Biosphere Climate Change Daily Earth Science Repost

Return of the Mindo harlequin toad: Good news in the amphibian extinction crisis

One of the first articles posted on my blog involved the demise of the golden toad in the Costa Rican cloud forest. But the golden toad species was not alone. An estimated 168 amphibian species have gone out of existence in the past several decades, and at least 2,469 species (43% of the known amphibian species) show populations in decline. The recent sighting of a Mindo harlequin toad in the cloud forests of northern Ecuador provides a ray of hope.

In August 2019, on a cool evening, researchers spotted a Mindo harlequin toad in the forest. The excitement that evening among the conservation biologist was high because this was the first sighting in 30 years. Before this sighting, most scientists believed this species was extinct. It was thus considered one of the many amphibian species fallen prey to the fungal disease, chytrid.   


During the past three decades, chytrid wreaked disaster on amphibian populations around the world. The chytrid fungus (Batrachochytrium dendrobatidis) is a pathogen that attacks the skin tissue. However, it doesn’t necessarily kill the infected amphibian. But it does lead to a gradual degradation of the skin tissue, lethargy, weight loss, and potentially death. Biologists don’t fully understand the actual physiology of chytrid-induced death. But the disruption of the skin’s ability for fluid transport and gas exchange is a suspected cause.

The origins of the current chytrid devastation are also not well understood. One hypothesis is that the fungus was local to some African ecosystems but has since been globally transported to other environments. When introduced into a new environment, chytrid is a novel pathogen, and the amphibians lack defenses to fight it. Therefore, the disease spreads rapidly and decimates populations of susceptible species.  A second hypothesis holds that the pathogen is naturally present globally. However climate change and habitat destruction weakened the ability of some amphibian species to fight it off.

A ray of hope

The return of the Mindo harlequin toad from the brink of extinction offers the possibility that the species has developed a resistance to the chytrid fungus. Development of resistance to this fungus occurs in a few species, including rocket frogs, harlequin frogs, and Sierra Nevada yellow-legged frogs. 

This ray of hope is anticipation that this small bit of evolution-in-action will allow some of the affected species to return from the edge of extinction and thrive again in their native ecosystems. Rapid loss of amphibian species is a blow to many ecosystems. But perhaps the tides are turning in favor of the species that remain.


Species Loss: Rate of Change Matters (Source: ArcheanWeb) –  Also:


‘Extinct’ toad rediscovery offers hope amid amphibian apocalypse (By Jason Bittel; National Geographic) –  Also:

Chytrid Fungus (Source: UC Riverside Center for Invasive Species Research) –  Also:

Feature Image: Female limosa harlequin frog (Atelopus limosus) (Modified)  – By Brian Gratwicke – Flickr, CC BY 2.0,

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.