Estimates of marine turtle nesting populations in the south-west Indian Ocean indicate the importance of the Chagos Archipelago
journal contributionposted on 2020-05-01, 00:00 authored by J A Mortimer, N Esteban, A N Guzman, Graeme HaysGraeme Hays
Copyright © Fauna & Flora International 2020. Global marine turtle population assessments highlight the importance of the south-west Indian Ocean region, despite data gaps for the Chagos Archipelago. The archipelago hosts nesting hawksbill Eretmochelys imbricata and green turtles Chelonia mydas, both heavily exploited for 2 centuries until protection in 1968-1970. We assessed available nesting habitat and spatial distribution of nesting activity during rapid surveys of 90% of the archipelago's coastline in 1996, 1999, 2006 and 2016. We quantified seasonality and mean annual egg clutch production from monthly track counts during 2006-2018 along a 2.8 km index beach on Diego Garcia island. An estimated 56% (132 km) of coastline provided suitable nesting habitat. Diego Garcia and Peros Banhos atolls accounted for 90.4% of hawksbill and 70.4% of green turtle nesting. Hawksbill turtles showed distinct nesting peaks during October-February, and green turtles nested year-round with elevated activity during June-October. Estimates of 6,300 hawksbill and 20,500 green turtle clutches laid annually during 2011-2018 indicate that nesting on the Chagos Archipelago has increased 2-5 times for hawksbill turtles and 4-9 times for green turtles since 1996. Regional estimates indicate green turtles produce 10 times more egg clutches than hawksbill turtles, and the Chagos Archipelago accounts for 39-51% of an estimated 12,500-16,000 hawksbill and 14-20% of an estimated 104,000-143,500 green turtle clutches laid in the south-west Indian Ocean. The improved status may reflect > 40 years without significant exploitation. Long-term monitoring is needed to captureinterannual variation in nesting numbers and minimize uncertainty in population estimates.
Pagination332 - 343
PublisherCambridge University Press
Link to full text
Publication classificationC Journal article; C1 Refereed article in a scholarly journal
Chagos Archipelagoconservation policyDiego Garciaglobal assessmentsIUCN Red Listnesting seasonalityregional management unitthreatened speciesScience & TechnologyLife Sciences & BiomedicineBiodiversity ConservationEcologyBiodiversity & ConservationEnvironmental Sciences & EcologyCHELONIA-MYDASGREEN TURTLESLONG-TERMERETMOCHELYS-IMBRICATAHAWKSBILL TURTLESALDABRA ATOLLGROWTH-RATESCONSERVATIONSEASONALITYISLANDZoologyEcology