The Osa Peninsula: Paradise Humidified

Rain splashes onto the metal roof of the cabina. Thunder rolls in the distance. Four college girls are fast asleep on the cold concrete floor, while others journal in their field notebooks or text their families the latest update, grumbling about the WiFi. Such was a typical scene that could be witnessed when we were not hiking in the massive rainforest of the Osa Peninsula.

According to certain geological data, the Osa Peninsula became attached to the mainland of Costa Rica approximately one and a half million years ago. The Osa, which covers less than 0.01% of Earth’s total surface area, houses around 2.5% of the world’s total biodiversity. This incredible influx of biodiversity began due to the area’s formation and continued to be affected by its geological surroundings, such as the Pacific currents that warm the ocean along its coastline. During the last ice age, the Osa experienced no full glacial freezing, and remained unpopulated with the exception of a few indigenous Costa Ricans until the early 1900s. These circumstances contributed to its plethora of unique flora and fauna, which define the peninsula to this day.

Around 1920, the Osa was engulfed in the country’s agricultural expansion and progression in to a plantation society. Government grants for farmers created a unique culture, which influenced the recuperation of the area as the Costa Rican government began to consider and support conservation efforts in the later 20th century. Many of the first reforestation programs supported by the government allowed for the preservation of the Osa and created much of the secondary forest we observed during our stay. Amazingly, 23% of Costa Rica’s total landmass is now part of the protected areas system, making it one of the only countries with both a rising GDP and a growing density of forested areas. One problem conservationists must consider is the isolation of the Osa Peninsula and possible effects on the endangered populations that live there. Due to the herculean efforts of more contemporary conservationists, the biodiversity of the Osa is now bolstered through a system of natural reserves connecting its protected areas to broaden the overall habitat for endangered species.

We had the opportunity to experience the rainforest that surrounds the Piro Biological Station, which is part of the Osa Conservation program. Scientists working at the station are primarily engaged in a rewilding and assisted restoration program for the area, allowing natural systems to regenerate as efficiently and holistically as possible. Although our research does not pertain specifically to the more recently rewilded areas of the rainforest, it was fascinating to see the effects of conservation practices in action, such as monitoring different species behaviors, habitats, and population size.

The first evening of our stay at the Piro Biological Station, May 26th, we learned the context and importance of the conservation work being done in the Peninsula, and oriented ourselves with the ins and outs of the station. We collectively marveled at the efficiency and sustainability of the entire community; everyone went to bed early and rose earlier than the sun, conducting various research and conservation projects.

The next morning, we took the opportunity to hike many of the trails that snaked throughout the forest, scoping out the best locations for camera and rodent traps. Our ultimate destination was the Greg Gund Conservation Center at the top, mainly used for conservation education camps. Along our hike we discovered a multitude of plant and animal species such as the very entertaining spider monkeys and ever-present leaf-cutter ants, inspiring many of us to begin or continue a species log for our travels. After returning to the station for lunch, Don David (our Costa Rican name for the intrepid Dr. Ribble) taught us how to set camera and rodent traps. The Sherman traps we will be using for the entirety of the trip were particularly interesting; not only were they foldable, but also were numbered using a special system to differentiate bait types. Even numbered traps contained seeds mixed with vanilla extract, while the odd numbered contained a mixture of oats and peanut butter. By organizing the traps in such a way, we eliminated confusion about which mice were enticed by which kind of bait. Don David explained to us how certain mice preferred the peanut butter and oats mix, while others were seed-eaters, and had little cheek pockets for their treasures.

To set the traps, we journeyed back into the looming and humid rainforest, unaware of the exhaustion that lay in store. Stumbling over tree roots, sliding through the bright red clay-mud, and drenching in sweat, we finally made it to the first transect: the river. After pretending to be jaguars prowling past the camera traps, we placed twenty sets of three traps twenty paces apart along the river’s edge. We repeated this process of setting camera and rodent traps in two more transects. Both were in increasing elevation: one still in the primary forest, and one in the secondary. By the time we made it back to the station, exhaustion and sweat permeated the atmosphere. Not surprisingly, we were more than happy to scarf down food and suffer through cold showers in order to collapse on our mosquito-netted beds.

