Starting off at Palo Verde

By Finote Gijsman

It’s been two weeks since the start of the OTS Tropical Biology on a Changing Planet program in Costa Rica, and I can say that it’s already been quite a journey. The first field site we went to was the Palo Verde National Park in the Tempisque Conservation Area. Palo Verde is home to the endangered tropical dry forest ecosystem and a large marsh ecosystem that attracts many species of birds year-round.

On our first few days in Palo Verde, we familiarized ourselves with the park and its different ecosystems. Prior to the program, I didn’t really know much about the tropical dry forest, so it was interesting to learn about and experience it first-hand during our walks. Considering that this ecosystem is highly threatened due to habitat conversion by humans, I feel very privileged to have the opportunity to study one of the last significant fragments of tropical dry forests in Central America. This ecosystem is considered a “tropical dry forest”, because precipitation is highly seasonal and more limited relative to other wetter areas in the tropics. With long dry seasons that last several months, many plants shed their leaves to conserve water. We, however, were there in the middle of the wet season, so we were lucky to see many birds using the marsh. These included the green heron, boat-billed heron, and black-bellied whistling duck.

Later in the week, we hiked up to a lookout point in the park for the sunset. Along the way, we were greeted by a pair of white-headed capuchin monkeys. The two were resting in the canopy and did not seem too happy to see us, as they flared their teeth at us. Once we made it to the top of the hill, we were able to briefly watch the sunset over the wetlands, after which we rushed back to the station to avoid the evening showers.

In the evening, we got a talk by one of the researchers at the station, Davinia Beneyto, who is studying the crocodile population of the Tempisque River basin. The male: female sex ratio of American crocodiles in this region appears to be very male biased, with approximately 3.4 males for every female. The cause for this skewed sex ratio has not yet been determined, but Davinia and her colleagues suspect that the use of a hormone, 17α-methyltestosterone (MT), in nearby tilapia farms may be the reason. Tilapia farms around the national park are known to raise fish using food that is laced with the hormone to convert females into larger, more profitable males. With these crocodiles being apex predators, it may be that fish from the nearby tilapia farms are being eaten by the crocodiles at the Palo Verde National Park and in turn affecting the crocodiles’ endocrine system. Such findings may have large implications for the vulnerable American crocodile population at the Palo Verde National Park and possibly even Costa Rica as a whole. The biased sex ratio may be even more startling, because climate change is predicted to affect the crocodile sex ratio in the opposite direction, by favoring females. Crocodile nests are known to be temperature sensitive, with the sex of the baby crocodiles being determined by the temperature of their nests and not genetically. Hormones may therefore be driving a major shift away from what is naturally predicted by regional warming at Palo Verde.

I personally found this crocodile research program fascinating. I had never really heard about temperature dependent sex determination, but to learn that what was being observed was the opposite of what was expected with climate change, was even more appealing to me. Being a plant biology major, I have mainly been exposed to the way research works within that field of study, so I came into this program hoping that I would get to explore other fields in biology and learn about how the research methods within them. While the program has been field-work intensive, I have really enjoyed getting to branch out and learn about other systems. It has been very refreshing to get out of the organized lecture/classroom setting and be able to interact closely with professors specializing in many different subjects.

Catching Túngara Frogs in Palo Verde National Park

By Genevieve Valladao

Up until a week ago, I had never touched a frog. I prefer big predators – jaguars, sharks, crocodiles – organisms that humans aren't able to just grab and play with. So, when I found out that one of the first research projects I was going to be working on in Costa Rica involved trapping frogs I was a little nervous. The project was designed to test for effects of Belostomatid (Lethocerus annulipes) predators on site selection of prey Túngara frogs (Engystomops pustulosus). It involved capturing Túngara frogs at ten different sites, marking each of them individually, applying a treatment of Belostomatid chemical cues to half of the sites the next day, and then checking the sites the next night to see how the dispersal patterns of the frogs were impacted. Túngara frogs mate in small pools of water, so the study sites for our experiment were large puddles along the dirt road outside of the Palo Verde Research Station. Our program was split into two groups, each going out to catch frogs a different night and I was assigned to the second group.  

Photograph courtesy of Ray Hopkins

            Group one caught 48 frogs individual frogs the first night of the project, but also came back covered in mud and mosquito bites. Their complaints made me even less excited to go out the next night. But when night rolled around the following day, I put on my rain gear, rubber boots, headlamp, and face mosquito net, and headed out. I was unsure of what to expect. “Okay,” Brian said about 100 meters from the station, as we came up on our first puddle and he handed each of us a small plastic bag. “This is our first site.  Surround the puddle, grab as many frogs as you can, and drop them in your bag.”  Before I could question how I was even supposed to catch a frog, Brian and the rest of the students were along the edges of the puddle, shining their lights in the water.  Two frogs were caught at our first site.  As Brian tagged and documented one of the frogs, I watched the way he held it by the back leg.  “Can I hold it?” I asked - I did not want the first time I had to hold a frog to be one that I was trying to catch for our project.  I was not at all confident that I would be able to hold it without either hurting it or letting it go away.  Brian handed the small frog off to me and I got to get a good look at it - it was a male so its throat was stretched out from calling to females, which was amazing.

