A quantitative analysis of the courtship acoustic behaviour and sound patterning in male sand goby, Pomatoschistus minutus

Many animal groups use sounds in reproduction in order to court mates or repel rivals. We describe the sounds and behavioural context of courtship sound production in male sand gobies, Pomatoschistus minutus, and examine the variability of acoustic parameters and the fine temporal patterning of sound units. Male sand gobies excavate a nest under a suitable solid substrate and attract females to mate, attaching the eggs to the ceiling of the nest. Before mating a female may repeatedly enter and leave a male's nest. Sounds were not detected during the courtship phase outside the nest, but were recorded when females were in the nest before spawning. Sounds were produced in 44-100% of such nest visits, varying with individual males. The sand goby sound consists of a train of pulses repeated at a rate of 23-29 pulses per second. The frequency spectrum of single pulses was continuous from 20-30 Hz to 500 Hz and reached a peak around 100 Hz. The absolute sound pressure level ranged from 118 to 138 dB re 1 mu Pa at 1-3 cm. The sand goby emits sound in distinct sound groups (bursts). Sound temporal features (duration, pulse repetition rate) vary systematically over the course of the burst. Within- and between-male variation of acoustic parameters was examined from sounds emitted by the male. Sound amplitude (peak-to-peak, mV) and pulse rate varied significantly among males, despite low individual stereotypy. Furthermore, sound pressure level correlated with body size. The potential informative content of acoustic parameters is discussed in the light of a possible role of the sand goby sound in mate choice.