The critically endangered harlequin frog (Atelopus varius), believed to be extinct in Costa Rica, has been rediscovered in the Talamanca Mountains of southern Costa Rica by an international team of researchers. 

The harlequin frog was a relatively common species in areas of Costa Rica and Panama until 1988, when populations declined rapidly, primarily as a result of the invasive, infectious chytrid fungus (implicated in extinctions of hundreds of amphibian species globally). The increasingly rare harlequin was believed extirpated from Costa Rica until 2004, when two individual harlequin frogs were spotted in a remote area near Manuel Antonio National Park in the western region of the country. Unfortunately, no harlequin frogs have been seen at this location since then.

Since 2004 scientists have continued to survey additional areas for A. varius and other lost frogs, resulting in finding a handful of individuals in Panama. In Costa Rica, ongoing surveys resulted in the 2008 discovery reported here.

Jan Schipper, director of Sierra to Sea Institute and an adjunct professor at Arizona State University, reports that the presence of harlequin frogs in Costa Rica contradicts expectations. Given the typical catastrophic impact of chytrid fungus, “This population shouldn’t be here. It provides hope that there are other populations surviving in other areas,” he says.

Location provides some protection to the frogs. According to José González-Maya, lead author of the report and scientific director of the Sierra to Sea Institute and ProCAT Conservation, “We have been studying this population of harlequin frogs since 2009. Fortunately, it is located in a private reserve, where access can be controlled to protect their habitat. After years of monitoring, we found that this population is healthy and shows no signs of infection by the chytrid fungus.” Tom Brooks, Chief Scientist of the International Union for the Conservation of Nature, concurs: “Rediscovering this population highlights the importance of the conservation efforts made by local residents to protect their natural resources. If their habitat hadn’t been protected, these frogs would never have had a fighting chance against this disease”.

The research team has focused on species survival, according to Sarah Wyatt, a biodiversity associate at the Global Environment Facility: “When the fungus first came through this area, scientists found many individuals of this species dead along this same river. So, we wanted to make sure the population is healthy and stable.”

González-Maya agrees: “The next steps are to pull together resources to implement a long-term monitoring and recovery program for the species. We have the difficult task of ensuring its survival against many odds. As we develop a recovery plan, we will need to bring together local and international partners to build a strong team with sufficient resources to ensure recovery.”

Robin Moore, Conservation Officer for the Amphibian Survival Alliance, tempers excitement with caution: “Finding this population is great news for conservation of harlequin frogs, and it raises a number of important questions about whether it is a resilient population that developed resistance to the chytrid fungus, or whether some individuals simply survived and are now repopulating. Regardless, there is much work. Globally, more than one in three amphibians is threatened with extinction; better understanding this population will shed light on conservation strategies for other species.”

Such concerns extend beyond the survival and well-being of a single species of frog. Amphibians, which live in water and have sensitive skin, are considered “bell-wethers” of environmental change. Their struggle for survival may point toward environmental damage that affects human beings, as well.

The research team on this project also works with a community of researchers around the world who are working to understand and control chytrid fungus, and who hope that this population can help scientists better understand the disease and help conserve other species.

This study was an international effort with researchers from the National Autonomous University of Mexico (UNAM), Mississippi State University, and the University of Arizona-West working with the Sierra to Sea Institute and ProCAT Conservation. The study was published in the Dutch journal Amphibia-Reptilia.

For more information, please contact the lead author of the study – José González-Maya at