Shillong Bush Frog: Ticking its Way Through the Monsoon

It was a Friday evening in early July 2021 when we landed in Shillong, and the monsoon rain was at its peak. After completing our weeklong quarantine, we met our academic supervisors (after 15 months) over an aperitif at our office. The rain had mellowed down to a drizzle when feeble “tick-tick” sounds rose from the garden and soon grew in number and intensity. I was told the sounds were the calls of Shillong bush frogs. I had never seen a bush frog let alone one from Shillong. At a moment’s notice, we were all outside, stooped over the flowerbeds, shining torches and trying to triangulate (a survey method to ascertain location) the frogs from their ticking calls. Though there were many frogs calling, we couldn’t spot them. Gingerly stepping on the grass and ensuring I didn’t trample any hapless frogs, I scanned the garden. Finally, my colleague Arjun caught and handed one to me. Resting in the palm of my hand was a critically endangered creature no bigger than a thimble, and this was in our office garden in the middle of a city.

Upon release, the brown coloured frog, all of two centimetres in length, hopped onto an ivy leaf and stabilised itself. Once it felt secure on its leaf perch, it inflated its bubble-like vocal sac and started calling — adding to the quintessential Shillong monsoon soundscape. Unfortunately, the frog calls, though fervent, were drowned by the blaring traffic sounds and other noises of the human condition. As I sat down for dinner that evening, I was full of questions. Why were these tiny frogs in the garden? If there were so many in a small garden, why were they critically endangered? Where do they lay their eggs in a garden without a pond?

A frog in the big city

The Shillong bush frog or Raorchestes shillongensis is an endemic bush frog of Meghalaya, mostly found within the political boundary of the East Khasi Hills district. It exists nowhere else. Distribution of this species covers an area of around 530 square kilometres and within an elevation range of 1,000 to 1,900 m above sea level. Within its distribution area, the species is encountered more at forest edges, near human settlements, and along stream banks, than inside forests. This explains why these frogs were found in the garden. During my evening constitutional in the neighbourhood, I heard frog calls from abandoned plots, small woodland patches, and even from creeper-laden walls.

It is the male frogs that sing as they are the ones with vocal sacs. Only during the breeding period, which overlaps with the rainy season from April-August, is the presence of these frogs evident, as that is the only time they call. Males clamber onto bushes and call incessantly, vying for the attention of a fertile female. A female filters the chorus of amorous calls and, based on some aural cue, heads towards her chosen mate.

The male frog is a tad smaller than the female. He hops onto the female’s back and assumes a mating position called amplexus which may last even longer than nine hours.

The amplectant pair descend to the leaf litter on the ground, and the female lays a clutch of eggs on the moist soil while the male fertilises them. After that, the pair separate. The female mixes the eggs with soil to protect them from desiccation (drying out)and possibly hide them from egg predators. That is the only thing the fertilised eggs receive in the form of parental care, as they incubate untended on the ground for one month.

The genus Raorchestes, to which bush frogs belong, are characterised by direct development. Embryos develop directly into juveniles within the eggs, foregoing the free-swimming tadpole stage. They hatch as tiny froglets, which are miniature versions of their parents. This evolutionary strategy of skipping the tadpole stage is advantageous for these tiny frogs as it removes their dependence on water for development. Though I could never observe the frogs mating, the presence of a tiny froglet was proof enough that the frogs were breeding in our garden.

As the rains retreated giving way to autumn, the office garden progressively fell silent during the evenings. Shillong, at an elevation of 1,500 m above sea level, experiences cold single-digit winters.

These frogs brumate in holes in the ground and in fallen rotting logs. Brumation is like hibernation. It is specific to reptiles and amphibians, who enter a state of “deep sleep” or torpor (inactivity) during winter or extended periods of low temperatures. During this period, these cold-blooded creatures have a low body temperature, reduced heart rate, and their overall metabolic and respiratory rates drop. They resume activity only when the temperature warms.

I continued to observe the frogs whenever possible. I recorded two colour morphs in our office garden: one was mud-brown with dark bands on limbs and another was a light greyish-brown. It took some effort to spot the frogs at night amidst the rambling ivy vines. It was impossible to spot these frogs in the daytime as they remained well hidden in the undergrowth, and with good reason. Though being small means they can hide easily, it also means they can easily fit into the mouths of bigger creatures in the garden. I observed garden skinks, Eurasian tree sparrows, and red vented bulbuls foraging for food in the undergrowth by day. At night, rats and house shrews scampered around searching for a meal. The frogs have adapted to handle natural predation risks and habitat-associated fluctuations. However, these ancient creatures are not adept at living in a fast-changing world driven by anthropogenic (human) influence.

An Amphibian in Peril

Amphibians, like frogs, are cold-blooded (ectothermic), produce unshelled desiccation-prone eggs and have highly permeable skin. Unlike birds and mammals, they have limited dispersal ability and cannot easily migrate to colonise new areas with favourable conditions. Hence, they are acutely sensitive to changes in temperature, moisture, and other physicochemical changes in their environment. On account of this, they are considered “bioindicator species” that help assess the health of the environment.

The Shillong bush frog shares space with the people of the city. This means that it is exposed to a range of threats like pollution, concretisation, and habitat fragmentation. Forest fires, unregulated tree felling, mining, garbage disposal at forest edges, and utilisation of harmful pesticides in gardens — all these are threats unique to the Shillong bush frog. Conversion of old gardens to manicured lawns and removal of shrub cover is also a major threat as shrub cover and ground leaf litter are very crucial for their survival.

This, coupled with a narrow distribution range, and the ever-looming threat of climate change and global warming, is why this endemic high elevation species is critically endangered. Shillong’s backyards and monsoons will not be the same without the “tick-tick” calls of these bushfrogs. Let us be conscious of their existence and act fast to save this potential flagship species before it slips away into an irrevocable silence.