Making Frogs Chytrid-Proof—One Hopper at a Time

Frogs are interstitial beings. They are born of water yet spend much of their lives on land. The amphibians transform from gelatinous orbs to tiny-tailed swimmers to land-hopping predators. Some burrow deep into the earth, Gollum-like, while others climb trees and spend their lives in the canopy. And these days, too many frog species straddle the line between extirpation and complete extinction. They're still around in zoos, but they've lost their homes in the wild.

Take the Panamanian golden frog. Yellow with black polka dots, these beautiful amphibians are a national symbol of Panama though they are thought to have disappeared from the wild sometime in 2007. The culprit? A nasty fungal infection known as chytridiomycosis, commonly known as chytrid for the species of fungus that causes the disease.

Over the past two decades, scientists have watched chytrid rip its way through frog populations across the Western Hemisphere. The disease’s impact appears to depend on the species it affects, with some, such as the common toad, suffering minor symptoms and others croaking by the score. A few species, like the African clawed frog, even seem to be immune to the fungus. But to all too many, chytrid might as well be the Black Death.

The good news, says Jonathan Kolby, a Ph.D. candidate at James Cook University, is that we’ve found a few ways to fight chytrid in captivity. One method involves applying enough heat to the frogs’ skin to kill the fungus and its spores; another employs the antifungal agent itraconazole. The bad news? Even if you cure a handful of frogs and toss them back into the wild, chytrid will still be out there waiting.

In fact, the threat looms so large that the San Diego Zoo has successfully bred almost 500 Panamanian golden frogs but doesn’t plan to reintroduce them to the Central American jungle until chytrid conditions improve, if they ever do.

Kolby, who is also a National Geographic Explorer, wants to try a different approach. “We have to accept the fact that chytrid will never go away,” says Kolby. “The long-term solution is getting frogs to survive in the wild despite the disease.”

A few weeks ago, through a partnership with Omaha's Henry Doorly Zoo and Aquarium, Kolby had two 20-foot ocean shipping containers delivered to Lancetilla Botanical Garden in Tela, Honduras, to save the frogs of Cusuco National Park in the mountainous cloud forests of Honduras. In one container, frogs already infected with chytrid will be “cleaned”(either with antifungals or heat); then they'll be released back into the wild. The other container will serve as an on-site captive breeding colony—a fail-safe in case sudden tragedy, fungal or otherwise, occurs in the wild. They’re calling it the Honduras Amphibian Rescue & Conservation Center (HARCC).

The basic premise behind HARCC is to play a numbers game against the fungus. Kolby has set out to save three species—the exquisite spike-thumb frog (critically endangered), the Cusuco spike-thumb frog (critically endangered), and the mossy red-eyed frog (endangered). In each of the populations, chytrid typically kills off about 80 percent of tadpoles and metamorphs (which are frogs fresh out of the water from metamorphosis). That means some young frogs (about one in five) do make it to adulthood. The hope is that, given enough generations of survivors, the frogs might be able to develop a population-wide resistance to the disease.

It’s tough to win a numbers game, however, when your team has really, really low numbers. Kolby discovered these unfortunate odds when he surveyed Cusuco National Park in 2007. As he swabbed literally every amphibian he could get his latex-gloved hands on, he learned that the species hit hardest by chytrid also tended to be those that were already endangered.

That’s why the herpetologist wants to get on the ground in Honduras and start pumping out as many frogs as possible from his shipping containers among the clouds. Ideally, he hopes to raise enough money, through this Indiegogo campaign, to sustain the operation for a couple of decades, during which he’ll continue to capture and clean several hundred sick baby frogs—say, 200 for each of the three species—and release several hundred healthy adults each year.

“Our vision is that if we do this as quick as we can and get going for 5, 10, 20 years, eventually we might be able to walk away,” says Kolby.

If this all sounds a little off-the-hip, that’s because it is. We have yet to find a chytrid cure-all, prompting many scientists and conservationists to err on the side of caution—much as the San Diego Zoo is doing with its captive golden Panamanian frogs. Other potential solutions include isolating chytrid-fighting probiotics found on the skin of other amphibians and somehow introducing these helpful microbes to the species in need. Manipulating the environment by pruning vegetation may also help, as areas with increased sunlight and airflow may be less hospitable to the deadly fungus. But Kolby’s catch-cure-and-release plan also has some precedent. Just this month in Australia, conservation planners are setting thousands of eggs from the critically endangered corroboree frog in the wilds of New South Wales in an attempt to boost the population beyond its current 50 individuals. So far, the releases seem to be working—some adult corroborees are being found where the frogs were once considered extinct.

That Kolby is willing to spend years of his life working in a shipping container on a remote mountain speaks to his dedication to frogs, but his approach, if successful, may be the salvation for more than just a few species of hoppers. “The more we can learn about what’s happened to frogs,” he says, “the quicker we can respond to the next wildlife disease.” As an example, he points to how white-nose syndrome in bats is similar to chytrid. (Each is a fungal epidemic that spreads rapidly and kills by attacking the skin.) “These things keep happening over and over.”

Snake fungal disease, seastar wasting disease, Bsal in salamanders—when diseases like these take hold, they can very quickly lead to extinctions. We need to get better at responding to wildlife pathogens before they reach the crisis levels chytrid has. Otherwise, we’ll arrive too late and be forced to to engage in ever more labor-intensive and expensive solutions. Like disinfecting frog legs one by one, by hand, in the Honduran cloud forest.