Land Conservation and Forest Restoration, Science and Research, Uncategorized

Variety is the spice of life: Monitoring the wildlife in our ecological restoration and rewilding plots

Blogpost by Alice Connell, Restoration and Rewilding Research Field Assistant

Alice monitoring the effectiveness of log piles in attracting amphibian and reptile species to the restoration and rewilding plots. Photo: Sophie Blow

My work is never the same from one day to the next on the Restoration and Rewilding Program, which encompasses many diverse projects that require frequent monitoring. There is plenty to do, I always arrive at lunch hungry and satisfied after mornings of hard work. I want to give you an insight into my first month of being a Restoration and Rewilding Research Field Assistant.

We are employing a variety of approaches and techniques across the rewilding plots in order to “rewild” an array of animals to return to recently reforested abandoned grassland. Our idea is that as the overall species diversity increases, inter- and intra-species interactions within the regenerating areas will begin to re-establish. With some patience and continuous monitoring, we the aim to demonstrate a restored harmonic ecosystem functioning of the Osa Peninsula, and its associated key ecosystem services.

A medium bird box installed to offer shelter for birds. Photo: Alice Connell

One project in the restoration plots is the installation of nesting and roosting boxes to attract birds and bats. To accommodate a variety of species, there are 5 bird box designs, each differing in dimension of the entry hole and the box itself. The frugivorous species belonging to both birds and bats play a vital role in increasing the rate of seed rain, and consequently, the rate of seed dispersal and reforestation.

One day of my week is dedicated to surveying the wonderfully diverse bats that are choosing to use the rewilding plots. The morning’s duty involves erecting mist nets in preparation for the evening’s bat survey. Come the evening time, the team heads back out into the field to open the nets. When the clock strikes six, the monitoring begins, and the excitement of the possibility of catching a new species record ripples through the team.

The species, Micronycteris hirsuta, was recently caught for the first time in one of the rewilding plots. Photo: Alice Connell

The following morning, decaying log piles and epiphytes (such as bromeliads) are translocated to the rewilding plots to increase microhabitat availability, in an effort to rewild amphibians and reptiles. Such microhabitats occur naturally in the primary forests, usually providing refuge for different invertebrates, such as centipedes and millipedes, and for amphibians and reptiles, such as leaf-litter frogs and sun-basking lizards. It is always a pleasure to find a fer-de-lance coiled peacefully within a log pile in a rewilding plot. While the log pile project is relatively new, we have already observed a rapid return and colonization of several amphibian and reptile species within a short period of time, which is highly encouraging.

Undeniably, a huge effort, in terms of time and determination, is required to create a biodiverse and ecologically restored forest ecosystem. Fortunately, the team of highly-motivated and enthusiastic people that constitute the Restoration and Rewilding Program indicates a promising future for Osa’s forests.

A fer-de-lance coiled peacefully within a log pile in a rewilding plot. Photo: Alice Connell

Community Outreach, Land Conservation and Forest Restoration, Sustainable agriculture

Into the wild: Revealing the secrets of wild vanilla

Blogpost by Charlotte Watteyn, doctoral researcher at KU Leuven (Belgium) and the University of Costa Rica, collaborating with Osa Conservation

If you think about vanilla, you immediately start to imagine delicious ice creams, cakes and other yummy sweets. But where does this vanilla come from? Well, it is extracted from the fruits (beans or pods) of orchid vines, producing an intense aroma resulting from a complex of molecules. These orchids belong to the genus Vanilla (Orchidaceae), a diverse group of climbing hemi-epiphytes growing around trees with their aerial roots. The genus contains over 100 species and is pantropic, meaning that they are present all around the tropics. However, the aromatic vanilla species, the ones that produce the lovely smelling pods, are native to the Neotropics.

Overview of the 5 different vanilla species growing in our study region ACOSA (Area de Conservacion Osa). Photo: Adam Karremans

Nevertheless, when you buy vanilla and take a further look at the country of origin, you will probably read “Madagascar.” But Madagascar does not fall within vanilla’s native growing regions, so only the introduced species that was brought over from Mexico a long time ago, Vanilla planifolia, is cultivated in Madgascar. Vanilla cultivators in Madagascar have to pollinate flowers by hand, because natural pollinators are absent, and use intensive production systems. Furthermore, the market chain involves several intermediaries that keep prices artificially high by holding back large quantities, explaining the currently high market prices. As a result, we realized there is a need for innovation in vanilla cultivation.