Enticed out of bed the next morning by the promise of a delicious breakfast, we were soon back on the trails, checking each and every trap we had placed the evening before in hopes that they had yielded a mouse. That particular morning we had no such luck, but ardently hoped that the next morning would produce more fruitful results. After lunch, we took a few hours to journal and record our observations of the forest and their adaptive significance. Shortly after our brief siesta, it was back to the trails to reset rodent traps. As a treat, we hiked a short ways to the rocky beach near the station, admiring the crashing waves, sunset, and infinitely Instagrammable moments. That evening we got to hear about an amazing project being done by a father-daughter team at the station on poisonous frogs and their prevalence and predation in the area. Thoroughly inspired, but utterly exhausted, we wound down from the day with our first group yoga session. Stretching our tired muscles proved the perfect way to end the day.

Forcing college students out of bed at five o’clock in the morning normally leads to loud complaints and terrible tempers; however, we had an exhilarating motive to wake up so early the next day: turtle eggs! A local researcher on staff at the station and his two assistants guided us down steep trails and across narrow bridges to the beautiful beach. As we hiked, they explained their conservation efforts to us. To start each morning, they looked for nests that were in dangerous areas, dug out the fragile ping pong ball-shaped eggs, placed them in a bucket with some of the sand from the nest, which contained special nutrient effects from the mother. Next, they transferred the eggs in a small bucket to the hatchery, along the way checking other nests in the area. If a nest was predated on, they would move the remaining eggs to a safer spot on the beach. Often they didn’t find new nests, as it was still very early in the season. Perhaps we brought good luck with us, because we found a nest in less than five minutes! After making sure that it was a turtle’s nest and not a crab infested lair, our gracious guides allowed us to help them rescue the eggs and create a new home for them in the nursery.

On the way back from the hatchery to where we had left our field boots, we spotted a coati, an infamous predator of turtle eggs, skulking next to a previously plundered nest. Blood pounding, we begun to run and shout, savagely driving away the animal in our frustration. A few in our group were prepared to turn around and guard the hatchery of invaluable eggs until they hatched, but the grumbling in our stomachs overruled and we headed back to the station for breakfast. After another filling meal of gallo pinto, we grudgingly trekked through our three transects to check traps. No mice were to be found. Sighing in disappointment, we reset the traps, giving a tiny prayer to each one to please have a mouse in the morning, so we wouldn’t have worked so hard for 0/270 potential captures. Then we sprinted back to the station, anxious for lunch and relief from the relentless humidity.

In the afternoon, we walked up the road to the farm that was producing most of our food, and learned about the conservation efforts of several plant species. Shocked by the size of some produce, we strolled through the farm in wonder, soaking in the beauty surrounding us. On our way back to the station, we spotted squirrel monkeys and a few other creatures. Then, after dinner, we held our first discussion about Costa Rican culture. The treatment of women and the concept of individualism were a common thread and we went to bed with mulling brains, full stomachs, and happy hearts.

Hauling ourselves out of bed at 4:00 am was certainly not the way many of us would have chosen to spend our last morning on the Osa Peninsula, but the early Reville was totally worth it when we checked our traps…. Lo and behold, we had finally caught a rodent! That solitary vesper rat (Nyctomys sumichrasti) was the embodiment of so many hopes, and we were absolutely thrilled to see our hard work pay off. This particular Nyctomys was a female, who we determined was not currently breeding and had never had a litter (nulliparous and imperforate, if you want to be sciency about it). After taking the necessary data, we reluctantly released our precious prize, and retrieved the rest of the traps. After breakfast we packed our bags once again, and prepared to say farewell to the Osa. Through the long days of mud, sweat, and tears, countless animal sightings and the joy of research and companionship, the vibrancy of the Osa had been clear. To become so intimately a part of such an incredible place, even for so short a time, was an experience none of us will soon forget.

Until next time,

Jenna and Sarah