Manta rays are among dive tourists’ most beloved swimming companions. But despite frequent interactions between humans and mantas, we did not know much about them — until now.
Since 2014, Conservation International (CI) and its partners (including the Indonesian Ministry of Marine Affairs and Fisheries, the Indonesian Institute of Sciences, S.E.A. Aquarium and Manta Trust) have been fitting mantas in Indonesia with satellite tags to learn more about their behavior and how we can best protect them.
Thanks to these tags, here are four things we’ve discovered so far.
- Wayag Lagoon is Southeast Asia’s first documented manta ray nursery.
Home to the most marine species on Earth, the waters of the Raja Ampat archipelago beam with life at every angle. Yet the region kept a secret that was only recently uncovered through our tagging study.
Wayag Lagoon, one of the most picturesque and best protected lagoon systems in Indonesia, is the first documented manta ray nursery in Southeast Asia.
When the team followed a tagged pregnant female into Wayag, they found groups of newborn and juvenile reef manta rays swimming above the colorful coral. Seizing the chance, the team tagged several juveniles in the following days. With the data that followed, they identified the lagoon as a primary nursery and pupping ground.
- Baby and juvenile mantas use their home in different ways.
As juveniles, manta rays sometimes venture out into the deep blue. However, they always return to the safe shallows of the Wayag Lagoon, their childhood home.
As babies, the mantas are less adventurous, preferring to float near the surface within the lagoon. This puts them at risk of being hit by passing speedboats.
This discovery has brought about swift action from the Raja Ampat government. We expect new regulations curtailing speedboat usage within the lagoon to be implemented within the next six to 12 months.
This is a major win — not just for conservation, but for people as well. Protecting baby manta rays is critical to ensure the continued survival of the species, which bolsters the dive tourism industry that provides jobs and income for thousands of locals.
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- Reef mantas can dive really deep.
At least 624 meters (2,047 feet) deep, to be exact. While previous tagging studies have revealed regular deep-diving behavior in reef manta rays — including one individual which reached 432 m (1,417 ft) in the Red Sea off Saudi Arabia — one of our mantas tagged off the coast of Borneo has now smashed the world record. Moreover, almost all of our tagged mantas recorded maximum depths of at least 200 m (656 ft), with five of them regularly diving below 400 m (1,312 ft).
Why are they diving so deep? And why do some seem to consistently dive deeper than others? Are they feeding on deep planktonic food sources? Diving to escape predators? Or perhaps looking for mates? Our team in Indonesia is currently analyzing data for clues about whether this behavior correlates with the size or sex of individuals, or may be related to the lunar cycle.
- Mantas move across known hunting grounds in southern Indonesia.
Photographic identification work by local environmental organizations Aquatic Alliance and Manta Watch has shown that mantas at least occasionally swim between the tourism hotspots of Nusa Penida (Bali) and Komodo National Park. Our satellite tagging program has now revealed the details of these movements, confirming that the mantas are passing through known hunting grounds off the southern coasts of Lombok and Sumbawa islands.
In recent decades, mantas have been hunted in some regions of southern Indonesia to supply the now-illegal trade in manta gill rakers to traditional medicine markets in southern China. While fishers can earn up to US$ 500 from selling the gill rakers off a single large manta, a “mantanomics” analysis we presented to the Indonesian minister of marine affairs and fisheries showed conclusively that killing mantas is bad business for Indonesia; the same manta can easily be worth more than $1 million in tourism income over the course of its lifetime — provided that the tourism is environmentally responsible.
This economic argument was enough to persuade the minister to declare Indonesia as the world’s largest manta ray sanctuary in February 2014.
Enforcing this sanctuary is a priority of the ministry. Indonesia has a lot of ocean to patrol, however, and a fundamental question remained about whether to spread protection efforts over the four main manta tourism areas in Indonesia, or to pinpoint enforcement efforts within the hunting grounds. This new data on manta movement has convinced the ministry that it must do the latter to ensure the end to illegal hunting.
The more we see, the more we know
Research is futile unless it is shared with the right people. CI’s numerous educational initiatives in Raja Ampat’s villages have helped shift local attitudes about the value of manta rays. In addition, our partner S.E.A. Aquarium in Singapore bridges the gap between the rays and people who are unable to see them in the wild. By enabling visitors to see mantas up close and teaching them about the threats these animals face, the aquarium can inspire people to advocate for their protection.
There are other ways non-scientists can get involved, too — particularly scuba divers.
While our satellite tags give us a detailed glimpse into the diving and movements of the mantas, these glimpses are quite brief; tags typically remain on the animals between one and four months.
To complement the tagging, manta researchers also compile long-term databases of manta sightings by divers — an exercise made easier by the fact that individual manta rays are recognizable by the unique spot patterns on their bellies (much like a human fingerprint).
By collecting “ID photos” of manta bellies in a given area, researchers can track manta movements, growth and reproduction over periods of years to decades. One such database, focused on the mantas of Raja Ampat and compiled by our partners at Manta Trust, was recently opened for public participation. It already contains photos of more than 300 individual mantas and is growing daily.
As more citizen scientists share their photos and researchers delve into this valuable database, who knows what new insights we will gain next?