Indian bull frog: the Andamans’ new colonisers
The Indian bull frog, a recent arrival from the mainland, is steadily occupying the islands’ ecosystem and threatening the local economy. Mohit M. Rao reports on the bizarre man-frog conflict brewing in the islands
A narrow road bifurcates the hyper-green paddy fields of Webi village in Middle Andaman, in the Andaman and Nicobar Islands. A clear stream flows around the Webi, home to the Karen community, brought to these shores from Myanmar 93 years ago.
At dusk, as fading sunlight paints the surrounding hills in silhouette, the calls of cicadas, crickets and frogs rise in crescendo. In the cacophonic stillness, a centipede winds its way across the empty weathered road. And then, in the blink of an eye, it’s gone, swallowed whole by a recent migrant to the island — the Indian bullfrog (Hoplobatrachus tigerinus).
Barely 10 cm long, this particular specimen is small. But the larger ones weigh at least half a kilo. The golden stripe on their backs and the glitter around their throats shine in the diffused light of a mobile phone. Less than two feet from the centipede-eater sits another frog. Next to that, one more, and another, and another… scores of frogs in varied sizes, basking in the warmth of the asphalt. Every now and then, one of them leaps toward the murky waters of the paddy fields. There is nothing frog-like about the deep, guttural croaks of these prolific breeders. Rather, they sound more like a bull with a sore throat.
“It wasn’t here even five years ago. Now they’ve taken over the village,” says Nau Thaw Raytoo, a mother of four, who lives in a concrete-bamboo house with her children, their wives, and her six grandchildren. Her broken Hindi shifts to fluent, high-pitched Karen when instructing raucous kids.
Webi is just among the scores of villages in the islands where the amphibian has arrived in hordes. An unusual man-frog conflict is brewing. The voracious animal gulps down anything that would fit in its jaws: centipedes, leeches, native frogs, lizards, small snakes, and even chicks and ducklings, which are an important source of food for the islanders.
“I’ve seen them eat chicks, swallowing the head whole,” says Raytoo, adding that of the 15 chicks hatched in the family’s chicken coop this year, only three have survived. Balakishore, whose father is Ranchi (an overarching term for Jharkhand tribals who were settled here to clear the forests decades ago) and mother is Karen, has lost 50 ducklings to the frogs. When grown, each duck would have fetched at least ₹300 in the local market.
One invader, many names
In the villages carved out of the virgin Andaman forests, the amphibian invader has evoked both surprise (“where did they come from?”) — and anxiety (“when will they go away?”). The bullfrog, found widely in mainland India and protected under Schedule IV of the Indian Wildlife Act 1972, is making the most of a free run that it’s enjoying in the erstwhile penal colony.
In the Andaman Islands, it can rain eight months of the year. The first rains in May are the signal for the bullfrogs to come out of the streams and agricultural ponds that have become their shelters. They breed by the hundreds, with each female able to lay between 3,500 and 20,000 eggs. Not all survive, but enough live to breed again, ensuring that the horde extends their range. With an average life span of seven years, and time to sexual maturity of 10-12 months, their population can dramatically shoot up in a very short time, which is precisely what happened once they landed in the islands.
“This is an invasion,” says Nitya Mohanty, a doctoral student at the Centre for Invasion Biology at Stellenbosch University (South Africa). His research, done with the Andaman and Nicobar Environment Team, has been on invasive species — first on the chitals (spotted deer) that have established their herds in the Andamans, and now on the bullfrog invasion.
So far, the bullfrog has been found in six out of the eight major inhabited islands. In 2017, it was even found in Little Andaman, which is separated from the Greater Andaman Islands by more than 55 km of sea. “This kind of incursion into remote islands is not naturally possible in such a short time,” says Mohanty.
The frog has acquired many names in the course of its journey through multi-cultural settlements of the island: shona beng (‘Golden frog’, for the prominent golden stripe) among the Bengali settlers; haramendak (‘Green frog’, for its olive-green skin) in Ranchi villages, where you could hear Oraon, Sadri or Munda being spoken; and dey-phala (‘Green frog”) in villages where the 2,500-odd Karen community stays. Whatever the name or language, the narrative of economic loss and ecological threat is a constant.