Reef manta ray social relationships depend on individual behavior differences

New research from an international team of scientists has uncovered new details about the variety of social personalities of reef manta rays.

The team from Macquarie University, Marine Megafauna Foundation, Université de Corse, University of Auckland, the Manta Trust, and University of Papua, published their latest study in Animal Behaviour, and used acoustic telemetry to capture the presence of reef manta rays (Mobula alfredi) across various sites in Dampier Strait, Raja Ampat, West Papua, and understand the dynamics of their social interactions. The study reveals that these rays regularly form social groups, and that their relationships depend on individual differences in movement behavior.

The researchers tracked 27 manta rays with acoustic transmitters to understand the link between their movements and social behavior. They discovered that certain individuals, groups and locations play an important role in sustaining the integrity of a wider social network.

They found that social "communities" were clearly defined by location, and that community structures remained stable over several weeks to months. The study showed that some manta rays had stronger attachment to their physical location, and forged strong social bonds with other "local" rays.

Other individuals that were more nomadic moved between different communities and were important in connecting the overall social network.

"Manta rays seem to have quite variable behavior. They form distinct social units in shallow reef areas focused around cleaning stations, but some individuals appear to move between these areas much more frequently than others," says lead author Dr. Robert Perryman from the School of Natural Sciences at Macquarie University and the Marine Megafauna Foundation. "It was intriguing to track the hourly social interactions of these highly charismatic rays. Up until now we have only had sporadic data on social groupings, so the fine-scale temporal nature of this study allows us new insight into their behavioral ecology."

The study's results suggest that manta rays may have distinct social "personalities," or change their social behaviors over time. "Understanding manta rays' social dynamics will help us to predict their movements, mating patterns and responses to human impacts. All of which are crucial for supporting conservation and ecotourism" says Dr. Perryman.

The study drew on more than 50,000 detections of the tagged rays at clusters of receiver stations, during several months of the peak manta ray season.

The results suggest that the rays' movements, habitat preferences and social relationships are linked behavioral processes, for which knowledge of each should be combined to help protect this vulnerable species from human impacts.

"To aid conservation, it is important to know how connected local populations are spatially and the extent to which individuals interact with each other over time," says Ph.D. Candidate Edy Setyawan from the University of Auckland and the Manta Trust.

Knowledge from the study may be used to help predict impacts of manta tourism related disturbance on social community structures, and on feeding, cleaning and mating behaviors that are all highly social in manta rays.

"Implementation of a strict code of conduct at every manta tourism site in the Raja Ampat region could help to minimize this potential disturbance," says Mr. Setyawan.