Uncategorized

A big thanks to volunteers

Blogpost by Mariam Weyand, Sea Turtle Biologist

Osa Conservation relies on the help and support of volunteers to maximize our conservation impact, like many non-profits. Fortunately, we have diverse people coming to discover, help and get involved in our programs. We can separate them into two important groups: short term participants, such as students, families and tourists, and long-term volunteers.

In 2018, we had the luck that many individuals came and helped us with field work in the Sea Turtle Program. They all came to discover the great experience and hard work of relocating sea turtle nests and releasing neonates. They all helped a lot, and I would like to thank them all in this blog, because, after all, what would we do without them?

Volunteers from UNED helping Mariam Weyand and the rest of the Sea Turtle team to reinforce the protective bamboo wall against the strong high tide by filling bags with sand behind it.

Here an example of the great work they did in 2018:

We really enjoy working with groups of volunteers and students, such as World Challenge, UCR (University of Costa Rica) and UNED (State University at Distance). Thanks to their help, we have been able to build a new hatchery! They first filtered the sand on the whole surface of the future building, then built the structure and reinforced it when needed by filling bags with sand behind the protective bamboo wall. They also participated in daily patrols, hatchling releases and beach clean ups.  Every helping hand really counts!

The long-term volunteers, like the groups, participated in many of the other projects at Osa Conservation and were a huge help to each program. The additional manpower they provided to the Sea Turtle Program allowed us to split into two teams, and perform double the amount of work! Moreover, each one shared their own knowledge to improve the different aspects of the projects. At the end of their stay, it was like saying goodbye to full-time team members.

Volunteers from UNED helping the Sea Turtle team to reinforce the protective bamboo wall by pushing a trunk in front of it. Without all of them, we wouldn’t have been able to do it.

Each and every volunteer did a great job at giving a hand in the day-to-day activities. By sharing their energy and knowledge, they participated in the constant improvement of the organization.

So, on behalf of the Osa Conservation Sea Turtle Team, THANK YOU everyone for your help! We hope that we will have the pleasure of working with you again and the opportunity to meet more amazing and dedicated people like you!

Dedicated to Pablo Rodriguez who was an exceptional UNED volunteer. May he rest in peace.

Uncategorized

Connecting hammerhead shark populations from the Eastern Tropical Pacific

Blogpost by Mariana Elizondo Sancho, Álvaro Ugalde grant awardee

Sphyrna lewiniis one of the nine species of hammerhead sharks, and it lives across the tropics worldwide. This species is categorized as Endangered, since its populations have declined more than 50% in the last 10 years, according to the IUCN. This shark is threatened by fisheries, both as bycatch and as directed fishing, since their fins are highly valued in the international fin market. 

Hammerhead shark school in the open waters from Cocos Island in the Pacific of Costa Rica. Photo: David Garcia

This shark has an interesting behavior in which females come to coastal waters called nursery areas to deliver their pups. Juveniles remain in these areas for their first years, so coastal marshes and wetlands are an important habitat for their nurturing. In Costa Rica, these areas are threatened both by habitat degradation and by fisheries. One of the most important nursery areas is the Golfo Dulce in the southern pacific of Costa Rica. 

After this first stage of life, adults move to open waters and islands, where constant migration is observed. Once in open waters and near the Cocos Island, this shark is specifically targeted for its fins. Protecting this highly mobile animal that can migrate long distances is a hard task since its populations are not in a specific geographic place during their whole lifetime. 

Also in the Eastern Tropical Pacific, population structure is not well known. Is it one population or are there several? Do females prefer specific nursing grounds to deliver their pups? Understanding population structure and movements of hammerhead sharks is vital to establish regional management and policies.

DNA extraction of hammerhead shark tissue. Photo: Mariana Elizondo

I have been researching the connectivity and genetic population structure of S. lewiniin various coastal nursing areas in Guatemala, Costa Rica and Panamá. The results of this research will be important to provide biological information for management plans that will aim to protect specific important geographical areas for this species’ persistence.


