Scientists Discover Hula Painted Frog Hasn’t Croaked After All

More than 150 frogs and tadpoles of elusive species have been found, after scientists realize they have been searching in the wrong place all along.

The Hula painted frog. Scientists were searching in all the wrong places.
Gil Eliahu

Just as a lone frog croaking at night will be joined by his friends until there’s a cacophony, the elusive Hula painted frog, rediscovered five years ago, is multiplying. More than 150 frogs and tadpoles have been found, and Prof. Sarig Gafni of the Ruppin Academic Center’s School of Marine Sciences says a few hundred patrol the watering holes of northern Israel’s Hula Valley.

According to Gafni, who is leading a study on the animal, when the search started about two years ago, only 20 of the species were found. Researchers looked in reeds and brambles, where the frogs dig down a few centimeters, their black and white skins almost perfectly camouflaged in the swampy soil.

But the scientists were looking in the wrong place, Gafni says. It turns out the Hula painted frog isn’t much of a land-and-water amphibian – it mainly inhabits the water, especially at night.

So Gafni and his research partners, including Prof. Eli Geffen of Tel Aviv University, Prof. Miguel Vences, and doctoral student Bina Perl of Germany’s Braunschweig University, have been looking for the frog at night and in the water. One night they caught about 40.

“Out of every 100 ordinary frogs, there’s one Hula painted frog,” says Gafni, who presented his team’s findings this week at a conference at Tel Hai Academic College in the Upper Galilee.

The Hula frog has an unusually shaped head, and white spots on the belly unique to each   individual. So when you photograph one, you can sure you won’t be mistakenly counting it twice when you find another one. 

The first Hula painted frogs were found in this country in the 1940s around Lake Hula. Two zoologists, Prof. Heinrich Mendelson and Prof. Heinz Steinitz, found two adults and two tadpoles. They preserved them in formalin solution, as was the practice in those days. 

But on the way back south, one frog ate the other. Steinitz took the remaining frog back to the Hebrew University of Jerusalem, while the Tel Aviv Biological Pedagogical Institute, Mendelson’s institution, “felt cheated.” The first tadpoles were taken to Jerusalem as well, but in 1948 they disappeared during the fight for the city in Israel’s War of Independence.

In 1955, zoologist Michael Kosta found another of the species and gave it to the Hebrew University – the only one of the species found at that time anywhere, Gafni says. Then the Hula Swamp was drained and the frog was thought to have become extinct.

When scientists discovered that the Hula painted frog had made a comeback, they initially thought it was a member of a group from Western Europe that had been around for some 20 million years. But a bone scan by paleontologist Rivka Biton of the Hebrew University revealed that the species found in 2013 was 50 million years old and was a member of the genus Latonia – giant frogs in Europe that went extinct around 1.5 million years ago.

The frog’s prehistoric ancestors were as much as 20 centimeters long, twice the average length of their Hula painted descendants.

The search for the Hula painted frog continued unsuccessfully for many years. In the 1990s, a Lebanese scientist reported hearing a Hula painted frog croaking.

According to Gafni, two delegations of scientists scurried to the area of the sounds, but found nothing. Gafni says that when he did reserve duty in Lebanon for the Israeli army, he went out armed with a butterfly net to catch a Hula painted frog if he came across one. But he never did.

In 1996, the Hula frog became the first amphibian to be declared extinct by the International Union for the Conservation of Nature.

But rumors of its demise were premature. In 2011, a ranger in the Israel Nature and Parks Authority, Yoram Malka, found one. A week later, following the report of the find in the media, a hiker realized he had photographed one two years earlier.

Since then, the Hula painted frog has become one of the most sought-after species in the world – and it seems it only lives in Israel.

As part of the research, scientists have been able to identify the Hula painted frog’s distinctive croak. Unlike other species of frog that make a racket at night, the Hula frog emits a low, soft sound that’s hard to pick up.

But they’re out there. According to Gafni, the species’ DNA has been found in 17 of 52 watering holes surveyed in the Hula Valley.