Hula painted frog. Credit: Frank Glaw
Hula painted frog. Credit: Frank Glaw

Reports of Frog’s Extinction Have Been Greatly Exaggerated

It’s been an eventful 75 years for the Hula painted frog. Having clung to existence while its closest relatives embraced the cuddle of extinction, it was then discovered by scientists, lost for decades, declared extinct and turned into a symbol of a conservation crisis, before literally hopping back into the limelight. It’s the Frog That Lived, Then Died, Then Lived Again.

The Hula painted frog was discovered in March 1940, when Heinrich Mendelssohn and Heinz Steinitz spotted two beautiful individuals in the wetlands of Israel’s Hula Lake. They had distinctive dark bellies with white spots, and streaks of olive, black and rust on their backs. A third adult was found in 1955, and that was the last anyone saw of it for decades. Many searched; none succeeded. In the meantime, the wetlands of the Hula Valley had been drained to make way for encroaching farmlands.

With its habitat degraded and its presence undetected, things didn’t look good for the frog. In 1996, after four decades of failed searches, it became the first amphibian to be classified as extinct by the International Union for Conservation of Nature (IUCN). That, unfortunately, was an omen of things to come. We now know that frogs and other amphibians are among the most threatened of all animal groups. Around a third of them are classified as “threatened” and up to 165 species might already have gone extinct. Their habitats are disappearing. Pollution is killing them. A deadly fungus is wiping them out.

The picture is certainly bleak, but that might partly be because many amphibians live in inaccessible places and are hard to find. They were seen once, maybe twice, and then never again. Have they actually died out, or are there small populations clinging onto life? If it’s the latter, we could double our efforts to protect the survivors, or enrol them in breeding programmes. But first, we’d have to find them.

To that end, Conservation International launched the “Search for Lost Frogs” in 2010—a huge search for 100 species that hadn’t been seen for at least a decade. They only found four of their wishlist, such as the Rio Pascado stubfoot toad, re-discovered after a 15-year absence. These were small consolations for a project that otherwise failed. The world still needed hopeful stories.

Enter—or perhaps, re-enter—the Hula painted frog. Since the last individual was seen, the lake where the frogs lived had been turned into Israel’s first nature reserve. Protected against the devastating drainage  project, it became a haven for migrating birds, rare plants, and fish. Yoram Malka, a range for the Israel Nature and Parks Authority, was convinced that the painted frog was still there. He had no evidence, just a gut feeling.

In 2010, Malka relayed his suspicions to Sarig Gafny, a river ecologist from the Ruppin Academic Center in Israel, who was studying invertebrates at the lake. “I told him: Until you get me a frog with a black belly and white spots, you don’t have it,” says Gafny. “He said: Give me a year and I’ll get you a specimen.”

Exactly one year later, in October 2011, Gafny returned to his office in the late afternoon to find 20 missed calls on his phone. It was Malka. Earlier that day, on a routine patrol, a Hula painted frog has just leapt out in front of him. “He told me: Sarig, we found it.” Gafny jumped into his car and drove to the reserve, armed with a copy of the original 1943 paper describing the frog. He checked off every physical feature against Malka’s specimen. It was indeed the right animal, in the not-extinct flesh.

View Images
Hula painted frog at the Hula Nature Reserve. Credit: Frank Glaw.

The frog’s reappearance is doubly important because it turns out to be the last survivor of an otherwise extinct genus called Latonia. Back in the 1940s, Mendelssohn and Steinitz classified it as Discoglossus nigriventer, making it one of several Discoglossus painted frogs. “It was a reasonable classification because they didn’t have DNA sequencers or CT scanners as we have now,” says Gafny. But when his team analysed the DNA from their newly-found specimens, they found that the frog isn’t part of the Discoglossus group, and had split away from them around 32 million years ago.

So what was it? Rebecca Biton from the Hebrew University of Jerusalem had the answer. She had been studying the bones of fossil frogs found in Israel, and showed that many “Discoglossus” skeletons actually belonged to Latonia. She eventually worked with Gafny and placed the four dead Hula painted frogs in a CT scanner. Sure enough, their bones had the distinguishing marks of Latonia, corroborating the story that the DNA had crafted.

There are no other living Latonia species. The rest died out during the Pleistocene period, with the last one living to around 15,000 years ago.  If the Hula painted frog—now Latonia nigriventer—had actually gone extinct in the 1950s, its entire genus would have disappeared too.

Gafny’s team have now found a total of 14 individuals. (Their new paper says 11 but they’ve found three more since, and one just in the last week!) One had been killed by a farmer (by accident) and three had been killed by kingfishers (probably not by accident). The rest were alive. And when news of the rediscovery broke in 2011, Gafny got an email from a tourist who had snapped a photo of a Hula painted frog two years earlier! “Our finding got so much media exposure that it reminded him of something, and he went back to his camera,” says Gafny.

“Rediscoveries like this are important in fostering interest in conservation and a generating sense of optimism,” says Robin Moore, who works for the IUCN and has visited the Hula Nature Reserve with Gafny.  “We need flagships for conservation to generate a sense of optimism and this story is about as good as it gets. The frog became a symbol of extinction in Israel. It is even included in school curricula, and my taxi driver to Tel Aviv airport knew its story!”

But if the frog was there the whole time, why could no one find it? Because, Gafny thinks, they weren’t looking hard enough. That’s not a slight; the frogs have only been found around a single pond and they live among dense vegetation. “You have to crawl into this very dense canopy of blackberries, which aren’t very polite to you,” says Gafny. “Then you have to dig into the decaying vegetation. They usually sit covered by leaf litter.”

The more hopeful answer is that the frogs’ population is increasing. Gafny says that the water in the lake has become cleaner and more plentiful since the nature reserve was set up. He hopes that by continuing to protect this delicate ecosystem, he can give the frogs a fighting chance. He’s especially hopeful because the deadly chytrid fungus that is killing frogs all over the world has never been found in the region. “I’m looking for it just in case, but we have no record of it,” says Gafny.

“Habitat loss remains the biggest threat to the survival of amphibians around the world, and it’s important to be reminded that strategies to address it can work,” says Moore, “We need these positive stories amid the doom and gloom.”

Reference: Biton, Geffen, Vences, Cohen, Bailon, Rabinovich, Malka, Oron, Boistel, Brumfeld & Gafny. 2013. The rediscovered Hula painted frog is a living fossil. Nature Communications

Note: A shorter version of this story appears at Nature News.

More on frog conservation: