A Panamanian Vacation

By Tyus Loman

            After a day of driving and crossing the Costa Rica/Panama border, our bus finally reached its destination, a small port town on the Atlantic coast. Our group exited the bus, and we loaded into a small motorized boat. We started our thirty-minute boat excursion through a picturesque setting; the sea was clear blue, the coast was visible in the distance, the sun radiated and reflected off the water, and mangroves were scattered throughout. We passed by numerous tranquil beaches, and eventually our boat slowed. The boat entered what appeared to be a man-made tunnel in the mangroves, and we reached a secluded dock on Isla Colón, one of the islands in the archipelago of Bocas del Toro. I looked out and saw a large pastureland flanked by dense forest in the background. As far as I was concerned, we had reached a tropical paradise.

            We emptied the boat and started across the pastureland, avoiding numerous cows and a lone horse until we reached a fenced off area. Within the fence was the biological station; it included a two-story living quarters, library, laboratory, dining hall and lounge area, and even a volleyball court. Peter, the man in charge of the station, gave us a quick introduction of the haven he called home. In the dining hall, a dart board hung on the wall, a hammock spanned across two pillars, and the room was furnished with multiple tables and a couch. I could not imagine more calm and ideal living conditions.

            The next morning, we set out for our swimming and buoyancy tests, followed by multiple hours of snorkeling, an activity we would become quite familiar with the next few days. Bocas del Toro has a considerable amount of living coral reef, especially relative to the rest of the highly bleached Caribbean reef system. The marine biodiversity we encountered was incredible; we saw numerous moon jellies, a group of squids, multiple sting rays, and various families of corals and fishes. As well, we studied the habits of damselfish, a territorial herbivorous fish, using planted sea grass. The fish would chase away any fish that neared their food source, even to the point that one nibbled my finger when I attempted to collect the sea grass for examination.

            The incredible biodiversity of Bocas del Toro was not limited to the marine life. On Isla Colón, a three-toed sloth appeared at the station. To intimidate us, the assumed predators, the sloth stood up and spread its arms wide. Despite its best intentions, the pose simply made the creature look adorable. Also, we came across a Boa constrictor in the leaf litter. As well, the forest was dense with a plethora of frogs, especially yellow Oophaga pumilio with black spots. We even stumbled across a Diasporus diastema, more commonly known as a dink frog, a species that is quite difficult to find.

           Our quaint research station on the secluded Isla Colón is a great example of an island left highly-undisturbed by human interaction. In contrast to the other islands of Bocas del Toro that had been highly impacted by tourism, Isla Colón has retained much of its natural beauty. Despite the great economic advantages of tourism, Isla Colón is an example of why many of nature’s beauties must be protected.

Fossorial Calling Behavior of an Endangered Frog

By Rowan Etzel

           Back at Las Cruces Biological Station, several of us found some frogs exhibiting new calling behavior for their species, which happens to be endangered. Because these observations appeared to be novel, I decided to take on the task of writing up our observations in greater detail, perhaps eventually for submission to a scientific journal. Here are those notes:

Ptychohyla legleri, Legler’s Stream Frog, is a moderately sized nocturnal red-eyed treefrog, usually found near small streams in premontane wet forest of southern Costa Rica and western Panama. Males are thought to call during February–July in vegetation above flowing water, and have been found calling from rocks in streams at Las Cruces Biological Station, Costa Rica. Amplexus and oviposition behaviors are unknown for the species in the wild, but observations in captivity observed males to be territorial and defend small egg-laying cavities under an artificial waterfall where eggs were laid below the waterline. Clearly, the naturally history is poorly described for this frog.

            On 10 October 2017, we found six male P. legleri making advertisement calls for females at a first-order stream at Las Cruces. At about 4 PM, we heard two individuals calling from a short seepage down a vertical bank of the stream. Upon closer examination, the individuals were located one each within two separate burrows in the bank. The burrows were elevated 30–50 cm above the stream, ca. 15 m apart, and were ca. 3–4 cm in diameter. Water coursed down the stream bank around the burrow entrances and was also present within the burrows.  The individuals were perched 3–4 cm within the burrows and were half-exposed from the water. Upon shining a flashlight into the burrows, the individuals both stopped calling temporarily and retreated beneath the surface of the water. After a few minutes without exposure to a flashlight, they resumed calling with the typical advertisement call. The individuals chorused together, with one individual leading and the second calling in response to the first. Shortly thereafter, we located a third individual ca. 15 m upstream that was calling from within leaf litter adjacent to the stream. A fourth individual was also calling here near the third, but it eluded visual detection.

