Missing hiss, absent croaks: Monsoon story in Karnataka forests

An erratic southwest monsoon is playing havoc with the breeding cycles of frogs and snakes this year in Karnataka's forests, shining a light on how crucial the weather phenomenon is to both prey and predator.

Researchers say missing frog calls and a lack of sightings of certain snakes, which feed on them, in the Western Ghats of Karnataka are signs of the "confusion" sown by the delayed monsoon. If the disruption continues, experts say, it could upset the delicate balance between the species and have wider ramifications for the ecology that is already under strain.

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The monsoon was scheduled to arrive in the Western Ghats in the first fortnight of June but ended up getting delayed, affecting the breeding season of frogs that depend on streams.

Herpetologists and batrachologists say the scanty rainfall in the first week of July could have resulted in the ‘decay’ of eggs laid by frogs during the short burst of heavy rains in the last week of June.

This year, researchers have not been able to record direct or indirect sightings of certain varieties of frogs and snakes, whose breeding season starts with the onset of the monsoon.

“We are not hearing the mating calls of many frogs in their natural habitats,” said batrachologist Gururaja K V.

Monsoon plays a vital role in the life cycle of frogs as they mate and lay eggs during the season. Frogs such as Kumbara night frog, Jog night frog, Malabar tree toad, bullfrog, Castlerock night frog and others need a continuous flow of stream water for the survival of eggs.

“Monsoon is the ‘cue’ for certain snakes and frogs to initiate their breeding season. The erratic rainfall is affecting the life cycle of frogs and their predators,” said Priyanka Swamy, Researcher at Kalinga Centre for Rainforest Ecology, Agumbe.

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Since March last year, her team has been working on a telemetric study of Malabar pit vipers, which are active during the monsoon. “There is a noticeable decline in the sighting of Malabar pit vipers in our research field compared to last year," she said.

"This monsoon is unlike the previous ones in Agumbe. We did not receive pre-monsoon showers, which are very vital for initiating the breeding process. And with the delayed monsoon, there is ‘confusion’ among the snakes and frogs about their breeding cycle."

Researchers say that several snakes have not been ‘seen’ in their habitats this season.

“By June first week, we should have spotted shieldtail snakes, sand boa and others. It is already August but the sighting of these snakes has been rare. One of the reasons could be that these snakes follow their prey frogs, whose cycle has also been altered due to the erratic monsoon,” said Hunasur-based herpetologist Gerry Martin.

And it has been no different with frogs.

“We are getting to hear calls of very few frogs. Not only is the diversity of the calls (different species) missing but also the numbers,” said Omkar Pai, who has been studying frogs in the Kumta division of Uttara Kannada district.,

Researchers warn it could get worse if erratic rainfall becomes the norm.

Karthik Sunagar of the Evolutionary Venomics Lab at the Centre for Ecological Sciences (CES), Indian Institute of Science (IISc), said it may "have larger ramifications on the ecology” if the "same rain pattern continues".