Photograph courtesy of Milena Cambronero

            We didn’t catch many frogs the rest of the night, possibly due to the puddles being small from a lack of rainfall.  And I stayed in the back of the group when we would approach a site, so the few frogs that we caught had already been captured by the time I came up on the site.  Sometimes, after a frog had been tagged and released, I would try to recapture it for practice.  Sometimes I would be able to catch it, and other times it would slip through my hands. I was relieved coming up on the last site – I hadn’t been the first to spot any frog so I hadn’t had the pressure of catching one.  But as I ran my headlamp over the puddle, my light illuminated something in the water – a Túngara frog.  I palmed it, just as Brian had instructed, and was able to pass it off to be marked.  I had caught my first frog for our project!

            The day after our experiment was supposed to be finished, it poured rain.  Frogs love rain.  So Brian asked for volunteers to go out one more night and survey all of the sites again.  I had practiced capturing frogs so much the prior night, but only caught one that contributed to our dataset.  So I geared up, this time in a full body bug net, and headed back out.  As soon as we got down to the road we could hear the Túngara frogs calling.  Every site was full of them, we caught 58 frogs for the night and I caught almost a quarter of them.  By the end of the second night, I was completely comfortable handling the frogs and would catch them for fun to try to identify their sex or just to watch them swim away after being released.  I even caught a large toad I saw along the road just to further examine it.  Having to catch frogs during my first week in Costa Rica was a great introduction to my OTS program.  It immediately forced me out of my comfort zone and taught me to not be afraid to try new things. I know that catching frogs is the first of many experiences that will push my comfort zone this semester in Costa Rica, and I can’t wait to see what direction I will be pulled next.

Sustainable Conservation in the Highlands of Costa Rica

By Dennis Bolshakov

Costa Rica often shown as an example of how conservation should work: around 25% of the country’s land is protected, and a wide system of national parks and biological research are hallmarks of recent Costa Rican developments (since the 70s). The reality is that conservation has a convoluted past here, with the government often imposing rules without little to no compensation to landowners, and the park system being too expensive for locals to peruse and enjoy, meaning the budget for the parks is small and the visitors to the parks often being foreigners. In fact, “eco-tourism” is a major part of the Costa Rican economy.

When the system of protecting the nation’s lands first started emerging, many people had trouble understanding why protecting the forests was important. The conservation movement was spear-headed by university graduates who understood the importance of the incredible biodiversity found here, while many rural people did not understand why they suddenly could not chop trees down for firewood after generations of doing so. Even though now the literacy rate is around 98% and most people have access to an excellent education, the rigidity of Costa Rican conservation practices leads many people to dislike it, which could be a future reason for un-protecting the reserves. Recently, I heard a very interesting potential approach to conservation: sustainable use of the reserve’s resources can actually provide both protected land and high-quality resources to future generations living near protected forests.

To elaborate, let me first tell you about Cuericí. As part of the OTS Costa Rica Tropical Biology program, I travel to different ecosystems and biological stations to learn about the flora and fauna in the field. Our second station is located in the pre-Montane wet forest near the Cerro de la Muerte mountains in the Cartago Province. When most people think about the tropics, they imagine heat and mosquitos, but this place has neither. At night temperature falls below zero, and during the day I need to wear 3 layers to feel warm. It is an absolutely beautiful place, and I have never felt such a connection to the land as I do here.

The Cuericí biological station is run by Don Carlos Solano, a pioneer of conservation in the area. However, it was never easy to conserve the area. Most of the secondary forest on his grandfather’s land had been converted to pasture land and the primary forest above it was threatened. When he started conserving the land, government help was minimal (around $400 dollars per hectare). To sustain himself and his family he established a trout farm and started bringing in eco-tourists and researchers (like OTS). He planted a forest of alder to restore the top layer and allow the understory to flourish, and native species to rejuvenate. Such active conservation is rare but not unprecedented: to preserve the tropical dry forest in the Guanacaste province, teak trees have been planted, then removed after the native plants had a chance to recolonize.

Sunset over Cuericí. The mountain I took this from was allowed to overgrow with blackberries, which are harvested by the station and used to make juice for the tourists. This field, in addition to the trout farm helps Don Carlos fund his conservation efforts in the nearby mountains.

