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 m..., Collected in the field via video clips. Briefly:
We collected data on manta ray feeding behaviour at different times of day as part of the Manta Trust’s Maldives Manta Conservation Programme (https://www.mantatrust.org/maldives) during the Southwest Monsoon (May through November) when the highest numbers of mantas are present. Data collection lasted for 160 days in 2014, 156 days in 2015, and 155 days in 2016. We identified five sites on the eastern side of Baa Atoll that served as the main monitoring spots: Dhigu Thila, Hanifaru Bay, Hurai Faru, Reethi Falhu and Veyofushi Falhu. Due to the restriction on SCUBA diving at the main study site, Hanifaru Bay, all foraging data was collected by free diving. When we spotted foraging events, we free-dived beneath the animals to video their behaviour and record the unique identification spots on the ventral surface (Marshall & Pierce 2012), taking care not to impede or alter this behaviour. If, on entering the water, we observed more than o..., , # Data for: Manta rays in the Maldives foraging either in groups or solo

[https://doi.org/10.5061/dryad.8cz8w9gxd](https://doi.org/10.5061/dryad.8cz8w9gxd)

## Description of the data and file structure

The data file is an Excel spreadsheet containing the raw data collected in the field and extracted from video clips.

Empty cells indicate that the data are not available - i.e., they were not collected in the field or could not be seen on the videos.

Variable definitions:

* npid and id: unique ID of the animal
* day: Julian day
* year and nyear: year of observation
* site: Dhigu Thila, 1 = Hanifaru Bay, 2 = Hurai Faru, 3 = Reethi Falhu and Veyofushi Falhu
* clips: video clip duration (s)
* sex: 1 = Female, 2 = male
* size: score of relative size
* maturity: 1=juvenile, 2 = adult
* group_ID: unique identifier code of group
* group_size: number of mantas in observed group
* position: position in group - 1= 1st etc
* seconds: duration of observation (s)
* time...