Rediscovering the Cave Squeaker, a long-lost frog

Robert Hopkins, a researcher at the Zimbabwe Museum of Natural History, had been wanting to find the mysterious Cave Squeaker (or Chimanimani Squeaker) in the Chimanimani highlands of eastern Zimbabwe, for a very long time. It had been nearly 54 years since the late Dr Donald Broadley, a world-renowned herpetologist, had discovered the frog in a sinkhole in the year of 1962. Don had been collecting herps, particularly snakes, which was his favourite taxon. It was summer up in the eastern highlands, but the rain had not yet replenished the multitude of mountain streams that usually sparkle their way down the forest-covered mountain slopes to criss-cross along a huge central grassy plain flecked with Proteas. As the climb to this point was lengthy and treacherous, he had not been able to haul large amounts of water up the mountains, and his supplies were running low. He therefore made his way into one of the deep sinkholes that would unexpectedly eat their way to the surface, breaking through the soft topsoil and leaving great gaping holes and tunnels that opened unto the rocky abyss below. These provided a permanent, although often dangerous source of water, but one he was forced to enter now. As any good herpetologist would, Don decided to lift a few rocks while he was fetching water, to see if anything interesting was sheltering underneath. And there it was: a small Squeaker frog (genus Arthroleptis) which Don’s keen, morphologically attuned eyes quickly recognised as a new species. It was subsequently described by Prof John Poynton in 1963, from a handful of specimens that Don had caught later on the field trip (now 1962), in the same general area as the first frog.

Over the following decades, an increasing number of professional and amateur herpers were making the climb up to the Chimanimani mountains in the hope of finding the Cave Squeaker, but to no avail. Even Don himself had tried and failed to find them again. As the decades went by, the mystery surrounding the frog became well-known and in 2010, a highly capable and experienced team of herpetologists with Conservation International’s Lost Amphibian Species, tried to find the frog once more. After coming up empty once again, the Cave Squeaker was finally assessed by the IUCN SSC Amphibian Specialist Group as Critically Endangered or Possibly Extinct. Until this point, Don had been the only person to see these frogs alive, and very little was known about them beyond what could be gleaned from the bleached and aged museum specimens.

Robert Hopkins, for whom finding the frog had become something of a life goal, had also attempted the search several times with detailed directions from Don, who was a close friend of his. In 2016, shortly after Don’s passing, Rob decided to plan a last-ditch effort to search for the Cave Squeaker. After that, he would accept that it had probably gone extinct due to ongoing habitat degradation in the area.

I met Rob at the 2016 meeting of the IUCN South African Frog Re-assessment Group (SAFRoG) in Cape Town. He contacted me soon after to ask if I was willing to join him on his search for the mysterious Cave Squeaker. I was instantly keen for the adventure, knowing that the Chimanimanis are a very beautiful part of Zimbabwe with many interesting frog species. However, I was under no illusion that this was anything more than a near-futile endeavour. We decided to go in December, when the rains should have started and the frogs should therefore be active – anything to improve our chances! Rob had secured funding from the Mohamed bin Zayed Species Conservation Fund, and we both knew the Miekles who managed the Outward Bound at the base of the Chimanimani Mountains where we planned to start the hike up, so the trip was all set…

December finally came, and I had to leave a Statistics conference in Cape Town early to take the bus to Bulawayo. Despite telling myself repeatedly that we would probably return empty-handed, the challenge was enticing. My excitement helped to shorten the arduous two-day bus journey and long night’s queuing at the crowded border-post into Zimbabwe. Rob had been having some health difficulties, and decided not to join us up the mountains, but would stay at the base camp near Outward Bound whilst four of us would go up the mountains: Scott Herbst, a student, Fungayi Marema and Tor Simonson, two guides from Outward Bound who lead the way, and myself. We were an inexperienced but optimistic team, and as we started the climb it started raining. I told everyone that this was probably a good sign.

The climb into the highlands was beautiful – creeping over steep rocky cliffs draped with orchids and lichen, then snaking through dense mountain forests, and finally zig-zagging down into a vast grassy highland plain that lay surrounded by majestic mountains. It was a paradise! We walked across the great highland plain for several kilometres, crossing little streams here and there and curving past stands of Protea before reaching another mountain. On top of this mountain was the hut we were to stay in. Exhausted by the long climb, we had a short recovery nap before scouting the surrounding area. I wanted us to search several different habitats I had previously identified on Google Earth. We eventually decided that the large sinkhole, about a kilometre to our SE, was a good place to start. Don had found the first individual in a sinkhole like it (possibly that particular one), and the others under rocks in or near sinkholes and crevices. The sinkhole turned out to be a deep cave that turned and twisted its way into the bowls of the earth. We entered it cautiously and flipped some rocks, but found nothing but a rabbit in the blackness. We ventured into a few other sinkholes and crevices, some of them so treacherous that you could easily find yourself plunging several stories down to a rocky death if you lost your foothold. When it started getting dark, we decided that it was probably safer to continue the next day. We set out several pitfall traps with drift-fences before making our way back to the mountain hut, thoroughly tired out and ready for supper.

