There are around 7,000 species of frogs throughout the world, who mate in one of the six different positions known. Most of these positions involve the male grabbing the female around the waist or under the armits – the position is known as amplexus, a term given to frog mating behaviour.

But now, a new amplexus among frogs has been discovered in the monsoonal forests of India.

Bombay night frogs (Nyctibatrachus humayuni) mate by having the male straddle the female without grasping her. Instead of releasing the sperm near the female’s cloaca, which is usually the case in the six commonly known mating positions, the male frog ejaculates the sperm on his partner’s back. The female then lays eggs, allowing the sperm to trickle down her back and fertilize the eggs externally.

Scientists led by Sathyabama Das Biju, an Indian amphibian biologist and wildlife conservationist who heads the Systematics Lab at the University of Delhi, Department of Environmental Studies, staked out a dense monsoonal forest near Humbarli village in Maharashtra, for forty nights to study the process of mating in Bombay night frogs closely. He gathered enough photographs, notes and infrared night-vision video footage to reveal about the unique breeding habits of Nyctibatrachus humayuni.

“So far, this mating position, is known only in Bombay night frogs,” said study leader SD Biju.

“It has been a wonderful experience to observe the entire breeding sequence of this unique frog. It’s like watching a scripted event,” he further added.

Until Bombay night frogs came into light, scientists had identified six amplexus among the 6,650 frog species in the world. Most of these mating positions involve the male clasping the female around the waist, grab her armpits, hold her head, attach himself to her back and perhaps sit on her head.

The Bombay night frogs, however, do none of these. Instead, the female sits on rain-soaked leaves and branches and makes mating calls to the male frog. She then touches his head with her toes. What happens next is now identified as the seventh mating position, ‘dorsal straddle’, which is believed to have been found only among Bombay night frogs till date.