A total of 86 Darwin’s frogs are now being housed at London Zoo to keep them safe from a deadly infectious disease that has affected more than 500 species of amphibians worldwide.
In October 2024, conservationists from the Zoological Society of London, the NGO Ranita de Darwin and other partners rescued 53 southern Darwin’s frogs (Rhinoderma darwinii) from the forests of Tantauco Park, Chile. They collected the frogs before they could be affected by the chytrid fungus, which caused a 90% population decline in the frogs in one year in the park, according to ZSL.
The chytrid fungus (Batrachochytrium dendrobatids) causes a disease called chytridiomycosis, which is “one of the most devastating wildlife diseases ever recorded,” Benjamin Tapley, London Zoo’s curator of amphibians and reptiles, told Mongabay by email. The disease disrupts a frog’s ability to breathe through its skin, killing it in just a few weeks.
“Unfortunately, the spread of chytrid fungus is difficult to control in the wild as chytrid fungi can persist in the environment and are easily spread,” he said.
Tapley said the rescue of the frogs from Chile was “a crucial step in safeguarding this species, which has suffered devastating population declines due to chytridiomycosis.”
“Successfully establishing a healthy population will facilitate the future recovery of this frog, and at the same time, provide us with an opportunity to learn more about the biology of this species and how to combat the devastating chytridiomycosis,” he added.
The rescue mission was captured in a ZSL documentary released in February 2025. Rescuers mimicked the frog’s vocalization, and caught 53 frogs, including 11 male frogs carrying fertilized eggs. Those eggs hatched into 33 new froglets born at London Zoo. Darwin’s frogs are among the few animal species in which males carry their offspring in their vocal sacs.
“Our Darwin’s frog population at London Zoo has continued to thrive since their arrival back in October 2024. The original rescued frogs, along with the 33 froglets born here, are doing well and are monitored every day by our herpetology team,” Tapley said.
All the frogs remain in “a specially designed unit with strict biosecurity measures” within the zoo. Routine health screening is done to ensure the population is free of chytrid fungus and other pathogens.
In January 2025, another 32 chytrid-free Dawin’s frogs were rescued from Tantauco Park and sent to a breeding and research station at the University of Concepción in Chile. Tapley said keeping the frogs in multiple institutions reduces risks and increases the species’ chance of recovery.
ZSL’s conservation partner Ranita de Darwin is working to understand the disease dynamics and implement disease mitigation strategies in Chile. ZSL, whose scientists were among the first to identify the chytrid fungus as a major cause of amphibian population declines, continues to study how the disease spreads and affects different species, Tapley said.
Banner image of a Darwin’s frog and newborn at London Zoo, courtesy of Benjamin Tapley/ZSL.
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