Cicadas in southern India have been found to synchronize their early morning songs with a specific level of pre-dawn light, according to new research published in Physical Review E. Scientists from India, the UK, and Israel studied weeks of field recordings near Bangalore and discovered that cicadas begin their daily choruses when the sun is 3.8 degrees below the horizon, during civil twilight.
The research team applied methods from physics usually used to study phase transitions in materials to analyze how cicadas respond to changes in light. “We’ve long known that animals respond to sunrise and seasonal light changes,” said co-author Professor Raymond Goldstein, from Cambridge’s Department of Applied Mathematics and Theoretical Physics. “But this is the first time we’ve been able to quantify how precisely cicadas tune in to a very specific light intensity — and it’s astonishing.”
Researchers noted that the build-up of cicada song takes about one minute each day, with the midpoint occurring at almost the same solar angle regardless of when sunrise happens. The threshold for singing varies by only about 25% during this period.
To explain this behavior, the team developed a mathematical model inspired by magnetic materials, suggesting that cicadas base their decision both on ambient light and sounds from nearby insects. “This kind of collective decision-making shows how local interactions between individuals can produce surprisingly coordinated group behaviour,” said co-author Professor Nir Gov from the Weizmann Institute, who is currently on sabbatical in Cambridge.
Field recordings were provided by Bangalore-based engineer Rakesh Khanna, who collaborated with Goldstein and Dr Adriana Pesci at Cambridge’s Department of Applied Mathematics and Theoretical Physics. “Rakesh’s observations have paved the way to a quantitative understanding of this fascinating type of collective behaviour,” said Goldstein. “There’s still much to learn, but this study offers key insights into how groups make decisions based on shared environmental cues.”
The study received partial support from the Complex Systems Fund at the University of Cambridge. Professor Raymond Goldstein holds the Alan Turing Professorship of Complex Physical Systems and is a Fellow at Churchill College, Cambridge.
Reference: Khanna, R.A., Goldstein, R.E., Pesci, A.I., & Gov, N.S. ‘Photometric Decision-Making During the Dawn Choruses of Cicadas.’ Physical Review E (2025). DOI: 10.1103/4y4d-p32q