We want to determine the possibility of contributing to a more sustainable vanilla provision through a joint land sparing and land sharing approach (SPASHA), ensuring the conservation of wild vanilla populations while cultivating the economically interesting ones in a sustainable agroforestry system. There are several wild vanilla species, known as crop wild relatives (CWR), growing in the lowland tropical rainforests of the Neotropics, with presence of pods (that smell very nice!), indicating natural pollination. However, there is very little known about the distribution, biology and ecology of both the orchids and their pollinators. We are interested in determining the potential to cultivate wild vanilla and therefore create an alternative income source for local communities.

Left: The beautiful flower of Vanilla trigonocarpa. Middle: Fruits (green beans) of Vanilla hartii, the result from natural pollination, a mysterious process that we will study in more detail during the coming year. Right: Flower buttons of Vanilla hartii. All three species are native to the lowland tropical rainforests of Costa Rica and are growing within our study region ACOSA. Photos: Charlotte Watteyn & Ruthmery Pillco Huarcaya

As part of the study, we made experimental plots, where we planted four aromatic vanilla CWR—V. hartii, V. odorata, V. pompona and V. trigonocarpa—in both reforestation areas and organic cacao plantations. One of the plots is located at Osa Conservation’s Osa Verde Agroecological Farm. We will measure growth and survival rate over time, as well as production and pollination processes during later stages.

We will be monitoring the vanilla’s success over the next few months and keep you updated with the first results of this exciting (and delicious) research!


The planting team at Osa Verde (Marvin, Johan, José, Ruth and Charlotte). We planted 120 vanilla plants, 30 plants of each of the four species, in our experimental plot within a 3-year old reforestation area with a mix of native tree species that act as tutor trees. Photos: Charlotte Watteyn and Ruthmery Pillco Huarcaya

Science and Research

Massive treefrog breeding aggregations at Shampoo Pond

Blog Post by Brandon André Güell, NSF Pre-doctoral Fellow and Ph.D. Student, Warkentin Lab, Boston University

Brandon Güell observing a breeding aggregation at Shampoo Pond. Photo: Brandon Güell

It was about 06:00 after night-long heavy rains ended a short dry spell, and already you could hear a deafening chorus of creatures gathering at the pond. Though sleepless and mosquito-ridden, we trudged chest-deep through the murky swamp waters with notebook and camera in hand to reach the source of the chaos. That’s when we saw it: One of the largest aggregations of treefrogs likely ever to be witnessed.

Tens of thousands of adult gliding treefrogs (Agalychnis spurrelli) literally poured over each other in attempt to breed and lay eggs. And for two Costa Rican tropical biologists and herpetologists, this rare biblical magnitude of frogs was like heaven on earth. This is Costa Rica. This is Osa. This is “Shampoo Pond”.

Agalychnis spurrelli breeding aggregation on palm leaf at Shampoo Pond. Photo: Brandon Güell


Since 2015, I have been studying how frog embryos use environmental cues to change their behavior. My current Ph.D. research in the Osa aims to understand how specific reproductive strategies interact with both environmental cues and development to affect embryo behavior and survival. For these gliding treefrogs, tens of thousands of reproducing adult frogs mean hundreds of thousands of frog eggs and embryos. And in this species, embryos are left alone to fend for themselves after they are laid. That means this event leaves behind a massive all you can eat frog-egg buffet for hungry predators

Why have a massive population lay their helpless eggs all at once in one location? That’s a great question, and it’s one I hope to answer!

In some cases, an overwhelming amount of prey can function as an antipredator adaptation if, for example, the overabundance of frog eggs decreases the probability of any one egg’s chance of being eaten. Basically, it can serve as a form of “safety in numbers”. This is known as predator swamping (or predator satiation). Shampoo Pond offers a pristine ecosystem where this hypothesis can be tested using these treefrogs.

In 2018, with the assistance of Katherine González, a Costa Rican tropical biologist, we conducted initial egg clutch monitoring studies in the hopes of determining whether this reproductive strategy has any impact on offspring survival. But this system has even more to it!

