In 1962, researchers exploring the sinkholes, caves and montane grasslands of eastern Zimbabwe's Chimanimani Mountains stumbled across a dark brown frog no bigger than a dollar coin. The tiny amphibian turned out to be new to science, and it was dubbed the cave (or sinkhole) squeaker in a nod to its unique, high-pitched call. Then, as suddenly as it had appeared, it vanished.

Half a century passed without another recorded sighting of the elusive frog, and many feared the species had squeaked its final squeak. That is, until December last year, when an expedition organised by Robert Hopkins – a research associate at the Natural History Museum in Bulawayo – uncovered a population of sinkhole squeakers (Arthroleptis troglodytes) eking out an existence in Zimbabwe's Eastern Highlands.

Image © Francois Becker

The team's findings have sparked hope for the rare species. "A great deal of data was gathered," says Hopkins, who has been searching for the squeaker for eight years. "And most interesting of all is that I am able to state that this species is alive and well on the summit of Chimanimani, and is breeding well – there seems to be a very viable population."

Also part of the search were fellow scientist Francois Becker from the University of Cape Town and Zimbabwean entomologist Scott Herbst. It was Becker who managed to track down the sought-after squeaker by following its unusual call. "Francois had done a great deal of work on [similar species] in South Africa, and had paid particular attention to their calls," Hopkins says of the discovery. "He heard a call which he recognised as that of an Arthroleptis, but did not or could not identify it, so he tracked that call and ultimately found the first specimen."

The research trip was certainly not the first attempt by scientists to track down this herpetological trophy – other research surveys have been trying and failing over the last 50 years. It's possible, however, that they were all looking in the wrong place. According to Hopkins, most researchers have been searching for the species near water, which is where they were first found 55 years ago. "Our (latest) finds place the breeding sites away from water, and certainly not at any time in caves or sinkholes," he points out.

If Arthroleptis troglodytes is anything like other species in its genus, then it isn't necessarily dependent on water bodies during the early stages of life. These frogs are believed to undergo direct development, which means that unlike most other amphibian species they skip the tadpole stage and hatch from their eggs as fully formed, miniature adults.

Image © Francios Becker

Although the squeaker frogs prefer a fairly isolated, lofty lifestyle within Chimanimani National Park, the species may still be at risk from development. On the Zimbabwean side of the reserve, small-scale mining is known to have caused significant damage to a key river system, and there have been rumours in the past of government plans to de-proclaim part of the national park for a commercial gold mine. "The biggest threat is their restricted habitat," Hopkins warns. "They are found only on the western side of the Chimanimani Mountain, in an area some four to five acres [in size]." Illegal mining activity around this tiny habitat poses a threat not only to the cave squeakers, but to all wildlife in the area, he adds.

Three specimens of the newly rediscovered species now have a home at Hopkins's laboratory in Bulawayo, where he hopes to breed them. "They are doing well and I am of the opinion that the female has nested, and that she has laid eggs," he tells us. 

So is there hope for the species? Hopkins is optimistic. After meeting with the Zimbabwe National Parks and Wildlife Authority, he is confident that measures are being put in place to protect the tiny frogs. The Mohamed bin Zayed Conservation Fund, the organisation that funded the expedition, has also volunteered to continue assisting in future conservation initiatives.

Hang in there, cave squeakers, help is on the way.