The turtles of Saint Brandon
The story of sea turtles is one of the longest in the ocean. Their lineage stretches back more than a hundred and ten million years— older than the breakup of the supercontinent that produced Saint Brandon itself. They survived the asteroid that ended the dinosaurs. They survived the cooling of the ancient seas and have also outlived almost every other marine reptile that ever existed. What they may not survive is us.
Of the seven species of marine turtle in the world today, six are listed as threatened or endangered. Saint Brandon supports two of them: the green turtle and the hawksbill turtle. Together they make the archipelago one of the most important sea-turtle nesting sites in the western Indian Ocean, with an adult female nesting population estimated at between 600 and 1,500 individuals across the islands. The 2017 Bossert and Teker survey recorded over 350 nesting events at the southern atoll in a single year. Hatchling success is high. Adult mortality, historically catastrophic, has been reduced by the long-term protection of the islands and the limits on fishing pressure within the lagoons.
A female sea turtle returns, after thirty years at sea, to the exact beach where she herself was hatched. The mechanism is not fully understood. It appears to involve a learned magnetic-field signature imprinted in the first days of her life. She comes ashore at night, drags herself above the high-tide line, digs a chamber in the sand with her hind flippers, and lays around a hundred soft-shelled eggs the size of ping-pong balls. She covers the nest, returns to the sea, and may never see that beach again. The eggs incubate for around sixty days. The sex of the hatchlings is determined by the temperature of the sand — warmer nests produce more females, cooler nests produce more males. The hatchlings emerge at night and run for the sea, navigating by the lightest horizon, which is normally the moon on the water.It is the run to the sea that has, in our time, become the most dangerous part of a turtle’s life. Hatchlings disorient on artificial light. They run inland toward streetlamps or houselights and die of exhaustion or predation. They wedge in plastic. They suffocate on the bags they mistake for jellyfish. They emerge from the sand into a beach their mother could not have imagined.Saint Brandon is, by global standards, one of the cleaner nesting sites left. But it is not clean enough.
A turtle, witnessed
On Île Raphael, in the company of one of the Fly Castaway guides, I came across a female green turtle attempting to nest near the upper beach. She was breathing heavily after her crawl, in the digging stage of the nesting process, using her hind flippers in slow alternating strokes to scoop a chamber in the sand. The problem was that the sand around her was a drift of plastic bottles, jerry-can lids, fishing line, polystyrene fragments, lighters, and the unidentifiable smaller pieces that everything eventually becomes.
She would dig, encounter resistance, pause, and dig again. The flipper would catch on a bottle and the chamber would collapse. She tried for some time. We watched from a respectful distance, the guide and I, the way one watches something one cannot help.
She did, eventually, find a passage of sand clean enough to lay in. I do not know how many of those eggs reached the sea. The trash that interrupted her did not come from Saint Brandon. It came from elsewhere — from South-East Asia, from the Indian subcontinent, from the Arabian Sea — carried thousands of kilometres by the gyre that delivers everything the Indian Ocean cannot digest to the windward shores of small, low islands where there is no one to clean it. A 2016 study counted fifty thousand individual items along the shores of Saint Brandon’s outer islands. Seventy-nine percent were plastic. That is the figure. The figure is one female green turtle, in the dark, trying to make a chamber for her eggs through what other people threw away.
I thought afterwards about how many of those eggs would have hatched even if she had laid them cleanly. About how many of the hatchlings would have made the sea. About the magnetic signature that would carry the survivors home, in three decades, to a beach that might by then be entirely lost to plastic, or to sea-level rise, or to both. I thought about how the work of paying attention is itself a small refusal of the indifference that has produced this. And I thought that the turtle, in her ancient and patient way, was teaching me something my whole trip had been arranged to learn: that the place is still alive, and that what we do or do not do in the next short stretch of years will decide whether it stays that way.
Green turtle — Chelonia mydas
Saint Brandon is the most important green turtle nesting site in the Republic of Mauritius. Newlands’ 1975 survey reported a catastrophic historic decline due to overexploitation. The 1997 World Bank survey counted 240 tracks across the inspected islands over a single month, suggesting a total adult female nesting population of between 600 and 800 — possibly as high as 1,500. Females return to the beach where they themselves hatched, decades earlier, to lay their own eggs. Gestation is around sixty days. Hatchlings emerge at night and run for the sea. Their natural predators include crabs, frigate birds, sharks, and groupers.
Hawksbill turtle — Eretmochelys imbricata
The hawksbill is critically endangered globally. Saint Brandon is one of the few western Indian Ocean sites where they are still confirmed to nest. They prefer rockier substrates than the green turtle and a more vegetated approach to the beach. The 2017 Bossert and Teker survey confirmed both species nesting at Coco and elsewhere.