Loudly heard, little seen, and rarely understood: Spatiotemporal variation and environmental drivers of sound production by snapping shrimp

Abstract

Snapping shrimp are abundant soniferous crustaceans that form large aggregations, creating a pervasive crackling in many coastal environments worldwide. The short-duration broadband "snap" generated by their specialized claw is among the loudest bioacoustic sound in the marine environment. Variation in snapping shrimp acoustic activity can substantially alter ambient soundscape characteristics, yet relatively little is known about snapping shrimp sound production patterns, the underlying behavioral ecology or role of environmental factors. Our analyses of acoustic data from tropical and sub-tropical reefs show that snap rates exhibit diurnal rhythms, but that these rhythms vary over small spatial scales (e.g., opposite diurnal patterns between adjacent reefs) and shift over time (e.g., daytime versus nighttime dominance in different seasons). Snapping patterns correlate to abiotic variables such as temperature and light, but the underlying causal mechanisms remain unclear. Ongoing lab experiments to investigate snapping patterns in Alpheus heterochaelis find that isolated individuals produce snaps in the absence of external provocation, and that individual snap rate relates to temperature, time of day, and sex. By combining detailed snap analysis of field recordings and manipulative lab experiments, progress is being made towards understanding the sound producing behaviors and environmental factors that drive variation in snapping shrimp-dominated soundscapes.