Save for one “lonely” survivor in captivity, the Sehuencas water frog hadn’t been seen in the wild since 2008. That’s when its numbers collapsed, primarily due to chytridiomycosis, a fungal disease that has devastated frog populations worldwide. Fearing the species might be extinct, some scientists spent 10 years searching the Bolivian mountain forests for the amphibians. Now, they’ve found a tiny population of five.
“It’s just incredible,” says herpetologist Robin Moore, communications director at Global Wildlife Conservation in Austin, Texas. He was among the scientists who announced the discovery on January 15.
With no current way to get rid of the lethal chytrid fungus in the wild, scientists are keen to study the survivors, Moore says. The five Sehuencas water frogs (Telmatobius yuracare) were found in their native habitat: the Bolivian mountain cloud forests, where the climate is moist and cool — and ideal for chytrid to grow. “It could be that this small population has immunity” or genetic resistance, Moore says. “It could be an environmental factor,” such as an unusually warm microclimate.
It could also just be nature’s luck. “Many species of frogs that disappeared for years — decades in some cases — have been seen again later,” says ecologist Karen Lips of the University of Maryland in College Park. In December 2018, for example, researchers announced they had rediscovered Ecuador’s marsupial horned frog, more than 10 years after the species disappeared.
Reappearances can occur for several reasons, including changes in the frogs, the fungus or the environment, Lips says. “The simplest explanation is that once most of the frogs are gone, the fungus declines” from having fewer hosts to infect, and the frogs, in turn, slowly rebound until they’re seen years later (SN Online: 3/29/18).
These newly found frogs raise hopes that more populations exist in the wild, and also offer researchers a chance to help the species recover.
“Each case that we have a frog that we thought had succumbed to chytrid fungus but survived, it’s just an opportunity to understand a little more about how this pathogen works,” Moore says, “and the prospect for bringing these frogs back.”