Cocoa Croakers: Exploring the World of Monteverde’s Amphibians

Nidhi Noronha

Just as chocolate lovers might appreciate the unique flavors of cocoa grown in Costa Rica, individuals interested in Neotropical amphibians might find themselves drawn to the diverse amphibian species found in the country’s rich ecosystems. Since their discovery in 1989, global populations of these captivating creatures have steadily decreased, facing unforeseen challenges similar to those encountered in agricultural contexts. The effects of climate change present profound challenges to the world of amphibians, akin to navigating through a complex and changing landscape. Climate change has left amphibians struggling to adjust to the shifting environmental conditions caused by global warming. In the lush forests of Costa Rica’s Monteverde, the decline in mist and drying trends paints a poignant picture, highlighting the impacts of climate change on their habitat.


Imagine the habitat destruction and fragmentation as a delicate chocolate cake crumbling under pressure, mirroring the fragmentation of once contiguous habitats. Similar to how layers of a delectable dessert disappear, the same occurs with portions of the amphibians’ habitat, restricting their freedom of movement. Once brimming with biodiversity, the lush tropical forests in the mountainous areas (aka montane forests) now face vulnerability due to human activities like habitat destruction and fragmentation. Contamination also poses a significant challenge to amphibian life, representing impurities that compromise ecological integrity. These pollutants infiltrate their habitat, with unwanted additives slowly impacting these creatures in an ecosystem. Amphibians unknowingly absorb these contaminants, impacting their well-being and contributing to population decline.


As we continue to explore the challenges facing amphibians and their significance for ecosystem health, we must consider another important aspect: the unique characteristics of tropical mountain forests. Amphibians, with their connection to the environment, serve as indicators of ecosystem health. They accentuate the delicate balance between nature and human activity. Amidst these challenges, neotropical amphibians embark on a journey navigating through complex terrain, shifting and adapting to climatic changes. Their resilience, reminiscent of the nuanced layers of a well-crafted chocolate, adds depth to their ecological journey and reveals the intricacies of both nature and conservation efforts.


Amidst the challenges, conservation efforts offer a glimmer of hope. Protected swathes of montane forest serve as a sanctuary within the landscape, emphasizing the importance of preserving habitats and biodiversity. Yet, the “enigmatic decline” of amphibians persists, highlighting the intricate aspects of conservation challenges. Several monitoring efforts, ranging from diligent surveys observing and recording changes in the environment, have been carried out. This includes UC-EAP student Elizabeth L. McDonald’s surveys, which provide valuable insights into amphibian species distribution and richness. “Richness” refers to the diversity or abundance of amphibian species within a particular area or habitat. These surveys, conducted in Monteverde in 2019 and 2023, contribute to our understanding of the dynamics, offering a foundation for ongoing monitoring and conservation efforts.

These surveys were carried out in Holdridge life zones, a classification system used to categorize different types of ecosystems based on their climate conditions and the types of vegetation they support. Think of Holdridge life zones as different flavors that make nature diverse. It is generally thought that more amphibians are found lower down the hill; however, animals moving uphill are thought to be reacting to changing weather—a twist that makes nature more interesting. This idea, corresponding to Holdridge life zones, was initially proposed by McDonald.


The primary goal of the expedition carried out by Taryn Cornell, the author of the paper on which this articles is based on, was to unravel the mysteries of Neotropical amphibians; the study aimed to discern whether the distribution and richness of amphibian species had undergone a metamorphosis since 2019. She hypothesized that the richness of species would exhibit a downslope trend. The study predicted a scenario where amphibian species would ascend the slopes in response to the altered climate to settle in cooler places that matched their previous habitat.


The study sites, nestled in the Cordillera de Tilaran mountain range at elevations between 1200-1700 m, are like carefully chosen ingredients for crafting a unique chocolate blend. The Monteverde region, adorned with urban communities, the Children’s Eternal Rainforest, and the Santa Elena Cloud Forest Reserve on both Pacific and Caribbean slopes, house seven of Costa Rica’s twelve life zones. For this study, four Holdridge life-zones were incorporated: Tropical Premontane Wet Forest (Zone 2), Lower Montane Wet Forest (Zone 3), Lower Montane Rainforest (Zone 4), and Premontane Rainforest (Zone 5). The size of a Holdridge life zone is determined by factors such as topography, latitude, altitude, and prevailing climatic patterns.


The surveys were carried out in different places which are included in the Holdridge life zones like Santuario Ecológico Monteverde, Café Monteverde, Rachel and Dwight Crandell Reserve, Estación Biológica Monteverde, and San Gerardo Biological Station. The surveys, spanning fifteen nights in May 2019 from 7:00 pm to 10:00 pm, totaled 21.16 hours. The chosen study sites were selected for their unique ecological characteristics. Researchers conducted surveys from May 5, 2023, to May 23, 2023, during the transition from wet to dry season, to capture optimal conditions for studying amphibian diversity and abundance.


To sample amphibians, the researchers used techniques including Visual Encounter Surveys (VES) and Acoustic Encounter Surveys (AES). These methods collect information crucial for analysis, such as date, time, general location, species, temperature (°C), altitude (m), coordinates, and substrates. The inclusion of GPS coordinates, recorded using a Garmin global positioning system (GPS), ensured replicability for future studies.


Data analysis involved the use of various softwares to generate a linear regression model describing the relationship between species richness and elevation. Precipitation data collected from various sources, including the Monteverde Institute, provide insights into the climatic circumstances shaping the landscape of Monteverde.The study collected a total of 135 individuals, classified into 16 species spanning five families. The composition of amphibian families in 2023 resembled McDonald’s 2019 dataset but with some variations. The analysis showed a notable negative correlation, indicating that amphibian species were discovered at higher elevations than anticipated, in contrast to McDonald’s 2019 findings, which suggested a different trend. Two species, C. stejnegerianus, and C. bransfordii, were observed outside their expected Holdridge life zones, suggesting potential shifts in distribution patterns. The study additionally explored the influence of climatic factors, particularly precipitation, on amphibian communities.


Climate change is a potential driver of amphibian declines in Monteverde through effects on precipitation in the region. The study assessed precipitation data collected at ~1350 meters elevation, demonstrating increased variability in monthly and annual rainfall. A comparison between the 2019 and 2023 survey periods indicated a notable decrease in precipitation in 2023, but the correlation between precipitation patterns and amphibian data did not show a clear association.


Cornell’s findings raise interesting questions about the behavior of Monteverde’s amphibians in response to climatic changes. The unexpected distribution of certain species, such as C. stejnegerianus and C. bransfordii, hinted at the possibility of upslope migrations, further suggesting that alterations in precipitation patterns and temperature may prompt frogs to seek new habitats. The surveys offer a glimpse into the web of factors reshaping the diversity and structure of Neotropical systems. Ongoing studies at these locations are crucial for the sustained management and monitoring of endangered amphibian species. The study recognizes the importance of longitudinal studies, emphasizing the need for continued monitoring and conservation efforts to preserve the delicate balance and protect the essence of a Neotropical landscape in transition.