Rediscovering the Cave Squeaker, a long-lost frog

Live specimens of Arthroleptis troglodytes in a natural setting, to show colour variation among individuals

Live specimens of Arthroleptis troglodytes in a natural setting, to show colour variation among individuals

Live specimens of Arthroleptis troglodytes in a natural setting, to show colour variation among individuals

Live specimens of Arthroleptis troglodytes in a natural setting, to show colour variation among individuals
Figures 1-5. Live specimens of Arthroleptis troglodytes in a natural setting, to show colour variation among individuals

Scott offered to make supper the first night, and both Fungayi and Tor stayed to help. Having gained my second wind, I decided to explore the other side of the mountain in the moonlight to scout out more habitats. I also found the solitary stroll useful to plan and think, and to pray, feeling somewhat overwhelmed by the undeniably large odds stacked against us. Nonetheless, I was determined to spend every minute of the trip productively searching, and so after having cleared my head, I started listening to the night sounds. I noticed a soft, high-pitched chirping call up the mountain slopes on the other side of a stream. I had to clamber through a bit of forest to get there, and soon realised that tracking this call would not be easy. The terrain was a tangle of thick bushes, bracken and dead vegetation, and was littered with huge sandstone boulders that were dangerous to navigate in the dark. But there was something about the soft chirps that suggested they might be worth investigating, so I continued climbing over boulders and fighting my way through bushy thickets. The calls were quite soft and the animals making them were skittish, so they stopped calling before I got near them. I went back to the hut to report the strange calls, and to fetch my cell-phone. After playing through many of the calls from the Complete Guide to Frogs of Southern Africa which I had on my phone, I established that this call, if it was a frog, was certainly not a known species! However, I had certainly heard crickets making similar noises before – so was this even a frog? Nevertheless, my curiosity got the better of me, and I announced my intentions to return and search for the calling creature. The others encouraged me to do so, but decided that they had had enough of fruitless call-chasing for the day – we had spent at least an hour chasing the call of a bird on the way up that day.

I wasted no time getting back into the thickets, and soon found myself surrounded by a small chorus of the calling creatures. The closer I got to them, the more I was convinced that this could be the frog we were looking for! Knowing the drill well, I zoned in on one of the callers, approaching it cautiously. When it stopped calling, I waited patiently and silently until it started calling again. After almost an hour of tracking, I was close enough to one of the callers to record it on my cell-phone, and started using the playback to stimulate it. This seemed to work fairly well, and soon after I had narrowed down its position to within a metre. I switched on my torch and started searching the leafy undergrowth. Before long I saw it hop, and immediately I knew: this was it! I had seen museum specimens before and recognised its shape in a split-second. Frantic with excitement now, my shivering hands desperately clawed at the fleeing little frog, but I missed! Within seconds it was all over – the frog had managed to dive into a deep crack between two large boulders. I tried to shine my torch after it, but knew it was too late. I cursed myself for my clumsy first attempt, but it no longer mattered – I had found the Cave Squeaker!

After the first one’s escape, I went straight for the next calling frog. I refused to return empty-handed, and so I patiently tracked it for 30-40 minutes. Knowing what to look for now, I found it quite quickly, and this time my aim was true. I placed it in a small plastic holding jar and marvelled at my find in the torch-light. It was simply exquisite! This one had beautiful red legs and a dark dorsal colour pattern, as opposed to the beige-coloured individual I saw earlier. Finally having the frog in hand, I could hardly believe what had just happened, and certainly could not contain my excitement! I practically ran the few hundred metres back to the hut, and started shouting as I ran: “I found it! I found the frog! I found it!” I came bursting into the hut to find everyone staring at me with smiles on their faces. We had managed the impossible!

Although it was already quite late, I had to tell more people about our find straight away. I called my wife Tess, Rob Hopkins who was over the moon at the find, my supervisor Krystal Tolley, and Louis du Preez who also works on frogs. When I was satisfied that I had told enough people the wonderful news, I took a while to calm down and said a great many prayers of thanks. This was not something we had expected to succeed in, particularly after so many skilled and experienced herpetologists had not managed to find it before. But tonight, there was a victory over the mysterious, and it was ours to enjoy!

In the next few days, we collected and photographed a few more individuals, recorded calls and mapped the areas where we could hear their calls. Rob and I described for the first time the species’ call, habitat, colour in life and several other morphological characters not highlighted before (Becker and Hopkins 2017). We were also able to obtain the first viable genetic samples for the species. From our call surveys, we established that the frogs do not inhabit mainly caves, although some may have sheltered in caves during the dry season – this is probably why Don had found them there. There appeared to be a few healthy populations in several isolated rocky valleys or mountain slopes, but our surveys did not extend the very small known area of occurrence. Nonetheless, it was good to know that, after all the decades of doubt, this hyperendemic melodious mystery still persists in the Chimanimani highlands of eastern Zimbabwe.

Francois Becker
About Francois Becker 1 Article
Francois Becker is a keen Southern African herpetologist and conservation scientist. He is currently a researcher at Gobabeb Research and Training Centre in the Namib desert, where he is working on barking geckos (genus Ptenopus), and investigating the use of their calls in mating and its implications for their evolution. He is also involved in several taxonomic projects on thread snakes and reed frogs, and on the conservation ecology of the Critically Endangered Rose’s mountain toadlet, on which he did his MSc in ecological statistics, through the University of Cape Town and South African National Biodiversity Institute. He is also involved in the South African Frog Re-assessment Group (SAFRoG), which re-assesses all Southern African amphibians for the IUCN Red List, and in the Namibian Atlas project, which aims to gain a deeper understanding of the spread of biodiversity throughout Namibia. More of Francois’ work can be found on Research Gate.
Contact: Website

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