Rangers and international volunteers from Fundação Tartaruga reach the beaches at dusk. The foundation is one of several NGOs on Boa Vista, founded to protect sea turtles – mostly loggerheads – that come to the island to nest. Every night from June to October, the foundation’s teams of marine biologists and local rangers patrol dozens of kilometres of beaches in search of females who have come to the island to lay their eggs. Every year, thousands of turtles come to the Cape Verde Islands to nest: the West African archipelago was once the world’s third largest nesting site for loggerhead turtles (in number of nesting females), after Florida and Oman, but the number of nests has increased so dramatically in recent years that it is almost certainly now the second largest globally, or perhaps even the largest.

Of the Cape Verde islands, Boa Vista is the favoured nesting site for loggerheads, a species listed as ‘Vulnerable’ on the IUCN Red List. Although the Cape Verdean government has placed turtles under protection, they are exposed to an extensive list of dangers.

Poaching of nesting females is still widespread, killed for their meat and their eggs, taken for human consumption. Other human activities putting them at serious risk include light and environmental pollution from large hotels; the flow of tourists trampling their nests; the massive accumulation of plastic that suffocates their favoured beaches; fatal collisions with ships and boats; and industrial fishing that accidentally – yet routinely – ensnares them in their indiscriminate fishing practices.

Volunteers monitor hundreds of kilometres of sandy coastline every year during the nesting season. Patrollers are tasked with protecting as many turtles as possible on a designated stretch of beach. It’s delicate and complex work: each turtle must be examined, measured, equipped with a tracking chip, and monitored to ensure it returns to the sea safely. The first difficulty for operators patrolling the sandy coast is spotting them in the pitch black of night.

“We can’t use torches. The white light scares the turtles, disorients them and there’s a risk that they’ll return to the sea to look for another, quieter place,” explains Franziska Haas, a 22-year-old German biologist from Leichlingen.

This is her third year as a volunteer on Boa Vista and she has mapped hundreds of nests dug into the white sand of Lacacão, in the south of the island. “When we spot them, we approach from behind so as not to be seen, silent as fish; even noise can scare them and send them away. Then we illuminate them with a very dim, red light. It’s just for a moment, to understand if they are laying their eggs or if they are still digging their hole.”