Status and biology of hawksbill turtles at Poilão Island, Guinea-Bissau: a key stronghold for the species in West Africa

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Abstract This study provides the first detailed assessment of the hawksbill turtle (Eretmochelys imbricata) nesting population from Poilão island, in the Bijagós archipelago of Guinea-Bissau, the only documented regular nesting site for this species in West Africa. Over 17 years, from 2007 to 2024, 29 females were tagged, with one to six individuals nesting annually, some for more than 10 years. Nesting occurs from July to November, coinciding with the green turtle (Chelonia mydas) nesting season. Female hawksbills at Poilão are among the largest within the East Atlantic Regional Management Unit (EARMU), with average carapace length of 89.3 ± 4.3 cm. Satellite tracking revealed females remained year-round within the Bijagós archipelago, with small home ranges both during the inter-nesting (∼ 26.13 km2) and foraging periods (∼ 38.41 km²). Genetic sequencing identified two haplotypes - EiBr5 and EiBr7 - linking this population to others from within the EARMU and across the Atlantic, highlighting this rookery’s broader regional significance. Poilão is the single known rookery of origin of the orphan haplotype EiBR5 (also known as EiA49). Despite its importance, the minute size of this population and the lack of evidence for recent recruitment pose challenges to its potential for recovery and effective conservation. This study underscores the need for archipelago-wide sustained conservation measures to ensure the future of the hawksbills from Poilão, and West Africa.