By Bhaskar Saikia, Zoological Survey of India, Shillong
With the onset of pre-monsoon showers in Shillong, townspeople are woken at night to a constant cacophony of ‘tick-tick-tick that can be heard from the nearby forests, streams, bushes and pretty much everywhere. While most people may confuse this sound with that of insects, but actually it belongs to a species of tiny bush frogs, which was discovered in Shillong in 1973. Interestingly, it is a species critically endangered in addition to being endemic to East Khasi Hills. The scientific name for this species of frog is Raorchestes shillongensis and is commonly known as the Shillong Bush frog, as they are commonly found in the forest bushes of Shillong.
Frogs of this species are so small that a fully grown adult can sit on a coin while leaving more room for another frog! This makes the Shillong Bush frog one of the smallest vertebrate species in the world!
The story of the discovery of this species of colorful frog is intriguing. Scientists from the Zoological Survey of India (ZSI), Shillong, came across a number of frogs huddled in the ground of nearby Malki forest, where land ‘cutting’ or loss of forest was in progress. course, making a “kucha” forest road in 1971. As the frogs were examined, they turned out to be unknown to science, then were officially published in 1973 as a new species. Since then, many research works have been conducted on this species such as its population status, distributions, morphological variations, breeding biology, by the scientists of ZSI and Wildlife Institute of India, Dehradun (WII).
Found mainly in forest bushes up to a height of two meters from the ground, but descends to the ground to lay eggs under fallen leaves, after which the female covers the eggs with moist soil, after which they turn into froglets. Contrary to the idea that all frog eggs hatch into tadpoles which later undergo metamorphosis to evolve into frogs is incorrect. In the case of Shillong Bush frogs, development is instantaneous and the froglets that hatch are miniature versions of adult frogs. Biology is therefore considered the science of exception because living organisms show great variation due to evolution, mutation and genetic recombinations, and bush frogs are a classic example.
The population of Shillong Bush Frogs is on the whole restricted to Shillong and its suburbs, with pockets of known populations in the areas of Mawphlang, Kharang, Mawlyngot, Pynursla and Dain Thlein Falls – all located in the East District Khasi Hills. This restricted distribution of this species makes it vulnerable to any degradation of its habitats, which justifies its classification as Critically Endangered (species in serious danger of extinction) of the Red List of the International Union for the nature conservation (IUCN). The IUCN, an international organization committed to the conservation and sustainable use of nature, also classifies categories of threat to biodiversity. However, the high population density (and its cacophony) of the Shillong Bush frog in the city and its suburbs, especially during the monsoons, suggests that its population is stable and healthy. It’s good news for all nature lovers that Shillong is home to such a fragile species, whose stable population is a testament to the town’s favorable environment for wildlife. Nevertheless, this apparently stable population does not mean that the Shillong Bush Frog is not vulnerable to extinction pressures, as the city and its urban outskirts have witnessed massive construction activities, increasing pollution of its bodies of water as wow Omkhrah and wow Umshyrpi, and a general trend of habitat degradation in recent years. These could be catastrophic for any species restricted to a small range, and especially for a perianthropic species like the Shillong Bush Frog.
What might still intrigue readers is where the seemingly thousands of bush frogs disappear during the winter and why the forests, streams and farms go silent then. This is explained by the intrinsic nature of frogs being cold-blooded species that hibernate during the cold. When ZSI scientists first collected frogs of this species in 1971, the month was February; they hibernated in the ground and rotting logs during the winters, as they changed body color to camouflage its surroundings.
Shillong has the epithet of being the Scotland of the East. Can we now think of another nickname for Shillong to reflect that it is an abode for a critically endangered animal species?