Sound production patterns of big-clawed snapping shrimp (Alpheus spp.) are influenced by time-of-day and social context.

Snapping shrimp are perhaps the most pervasive sources of biological sound in the ocean. The snapping sounds of cryptic shrimp colonies in shallow coastal habitats worldwide create a near-continuous crackling with high spatiotemporal variability, yet the underlying acoustic ecology is not well understood. This study investigated sound production rates and acoustic behavior of snapping shrimp species common in the Western Atlantic Ocean and Gulf of Mexico (Alpheus heterochaelis and Alpheus angulosus). Snap rates were measured in a controlled laboratory setting under natural light, temperature, and substrate conditions for shrimp held individually, in pairs, and in a ten-shrimp mesocosm, to test hypotheses that acoustic activity varies with time-of-day and social context. Spontaneous snapping was observed for 81 out of 84 solitary shrimp monitored. Time-of-day influenced snap output for individuals and same-sex pairs-higher rates occurred during dusk and night, compared to daylight hours, but this pattern was inconsistent for opposite-sex pairs and a mixed-sex group. These laboratory results provide insight into behavioral rhythms that may influence snapping patterns in natural populations, and underscore the limited understanding of a major sound source in marine environments.