Tracking sea turtles and the threats they face

It’s Hawksbill turtle (Eretmochelys imbricata, Kare) nesting season once again. Several islands have reported nesting activities on beaches as females crawl up onto land to nest. After a false start in August, Cousin Island had its first egg-laying female - another untagged female - in September.

Green turtle nesting on Cousin Island

But prior to this, there has been increased laying activity by Green turtles (Chelonia mydas, Torti-d-Mer), a surprising but encouraging turn of events.

While the island is one of the most significant nesting sites for Hawksbills, it does not receive many Green turtles. This turtle is generally rare on the inner granitic islands due to heavy exploitation in the past, which greatly reduced their numbers.

Towards the tail end of last month, a Green turtle washed up dead on the beach. It was immediately obvious that a shark bite caused its death. There was extensive damage to the shell and a flipper was missing. Despite these injuries, it looked like the turtle still evaded the shark before dying.

Sharks are sea turtles’ natural predators. Several are seen during nesting season missing flippers or parts of the shell from shark bites. In fact, the island’s team often calls these individuals “shark bite”. Most of them are still able to dig nests and lay their eggs despite missing a limb or part of their shell, and their fortitude is truly humbling to see.

Predation on sea turtles can happen at all stages of their life cycle. Juveniles and adults are more likely to fall prey to sharks as mentioned. On Cousin, eggs are eaten by Ghost crabs and become an opportunistic meal for skinks when nests are exposed. Ghost crabs kill hatchlings on the nature reserve, picking them off as they dash to the sea.

However, it is imperative to note that human-related activities still pose the biggest threat to sea turtles.

Climate change-induced erosion has severely affected nesting beaches

Climate change-induced erosion, in particular, has severely affected nesting beaches on Cousin Island. Apart from eating away at the beach turtles need for nesting, it creates steep beach crests that females have to scale to find a suitable spot to lay their eggs. Many nests laid in eroded areas are at risk of becoming waterlogged during high tide and unviable.

There were more turtle nests relocated last season than in previous years. It is projected that more nest relocation will be required during the upcoming season. The report also showed that translocated nests hatched with varying success rates. Similarly, erosion has led to many trees falling or having their roots exposed, which also affects turtles.

The Hawksbill and Green turtle are listed as “Critically Endangered” and “Endangered” respectively on the IUCN Red List. Globally, human activities including poaching, habitat destruction, pollution, and overfishing continue to pose a threat to both species.