Manta Rays: Acrobats of the Reef

Two Species, Very Different Lives

Until 2009, the manta ray was considered a single species. Genetic analysis established that there are two distinct species with different ranges, sizes, and behaviours:

• Reef manta ray (Mobula alfredi): Smaller (up to 5.5m wingspan), stays in coastal waters, returns repeatedly to the same cleaning stations and feeding grounds. Found throughout the Indo-Pacific and in the Red Sea.
• Giant oceanic manta ray (Mobula birostris): Larger (up to 7m wingspan), wide-ranging and migratory, found in open ocean as well as near productive coasts. The mantas at Socorro, Isla de la Plata (Ecuador), and the Maldives's outer atolls are typically this species.

Both species have been reclassified from the genus Manta to Mobula, making them technically the largest mobulid rays — relatives of devil rays and eagle rays.

Exceptional Intelligence

Manta rays have the largest brain-to-body-size ratio of any fish. Laboratory research has demonstrated that reef manta rays may pass the mirror self-recognition test — a benchmark of self-awareness that very few non-human animals pass. Their social behaviours, including what appear to be play interactions and long-term individual relationships, are increasingly studied.

Divers who have watched mantas at cleaning stations frequently remark that the rays seem to engage with human observers — hovering, circling, and making repeated passes that appear to be more than incidental. Whether this constitutes curiosity in the cognitive sense is an open research question.

Cleaning Stations

The essential manta dive experience is the cleaning station — a specific coral or rock structure where small reef fish (particularly bluestreak cleaner wrasse) pick parasites from the mantas' skin and gill rakers. Mantas visit these stations repeatedly, sometimes daily, hovering with their gill plates open and their wings slightly curved.

At a good cleaning station, a diver who descends quietly and remains motionless can watch manta rays pass within arm's reach — a theatrical performance where the ray is the actor and the diver is the audience.

Best cleaning stations:

• German Channel, Palau — reliable year-round; up to 20 rays on a single dive
• Hanifaru Bay, Maldives (June–November) — reef mantas aggregating by the hundreds; the most spectacular manta event on Earth
• Komodo's Karang Makassar — the 'Manta Point' cleaning station in the Flores Sea
• Nusa Penida, Bali — day trips from Sanur; Crystal Bay and Manta Point
• Black Rock, Mergui Archipelago (Myanmar) — remote, undervisited, extraordinary

Barrel Rolling and Feeding

When conditions are right — a convergence of plankton-rich water near the surface — manta rays feed by barrel rolling: swimming in continuous vertical circles through a patch of dense plankton, their mouths open, their cephalic fins (the horn-like lobes on their heads) unfurled to funnel water in. A single ray barrel-rolling in a plankton bloom is elegant. Fifty rays barrel-rolling together in formation, as happens at Hanifaru, is one of the great wildlife spectacles anywhere.

Conservation Status

Both species are classified as Vulnerable on the IUCN Red List. Gill rakers — the filter structures inside mantas' mouths — are sold in traditional Chinese medicine markets, and targeted fishing has dramatically reduced populations in some regions. A living manta generates up to USD 1 million in dive tourism revenue over its lifetime; a dead manta sold for gill rakers brings a few hundred dollars.