Tagged south of the island, an adult giant manta ray crossed the open-ocean gap along the submerged Cocos Ridge in five days, traveling about 43 miles a day before going silent 1,138 miles away. Researchers tracking the endangered fish off Central America discovered that juveniles stay close to protected coastal shallows to evade predators, while mature adults undertake long-distance migrations across international borders into unprotected waters.
Observing a manta ray drifting gracefully above a coral reef reveals the seemingly unhurried nature of these sea creatures.
Yet researchers working off Costa Rica found their movements vary drastically by age.
Giant manta rays rank among the ocean’s largest fish.
They boast wing-like fins that span up to about 8 meters, or 26 feet, alongside the largest brain of any fish.
Scientists tracked endangered oceanic manta rays between 2018 and 2025 using a combination of technologies.
Combining Technologies to Map Central American Manta Ray Movements
The research team fitted 59 manta rays with acoustic transmitters.
They tracked 12 individuals with satellite tags, and utilized photo identification to piece together their behavioral patterns.
Jeffry Madrigal-Mesén leads the Mantas Costa Rica research team.
He wrote the study published in Frontiers in Fish Science as lead author.
By combining different technologies … we were able to piece together a highly detailed map of their movements and their use of coastal cleaning stations.
Jeffry Madrigal-Mesén, director of Mantas Costa Rica
Of the 59 acoustic tags deployed, 42 produced data.
17 never registered on a receiver.
Divers’ photographs filled those gaps.
They successfully identified 10 of the untracked animals through the unique spot patterns on their undersides.
Juvenile Manta Rays Confine Themselves to Coastal Refuges
Smaller, immature mantas measuring around 3 to 3.5 meters across stayed strictly within Costa Rica’s coastal waters, known as its exclusive economic zone.
Two satellite-tracked young mantas, each about 10 feet across, swam long distances exceeding 1,200 miles each over periods of 108 and 64 days without ever leaving Costa Rica’s waters, keeping close to the continental shelf.
Scientists attribute this localized behavior to predation risks.
While a 3-meter juvenile appears enormous to human swimmers, it lacks the size and diving capabilities needed to escape apex marine predators.
Mature adults can rely on their massive body size and their ability to dive deep to evade threats. But juveniles don’t have that luxury.
Jeffry Madrigal-Mesén, project leader of Mantas Costa Rica
Jeffry Madrigal-Mesén noted that it is quite common to encounter animals missing portions of their bodies.
Wound shapes strongly suggest bites from other large marine predators such as orcas and tiger sharks.
Coastal shallows offer pups ample food, hiding spots, and essential hygiene services from cleaning stations.
Adult Migrations Span Across International Borders
Larger, mature animals measuring 4 to 4.5 meters across execute long-distance journeys.
Nine of the 12 satellite-tracked mature adults traveled north into the waters of Nicaragua, El Salvador, Honduras, and Guatemala, eventually reaching the high seas.
Together, the 12 tagged rays logged 13,555 miles.
One adult demonstrated the long-suspected link between Cocos Island and the mainland.
Tagged south of the island, it crossed the open-ocean gap along the submerged Cocos Ridge in five days—traveling about 43 miles a day—before heading north along the shelf edge and going silent 1,138 miles away.
Researchers observed that mature rays frequently return to familiar coastal cleaning stations, which serve as rocky reef sites where small fish remove skin parasites.
Observations of courtship and mating suggest these hubs also act as social centers before adults depart on regional migrations.
Exposure to Zero Legal Protection Outside Marine Reserves
Costa Rica maintains no-take reserves around Cocos Island and coastal hubs like Cabo Blanco.
Legal protections vanish the moment the animals venture into open waters.
When researchers mapped the satellite tracks against regional protected areas, migrating adults spent zero percent of their offshore travel inside a reserve.
Once outside protected boundaries, the rays encounter industrial fisheries, including tuna purse-seine fleets and longliners, alongside vessel traffic hazards.
In March 2024, researchers photographed a male with both pectoral fins intact.
They found him two months later with one fin cleanly amputated due to a likely boat strike.
To address these threats, the study’s authors urge the creation of multinational conservation swimways linking coastal nurseries to adult migratory corridors.
Closer to shore, researchers recommend that boaters reduce their speed when approaching aggregation areas.
