![]() "The tags also record where in the water column they are," he said. So why don't mantas seasonally roam the oceans as other massive predators do? Greater flexibility in their diet might be the answer, Stewart suggested. And their genetic analysis confirmed that mantas in the different sample sites were not, in fact, the same individuals traveling from place to place, but rather established groups that staked out their ranges and stayed put. But every tag they deployed after that returned the same results over a six-month period. Stewart said their initial reaction was, "Well, that's interesting," though they needed to collect more data to be sure. In the very first batch they collected, Stewart and his colleagues noticed something unexpected: The tags popped off within about 62 miles (100 km) from where they were originally attached, and when the scientists mapped the mantas' movements over months, they found that the tags remained in largely the same area. (Image credit: Scripps OceScripps Oceanography / Joshua Stewart) The tags were programmed to detach after six months and then float to the ocean surface, where scientists could retrieve them.Ī giant manta ray swims in the Revillagigedo Archipelago, about 300 miles off Baja California, Mexico. Tagging technology has been used by oceanographers for more than two decades, but recent innovations have made devices much more robust and reliable, with a recovery rate of 80 to 90 percent, Stewart said. The researchers set out to tag and sample manta-ray populations at four sites that were up to 8,000 miles (13,000 kilometers) apart, to find out how far the rays traveled. They're certainly big enough and capable enough." "So we thought the mantas were migratory, too. ![]() "If you look at every other big animal that lives in remote pelagic environments, they're making long, epic migrations," Stewart said. And because mantas are so big, it was thought that they were simply doing what large migratory ocean creatures such as whales, leatherback turtles and bluefin tuna do - following their food. ![]() ![]() And in some locations, researchers would see the mantas for a few weeks or months, but they wouldn't find any at all for the rest of the year. Stewart, who is also the associate director of the nonprofit conservation organization Manta Trust, explained that individual mantas can be identified by unique patterns of spots on their bellies photos of mantas captured by researchers, dive tours and citizen scientists were used to track mantas over time.īut sometimes, nearly two decades would elapse between sightings, Stewart said. ![]()
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