Rare Bush Frog Breeds in Bamboo

Raorchestes chalazodes, a rare bush frog found in India, has developed the unique strategy of breeding and laying eggs in bamboo despite their extremely narrow openings, new research describes.

Slipping in between narrow bamboo slits - which are often less than five to 10 millimeters long and three to four millimeters wide - is a novel reproductive mode, or strategy used to increase reproductive success. The critically endangered white spotted bush frog is just one of two species known to adopt the tactic.

Until it was recently discovered in the wet evergreen forests of the Kalakad Mundanthurai Tiger Reserve in the Western Ghats, R. chalazodes was believed to be extinct for the last 100 years or so. Now, researchers have not only found them, but learned that these frogs make their way into bamboo through a very small opening, possibly made by insects, to breed. Adult male frogs, usually fewer than 25 millimeters in length, shimmy their way into bamboo slits where they vocalize to attract mates. Females then follow suit, laying about five to eight eggs inside the bamboo.

"This is a significant discovery in two ways," researcher David Bickford said in a statement. "First, it reiterates that natural history observations, often ignored, are fundamental for understanding evolutionary ecology. Second, it sets a theoretical foundation to ask several interesting questions about the diversity of reproductive modes and the evolutionary pathways behind such amazing amphibian behaviors."

Through their research, the team also found that R. chalazodes only breeds in bamboo that have openings at the base of the internode, whereas those with openings at the top might let water in and drown the froglets.

And with spotted frogs being an endangered species - occurring in fewer than five localities - ensuring that their bamboo breeding ground is intact remains essential. Unregulated overharvesting of bamboo for paper and pulp may destroy breeding habitats and threaten their long-term survival, according to the study.

"Amphibians are among the most threatened creatures on earth and yet, we know very little about them," added Mr. Seshadri K S, a PhD student involved in the study.

Learning more about these unique frogs, in particular, could help conservation of the species through developing frog-friendly harvesting techniques.

This work is described further in the Biological Journal of the Linnean Society.