We have now wrapped up fieldwork at our second site, the incredible rainforests of Ranomafana. Our goal there was to find individuals of another extremely small frog, actually described alongside Mini, namely Anodonthyla eximia. This particular species is especially interesting, because it represents yet another instance of independent evolution of miniaturisation in Malagasy narrow-mouthed frogs (family Microhylidae, subfamily Cophylinae); much smaller than all other Anodonthyla, and apparently totally terrestrial, unlike all of its arboreal cousins! It was described from an area called Maharira, a significant distance into the forest. This frog has previously been known only from a single specimen, so we knew this was an ambitious goal before we even set out.
Getting to Maharira was an arduous affair. An hour on good road followed by an hour on horrendous road, where we frequently got stuck, followed by six hours of hard hiking on terrible paths for about 18 km of up and down and up and down, through rivers up to our thighs, partly in the rain, with 21 porters to carry our equipment and food—it certainly was an adventure!
But we finally got to the campsite used before by a few different teams, and set ourselves up for work. Alongside A. eximia, we were continuing the herpetofaunal inventory of this rather remote area, and searching for a few other taxa for the GEMINI project as well. Already the first night was a productive one, although we hardly strayed away from the campsite. Heavy rain had brought out quite a few frogs to sing happily into the night.
Our time in Maharira was limited to just four nights, so we put in hard work to try to capture as much of the diversity as possible. But at the back of my head was always the problem of A. eximia. We just couldn’t find them. Finally, on the third day, we set out before six in the morning, because knew that they should be calling in the morning. We hiked for a ways down a path until finally we heard small whistling calls that could only be them or other miniaturised microhylid frogs. We set ourselves to it, and finally, after almost an hour, we caught the first specimen, after slowly lifting leaf after leaf to find it in the litter. And indeed this was A. eximia! The second I found not long after, and managed to record it calling. What a thrill! To be the second person in the world to catch these frogs was amazing. And they are truly remarkable creatures.
Were it not for their unusual skull, hands, and pectoral girdle, they would be almost impossible to tell apart from Mini and Stumpffia. Even their behaviour is practically the same. But in this forest we found no trace of either of those other two genera, so it looks like this was just opportunity for them to explore an otherwise unoccupied niche. This is such a remarkable case of convergent evolution of both size and ecology, which I hope the GEMINI project will help shed light on through high-quality genomes.
That same night, we went for a walk into the forest and found Plethodntohyla inguinalis—possibly the largest microhylid in the world. Seeing the contrast was incredible. But I didn’t dare put the two side-by-side for fear of the larger eating the smaller—they’re voracious and indiscriminate predators.
Ironically, on the morning of the following day we realised that we could hear A. eximia calling just a few metres from our tents; the early morning hike hadn’t been necessary at all. But still, it was very much worth it to have a better understanding of their distribution and ecology. Fascinating little frogs!
The rest of the work was much more relaxed after this success, and we were able to continue the survey with full energy. The final night, after almost everything was packed, I went to look what frog was calling behind our toilet. It turned out to be almost certainly a new species of Anodonthyla!
The next morning we had to hike back out of the forest, this time in the scorching heat. But we were buoyed by the success of our search!
Now we have made our way back to Antananarivo, and today we will continue on to the Andasibe area for the third and final leg of our trip, searching for still more extremely miniaturised reptiles and amphibians!
