Insight into manta ray behaviour using animal-borne Crittercams

Abstract Animal-borne video cameras equipped with depth and temperature sensors were deployed on 16 reef manta rays ( Mobula alfredi ) in Raa Atoll, Maldives and 12 oceanic manta rays ( Mobula birostris ) in the Revillagigedo Archipelago, Mexico. These deployments provided descriptive behavioural data that give vital context to existing biotelemetry data and enabled a comparison of the social dynamics between the two manta ray species. Overall, cruising was the most dominant daytime behaviour recorded for both species. For M. alfredi , cleaning was the second most common behaviour, followed by courtship and feeding. No courtship behaviour was recorded for M. birostris . Across M. alfredi and M. birostris deployments, individuals spent an average of 43 and 8% of recorded time interacting with conspecifics, respectively. Sociability was higher in M. alfredi than M. birostris , however the findings should be interpreted with caution beyond the two deployment populations and times. Crittercams captured multiple courtship events of M. alfredi at depths greater than recreational scuba diving limits and captured previously undocumented interspecific interactions with M. mobular . Crittercam deployments also recorded M. alfredi travelling in groups and hugging the contours of the ocean floor, possibly as a tactic to reduce predation risk and/or improve swimming efficiency, enforcing the importance of this novel technology as a valuable tool to gain new insight into the ecological drivers of habitat use by these species. Lastly, these quantitative and descriptive results provide context for future hypothesis-driven research questions using animal-borne video cameras for mobulid rays.