           When we returned after dark, we captured three more individuals. First, we located who we presume was the undetected fourth individual from the afternoon; it was a male and he was calling from among gravel beneath a rock. The final two individuals were found ca. 15 m upstream from the third and fourth, and were found calling together from underneath two rocks adjacent to the stream and were situated within small puddles with leaf-litter and twig organic detritus.

            We think our observations represent undescribed calling behavior for P. legleri which may provide insight into the breeding biology of the species. First, we observed individuals calling from subterranean burrows. It’s unclear whether those individuals constructed the burrows themselves, or used pre-existing burrows created by other mechanisms. In addition to the more typical nocturnal calling behavior, we also observed individuals that called diurnally in the late afternoon from within hidden calling sites such as terrestrial burrows and retreat sites beneath rocks. To us, terrestrial advertisement is uncommon among the hylid frogs of Central America, so this is atypical. Calling from covered locations such as terrestrial burrows may provide two functions. First, concealed calling sites may afford individuals additional protection and concealment from potential predators. In addition, these sites also resemble oviposition sites used by individuals in captivity. So, we think that these observations of terrestrial/fossorial calling may provide insight into where the frogs may lay eggs. 

Curiosities from Greater Depths

By Michael Cornish

            Gliding over reflective turquoise waters towards an island destination was as thrilling as we had hoped; the smell of salt and whichever organic compounds that give the sea its signature scent was new to this course and we were all apt to embrace it.  A new country, new ecosystems to discover, what could be more exciting?

            We had just spent nearly two days in a bus traveling from the cloudy mountains of Monteverde, Costa Rica, to the coastal Bocas del Toro region of Panama where we were to spend a week studying marine life.  Mountains touched the clouds behind us as we motored away in colorful fiberglass boats pushed along by sputtering two-stroke Yamaha engines. Split between two boats, we made our way from the mainland towards a research station on the island Isla Colón.

            Steaming along while thinking about the excitement ahead, I heard a familiar noise.  Sounding like a draining bath tub, I remembered that it was the sound of a fouled propeller, a sound I have heard many times while navigating dinghies through seaweed. We abruptly stopped so our captain could remove the piece of rubbish caught in the prop. Problem solved, we continued on our way.

            Eventually, we approached an island and I expected, anytime, to see a beach we would land on. All of a sudden, while passing some mangrove trees, we, at a considerable pace, shot into a hole in the trees and cruised through a tunnel in the mangrove swamp.  A few hundred feet into the swamp, the captain slowed the boat as we approached a clearing with a small dock and bodega signed “[the] Institute for Tropical Ecology and Conservation”.  We got out of the boat and made our way, about a quarter of a mile, up a hilly pasture to the station.  Small, neat buildings made of yellow pine with red metal rooves were to be our base for the week.

            Early the next morning, we went back out in the boat to a small reef bordered by a lush mangrove swamp. When we arrived, our only instructions were to say within site of the boat and look for interesting things. Snorkeling though the clear water revealed some amazing creatures; the patch reef was dominated by the delicate fingers of fire coral, domed brain corals, and the thumb-shaped fingers from corals of the family Porites that were home to countless species of invertebrates, fish, and algae. Between colonies of these calcified reef-building species were a plethora of other sessile (unmoving) invertebrates. Green, blue, and red sponges of all shapes and sizes formed colorful rock-like structures that were often inhabited by brittlestars, gorgonian corals (soft corals that look like small, leafless trees), feather duster worms (which filter feed using feather-like appendages), crawling fire worms, yellow mantis shrimps living in small holes, amongst many others.  These coral flats were also patrolled by many different fishes.  Small yellow and black gobies (shark-nose gobies) were numerous-often perched on a small coral branch or on top of a brain coral, sand-colored blennies cruised the sandy bottoms between coral patches, and wrasses of all different colors cruised above the reef. Herbivorous fishes, such as the French angelfish (when juveniles), parrotfish and surgeonfish (Caribbean blue tang), swam about the reef searching for algae to graze upon.

            Towards shore, the mangrove swamp was home to even more fish. The roots of the mangrove trees sat in crystal clear waters that teemed with the juvenile fish which use these habitats as nurseries.  Because of this, the disappearing of mangroves threatens commercially-fished species that live in mangroves as juveniles. As I swam across the reef towards it, a layer of cold, fresh water grew as I got closer to the mangrove.  The water went from a turquoise to an emerald color which was surprisingly clear. The tubers from the mangrove trees shot into the water as if they were trees placed upside down in the water. On them were numerous oysters and other mollusks.