Sea Turtles, Volunteers and Visitors, Wildcats

More than a green patch on a map: Osa’s biodiversity and charm must be experienced in person

Blogpost by Thomas Kao, Volunteer, Age 14

In this modern day and age, we often forget there is more on this planet than just your home. As a young student with a love for maps, I have always set my eyes on this little corner of the world, an untouched paradise: Osa Peninsula.

As I mentioned, I absolutely love maps. I have laid my eyeballs over thousands of them, hungry for locations and searching for something new. However, maps can only tell you so much, and in reality they are portals to the lands they project.

Thomas and his mother, Lynn, taking a break under a giant old Ajo tree while hiking the Ajo Trail. Photo: Lucia Vargas

For Christmas, Santa delivered me a beautiful atlas, however, this atlas was a very recent edition. Thanks to the work of scientists in the field, preserving the ecosystem has never been more highlighted in history and this new atlas revealed every single National Park in the world. While browsing the atlas, Costa Rica really stood out. National Parks practically litered the page, and the Osa Peninsula was drowned in a sea of green labels. One minute I found myself staring at a page in a book and in the next I found myself in a plane leaving Los Angeles. Life can be hilarious sometimes.

Once at Osa Conservation, we participated in hatchery checks where we released hundreds of sea turtle babies. Everyday, I watched them crawl into the ocean with a smile on my face. Once the turtles made it home, we would trek back to the camp through a beautiful rainforest, and we could see tons of different animals that Osa provides with its limitless biodiversity.

A happy group of volunteers and Sea Turtle Research Field Assistants headed back from a morning sea turtle patrol of Piro Beach. Photo: Shannon Millar

The forest is never quiet and is always so full with life and magnificent greenery. Butterflys float around the fields and birds soar across the blue sky with grace. Monkeys of all types leap across the forest canopy whilst snakes slither across the forest floor. In the rivers and swamps you can find basoliths, lizards capable of walking on water, and small schools of fish swimming through the clear water. In California, almost none of the animals found here exist; the two enviroments are polar-opposites. If there is something I will never forget about Osa, it must be the local fauna and plantlife.

While living at the Osa Verde BioStation was at first out of my comfort zone, it quickly became a lovely and comfortable second home. The first day, I found a large spider sitting on a counter the size of my hand, that certainly give me a heart attack! However, each night the sky is covered with stars, a view I never saw in the USA. When staring at the stars, you will always hear monkeys, insects and birds, a non-stop noise but not an annoying one. It gives the surrouding forest livelihood and soul, showing you just how active Osa is.

Thomas excitedly holding a butterfly he encountered at the Osa Verde BioStation. Photo: Lynn Kao

Once in bed I fell asleep, the living quarters were extremely clean, something you definently wouldn´t expect. In fact, I have never slept better in my life; I was sound asleep like a baby. Three times a day meals were served, and all of them were delightful. All things considered, the food served here is best I´ve had in a long time.

I have been in other countries before with rainforests, but Costa Rica´s Osa Peninsula tops the list as the best one. I definently will have plenty of stories to tell my friends, I´m very glad and grateful that I had the opportunity to set foot in this foreign land.

Maps can only take you so far; there are no turtles, stars and monkeys on a map. It is only when you set foot in a new location, will you actually feel and experience an entirely new world.

Uncategorized

Necesitamos una transformación cultural permanente para la cacería de la vida silvestre en la Península de Osa

Blog por Marco Hidalgo, coordinador del programa de resiliencia del ecosistema y alcance comunitario

La cacería de animales silvestres, en el caso de la Península de Osa, tiene claras características para ser considerada como un elemento cultural de las personas que la practican. Estas características se cumplen mayormente con quienes practican el monteo y con quienes cazan exclusivamente para consumir la carne. La gran mayoría de estos casos ya no se considera una práctica, sino una costumbre o tradición. Pero esta valoración de elemento cultural no es válido para otros tipos de cacería, por ejemplo, hay quienes cazan, venden la carne o quienes lo hacen como “deporte”, pues median otras razones, que nada tienen que ver con arraigo o costumbre, como es el uso de la carne para negocio o la utilización de la cacería como una manera de canalizar “gustos” como el uso de armas o el solo “placer” de matar animales indiscriminadamente.

