Scientists re-discover tiny lost frog species in Zimbabwe

For herpetologist and self-proclaimed “frog guy” Francois Becker, laying eyes on a frog lost to science for five decades was a moment of pure joy, not so unlike the jolt of adrenaline that comes with being hit by Cupid’s arrow.

“Of the big moments in my life, this one is pretty close to the top,” Becker says. “This is probably one of the biggest African frog-finds in the past few decades. A lot of people have been looking for this species for a long time. Many people thought it was extinct.”

The Search for the Squeaker is On

It took Becker and his team a full year to plan the December 2016 expedition to Zimbabwe’s Chimanimani Mountains, funded by the Mohamed bin Zayed Species Conservation Fund. The trip was meant to be a last-ditch effort to look for the Sinkhole Squeaker (Arthroleptis troglodytes), which was last seen in 1962—the year it was discovered in sinkholes on the eastern side of the mountain range. Becker, who is a master’s student at the University of Cape Town, says he anticipated that they would return empty-handed like the many previous expeditions.

It wasn’t until after the first grueling day of digging through sinkholes and clambering through deep caves in search of the small frog, which is no bigger than a bottle cap, that hope arrived in the form of a distant and peculiar whistling call. Becker was out on a moonlit walk while the rest of the team cooked dinner at camp when he heard the first call and suspected right away that the squeaky call belonged to a frog species in the Arthroleptis genus. It took him 45 minutes to track the source, but when he finally got eyes on the individual, Becker says he knew immediately that he had done what many expeditions before him had failed to do: re-discover the elusive Sinkhole Squeaker.

It was love at first squeak.

“The closer I got to the call, the more I was convinced that this had to be it,” Becker says. “When I finally narrowed my search down to a small patch and saw the frog hopping, there was no doubt. I had seen the museum specimens and knew what it looked like. When I grabbed the frog, my hands were shaking so badly from excitement that it got away and jumped into a deep crevice.”

Becker persevered and was able to track down another individual shortly before midnight. “I couldn’t return to camp empty-handed,” Becker says. He ran back to camp, frog in hand, triumphantly shouting to his team—Zimbabwean entomologist Scott Herbst and two Outward Bound guides, Fungai Marema and Tor Simonson. He didn’t sleep much that night, he says, and immediately called his supervisor, his wife Tessa, and colleague Robert Hopkins, an associate researcher with the Natural History Museum in Bulawayo, who had launched several expeditions since 1999 to look for this frog.

Finding the species was especially significant for Hopkins, who was a close friend of Don Broadley, the herpetologist who discovered the species in the 1960s. Broadley died just months before this rediscovery. Broadley was “the greatest herpetologist in the world,” Hopkins told the Zimbabwean.

Taking the Squeaker Road Less Travelled

 When Becker and his colleagues planned the expedition, they intentionally planned to be in the field during the rainy season when the frogs would be active and likely calling.

And according to Becker, the chorus of calls indicated a healthy population of tens or hundreds of squeakers, clearly breeding successfully. Unlike many other frog species, frogs in the Arthroleptis genus experience direct development, skipping the tadpole stage and hatching as mini adults.

Becker and his team focused on mapping the species’ distribution, collecting data about its habitat and describing the frog’s unique call. They also collected four individuals, three males and one female, which they transferred to Hopkins’ lab at the Natural History Museum to become part of a breeding program. According to Hopkins, the frogs are doing well so far, feeding well and living in a terrarium that mimics their natural habitat as closely as possible.

The breeding program, which aims to someday be the source of additional wild populations placed in suitable habitat, is only one important step in the conservation of the species, which the IUCN Red List has most recently classified as Critically Endangered (Possibly Extinct). Even though the population Becker re-discovered is in a protected area in a national park, it is limited to a small area, four or five acres at the most, making the species particularly vulnerable to any sort of habitat change or destruction as the result of extensive fires, climate change, illegal mining or increased forestry in the area.

As such, Becker recommends that the IUCN Red List continue to list the species as Critically Endangered, and Hopkins is working with Zimbabwe’s National Parks Authority to help ensure the habitat remains intact and to prevent any illegal collections by private individuals. Hopkins is aiming to establish a research and monitoring program for the wild populations in the future.

Squeaker Amore

Not long after Becker snapped photos of the three Sinkhole Squeakers the team brought into captivity, Becker’s wife Tessa pointed out the two heart-shaped markings on the back of the tiny female frog. It seemed an appropriate emblem for a re-discovery that can only be described as an extraordinary labor of herpetological love.

And if it is love and passion and hope that drives scientists to search for the seemingly impossible, then Becker seems to be brimming with the sense of possibility as he shares his tale of re-discovery. Ultimately, he says he is now confident that the Sinkhole Squeaker has a bright future.

“This species has been there all this time, without human intervention, and it has been fine,” Becker says. “As long as we can help keep its habitat intact, I’m hopeful the Sinkhole Squeaker will never be lost again.”

By Lindsay Renick Mayer

Photo: Sinkhole Squeaker (Arthroleptis troglodytes) © Francois Becker