New study reveals a unique camouflage mechanism in the endangered Jayarami bush frog.

In the misty cardamom highlands of Kerala’s Western Ghats, a tiny, elusive frog has been found using a remarkable trick — it “sees” light through its skin to change its body colour and blend perfectly with its surroundings.

In a study published in Biotropica (2025), researchers from Aranyakam Nature Foundation, University of Calicut, and St. Albert’s College observed the endangered Jayarami bush frog (Raorchestes jayarami) for nearly two months. They found that even while inactive during the day, these frogs adjust their dorsal colour to match the leaves they rest on — an ability triggered directly by light hitting their skin, bypassing the usual brain or hormone-controlled pathways.

“Our findings show that these frogs use what is called a primary response — an unconscious skin-based mechanism — to adjust their brightness based on the light intensity rapidly,” said lead author Jishnu Narayanan. “In other words, their skin senses light and changes colour on its own, allowing them to stay camouflaged without actively thinking or moving.”

In a striking experiment, the researchers partially covered the frog with a leaf. Only the exposed half changed colour, creating a sharp two-tone effect — a clear sign that the skin itself, not the eyes or nervous system, controlled the shift.

“This unconscious adaptation may help the frog stay hidden from predators while conserving energy,” said Dr. Sandeep Das, co-author and supervisor of the study. “Interestingly, the frog returned to the same leaf every day for weeks, suggesting it deliberately chooses the best resting spots for camouflage and comfort.”

The Jayarami bush frog, found only in the southern Western Ghats, is already threatened by habitat loss. This study adds to the growing understanding of how such species survive in complex forest environments — and highlights yet another marvel of evolution hidden in the rainforest canopy.

The study was supported by the Science and Engineering Research Board (SERB) and the University Grants Commission (UGC).

Full Author List:
Jishnu Narayanan¹²³, Dhruvaraj Subashchandran², Aneesh Embalil Mathachan¹, Retina Irumpanath Cleetus³, Nihal Jabeen², Aiswarya Swapna Lohithakshan¹², Vardha Nourin Puthiyodath², Amrit Krishna Suresh², Sandeep Das¹²

¹ Department of Zoology, Centre for Research in Emerging Tropical Diseases, University of Calicut, Thenhipalam, Kerala, India
² Aranyakam Nature Foundation, Kochi, Kerala, India
³ Department of Zoology, St. Albert’s College (Autonomous), Ernakulam, Kerala, India

Citation:
Narayanan, J., Subashchandran, D., Mathachan, A. E., Cleetus, R. I., Jabeen, N., Lohithakshan, A. S., Puthiyodath, V. N., Suresh, A. K., & Das, S. (2025). Inactive tropical bush frog detects light through skin to adjust body colour intensity for camouflage. Biotropica, 57, e70067. https://doi.org/10.1111/btp.70067