Investigaciones en la Península de Osa dan una razón social para entender que la cacería de fauna silvestres es de autoconsumo y no de subsistencia, ya que no es la principal fuente de proteínas,  aunque los mamíferos, tepezcuintle (Cuniculus paca), chancho de monte o chancho cariblanco (Tayassu pecari) y saíno (Pecari Tajacu), son los más cazados.

Los perros son un componente importante para la actividadad de la caceria. Foto: Marco Hidalgo-Chaverri

El protagonista principal de la actividad de caza es el perro, que es criado y entrenado para ese propósito, con énfasis en perros identificados como “tepezcuintleros” o “saineros”. Hay una fuerte valoración y admiración por el “buen perro”. El objetivo principal es observar y escuchar al perro “rastreando al animal en el monte”, y hay una fascinación especial con respecto a la forma como este ladra en tanto está tras el rastro de la presa.

La cacería en Osa es una actividad que se debilita, posiblemente por la generación actividades económicas alternas como es el caso del turismo rural comunitario, y donde la experiencia de conocer nuestros bosques es valorado, y la vida silvestre paso hacer un atractivo del producto que se ofrece, además de haber encontrado un mundo laboral, donde la gente que caza ha encontrado otras oportunidades. Otra posible explicación, es la participación activa de miembros de las comunidades en grupo de monitoreo biológico comunitario, que han dado respuesta al interés de sus pobladores por entender y proteger la naturaleza que heredaron.

El cazador con su perro dentro de una madriguera de Tepezcuintle. Foto: Marco Hidalgo-Chaverri

La cacería como elemento cultural ha resistido el tiempo, sin importar las vicisitudes, ahora es el peor de los escenarios en un contexto de desarrollo que quiere cambiar por el bien de todos, donde la cacería ya no se justifica, por eso Conservación Osa asumió el reto a través del Proyecto de “Prevención del colapso de los ecosistemas: una alianza de vigilancia basada en la ciencia ciudadana” con el financiamiento del International Conservation Fund of Canada, de realizar un esfuerzo integral de acciones de manejo de vida silvestre y restauración de los ecosistemas en buscar con los grupos organizados locales la reducción del impacto sobre la fauna.

Aves, Birds, Community Outreach, Science and Research

Descubriendo la ecología de un ave endémica y en peligro en Osa: Habia atrimaxillaris

Blogpost por Arlet Quiros-Calvo, ganador de la Beca Alvaro Ugalde y estudiante de maestría en la Universidad de Costa Rica

Macho y hembra de izquierda a derecha de tangara hormiguera carinegra (H. atrimaxillaris). Fotos: Arlet Quiros-Calvo

 Me llamo Arlet, trabajo con una especie en peligro de extinción, especial porque se encuentra en un único lugar del mundo. La tangara hormiguera carinegra, Habia atrimaxillaris, habita solamente en la Península de Osa y en el Refugio Nacional de Vida Silvestre Golfito-Parque Nacional Piedras Blancas en Costa Rica.

 Se cree que su población está disminuyendo rápidamente dentro de su pequeño rango geográfico debido a una gran reducción de su hábitat, resultante de la deforestación y la expansión de la frontera agrícola en el Pacífico Sur.

