Shocks and Tremors: Hitchhiking Fish Travel on the Backs of Manta Rays

A long-term study has revealed a novel type of interaction between remoras and manta rays: “cloacal hitchhiking,” which appears to be a rather perplexing experience for the latter.

Remora Taxi

In fifteen years, such behavior has been documented seven times, involving different species of manta rays. Specifically, remoras, known for maintaining mutualistic relationships with many large marine animals, approach their “victim” discreetly, then slip, in the blink of an eye, into its cloacal opening.

Lead author of the new study, published in the journal Ecology and Evolution, Emily Yeager describes the interaction observed in July 2023 in the waters off Florida.

“During the approach phase, a medium-sized remora was visible near the pelvic fins of an adult manta ray,” she notes. “When the hitchhiker found itself beneath its belly, it inserted its head into its cloacal opening. Its host seemed to shudder, before continuing on its way, the remora still firmly lodged in that orifice.”

According to the team, this form of phoresy would offer several notable advantages for remoras. In addition to providing protection from predators, it would also allow them to conserve their energy, and it is also possible that these fish feed on the fecal residues inside the cloaca. On the manta side, such prolonged intrusions could potentially hinder mating, birthing, or defecation.

Relationships More Complex Than Expected

Overall, such discoveries help illuminate the behavior of remoras, already known for slipping into the mouths or gills of various shark species.

“Although the exact mechanisms underlying this behavior remain unclear at this stage, it is evident that the relationships between the Echeneidae and their hosts are more physiologically and ecologically complex than previously assumed,” Yeager concludes.

A few years ago, experiments had suggested that tardigrades could also use snails to travel farther.