Manta Ray Populations Have Complex Social Structures
Manta Ray Populations Have Complex Social Structures

Manta Ray Populations Have Complex Social Structures

Reef mantas in Indonesia exhibit social preferences and form distinct social groups.

Nov 1, 2019
Catherine Offord

   ABOVE: © Rob Perryman

EDITOR’S CHOICE IN ECOLOGY & ENVIRONMENT

The paper

R.J.Y. Perryman et al., “Social preferences and network structure in a population of reef manta rays,” Behav Ecol Sociobiol, 73:114, 2019.

Reef mantas (Mobula alfredi) are some of the largest fish in the ocean, but much about their biology, particularly when it comes to their social lives, remains mysterious. Grad student Rob Perryman at Macquarie University in Australia has been trying to fill in the gaps by studying mantas around the reefs of the eastern Indonesian archipelago Raja Ampat, where the rays come to feed and be cleaned by smaller fish.

For Perryman and colleagues’ latest study, the team observed hundreds of mantas at multiple sites between 2013 and 2018. The researchers counted how many times each individual appeared at each site, and noted an association between two rays if they visited the same place at the same time. Focusing on 112 mantas sighted 10 or more times each, the team plugged these associations into a computer model to construct social networks.

Even when controlling for individuals’ site preferences, the researchers found that some mantas associated with particular individuals more frequently than would be expected due to chance. The network also revealed two distinct communities—one dominated by older females and the other comprising a more-even mix of sexes and ages. Evidently, “being social is a pretty fundamental feature of the species’ biology that’s going to affect reproduction, movements, habitat use,” says Perryman—“all things that are really important for conservation.”

The findings “suggest a complexity of social behavior in mantas that was suspected, or perceived as being possible, but as yet unproven,” says Callum Roberts, a marine conservation biologist at the University of York who was not involved in the work. “It’s quite a groundbreaking study in that respect.” He adds that tagging studies could help collect data on manta behavior outside of the handful of locations studied here. “We need to try to unlock . . . the lives of these animals away from the focal aggregation sites.”

Catherine Offord is an associate editor at The Scientist. Email her at cofford@the-scientist.com.