Can salamanders, the silent amphibians, speak?
Recent findings by two Indian filmmakers and a Delhi University scholar challenge the longstanding perception that salamanders are silent amphibians
Salamanders have long been considered “silent amphibians”, but a newly published paper by Robin Suyesh in Salamandra, the German journal of herpetology, threatens to challenge conventional wisdom by documenting males of a certain Himalayan salamanders vocalising for the first time ever.
This startling discovery was made “serendipitously” by Vijay and Ajay Bedi— also known as the Bedi Brothers—last year. The Bedis are filmmakers, whose documentary, The Secret life of Frogs, won several national awards and an Emmy nomination in 2019.
During editing the footage of the documentary collected from a research site in Nakapani in Mirik, in West Bengal’s Darjeeling district, the filmmakers chanced upon few and far between “ptaak” sounds made by a species of salamander the video captured. The Bedi brothers then contacted Suyesh, Assistant Professor at Sri Venkateswara College at Delhi University, who undertook the project to analyse and discuss their field recordings, which led to him co-authoring the recent paper.
The collaboration has led to the publication of the first ever recorded vocalizations in Tylototriton himalayanus, a species from eastern India and Nepal discovered in 2015. Known variously as the Himalayan crocodile newt or Orange-warted salamander, T. himalayanus is one of two known salamanders found in the Himalayan biodiversity hotspot in India.
Salamanders have hitherto been considered not to make much use of acoustic signalling, so much so that the species has not even evolved external ears. However, recently this wisdom has been called into question as new evidence of salamanders following, for example, frogs’ sounds in order to better adapt to their surroundings have been shown. Most of the research before this recent paper was also based on observations made on salamanders in captivity, without documentary evidence to be shared with other researchers. The paper now documents first ever in-situ recordings of mating behaviour of these salamanders.
“Conditions of captivity distort the natural behaviour of animals,” says Suyesh. “A proper understanding of [its] reproductive biology is imperative for the conservation of the species and its habitat.” The paper goes on to say that documented observations of mating habits are best observed in the wild. The new findings are expected to open new avenues available to researchers for the first time.
The study was conducted in the natural habitat of 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) of the breeding population was skewed towards males, as generally observed in amphibians. Physical competition was noted among males for the possession of females, and the males were also observed to produce very feeble and extremely rare ‘ptaak’ sounds.
“What this study suggests is that these salamanders could also have evolved vocalisations as an adaptation due to the increase in noise pollution and influx of tourism in the Darjeeling area,” says Ashish Thomas, assistant professor at Guru Nanak Dev College in the Delhi University and a herpetologist. Amphibians have been widely known to show vocalisation as part of their mating strategies, and both Suyesh and Thomas suspect that further research into salamanders would throw new light into their reproductive behaviour .
“This opens up new avenues for scientific research as calls have rarely been tested as part of behavioral study on the salamanders. Testing new hypotheses using these low frequency calls produced by these salamanders can provide new insight into the reproductive activity as well as evolutionary future of the species,” Suyesh said.
The footage used in the paper took the Bedi brothers over three years to accumulate in very trying conditions. “The monsoon made handling the equipment a major challenge, and the constant humidity posed a health hazard as well,” says Vijay Bedi. Because of the rare sighting of salamanders and the feeble nature of the vocalisation, extremely sensitive equipment was used as little as one meter from the vocalising males.
“I have studied this species for more than 6 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. I thought it would be great to use their unique footage for science in a research paper where more people can refer to this great finding,” adds Sarbani Nag, former research fellow at Wildlife Institute of India and founder-secretary of Wish Foundation, an NGO dedicated towards the conservation of amphibians around the Darjeeling area.
Apart from the advances in scientific research, the paper also hopes to shed light on the issues of environmental conservation and preservation of the amphibian species in Darjeeling, a mega biodiversity hotspot in India. Lately, Darjeeling has experienced crowding and noise due to increased settlements and tourists. These conditions may have forced the Indian species to adapt by using vocalisations, according to Thomas. Noise pollution from overcrowding will affect the mating activities of the species in the long term.
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 the water bodies.
The researchers expect the paper to bring necessary attention to the preservation of these amphibians at a time when even a survey of their total numbers in the wild remains obscure. With a global community of researchers able to take the conversation further, the silence around these amphibians could well be at an end.
Binit Priyaranjan is a freelance journalist, author and poet.
FIRST PUBLISHED03.03.2021 | 08:00 AM IST