If undisturbed, gliding treefrog embryos develop and hatch into the pond as tadpoles in 6 days. But with so many threats, many wouldn’t survive that long.

Brandon Güell and Katherine Gonzalez headed out to the field from the research station. Photo: Brandon Güell

How can frog heaven get any more interesting, you say? Well, what makes these treefrogs particularly interesting is their ability to respond to threats by hatching prematurely!

That’s right! These embryos can hatch almost 40% early to escape the jaws of a hungry predator like snakes, wasps, and even monkeys! However, many of them don’t hatch early, and thus will die during predator attacks. We know the embryos have the ability to hatch early, but sometimes they don’t. Why?!

In addition to predation, these embryos are susceptible to desiccation, fungal infection, and flooding. These threats provide unique cues, which the embryos use to inform their decision of when best to hatch. This is called environmentally cued hatching, and it’s presumable a very adaptive embryo behavior— it increases their survival and fitness. But for the gliding treefrog, this behavior may not be as plastic or adaptive as in other species. Here in the Osa, another focus of my research is understanding the mechanisms which cause these embryos to hatch or not to hatch in these contexts at different developmental stages.

Our work has only begun at Shampoo Pond, and we hope that it will elucidate the conservation importance of this fragile ecosystem and its inhabitants, particularly amidst the current anthropogenic environmental changes in Neotropical rainforests.


Above: A series of gliding treefrog (Agalychnis spurrelli) embryo developmental stages. After embryos undergo early and late cleavages (cell divisions with visible nuclei), they form the dorsal lip and the yolk plug becomes visible. Later, embryo bodies rise and begin to show muscular response as the external gills form. Then, their hearts begin to pump blood throughout the body and external gills, and they begin to develop pigmentation. At three and four days, embryos begin to respond to environmental cues and can hatch prematurely to escape flooding and predators respectively. In the last picture, Brandon collects eggs in the swamp to study. 


Land Conservation and Forest Restoration, Science and Research

Restoration’s exciting night life

Blog Post by Elène Haave Audet, Restoration and Rewilding Research Field Assistant


Elène holding a Noctilio leporinus, the Greater bulldog bat, which fishes from streams. Photo: Doris Audet

For many of us, the creatures of the tropical forest that dare venture at night remain elusive and mysterious beings, their ways of life foreign to us daytime dwellers. Among these enigmatic animals are bats, the group of mammals with the second largest number of species in the world, whose charismatic presence in the tropics will not go un-noticed to the keen nocturnal observer.

Like many sensitive animals, bats are particularly special as a group, since many species require natural areas that have not been disturbed by human activity to find food and places to live. Thus, the presence of many different bat species can provide information about the health of an area. For this reason, Osa Conservation has started sampling the diversity of bats in areas that are being actively restored into forest, after years of use by humans. Overtime, the presence of different types of bats in these areas will help determine the success of restoration.

Vampyrodes caracciolli, the Great striped-faced bat, the second of two new fruit eating bats on the OC property, enjoying a well- deserved fig. Photo: Hilary Brumberg

After seeing the restoration plots for the first time this May, I was convinced that the bat diversity in these areas would not be exciting: that is, I expected to find very little diversity, since the restoration areas are in their infancy and have very little forest cover.

Was I ever wrong! The bat life in the restoration plots is teaming with diversity. After four months of sampling, we have recorded 24 different species of bats, ranging from those that eat insects, fruits, nectar, fish, and yes, even blood. To add to this excitement, two species of fruit eating bats recorded in the restoration areas had not been previously detected on the Osa Conservation property!

Why, then, has the bat nightlife been much more exciting than anticipated? Although the restoration areas have very few trees, the surrounding areas are lush with tropical forest, providing ideal habitat for these endearing creatures. This is very encouraging news for restoration initiatives, as connecting the surrounding forests with restored habitats will continue to support the diverse lifestyles of our nocturnal friends, so they may continue hunting insects, fishing bats, and snacking on figs.

Now every night of sampling is an adventure, and I cannot wait to see what other bats we will encounter in these deceptively rich areas!

