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Operational sex ratio estimated from drone surveys for a species threatened by climate warming
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posted on 2023-02-03, 03:46 authored by MN Staines, CE Smith, CA Madden Hof, DT Booth, IR Tibbetts, Graeme HaysGraeme HaysAbstractRising sand temperatures resulting from climate warming may cause the ