Individual flexibility in group foraging behaviour of reef manta rays (Mobula alfredi)

June 2024

Annie Murray, Raphaël Royauté, Guy M. W. Stevens, Callum Roberts & Kathryn E. Arnold

Keywords: Foraging Specialists · Repeatability · Personality · Leaders · Plankton Feeding

Summary: Flexibility in animal foraging strategies boosts feeding efficiency. Group foraging enhances resource exploitation, while solo foraging reduces competition at low resource densities. Over three years in the Maldives, 343 identifiable reef manta rays exhibited flexible foraging, feeding solo or in groups. They foraged in groups when food was abundant and near high tide, with females often leading. High behavioural variance indicated significant individual flexibility due to this species reliance on spatially and temporally ephemeral resources.

Abstract

“Flexibility in animal foraging strategies can increase overall feeding efficiency for individuals. For example, group foraging can increase the efficiency of resource exploitation; conversely solo foraging can reduce intraspecific competition, particularly at low resource densities. The cost–benefit trade-off of such flexibility is likely to differ within and among individuals. Reef manta rays (Mobula alfredi) are large filter-feeding elasmobranchs that often aggregate to feed on ephemeral upwellings of zooplankton. Over three years in the Maldives, we free-dived to film 3106 foraging events involving 343 individually identifiable M. alfredi. Individuals fed either solo or in groups with a clear leader plus between one and eight followers. M. alfredi were significantly more likely to forage in groups than solo at high just prior to high tide and when aggregations were larger. Within aggregations, individuals foraged in larger groups when more food was available, and when the overall aggregations were relatively large suggesting that foraging in large groups was more beneficial when food is abundant, and the costs of intraspecific competition were outweighed by the efficiency resulting from group foraging strategies. Females, the larger sex, were more likely to lead foraging groups than males. The high within-individual variance (over 70%), suggested individuals were unpredictable across all foraging behaviours, thus individual M. alfredi cannot be classified into foraging types or specialists. Instead, each individual was capable of considerable behavioural flexibility, as predicted for a species reliant on spatially and temporally ephemeral resources.”

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Author Affiliations

  • Department of Environment and Geography, University of York

  • The Manta Trust

  • Université Paris-Saclay, INRAE, AgroParisTech, UMR EcoSys

  • Maldives Manta Conservation Programme

  • Centre for Ecology and Conservation, University of Exeter

Funded by

  • The Manta Trust

  • Maldives Manta Conservation Programme