Chiroderma villosum, the Hairy big-eyed bat, one of two new fruit eating bats encountered on OC property, posing handsomely. Photo: Elene Haave Audet



The Prevention of Ecosystem Collapse Project

Blog Post by Marco Hidalgo, Coordinator for Prevention of Ecosystem Collapse

Our tropical forests, including the extensions of mangroves that slope down the south pacific, suffer a constant threat from different man-made factors. One of the most significant threats is the lack of predators and their prey, which have decreased due to recreational and cultural hunting in the Osa Peninsula.

In the search for practical solutions on the ecosystem-level, Osa Conservation’s Prevention of Ecosystem Collapse project hopes to increase the resilience of ecosystems in the Osa Peninsula through the use of citizen science and rewilding practices. Osa Conservation also aims to connect their existing science network with the local ecotourism industry.

This initiative implements acoustic devices that detect the remote activities of the biodiversity in the Osa, which provides us with unique biological data, fast answers, and reliable wildlife monitoring from the canopy of our forest.

The project also offers education workshops and seeks to develop alternative opportunities with the goal of transforming hunters and their children into defenders of wildlife. This project has hosted talks in educational centers where our researchers and local hunters come together to learn about the importance of wildlife in our forests.


Connecting Golfo Dulce’s Fish Populations

Blog Post by José Luis Molina Quirós, Alvaro Ugalde Scholarship Awardee

Costa Rica has a great diversity of species and marine ecosystems that protect and provide food to hundreds of organisms in various phases of their life cycle. For example, El Golfo de Papagayo and Golfo Dulce are just a few of the many hot spots that harbor this diversity of marine species and ecosystems, but these species have not been completely protected.

Sampling of species (Lutjanus guttatus, L. peru and Centropumus viridis) product of artisanal fisheries.

Currently, our country lacks the basic information necessary to evaluate the population structure of bony fish species, which have been exposed to heavy fishing pressure that make a natural recovery of their populations impossible. This problem not only afflicts Costa Rica but also all of Latin America, since there is no scientific data that gives real support and defines the units of a given fishery. For this reason, it is critical to clarify the degree of genetic connectivity among fish populations throughout their geographical distribution in order to maintain the productivity of the populations and ensure the sustainability of fishery resources over time.

Sampling and release of Sailfish (Istiophorus platypterus) in offshore sport fishing with Crocodile Bay in Puerto Jiménez.

Therefore, the present research proposal aims to study the genetic connectivity of several species of teleosts that play a critical role at the ecological and economic level (tourism, sports, and crafts), such as roosterfish (Nematistius pectoralis), snappers (Lutjanus peru and L. guttatus), bass (Centropomus viridis) and sailfish (Istiophorus platypterus). Through the use of nuclear molecular markers (microsatellites), it will be possible to define regulations and estimates of the maximum sustainable level at which a stock can be exploited.

Sampling and release of Roosterfish (Nematistius pectoralis) in inshore sport fishing with Captain Roy Zapata in Quepos.

The results of our research will allow us to generate the first biological-fishery information of these species along the Pacific coast of Costa Rica and establish baseline information that could suggest possible fishery management strategies and measures.


Research Field Assistant Journals

Blogposts written by Research Field Assistants Mariam Weyand, Bryan Graybill, and Alexandra Mörth

Rewarding Research

Working as a research field assistant (RFA) for the Sea Turtle Conservation Program with Osa Conservation is really different from the other places I have worked for, and so far, it has been really rewarding.

Every day, we conduct morning patrols to register any activity from the previous night and relocate nests that are at risk to the hatchery. I wake up between 3:45 and 5:00 a.m. depending on which beach I am going to patrol and on the presence of groups. At first, it was a bit hard to get used to the rhythm, heat, and humidity, but now that it’s been a month and a half, I only see the bright side of this job.

Every day is different; the diversity and abundance of fauna on the Osa peninsula is amazing and surprising, not to mention the breathtaking sunsets. When it comes to releasing baby sea turtles and protecting them from predators, it is the best reward I could get and I wouldn’t trade it for anything. Moreover, it is really satisfying to be able to share our experience and knowledge with groups and volunteers, spreading awareness about sea turtles’ status.

It is also really interesting to work with Osa Conservation due to its diversity of projects and conservation programs.

-Mariam Weyand

RFA Mariam taking care of olive ridley babies after releasing them.


