Few animals seem to encapsulate the magical qualities of the Bornean jungle more than gliding frogs. Armed with huge webbed feet and flaps of skin along their limbs, these colorful amphibians sport the uncanny ability to paraglide down from the tree tops and even change directions in mid-flight. Once, during a visit to the canopy walkway in Danum Valley Conservation Area in Sabah, I witnessed firsthand just how effective the gliding ability of these frogs can be. Upon arriving at a tree platform in the middle of the walkway, perhaps 50 meters above the forest floor, I noticed a small orange frog (Rhacophorus pardalis) perched on one of the wooden planks near the edge. As I approached for a closer look it abruptly leapt off the platform and I watched as it soared down through the air, carved a wide arc around a lower tree and disappeared into the forest below.
Several gliding frog species occur in Borneo, all in the genus Rhacophorus and all equally charming with their gaudy colors and oversized (seemingly ungainly) floppy feet. The most well-known is undoubtedly the large and spectacular Wallace’s Flying Frog (Rhacophorus nigropalmatus), made famous by Alfred Russel Wallace’s description and illustration in The Malay Archipelago. Smaller, but no less attractive is the Harlequin Flying Frog (Rhacophorus pardalis) which is perhaps the most common of the species, being found all across the island around muddy pools of water in the forest.
Last month a scientific paper published in Current Herpetology brought to light an entirely new species, the Bornean Gliding Frog (Rhacophorus borneensis). Perhaps the most colorful of all the Rhacophorids, R. borneensis is a pale lime-green with an orange underside and interspersed with patches of black and brilliant sky-blue. This frog had been known previously from a few scattered collections and photos from Sarawak and Sabah, but was thought to belong to the Javan Flying Frog (Rhacophours reinwardti). The new research compared both color patterns, size, and DNA, and showed that the Bornean specimens are indeed distinct from R. reinwardti, which is now believed to occur only in Java.
Like other gliders, R. borneensis is a true tree frog, and it is believed to live almost its entire adult life in the forest canopy, descending to pools of water only to breed and lay eggs. Simply judging by how rare encounters with this species are, its visits to ground level are probably even more infrequent than R. nigropalmatus or R. pardalis. The presence of R. borneensis in the forest is often only detected by the distinctive call of the male, sounding somewhat like a woodpecker drumming on a hollow tree.
So far the life-history of the Bornean Gliding Frog remains almost completely unstudied, but further research is certainly warranted for this newest member of Borneo’s magnificent gliders.
M. Matsui, T. Shimada, A. Sudin. A New Gliding frog of the Genus Rhacophorus from Borneo. Current Herpetology, August 2013; 32(2): 112-124.