Manta rays are renowned as one of the giants of the oceans, reaching up to a whopping 7 meters (23 feet) wide. And yet despite their gigantic proportions, we know surprisingly little about their lives, including where they actually grow up. However, that might soon change.
Researchers think they have discovered the world’s first – and so far only known – manta ray nursery, and it’s right off the coast of Texas. Located in NOAA's Flower Garden Banks National Marine Sanctuary (FGBNMS), scientists have observed juvenile manta rays hanging out over a coral reef system that juts out of the Gulf of Mexico. The scientists have published their findings in the journal Marine Biology.
“This is exciting news for the manta rays in the northwestern Gulf of Mexico,” says George P. Schmahl, the superintendent of FGBNMS, in a statement. “The understanding that the mantas are utilizing the Flower Garden Banks National Marine Sanctuary, and possibly other reefs and banks in the region, as a nursery has increased the value of this habitat for their existence.”
Found in temperate and tropical waters around the globe, manta rays are a wide-ranging pelagic species that travel across open oceans in search of tiny zooplankton prey, which they filter from the water with their gaping mouths. Yet while courtship and mating rituals have been observed – in which the massive rays form mating trains swimming closely behind each other – where these majestic giants hide out as they mature has eluded researchers.
The sheer size of adult mantas means they have few predators to fear during their nomadic wanderings; however, in the years to reach those sizes, the younger rays need to be wary of sharks. The researchers suspect this is why the juveniles hang out in the Flower Garden Banks National Marine Sanctuary.
Most of their favored zooplankton live at depth, meaning the rays have to dive down into the deep cold ocean to get it. But while the adults can simply return to the surface and warm up with little worry, the youngsters may instead retreat to the outcrop of coral reef for added protection from any hungry sharks looking for lunch.
“Nowhere else in the world has a manta ray nursery area been recognized-which heightens the importance of the sanctuary for these pelagic species,” explains Schmahl. The hope now is to continue studying this region to help answer some of the most pressing questions about the lives of manta rays, as well as use the finding to help inform better management of the sanctuary.