The Importance of the Work

Six days a week, I wake up around 4:00 a.m., get dressed, slip on my rubber boots, turn on my headlamp, and begin the day with a hike through the jungle to one of two beaches that the research field assistants (RFAs) patrol. Along the way, I am greeted by the sounds of frogs’ mating calls, howler monkeys’ gravelly morning bellows, and bats swooping in and out of my vision.

When my co-RFAs and I reach the beach, we begin the patrol looking for sea turtle nests laid the night before. If we find nests in a vulnerable location, we’ll open the nest, delicately extract all 60-130 eggs, and move them to a walled off hatchery where they will be protected from the tide and predators. When the patrol finishes a few hours later, I’ll hike back through the jungle to the Biological Station for breakfast with the other researchers living at the station, praying that today is pancake day.

Though the ability to participate in sea turtle conservation is a reward in and of itself, the surprises and differences between each day are what make the work truly special. It could be a sunrise that fills the sky with colors, a miniature blue jellyfish that has washed up on shore, or a sea turtle making a nest in the sand for a new hatchery we haven’t started using yet. The holy grail are the days when we enter the hatchery and, after opening the mesh net that covers each nest, we see a teeming mass of newly hatched sea turtles, full of energy and eager to get to the ocean.

Of course, there are also the days when we get to the beach and find mostly empty nests, either poached by humans or dug up and eaten by dogs or coatis, or we find the whole beach littered with garbage that has floated across the ocean from countries as far away as China. But these are the kind of daily experiences that remind me why conservation is such an important field right now, and why we all need to constantly strive to be more responsible consumers.

-Bryan Graybill

RFA Bryan with an olive ridley going back to the sea after nesting at Piro Beach.


Self-discovery in the Osa

My time as a Sea Turtle RFA has been an intense experience—rewarding and challenging at the same time.

Waking up every morning between 3:30 and 4:30 and hiking straight to the beach for the morning patrol before breakfast is quite a change of lifestyle, especially for a “night owl” like me who is used to going to bed late, getting up late, and can’t start the day without a cup of coffee.

We start the day with a hike through the still, dark rainforest and arrive to one of the beautiful and wild beaches we patrol. Watching the sunrise with this breathtaking view while patrolling the beach for sea turtle nests makes waking up so early more than worth it. During morning patrol, we relocate nests from critical spots to our hatchery, triangulate nests in non-critical parts of the beach, check predated nests, and hope to find nests hatched the night before in order to enjoy the best part of the job: releasing baby sea turtles into the wide ocean.

After morning patrol, we head to the Biological Station for breakfast. The rest of the day we work on the database or on our own projects. In the afternoon, we check if any nests have hatched, and if the season and weather allow, we go on a night patrol to look for females nesting. In the late afternoon we usually have time to enjoy this incredible place and hike at one of the various trails, spot animals, go to the beautiful Laguna (Kalman included) and the beaches, or just rest in a hammock and read a book. Every day is different!

A great thing here is definitely the community. There are many young researchers, assistants, farmers and kitchen staff living near each other in various houses and camping platforms. At lunchtime and in the evening it’s a great chance to spend time with very different people from countries all over the world.

I came here because I was looking for a life more connected to nature and to become a part of protecting the two ecosystems I love most, and which are, in my opinion, the most important to protect: the rainforest and the ocean. So, I started living the life I dreamed of here, although I really wasn’t expecting it to be so challenging. Arriving from cold Germany just three days before starting my position here, it took quite a while to get this European used to living and working in the jungle.

While becoming friends with my new roommates, cockroaches, ants, wasps, toads, geckos, a tarantula and fungus, worked out very well, the heat, humidity, and getting sick at the beginning really gave me a rough start. But by hiking, sitting in the middle of the rainforest and at these wild beaches, taking in the incredible biodiversity of giant trees, various frogs, monkeys, birds, and of course, sea turtles, and listening to the sound of the jungle and the waves of the Pacific Ocean gave me so much energy and peace that after a while I felt fitter than before and learned to adapt to everything.

This place has taught me a lot about nature and conservation as well as about myself. Seeing how many threats a sea turtle has to face during her lifetime—from the risk of rising sea levels, the exhausting first trip to the ocean, and predators and poachers, to the the dangers in the giant ocean—and knowing only one in a thousand survives, showed me how important our work is here. I am really happy that I am able to contribute to this hard work. Now, after two months, I can’t imagine a life without walking back at night through the rainforest in the moonlight surrounded by lightning bugs, crossing a river to get to my mosquito-net-sheltered bed, listening to the tropical rain while falling asleep and starting the day early with the sounds of the Howler Monkeys and a hike, all before having a coffee.

