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A Season of Mixed Fortunes for Hawksbill Turtles on Cousin Island

It has been a memorable turtle nesting season on Cousin Island Special Reserve. The island, a critical nesting site for Hawksbill turtles (Eretmochelys imbricata) in the Western Indian Ocean, continues to see nesting turtles arrive despite the challenges posed by climate change. The Special Reserve’s ongoing long-term monitoring collects data to track population trends for conservation efforts.

One of the observations, which has been made is the arrival of a larger number of untagged turtles. Tags are applied to turtles in Seychelles to identify each nesting female. They typically have a three-letter code followed by 4 digits. Knowing an individual turtle allows scientists to investigate when and where it was first tagged, the number of times it has nested in a season, the number of active seasons, the number of eggs laid and hatching success, locations of the beaches where she has nested, and growth and rough estimation of age. This can be useful to answer questions about reproductive biology, population size, movements, strandings, residency, and growth rates. Tagging is done by trained personnel and volunteers, and this season provided the opportunity to train new staff who have joined the team this year. A standout moment was observing turtle number SXX 1916, who astonished the team with the number of eggs she laid. She came up four times and, in each instance, she laid over 200 eggs, including a record-breaking 264 eggs in one case.

Seeing multiple nesters in one beach section is a thrill, as is witnessing hatchlings emerging and heading to the sea. The team has sometimes observed both occurring simultaneously this season.

Nesting turtles are also exceptionally resilient. A female turtle missing half of her front left flipper was encountered as she finished nesting. Fully or partial amputee turtles are uncommon, but not unheard of. They might lose a flipper to a shark, boat strike or other mishap, but on Cousin they have shown that they are still capable of recovering and nesting. This turtle had emerged, crawled up the beach, laid and covered her eggs, and was returning to the sea all with a missing limb.

While Cousin’s beaches are the stage for such highlights, they also reveal challenges. The heavy January rains adversely impacted nests, sometimes drowning hatchlings. Amidst the devastation, however, the team managed to save some hatchlings through nest excavations. Severe erosion this season also led to more nest relocations.

The island’s Aldabra Giant Tortoises made an unusual impression this season. On more than one occasion, the tortoises displayed curiosity towards nesting turtles. In one surprising incident, a male giant tortoise approached a nesting female Hawksbill turtle and made what looked like a mating attempt. The conservation officer intervened quickly to protect the turtle. All ended well, with the turtle continuing to cover her eggs, but the incident added a fascinating layer to the season.

Beyond these, the season likewise provided plenty of moments for education and awareness creation. Delighted tourists and visiting school children got the opportunity to see turtles nesting or a turtle-related activity such as nest excavations. The team used every occasion to create awareness about this endangered turtle species.