headed up the mountain to start our journey. As we began to climb, the heat and humidity was intense — our clothes were soaked in less than an hour.  Large biting ants were swarming our boots as the incline steepened, and we came to a crossroads in the trail. We had reached the GPS coordinates but realized that these coordinates could not be correct. At this point, we decided to attempt to leave the trail and start climbing up what seemed like a cut in the dense jungle, which may have been caused by mudslides and heavy rains, certainly nothing even resembling an actual trail. The going was difficult as the clouds began to gather. Buckets of heavy rain soon began dumping on us, causing the mud to loosen and give, making the more vertical sections especially precarious. In addition to watching your footing in the jungles of Panama, it is also important to watch where you put your hands. Eyelash vipers and stinging insects of all kinds tend to rest on branches and sticks at about eye level. All of these thoughts were keeping our senses sharp as we broke through clearing after clearing, each time hoping that this was the top of the mountain and the audio logger would appear like a shining beacon amongst the dense jungle. Yet, each time the clearings revealed even more vertical walls of vines and thick jungle vegetation to climb. Our resolve was fading, but we pressed on. At one point, my balance gave way, and I fell face first into the side of the muddy slope. As I raised my head, I noticed I was face to face with a tiny gem of a frog. It was a blue-bellied poison frog (Adinobates minutus). This toxic little frog was just staring back at me, probably wondering why a silly, hairless ape had bothered to climb this far up a mountain during a thunderstorm. 

A rainforest rocket frog was identified in the area.

The rain was finally letting up, and this gave us a little boost as we could see some sunshine emanating from what looked like a break in the jungle ahead. As we approached, sharp painful sensations started overwhelming my hands and wrists. We were wading through a large column of sharp bladed grass, which when brushed against, caused a paper cut like lacerations on the skin. Once we emerged from the brush and into the clearing, we realized we had reached the top. The jungle was so dense there was no real spot to even look out to enjoy the view. We immediately got to work searching for the audio logger.  I looked left then right and passed through some thick brush. Then I saw it — a strip of white that stood out in the landscape of green. It was one of the zip ties used to attach the logger to the tree. We had found it! After several minutes of exulted celebrations and numerous high fives, we swapped out the SD cards and batteries, the unit was reprogrammed, and we locked up the protective case. The trip down was more like a ride down a luge course made of mud. This did make the process faster but certainly not any safer. 

Once we finally arrived back at the EVACC grounds, we were exhausted and coated in mud and insect bites but satisfied and content that we had achieved a seemingly insurmountable challenge. After a shower and a cold beverage, I walked out into the moonlight on the grounds of EVACC. Once again, the clouds were beginning to gather around the El Valle mountains, and my eyes settled on the tips of those green jungle peaks, wondering if the logger we had reset for another four months would record a sound of hope.

Learn more about the EVACC foundation and make a donation online to help them ensure the survival of Panamanian amphibian species for generations to come.

Mark Vassallo is pictured with an audio logger.

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