Guwahati: In a quiet corner of a college campus in Arunachal Pradesh, a water tank turned into a stage for a rare and dramatic amphibian spectacle—one never before documented in the wild. Polypedates teraiensis, known to predominantly occur in the Himalayas and Northeast India, is a seasonal breeder, breeding from March to August with the onset of rain. A number of recent lab-based studies have been conducted on the developmental biology of the tadpoles of this species, without much documentation of the breeding process.
Only a lone study has briefly documented the courtship and breeding behaviour in the natural environment. In the laboratory, amplectant pairs have been recorded laying eggs in foam nests within 12 hours; in natural conditions, the same process was completed in 41 minutes.
In April 2024, scientists captured an extraordinary natural history moment in the heart of Itanagar: a group of male Polypedates teraiensis, a treefrog species native to the Himalayan foothills and Northeast India, was seen engaging in coordinated group spawning—a rare reproductive behaviour in the frog world.
The discovery unfolded at an unlikely location—a water tank on the campus of Dera Natung Government College. It began when Dr. Prasanta Nanda, a faculty member at the college, noticed an unusual flurry of frog activity.
Sensing something special, he contacted Bhaskar Saikia of the Zoological Survey of India (ZSI), Shillong, to help identify the species. What followed was a collaborative effort that resulted in the first detailed documentation of multi-male mating behaviour in this elusive amphibian.
Over two nights, on April 22 and 23, researchers observed up to six males simultaneously courting one or two females, taking turns in amplexus—the mating embrace of frogs—while producing frothy nests above the water. The foam nests, formed by vigorous hind-limb movements, act as both a protective cradle and a fertilization chamber for the eggs.
What stood out, however, was not just the crowd around the females—but the remarkable absence of aggression. Unlike many frog species where males jostle and wrestle for dominance, these treefrogs showed no signs of territorial behaviour. Instead, they appeared to cooperate, contributing collectively to the creation of foam nests and the fertilization process.
“This isn’t just rare—it’s almost unheard of,” said Dr. Nanda. “Group spawning is known in only a handful of frog species worldwide. To see it so clearly in Polypedates teraiensis—a species barely studied in the wild—was astonishing.”
Scientists believe this behaviour may hint at a cooperative reproductive strategy, where shared mating opportunities could offer evolutionary advantages in specific environmental settings. The team hypothesizes that by working together rather than competing, the males may enhance overall fertilization success, especially in habitats with limited breeding sites.
Prior to this, the breeding biology of Polypedates teraiensis was largely understood from lab studies, with just one brief field record mentioning courtship. This new observation sheds fresh light on the species’ natural behaviour and underscores the ecological richness still hidden in India’s biodiversity hotspots.
The findings have been published in the latest issue of Herpetological Review, a leading US-based journal specializing in amphibian and reptile research.
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