 Según investigaciones en la Gamba de Golfito, esta especie tiene una preferencia por los bosques primarios y bosques secundarios maduros. Al ser una especie que forrajea en el sotobosque, es decir, en la vegetación que se encuentra por debajo del dosel, puede ser muy sensible a las fragmentaciones del bosque. Aún así, el estado de conservación actual de la especie y el conocimiento sobre sus preferencias de hábitat es muy limitado en la Península de Osa, por lo que decidí ampliar la información existente sobre esta ave con la beca Álvaro Ugalde de Conservación Osa.

Los asistentes monitoreando día a día los nidos (izquierda). Realizando mediciones de las parcelas en Dos Brazos del Rio Tigre y la Tarde (derecha). Fotos: Arlet Quiros-Calvo

Desarrollamos esta investigación en sitios ubicados en la comunidad llamada La Tarde y la comunidad Dos Brazos de Rio Tigre, donde localizamos individuos en dos parcelas. Cuando nos dispusimos a monitorearlos, día a día, ¡descubrimos algunos secretos de su reproducción! 

Hasta el momento, hemos descubierto información muy valiosa para la conservación de esta peculiar especie. En los meses de época reproductiva (febrero-abril), observamos su comportamiento de cortejo y apareamiento, la selección del sitio de anidación, preferencia de hábitat, el número de huevos, su alimentación, e incluso anotamos datos de polluelos depredados. Además, mediante videos, llegamos a ver actividades cotidianas como forrajeo, búsqueda de alimento e incubación, lo cual nos ayuda a entender la complejidad reproductiva de la especie y su adaptabilidad en Osa. Adicionalmente, el comportamiento reproductivo es diferente en Dos Brazos de Rio Tigre y la Tarde, por la misma razón: la fragmentación de propiedades vecinas al Parque Nacional Corcovado.

Nido encontrado en la palma suita Asterogyne martiana en Dos Brazos de Río Tigre. Foto: Arlet Quiros-Calvo

A pesar de que en la literatura se menciona que la distribución de la especie se limita a hábitat maduro, nosotros ubicamos nidos en bosques de galería (bosques en los bordes de cuerpos de agua), áreas abiertas, bosques en regeneración y zonas de pendiente.

Al visualizar todos estos datos obtenidos, podemos generar información clave para proteger los bosques de Osa, sus aves y en general toda la biodiversidad presente en esta pequeña área de Costa Rica.

Diseño del nido de H. atrimaxillaris encontrado en Dos Brazos de Rio Tigre. Foto: Arlet Quiros-Calvo

Land Conservation and Forest Restoration, Science and Research, Uncategorized

“Restoring forests for bats” and beyond: NASBR 2018

Blogpost by Elene Haave Audet, Restoration & Rewilding Research Field Assistant

This October, I ventured out of the sanctity of the jungle to present at the 48thNorth American Symposium on Bat Research (NASBR) in Puerto Vallarta, Mexico. Over 300 researchers from across the globe gathered to share bat stories, communicate their research, and further our understanding of this hugely diverse mammalian group. Because of its location, the conference offered many opportunities to discuss the conservation of bats in the tropics, presenting a great opportunity to share Osa Conservation’s work on surveying bats in the restoration plots.

The Osa Bat Family, Priscila Chaverri, Gloriana Chaverri, Beatriz Lopez, Elene Haave Audet and Doris Audet, at NASBR. Photo: Elene Haave Audet

It was very exciting to see our Restoration and Rewilding efforts so well received by a bat-savvy audience. Researchers were curious to hear about the ways in which Osa Conservation is “restoring forests for bats”. This project is focussed on attracting bats to areas that are actively being restored, for example by planting flowering trees like the balsa, and installing two-meter-tall bat boxes, all with the aim of restoring bat diversity whilst the forest is regenerating.

