Researchers have tracked a green turtle migrating nearly 4000 kilometers from its home. That’s a record breaker for the species, but it’s bad news for some marine protected areas (MPAs). Such zones are off-limits to fishing, yet they may not be keeping these turtles—and other highly migratory animals—safe, according to a new study.

The work focused on an MPA in the Indian Ocean’s Chagos Archipelago. The 640,000-square-kilometer MPA contains numerous threatened and endangered species, including sharks and turtles. It was created in 2010 to protect the enormous biodiversity of the archipelago. To figure out how well the Chagos MPA safeguards its inhabitants, an international team of researchers attached GPS tracking devices to eight green turtles (Chelonia mydas) and monitored their movements as they made the trek to their foraging grounds.

“After we tagged the turtles, we had an informal bet about what they’d do,” says Graeme Hays, an ecologist at Deakin University, Warrnambool, in Australia and a co-author on the study. “None of us predicted they would travel as far as mainland Africa—nearly 4000 kilometers away!”

Out of eight turtles, only one foraged within the bounds of the Chagos MPA. The rest paddled much farther, reaching the Maldives and even the Seychelles, thousands of kilometers away. The turtle with the farthest migration traveled 3979 kilometers to Somalia in 68 days, the researchers report online this month in Conservation Biology.

“It’s amazing. We’ve been tracking and studying turtles for over 20 years, but we still can be completely surprised by these tracking studies,” Hays says. “It just shows how little we really know about sea turtle movement.”

Although MPAs can work well at protecting habitats like coral reefs and nonmigratory wildlife such as the coconut crab, the authors say that more effort needs to be made to protect migratory species such as the green turtle and the hawksbill turtle from poachers, marine debris, and fishing gear entanglement. The study found that turtles spend most of their time outside these protected areas, and suggests supplementing large protected areas with smaller MPAs. These smaller MPAs would target the main destinations of migratory species, offering protection that goes beyond nesting and hatching grounds.

Despite global commitments to increase the number of protected areas, less than 3% of the world’s oceans are now protected within an MPA. In many cases, MPA planning isn’t based on environmental science, Hays says. Often, the boundaries for a large MPA are simply the territorial limits around a nation’s oceanic islands, as is the case with the Chagos Archipelago.

The study shows that even the largest MPAs cannot work in isolation, says Janice Blumenthal, a research officer for the Cayman Islands Department of Environment in George Town who works with sea turtle ecology. “We need international cooperation in ocean conservation.”

Hays’s team is now advising the Seychelles government about future MPAs to ensure a healthy future for the developing island nation’s natural resources. “A lot of tourists go to Seychelles to see the marine wildlife, so there’s definitely a will to protect the turtles there,” he says. At the same time, Hays notes certain areas will likely remain open for fishing and other marine activities. “The key goal is to try and keep everyone as happy as possible.” Especially the turtles.