Potential Hierarchical Interactions of Megafauna Species at a Cleaning Station

Abstract

Cleaning stations on seamounts play a crucial ecological role in the health and behavior of marine megafauna, yet interspecific interactions at these sites remain understudied. This study investigates potential hierarchical dynamics between reef manta rays (Mobula alfredi) and pelagic thresher sharks (Alopias pelagicus) at two cleaning stations atop a seamount in the Philippines. Using over 960 h of autonomous video recordings across 119 survey days, we examined species-specific site preferences, visitation types, and behavioral responses to interspecific encounters. Results indicate that, while manta rays used both stations equally, thresher sharks showed a strong preference for the deeper, sloped station. Interruptions during cleaning suggest a hierarchy: all manta-to-shark interactions resulted in thresher sharks vacating the station prematurely, possibly before completing cleaning. In contrast, manta–manta interactions showed more balanced outcomes, with no significant impact on cleaning duration. Shark presence decreased as the flow speed intensified and was lowest during high tide, suggesting that sharks’ decision to clean may be dictated by factors affecting the effectiveness of the cleaning process. These findings also suggest that manta rays may outcompete thresher sharks for access to cleaning services. Understanding such interspecific dynamics is vital for effective marine habitat management and the conservation of vulnerable pelagic species.