Behavior, site use and demographics of shortfin devil rays, Mobula kuhlii, at a newly-discovered cleaning area in South Africa

May 2024

M. M. Carpenter, R. J. Y. Perryman, A. D. Marshall & C. L. Grifths

Keywords: KwaZulu-Natal • Mobulidae • Aliwal Shoal • Marine Protected Areas • Animal Behavior • Generalized Additive Models • Mixed Models

Summary: Many shark and ray species rely on specific sites like cleaning stations for health, social gatherings, and mating. This study identifies a cleaning station for the shortfin devil ray (Mobula kuhlii) in Aliwal Shoal Marine Protected Area, South Africa. Using remote underwater video and environmental models, researchers found sea surface temperature and current direction influenced ray presence and cleaning duration. These findings can inform conservation efforts for this endangered species.

Abstract

“Many shark and ray species show afnity to specifc sites, making these areas critical for their survival. These include cleaning stations: locations on reefs where cleaner fsh remove parasites and clean wounds, which is important for maintaining health. Cleaning stations also function as social gathering sites, or resting points, where courtship and mating can occur. In this study, we identify an aggregation site for the shortfn devil ray, Mobula kuhlii (Family Mobulidae) within the Aliwal Shoal Marine Protected Area in KwaZulu-Natal (KZN), South Africa, and document their behavior. Remote underwater video was used to collect footage of M. kuhlii being cleaned by blue streak cleaner wrasse, Labroides dimidiatus. Generalized additive models (GAMs) were used to assess environmental predictors of M. kuhlii presence on Aliwal Shoal. Mixed models were used to assess the same environmental predictors and their correlation with mean M. kuhlii cleaning duration and number of L. dimidiatus bites per second at the identifed cleaning station site. M. kuhlii were present in 56% of observation days, with group numbers up to>150 individuals. Sea surface temperature was a signifcant predictor for M. kuhlii presence, while a north to south current was signifcantly associated with longer mean cleaning durations. These results support fndings of mobulid studies in KZN that show increased habitat use during summer temperatures (24–25 °C) and suggest these sites to be important for individual health and social interaction. We hope these fndings can be used for development of locationspecifc management plans to safeguard this Endangered species.”

Video

Author Affiliations

  • Department of Biological Sciences, University of Cape Town

  • Marine Megafauna Foundation

  • Macquarie University

Funded by

  • University of Cape Town

  • Ruford Foundation