Micronycteris microstis bats are feeling at home in this bat box, installed by Dr. Chaverri’s team at Osa Conservation. Photo: Elene Haave Audet

Excitingly, the bats of the Osa Peninsula were able to reach the audience in Puerto Vallarta beyond the scope of the restoration project, by researchers conducting work at and around the Osa Verde BioStation. Beatriz Lopez, from the University of Florida, discussed gathering bat echolocation calls on the Osa Peninsula to document species diversity, and Dr. Doris Audet from the University of Alberta, shared her research on bat exploratory behavior in the field. The conference was also a wonderful opportunity to discuss advances in bat research in Costa Rica with Dr. Gloriana Chaverri from the University of Costa Rica, who has planted deep roots of bat research on the peninsula over the course of her career. 

The presence of bat research on the Osa Peninsula, and Osa Conservation’s important contributions to supporting that research, was very well represented at NASBR 2018. The Osa Verde Biostation is truly a gem for bat diversity, with over 50 recorded species of bats to date, and sharing Osa Conservation’s involvement in conserving and restoring habitats for bats ensures that those contributions are recognized and appreciated by the bat community at large. 

Elene, identifying a bat by measuring its forearm, as part of the diversity surveys in the restoration plots. Photo: Elene Haave Audet

Aquatic Health, Volunteers and Visitors

Pumas en el sendero

Blog por Lucía Vargas Araya, Coordinadora de Experiencia de Conservación.

La autora Lucía Vargas Araya disfruta de la búsqueda de vida silvestre en el sendero. Photo: Laurien Dwars

“Hay dos pumas en el sendero”- me dijo mi compañero Leiner por un mensaje que recibí estando sentada en mi oficina en la Estación Biológica Osa Verde el otro día. Emocionada, le avisé a los compañeros que estaban cerca mío, nos pusimos zapatos y salimos rápidamente hacia El Sendero Las Tortugas, donde esperábamos encontrar a los felinos.

La entrada del sendero está justo al costado de La Estación y continúa hasta llegar a Playa Piro. Como Leiner no especificó en qué parte del sendero estaban los animales, desde que entramos al mismo y nos encontramos rodeados del bosque, el corazón latía fuerte; podían estar ahí camuflados detrás de cualquier árbol.

Rayos de luz solar caen en el camino cerca de la estación de investigación. Foto: Lucia Vargas Araya

Continuamos a un punto del sendero donde se debe de cruzar el Río Piro y entonces, el suspenso aumentó. Caminaba poniendo mucha atención a mi alrededor, cerca y hacia la distancia, tratando de detectar a los pumas, pero también viendo el barro que pisaba para no resbalarme.

Quienes estábamos en búsqueda de los pumas, íbamos con los ojos alertas y nos hablábamos en un tono muy bajo, casi como un susurro, para no espantar la ilusión de verlos de cerca. Continuamos el sendero, paralelo al río, hasta llegar a un cruce. ¿Cuál camino debíamos escoger? Ahí nos quedamos unos segundos hasta que decidimos tomar el de la izquierda, el que se aproxima al vivero de huevos de tortuga en Playa Piro. Nuestro caminar se volvió más pausado y esperamos a que Leiner respondiera el celular para saber si aún teníamos esperanza, pero no respondió.

Finalmente, nos topamos con quienes habían tenido la oportunidad de verlos y nos dijeron que ya los habían perdido de vista, se habían ido. Sin embargo, se sabía que estaban cerca porque escuchábamos aún el aullido típico de un mono que está observando a su potencial depredador.

Sereno Río Piro, el río que pasa por la estación de investigación. Photo: Lucia Vargas Araya

Esa tarde no encontré al puma, pero sentí una profunda gratitud de que el bosque de Osa se hubiera convertido en mi nuevo hogar. En este rincón palpitante de vida las posibilidades son infinitas. Aquí cada día estamos a la merced de la naturaleza; cada día puedo ver algo que nunca había visto antes. Y, además, aquí todos los días aprendo.

Esa tarde tuve una excusa para distraerme en el bosque y visitar el río Piro un rato. Además, iba en compañía de espíritus aventureros, que luchan por proteger lo que aman: la naturaleza; de la cual son parte. 

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 Northern Cat Eyed Snake 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.