Lady Elliot Island, at the southern end of the Great Barrier Reef, is a hub of biodiversity. Its clear waters are home to mangroves and seagrass beds as well as turtles, birds, and, apparently, some rather special manta rays.
This haunting black ray, spotted this week by marine biologist Jacinta Shackleton, is a relatively rare occurrence, though not apparently in these waters. According to Asia Haines of Project Manta, about 80 of the 1,400 individual mantas identified from Lady Elliot Island are melanistic, meaning 7.5 percent of the local population sport the gothic getup. Worldwide, the picture is even more impressive, because of all the hundreds of species of cartilaginous fish in the ocean, manta rays are the only ones to exhibit melanism. And yet for some reason, at Lady Elliot Island, they don’t seem out of place at all.
Melanism is a term used to describe living things whose body tissues are darkened as the result of excess melanin and it results in some beautiful, jet-black variations of a host of animals, including reptiles, birds, seals, and most famously, big cats.
"I’m uncertain if this individual is new to the database as I didn’t photograph its underside," Shackleton told IFLScience, as not all melanistic animals are jet black and some can be identified by spots or patterns.
Lady Elliot Island has already made a name for itself in the manta ray fandom, being home to the world’s only known bright pink ray, Inspector Clouseau. The so-called “home of the manta ray” also plays host to varying degrees of pale and white rays, as well as Taurus, the oldest recorded manta ray in the world at the ripe old age of 40-something.
Manta rays may look like a catfish’s larger, floppier cousin, but they’re actually one of the most impressive denizens of the ocean. They are highly social creatures among themselves, and have even been spotted "asking" humans for help when they’re in trouble.
And while the pictures are no doubt beautiful, something they may not quite convey is the sheer size of the aquatic alphas. According to Shackleton, these rays are more than twice the size of even the tallest humans.
“These are reef manta rays (Manta alfredi) which grow to a maximum of 5 meters wingtip to wingtip," Shackleton told IFLScience. "There is a second, larger species called an Oceanic manta ray (Manta birostris) which has been recorded reaching up to 8 meters of length!"
Nobody knows why some rays show this black coloration but a 2019 study did rule out a couple of reasons. Scientists had thought the variation in color might play a role in camouflage, but a long-term analysis showed no difference in the survival rates between black and white mantas.
Something that paper did find, though, is that the rates of melanism differ starkly depending on location. With 7.5 percent of the local manta population exhibiting the dramatic coloring, Lady Elliot Island places somewhere in the middle – about the same rate as Nusa Penida or Komodo National Park in Indonesia, but far less than the whopping 40 percent of mantas in the Raja Ampat islands.
Of course, perhaps that just makes this latest sighting all the more special. Shackleton, no stranger to the local manta population herself, even has a local individual named after her. "It’s also a melanistic individual and can be recognized by its very short tail and spot pattern," she said. "I submitted around 150 images before I was lucky enough to see a new one!"