-Alexandra Mörth


Un Día de Tortugas: An Intern Experience

Blog Post by Breanna Hart

Mahatma Gandhi once said, “Live as if you were to die tomorrow. Learn as if you were to live forever.” Osa Conservation has allowed me to both live and learn in a beautiful environment that no other place in the world can contest with. The spectacular view of the ocean and rainforest back-to-back lead me to a tropical wilderness and the fascinating creatures within it. One magnificent creature that spends time on the unique beaches is the turtle, and this is my experience with them:

4.30 a.m – Morning Patrol: We get up, rain or shine, and meet at the pavilion with others to head down to the beach. Then, we start searching for turtle tracks to locate nests using the first light of day.  Two different turtles come to the coasts of Piro beach at this time of year – Green Turtles and Olive Ridley Turtles. After we find the tracks and locate the nest, we dig a small hole to take the eggs out. When taking the eggs out, we have to be careful not to rotate them because they are still developing. We move the nests that are in danger of possibly drowning from high tide or river flooding.

The tractor-looking marks on either side of the log in the middle of the picture are Olive-Ridley tracks.


For each nest we relocate, we mark the date, the sector of the beach it was found in, the time it was found, count the eggs, and measure the width and depth of the nest to simulate a similar nest in the hatchery.

After collecting the eggs, we go to the hatchery, where we safely relocate the eggs to ensure a better survival rate by recreating a similar nest to the original one. Before we start placing the eggs in the new nest, we record the weight of the first 20 eggs that are put in the nest. Their average weight is an indicator of whether or not a female is laying eggs for the first time this season. For the first few nests a turtle lays, the eggs are stronger, and therefore heavier. Finally, we cover the nest with a mesh net to keep predators out.

After collecting the eggs, we go to the hatchery, where we safely relocate the eggs to ensure a better survival rate by recreating a similar nest to the original one.

3pm – Hatchery check: We check the hatchery for newly born turtles. It is a simple process where we lift open the mesh nets and pat the sand for any indication of baby turtles. It takes about 60 days for the turtles to hatch and make their way out of the sand.  Almost every other day, we run across a newly hatched nest. Then we release them!

The line which people stand behind and from where we release the tiny turtles. The line is 6 yards from the water line to ensure that the turtles use their muscles before they make their way through the ocean.

8 p.m. – Night Patrol: We make our way again to the beach to begin our search for nests. If we see a turtle coming up on the beach or already creating a nest, we wait back to avoid disturbing the turtle. When she starts to lay her eggs, she goes into a trance-like state, and we tag both of her front flippers. We also record the length and width of her shell as well as the number of scales on her back and between her eyes.  After she finishes laying her eggs (this process can take up to an hour), we turn off the lights and watch her go back into the ocean. If the nest is in a dangerous spot, it will be dug up and moved to the hatchery.

During night patrol, red lights are necessary as not to disturb the turtles.

This schedule reflects what my days have been like during my two weeks in the Osa peninsula. It was a wonderful and amazing experience, from witnessing the mother turtle lay her eggs to watching the little babies make it to the sea. I was fortunate enough to see this little part of the circle of life with my own eyes. I can’t wait to one day come back to this magnificent corner of the world.


Potoos and Point Counts

Blog Post by James Purcell, Restoration and Rewilding Intern

The daylight was rapidly disappearing, as we clambered through the thick undergrowth, over vines and palm leaves bigger than me, then across a muddy stream and still more dense brush. Then, we heard it again –  a long, mournful series of calls that sounded like a child laughing, or perhaps crying, in the distance. We all stopped, holding our breath; the only sounds were the omnipresent croaking of the frogs and the pumping of our excited hearts.

Then, as casually as if he were pointing out a Balsa tree, Manuel said, “There it is,” as he pointed into the canopy of a large tree overhead. Sure enough, the Common Potoo that two other young eager birders and I had been seeking was sitting calmly on an overhanging branch high above, perfectly camouflaged against the bark in its mottled gray plumage. The potoo, which is a nocturnal bird related to nightjars and nighthawks, was just starting to wake up from its daily snooze as the light began to fade. This was just one of the many exciting moments from several weeks of intense birding around the environs of Osa Verde Lodge and Osa Biological Station.

