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Can you hear the salamander?

Binit Priyaranjan | Updated on March 24, 2021

Found a voice: The Himalayan crocodile newt or Orange-warted salamander, known to be mostly silent, was caught on camera making a rare sound   -  BEDI BROTHERS PRODUCTION

A film on frogs has led to a discovery that’s music to herpetologists’ ears

* Salamanders are usually known as ‘silent amphibians’ because of their low proclivity for sound-based signalling

* The study was conducted in the natural habitat of the T. Himalayanus during its breeding season

*Salamanders are important cogs in the ecosystem; excellent pest controllers, they prey on insects such as mosquitoes, and serve as food for animals higher up on the food chain

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Serendipity and science have always had a fortuitous connection. Often, breakthrough discoveries in one field of science happen as accidents in another discipline. Scottish biologist Robert Brown discovered the Brownian motion, a phenomenon from physics that bears his name, by accident in 1827, while the Cosmic Microwave Background Radiation, the earliest echo of the Big Bang and a ground-breaking discovery in cosmology, was discovered by accident at the Bell Telephone Laboratories in 1964.

Now fortune has smiled upon the arts and nature as well, as a paper published in Salamandra, the German journal of herpetology, the study of amphibians and reptiles, tells us. Published on February 15, it documents the first ever recorded evidence of vocalisation in Tylototriton Himalayanus, one of two known species of salamanders found in the Himalayan biodiversity hotspot in India.

Also called the Himalayan crocodile newt or Orange-warted salamander, the species, known to be mostly silent, was caught on camera making a rare signal — a “ptaak”-like sound — during the filming of a documentary in 2019 by film-makers Vijay and Ajay Bedi, known as the Bedi Brothers. The salamanders did not have a role in the film; the brothers were filming frogs.

By accident: Filmmakers Vijay and Ajay Bedi caught the sound of the salamanders while shooting a film on frogs in 2019   -  BEDI BROTHERS PRODUCTION

 

The documentary The Secret Life of Frogs bagged multiple national awards and an Emmy nomination, but the accidental discovery made during the editing of footage took another year before it was properly analysed and documented in a research paper.

The Bedi brothers contacted Dr Robin Suyesh, assistant professor at Sri Venkateswara College and corresponding author of the paper. Suyesh has an expertise in studying vocalisation in amphibians such as frogs, and undertook the project to analyse and discuss their field recordings which led to him co-authoring the recent paper which has challenged conventional wisdom about salamanders amongst herpetologists.

Salamanders are usually known as ‘silent amphibians’ because of their low proclivity for sound-based signalling, so much so that the species hasn’t even evolved external ears. “This wisdom was brought into question by some studies involving salamanders following frogs’ calls, for example, but most of these studies have been conducted in laboratory conditions in captive populations. Our paper presents the first in situ documented evidence ever collected for the species.” Suyesh said.

Wildlife enthusiasts are toasting the find. “It’s really a big discovery,” said Sarbani Nag, former research fellow at Wildlife Institute of India and founder-secretary of Wish Foundation, an NGO dedicated to the conservation of amphibians around the Darjeeling area. “I have studied this species for more than six years and even I could not see what Ajay and Vijay could film. When they told me first what they filmed I could not believe it,” she said.

The study was conducted in the natural habitat of the T. Himalayanus during its breeding season. The observations were made in ephemeral ponds formed after the monsoon showers. Courtship behaviour and mating happened both during day and night. Operational sex ratio (males to female ratio competing for sexual selection in a population) was skewed towards males, as generally observed in amphibians. Physical competition was observed among males for the possession of females, and the males were also observed to produce very feeble and extremely rare sounds.

Amphibians are known to use acoustic signalling for key aspects of their reproductive life such as calling for potential mates. “What this study shows is that other salamanders could also show vocalisations that have gone under researched till now,” said Dr Ashish Thomas, herpetologist and assistant professor at Guru Nanak Dev College in Delhi University.

He believed the documented footage made available to a global community of researchers would help explore new paradigms within the reproductive behaviour of salamanders. “Darjeeling has been seeing an increase in noise pollution and large influx of tourism. It is possible that the salamander evolved producing sound as a reproductive adaptation to this change,” Thomas speculated.

Apart from the advance in scientific research, the film-makers and scientists alike hoped the discovery would help conservation efforts of these amphibians. “Even a survey of the number of these species in the wild is currently not available,” said Nag.

The species currently also face various threats, such as siltation in ephemeral ponds, destruction of host plants as fodder for domestic animals, household waste leading to eutrophication (an enrichment of water by nutrient salts that causes structural changes to the ecosystem), road kills, pesticide pollution, and detergent in water bodies.

The paper documenting the vocalisations also presents the first ever observations of the reproductive behaviour of salamanders in the wild. To obtain this footage the Bedi brothers worked in Nakapani in Mirik, in West Bengal’s Darjeeling district, during the rain which is the amphibians’ mating season. Recording feeble vocalisations meant putting sophisticated recording equipment as close as one metre from the vocalising male, not to mention enduring countless hours in the rain and health hazards from over-hydration which the team endured for over three years.

Salamanders are important cogs in the ecosystem; excellent pest controllers, they prey on insects such as mosquitoes, and serve as food for animals higher up the chain. Their permeable skin makes them highly sensitive to toxicity in their habitat areas, which makes them key indicators of their ecosystem’s health.

“A proper understanding of its reproductive biology is imperative for the conservation of the species and its habitat,” the paper published in Salamandra said, and this documentation of a novel phenomenon, the researchers hoped, would end the silence around the species.

Binit Priyaranjan is a Delhi-based writer

Published on March 24, 2021

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