            The days that followed consisted of field work on the reef, conducting a project examining herbivory on seagrass we placed in the territories of aggressive damselfish. By placing pieces of seagrass at 0.5m distances from the middle of a territory, we looked at how much herbivory occurred and where, in hopes that it could indicate how far away from the territory center a damselfish was willing to defend.

            Reluctantly, we left at the end of the week, but not without a farewell from a pod of dolphins that swam past out boat on the trip back to the mainland. 

Enter the Dragon

 By Dennis Bolshakov

           Last week, the OTS Tropical Biology group went to the Bocas del Toro and Bocas del Drago regions in Panama. Arriving at midday on bus to the Caribbean coast, we unloaded our bags and placed them haphazardly onto a small boat, and got into another boat ourselves. That day, I glimpsed just a fraction of the beauty that is the sea: we rode quickly, bouncing gently on the waves while inhaling the fresh sea air. I did not touch the water, in fear of splashing everything and everyone on the boat, since even reaching into the water with my fingers creates a spray of water that expands behind me (I did however, test this thoroughly the following days).

The lifeguard, Ivan, looks out to sea on our first day of snorkeling.

            After a brief swimming and buoyancy test, we were good to go. Boating over to different areas surrounding Colon Island, we snorkeled through the reefs and mangroves that surround the island, like a cell wall and membrane. That first day was my favorite field day: partnering up with a friend and exploring the beautiful aquatic nature. The life was especially strange and wondrous to me, since we haven’t learned anything about the coral environment yet (except to avoid the fire coral!). Having only seen a few documentaries about the sea, I was bombarded with the new sights and sounds and smells of the shallow sea for the first time.

            During the following two days, we conducted an experiment with the damselfish as the focal species. Since damselfish are herbivorous yet highly territorial, we wanted to see if brackets of sea grass were less likely to be consumed close to the den of the fish where it would chase other fish away less, or further away. And so, we returned to the sites twice a day and hovered for ten minutes at each site, observing who and for how long the damselfish chase, and then collected part of the grass from the site to measure for herbivory later in the lab. Watching the fish chase others was mildly entertaining, but the experience was definitely augmented by the picturesque setting. We are so lucky to have seen such a healthy and beautiful reef, especially now, what with coral bleaching affecting reefs all over the world. Admittedly, there were occasional beer and cola cans at the bottom here, which was sad to see.

The damselfish, our focal species among a bunch of coral, urchins, and brittle-stars.

           Every day, we returned to the Institute for Tropical Ecology and Restoration (ITEC) station on Colon Island by boating into a tunnel of mangrove trees and to the small harbor there. In this mangrove, we saw bats sleeping, great egrets preening, and even a small three-toed sloth gently moving towards the foliage. Upon arrival to the harbor, we washed all our equipment and then walked about a kilometer through pastureland, sometimes shooing away the cows and horses from the path. Back at the station, there was a library, a dining room, our rooms and the volleyball net. Breakfast at 7:30, lunch at noon, and dinner at six. The electric generator was turned on only when it was used for cooking or during the evenings, so there was limited access to the outside world, which suited me just fine. I spent much of my free time reading old issues of National Geographic and playing cards and darts with the rest of the group. The place definitely has a charm to it.

           Our last full day was similar to the first: we went to a reef and got to explore it for upwards of three hours. We saw rockfish, parrotfish, jackfish. Again, schools of iridescent fry were hiding in the mangrove roots, this time pestered by some bigger fish. There was a squad of squid, calmly undulating, changing color when darting away from us, and even inking one of the students. During the afternoon, we visited the town of Bocas Del Toro, to learn about how tourism affects local nature, culture, and economics. The town was surprisingly big, with its own airport and a main road with many grocery stores, tourist stands, and expensive bars. On land, we saw a sloth crossing the lawn, and took some photos of it while the poor thing was sitting, arms out, in a defensive pose the whole time. We also saw a boa constrictor snake more than a meter in length, which was exhilarating, and many small critters (and biting bugs!) during a night hike. The next morning, we all reluctantly packed our things onto a boat and left, and, much to our surprise, a small group of dolphin swam up to our boat, as if to say goodbye. It was a wonderful and educational trip.