Don Carlos’ motivation for conservation was so his grandkids could enjoy the forest in the same way he did. However, with current laws, it is not even allowed to use a fallen oak tree. Don Carlos believes that if regulated use were permitted, conservation would not only be more palatable to rural citizens, but also more profitable in the long run. And I agree. I think that before using an ecosystem, there needs to be extensive research about the system to understand its limits, and that use should never even approach these limits. But some foraging and use should be permitted as long as it is well-regulated. That is how it was before widespread deforestation through agriculture, and that is how it should be if we want financially self-sustaining conservation.

An interesting example where such conservation is being done is the use of cattle at the Palo Verde National Park tropical dry forest to eliminate invasive species. Before it was made a national park, the area was mostly pasture land for cattle, and the dry forest was extremely fragmented and often chopped down to make room for more pasture (at one point, the government even subsidized deforestation!). After it became a protected land, the forest started recovering, but two species started choking out others in their respective environments: an African species of grass that is extremely resilient towards fire outcompeted native grasses, and cattails took over the adjacent wetland. After many failed attempts and much consternation, a controversial strategy was implemented: local ranchers were permitted to let their cattle roam on certain day in certain areas, and because the two species were so dominant, they were the primary food of the cows. Now, the African grass is mostly defeated, but the cattails remain a problem. Another way the researchers fight the cattail is using special tractors to mull it into the water in such a way it cannot regrow. I think that using the cattle is an excellent strategy because it is a win-win-win situation for the locals, the researchers, and ultimately the protected area. In addition, the fees the ranchers pay to use the land helps fund conservation. And I think that similar, regulated use of public protected areas should be implemented everywhere.

The Wetlands at Palo Verde National Park: observe how at the right, near the biological station the wetland is more green and open, while farther to the east (left) cattails (the brown patches) choke the landscape all the way to the horizon.

Theory and Practice

By Mikayla Kifer

Science is an amazing, beautiful mix of ideas on the page and observations in real life. People make their livings by studying the relationship between the two, and the quest to understand truth is realized by comparing what we see and what we think we know. As young students, we learn all the “laws” of the world. But as we start to experiment and read journal articles, we discover that the world isn’t as fully understood and stable as we thought. This is, or should be, the greatest joy of science—we should be filled with an insatiable need to understand the world around us and uncover truths that are hidden.

            The relationship between theory and practice has become abundantly clear to me this semester. Part of the reason I wanted to study tropical biology in Costa Rica was because I felt that I had been learning a lot of theory in college, but not the nitty-gritty details that reveal how it all fits together. I had a strong desire to be in the field and learn the specifics of the theories that didn’t make complete sense without their fundamental real-life components.

            Since I’ve been here, I’ve been learning that it’s all much more messy than that. Relationships that make sense according to theories, don’t always make sense in practice. It’s often not clear why animals behave the way they do. Studying plant taxonomy has taught me that there are always exceptions to the rule. Science is supposed to explain the world around us, but it needs a whole lot of tweaking along the way. Contrary to what it might seem, this experience hasn’t made me doubt the validity of scientific evidence, though I retain a healthy amount of skepticism. Rather, it’s given me more faith in the scientific process by demonstrating the immense complexity of the world around us and the care that goes into understanding it.

            Science is rarely about finding evidence in order to posit huge theories; it seems to me that it’s more about finding small truths, being certain about them, and using them to support big ideas. This small process seems much more exciting to me. It’s great that research has implications for big concepts and applied knowledge, but well-done studies are exciting because they are truth within the small scope that they're focusing on. Everyone has a different reason for doing scientific research; this one is mine and I think it gets at the fundamental reason of why we do science in the first place.

            Because the relationship between theory and practice is so complex, it's a real challenge to represent scientific findings and their significance accurately. Communicating what science is is one of the most difficult tasks of a scientist, but also the most essential. Understanding truth is not useful if you can’t share it. Unfortunately, there seems to be a fundamental disconnect between scientific truth and the public’s understanding of it. I believe this stems from nonscientists misunderstanding what science can do and what it can't do. Scientific research can indicate that there is a highly likelihood that anthropogenic climate change is happening. Scientific research cannot predict with 100% accuracy the effects of these changes and should not be discredited when it cannot do so.

            I’ve thought about this a lot and I don’t have a solution, but I think it would be a good start to begin to integrate scientific theory into everyday life. The scientific method is derived from basic logic (induction and deduction) and thus it is not overly complicated to understand. Asking nonscientists to have a basic understanding of the scientific method would help them have a greater understanding of the limits of scientific evidence. If this were the case, we would be better able to focus on the whole point of science—finding truth—and that truth would be more readily communicated and therefore more appreciated.

            It is my hope that one day everyone will be able to appreciate the complexity of scientific understanding, especially as it relates to small truths that fit into our big theories in interesting and unexpected ways. For now, I’m excited to continue exploring this relationship myself by learning with both my hands and my mind.