Chafing Behavior by Carcharhinid Sharks on Oceanic Manta Rays in North America’s Largest MPA

We report novel observations of chafing behavior involving two species of carcharhinid sharks—an adult tiger shark (Galeocerdo cuvier), an adult Galapagos shark, and a juvenile Galapagos shark (Carcharhinus galapagensis)—interacting with oceanic manta rays (Mobula birostris) at two dive sites within Revillagigedo National Park, México. This study provides the first formal description of chafing behavior by both tiger and Galapagos sharks directed at oceanic manta rays. Manta ray responses varied according to shark identity and size: evasive behaviors were triggered by the adult tiger shark and the adult Galapagos shark, consistent with their larger body size and the tiger shark’s known role as a predator of juvenile manta rays. In contrast, the juvenile Galapagos shark elicited only mild postural adjustments, suggesting greater tolerance and size-based behavioral discrimination by the manta rays. These interactions underscore the complexity of non-predatory elasmobranch behaviors and suggest that chafing may serve multiple functions beyond ectoparasite removal, such as social signaling or agonistic assertion. Sharks may also be using manta rays as mobile substrates for more localized or targeted ectoparasite removal, representing an alternative or complementary cleaning strategy in pelagic ecosystems. The establishment of Revillagigedo National Park—the largest fully protected marine reserve in North America—may be supporting the expression of a broader behavioral repertoire, enabling the observation of interactions not previously described in the peer-reviewed literature.