Sound production during male courtship behavior in the African cichlid fish Astatotilapia burtoni. Dominant territorial males (fish at left) produce sounds that consist of ~4-12 short (~15-20 ms) pulses during body quivering while they present their anal fin egg-spots (arrow) towards a female (fish at right). Courtship sounds are always accompanied by male quivering behavior, but not all quivers are associated with sound production, which supports the hypothesis of intentional sound production for communication. Representative waveforms of individual courtship sounds from three different dominant territorial males are shown. Recordings were made with a calibrated hydrophone (High Tech, Inc.; sensitivity -163.7 dB re: 1 V/μPa; frequency response 2 Hz-30 kHz) suspended in the tank above the spawning territory.