By Twan Leenders1, Michael Roy2 & Alex Shepack3

They are tiny and barely visible on the shaded, moss-covered rocks they inhabit. However, in spite of their miniscule size their continued presence represents something huge: metamorphs of the Limosa Harlequin Toad (Atelopus limosus) indicate that there is still hope for some Atelopus species. A seemingly thriving wild population in Eastern Panama now provides unique opportunities for research that can benefit conservation efforts worldwide.

The Limosa Harlequin Toad is classified as ‘Endangered’ by the IUCN because of its small geographic range and impacts of habitat fragmentation and degradation throughout its area of occurrence. It is a species of lower elevations and theoretically less vulnerable to Bd-related declines than the middle and high elevation species in its genus (1). Nevertheless the spread of Bd in eastern Panama is taking a toll on this species even though parts of its range include areas of pristine habitat within and outside of protected areas (e.g. Chagres National Park) (Brian Gratwicke, pers. comm.).

Amphibian Survival Alliance (ASA) Partner organizations Conservation through Research Education and Action (CREA) and the Roger Tory Peterson Institute of Natural History (RTPI) have implemented a long-term monitoring and research initiative in Cocobolo Nature Reserve (which is managed by CREA)that sets out to:
1. address the ecology and population dynamics of wild Atelopus;
2. assess the amphibian assemblage in the reserve; and,
3. investigate how certain species or populations persist in spite of Bd. 

Initial surveys of the Atelopus limosus in Cocobolo Nature Reserve, in cooperation with the Smithsonian Tropical Research Institute (STRI), indicated that Bd may not have been present in 2011 and that the population appeared stable. Recent field work has provided additional reason for cautious optimism: in March 2013 we were able to document the first wild breeding event of Atelopus limosus; subsequent field work in 2014 revealed the presence of about two dozen metamorphs and young juveniles in suitable habitat. Concerted efforts to document recruitment and population dynamics during field work in February and March of this year, just prior to the publication of this article, led to the discovery of more than 120 juvenile Atelopus limosus in two separate watersheds contained within the Cocobolo Nature Reserve. Standardized photographs of the unique dorsal pattern of each frog were taken to facilitate future analysis using pattern recognition software, and all were swabbed for Bd. In spite of the initial indication that Bd was not present in the reserve, very recent findings of (non-Atelopus) dead frogs in the habitat and the knowledge that nearby A. limosus populations have declined in recent years due to Bd (Roberto Ibañez, pers. comm.) may indicate that the situation is more complex. Analysis of the swabs and data gathered during the most recent field work will provide more insight soon.

Atelopus limosus habitat. Photo: Twan Leenders.
Atelopus limosus habitat. Photo: Twan Leenders.

Located on the continental divide in eastern Panama, Cocobolo Nature Reserve encompasses a significant range of elevations, habitats and historic land uses. Within its boundaries, Caribbean, Pacific, Central and South American faunas mix with influences from a still poorly understood zone of endemism in the Chagres Highlands (2). The resulting amphibian assemblage heightens the conservation value of Cocobolo Nature Reserve, where other species of conservation concern, such as Craugastor tabasarae (IUCN Critically Endangered) and a recently discovered undescribed species of minute salamander (Bolitoglossa sp.) have been found. Thus far, 49 amphibian species have been documented in Cocobolo Nature Reserve, but herpetofaunal surveys have only just begun and have been limited to the dry season, suggesting that many additional species can be expected to occur there. The reserve is part of the Mesoamerican Biodiversity Corridor and bordered by vast areas of uninterrupted primary forest in Kuna Yala territory and Chagres National Park. Based on climate and habitat characteristics, Cocobolo Nature Reserve has significant potential to harbor additional conservation priority amphibians.

Craugastor tabasarae. Photo: Twan Leenders.
Craugastor tabasarae. Photo: Twan Leenders.

The continued presence of sensitive species in a region where Bd is prevalent warrants further investigation. A significant amount of research has been dedicated to documenting declines associated with Bd throughout the world but far less effort has been dedicated to understanding how certain species or populations persist in spite of Bd. Numerous theories have been proposed, including innate resistance, changes in Bd pathogenicity, evolved resistance, climactic refuges, behavioural fevers, and several others. Cocobolo Nature Reserve and the local Atelopus provide unique opportunities to study possible causes for Bd resistant populations. Furthermore, the enigmatic abundance of the dendrobatid frog Silverstoneia flotator and several other amphibians that occur syntopically with the Atelopus population begs further research. In areas where Atelopus populations were extirpated, S. flotator persists in seemingly healthy numbers (Twan Leenders, pers. obs.) suggesting that it may play a role as a vector or reservoir for Bd, or possibly display elevated resistance to the pathogen.

Silverstoneia flotator carrying tadpoles. Photo: Twan Leenders.
Silverstoneia flotator carrying tadpoles. Photo: Twan Leenders.

Surveying and examining amphibian populations within Cocobolo Nature Reserve in the context of Bd prevalence and pathogen infection dynamics is a research priority for the coming years. However, a different angle to our studies involves the spatial analysis of amphibian population changes in light of historic land use patterns and ongoing forest regeneration in sections of the reserve. In conjunction, these studies will hopefully elucidate how the area’s amphibians have managed to persist and seemingly increase in a time when other populations and species are declining precipitously. The conservation implications of these studies are numerous: this project will benefit applied conservation programming and increase knowledge about how populations respond to stressors like disease and habitat change. Testing observed individuals for Bd will allow us to produce maps of infection throughout the reserve to analyze for possible climactic refugia and understand how infection prevalence varies by season. Analysis of the genetic structure of this population of A. limosus will determine whether there has ever been an impact by Bd or elucidate how this population has persisted in spite of Bd. If found to be present, samples of the local Bd strain will be cultured and analyzed for its phylogenetic position and relatedness to known pathogenic strains of the fungus.

Alex Shepack swabbing for Bd. Photo: Twan Leenders.
Alex Shepack swabbing for Bd. Photo: Twan Leenders.

Detailed habitat use data on the A. limosus population is being gathered along a 1,000m transect and correlated with environmental data collected by a series of automated loggers. It is our hope that the information gathered from this study will allow for predictive modeling and identification of other potentially functional Atelopus habitat. In addition, one of the potential future applications of this study is the restoration of riparian corridors in collaboration with neighboring farmers to create controlled release sites for A. limosus originating from ex-situ reassurance populations that are currently “stranded” in carefully controlled facilities. Although these programs have been successful in boosting captive populations of A. limosus, they have not yet been able to release individuals back into the wild due to the continued presence of Bd. Initial conversations on this topic have begun with the Panama Amphibian Rescue and Conservation Project and will evolve as the project continues. The combination of fundamental research, applied conservation and experiential education and outreach is at the core of CREA and RTPI’s mission. Opportunities for researchers, volunteers or student groups to get involved in this project, or other ongoing research and conservation initiatives, are available through both organizations. For more information, please contact Michael Roy (michael@crea-panama.org) or Twan Leenders (tleenders@rtpi.org).

Acknowledgements We would like to thank all the students, volunteers, teachers and researchers who have supported research and education in Cocobolo Nature Reserve, especially Laurie Doss and the staff and students from the Marvelwood School. A special thanks goes to Joel Gonzalez, Sabine Wischnat, Sean Graesser and Clay Bolt for their assistance with Atelopus surveys.

References 1. J. Bielby, et al., Conservation Letters, 1: 82–90. (2008). 2. C. W. Myers et al., Am. Mus. Nov. 3763:1–9 (2012).