Manta rays. These gentle giants are not only one of the biggest fish in the sea, but surely one of the most graceful and charismatic. They are relatively abundant in the waters of Komodo and a big draw for divers and snorkelers. I have been privileged to spend hundreds of hours observing them and take great pleasure in sharing this magical experience with divers.
Size matters. The reef mantas (Manta alfredi) most commonly encountered in Komodo live for up to 40 years and can reach up to 5m wingspan. Typically they average 3m wingspan, with the largest ones being females, but the combined effects of underwater magnification and excitement often result in first encounters with 4m+ giants! Komodo’s reef mantas are known to travel an impressive 450km to Nusa Penida in Bali, with repeat encounters recorded in just over a month, emphasising their hyper-efficient design. Conservation International deployed satellite tags to collect data on manta behaviour and recorded some interesting findings, with the reef mantas tracked at depths of over 200m in Komodo, and more than 600m in open oceans.
At certain times of the year, the oceanic manta ray (Manta birostris) makes an appearance in Komodo to feast on seasonal explosions of krill and plankton. I had the good fortune to meet the ultra-rare leucistic variation with almost completely white skin pigment, often described as manta unicorns. Quite how they know when and where these feasts are going to occur is wonderfully confounding. These giants grow up to 7m and are known to migrate much further distances than their reef dwelling cousins.
After the initial excitement of being dwarfed by a fish that looks like a stealth bomber, it’s a good idea to stay calm and find an unobtrusive position to observe the manta ray. Whilst brief fly-by encounters are always welcome, the most memorable encounters are when mantas are cleaning, feeding or mating.
Cleaning stations are by far the best way to enjoy quality time with mantas in Komodo with the dive sites at Karang Makassar, Mawan, and Manta Alley offering some of the finest spa facilities for manta rays in the national park. Look out for relaxed mantas hovering over the cleaning station with extended cephalic fins, allowing their huge body mass to be cleaned by a small army of reef fish. There are a variety of fish species involved in the cleaning process, with butterfly fish and moon wrasse going to work on the body area and cleaner wrasse focussing on the mouth and gills. By following codes of conduct to ensure the mantas have plenty of space to clean, lucky divers can sometimes experience enjoy curious manta rays at exceptionally close quarters, however, mantas are said to be highly spatially aware and unlikely to intentionally have contact with divers.
Manta rays feed in a number of ways, the most common being “ram” feeding: literally opening their huge mouths and extending their cephalic fins whilst swimming in current to draw planktonic food through their gills. Ram feeding happens at depth, but due to higher plankton concentrations, it’more common to see manta rays feeding at the surface, much to the delight of snorkelers. Sometimes there are concentrated patches of food, and manta rays can be seen barrel rolling repeatedly in the same spot to maximise plankton intake. The most impressive feeding spectacle happens when there is an extra heavy plankton bloom – sometimes known as a red tide – and it’s possible to encounter immense numbers of mantas on a dive site such as Karang Makassar, frenetically ingesting the concentrated plankton by barrel rolling and cyclone feeding in groups. Being completely surrounded by more manta rays than you can count for well over an hour…scuba diving doesn’t get much better!
Manta courtship is another wonderful spectacle for divers to experience in Komodo, with trains of male manta rays performing an elaborate ballet pursuit of a female in heat. She will loop and turn and they will follow suit, in a test of stamina that lasts for up to 48 hours until there is one male manta that has proved his dexterity. Although this behaviour is regularly witnessed by divers in bi-annual courting seasons, it’s also the only occasion when I have perceived a sense of aggression from courting mantas, emerging from the blue with little regard for encroaching scuba divers.
Mating is extremely rare to see and a much more short-lived affair, due to mantas being negatively buoyant copulation lasts only a matter of minutes. The male moves perpendicular to the female and bites onto the left wingtip (recognising mating scars are a good way to spot sexually mature females), positioning themselves belly to belly and then attempting to swim up the water column to prolong copulation.
Mantas can be spotted throughout the year in Komodo, although ironically there tend to be less around at the most accessible manta dive sites in the peak tourist months of July to September. Whether this is linked to increasing numbers of boats, people, noise and pollution, or simply a consequence of less food availability and natural migration cycles, remains to be seen. There is a definite correlation between the moon phase and manta sightings, with the week preceding full and new moon often lacking many mantas in the central Komodo sites. Outside of these peak tourist months, the mantas are generally abundant, if not guaranteed. Whilst the general weather and diving conditions may not be perfect in the quieter months of November to April, they are some of the most prolific months for manta encounters.
If you’ve made it this far I hope you’ve enjoyed reading this post. There are a wealth of resources available online for further reading and insights about manta rays, including Marine Megafauna Foundation, Manta Watch, Conservation International, and Manta Trust. Feel free to contact me with any questions about Komodo mantas and visiting Komodo in general.