Data for: Manta rays in the Maldives foraging either in groups or solo

Flexibility in animal foraging strategies can increase overall feeding
efficiency. 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 zooplankton levels, and at certain
locations. Both biotic and abiotic factors contributed to variation in
group foraging. Within aggregations, individuals foraged in larger groups
when more food was available, and when the overall aggregation was
relatively small suggesting that foraging in large groups was more
beneficial when food was abundant, and/or 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
55%), 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.