All of this birding was part of a citizen science project through Osa Conservation and partner National Geographic Eco Lodge Lapa Rios in order to establish a set of long-term point counts for bird biodiversity. We would pick spots in certain areas of the property around the lodge – including the primary and secondary forest, our restoration experiment plots, and open garden areas –  and we would record all of the bird species we could see and hear at that spot. This information was entered into eBird, a global database of bird sightings contributed by everyday people. Scientists then use this data to track movements of certain species, map distributions of birds in different places, and define key areas for species of conservation concern that need to be protected.

Throughout several weeks of conducting point counts, the other interns and I had many exciting discoveries like the potoo. Whether it was a Spectacled Owl perched up along the Tangara trail giving deep resonant hoots, a tiny American Pygmy-Kingfisher twittering above the swamp on the Discovery Trail, or a Tamandua snoozing in a small tree along the trail, there were always new and amazing things to find while interning at Osa Conservation.


Hidden Treasures: The Search for Caves on the Osa Peninsula

Blog Post by Stanimira Deleva, Alvaro Ugalde Scholarship Awardee

The Osa Peninsula is a place where, even after hundreds of exploratory expeditions, there is always something to be discovered. As one of the world’s most biodiverse sites, the Osa is home to a vast variety of bats, most who use caves as a refuge, that have not yet been fully explored. I first visited the peninsula in 2015 to study the bats. Several of the bats that we caught in mist nets were cave-dwellers. I wondered where these bats live, since no caves are officially known on the peninsula. There were two options: bats have either changed their ecology, or there are caves we don’t know about. As a specialist on cave-dwelling bats, I was intrigued by this question and started to plan a cave exploration expedition on the Peninsula. I knew that discovering large cave systems in Osa was unlikely because of the lack of limestone that rock caves are generally comprised of, but my experience in Costa Rica showed me that small volcanic or sea caves can be as populated with bats as large caves and just as interesting.

In front of the entrance of Catatatas Cave near San Josecito.

This year, thanks to the strong support of Osa Conservation, I was able to search and explore caves and other underground habitats on the Peninsula. I had previously identified several sites for searching, like an interesting old gold mine near La Palma. The landowner informed us about the mine when he found out that we were looking for caves, so we paid a visit this February. We managed to create a map of the interior parts, and marked bat colonies instead of gold treasures. For several hours in the cave, we described the specific features of the relief and microclimate and discovered that the cave was over 200 meters long and branched like a maze.  We also found two species of bats and an extremely rich invertebrate fauna.

The narrow entrance of the old coal mine.


Mapping the gold mine.


Goose barnacles discovered in one of the marine caves.

Next, we searched for sea caves on the west coast of Osa. On previous trips, we had known that these sea caves existed there, but we had not mapped them. So, after a few hours of hiking from the San Josecito beach, we set out to explore three caves. The cave near the Campanario research station shelters one of the biggest colonies of mustached bats in Costa Rica with several thousands of individuals from three species!

Exploring a marine cave.


A bat colony in the marine cave.


Exploring marine caves in Isla Violin.

I found out from local people about a cave on Isla Violin. This island is hard to reach, but I managed to organize a visit, thanks to the people at Violin EcoLodge who helped me with the field expedition and took us to the cave by boat. The “cave” turned out to be an abandoned gold mine once again. And this time we were fascinated by the variety of bats we found—over 500 bats of 6 different species! Difficult access to the cave has kept the bats undisturbed from any raiders. On the floor of the cave, we noticed many invertebrates. During this expedition we found another cave on the island, located on the seashore. We rode horses to cross the island because our boat could not stand against the intense waves around the beach. After reaching the beach, we had to compete with the coming tide by jumping between waves and climb several boulders in order to reach the sea cave. Finally, we found the cave, but alas, there were no bats. We made a sketch and left, racing with the coming tide.

The boat ride through the mangroves was an adventure on its own.


Bats in the Isla Violin cave.

Crossing the island on horseback.

Our next plans are to explore the southern part of Osa around Sirena station, where we learned of another promising bat cave. We hope to find other hidden treasures!


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