1. Capranica, R. R. The Evoked Vocal Response of the Bullfrog: A Study of Communication by Sound (Research Monograph 33, MIT, Cambridge, Massachusetts, 1965)
2. Glaw, F. & Vences, M. A Fieldguide to the Amphibians and Reptiles of Madagascar 2nd edn (Vences & Glaw, Köln, Germany, 1994)
3. Roy, D. Communication signals and sexual selection in amphibians. Curr. Sci. 72, 923–927 (1997)
4. Tobias, M. L., Viswanathan, S. & Kelley, D. B. Rapping, a female receptive call, initiates male/female duets in the South African clawed frog. Proc. Natl Acad. Sci. USA 95, 1870–1875 (1998)
5. Feng, A. S. et al. Ultrasonic communication in frogs. Nature 440, 333–336 (2006)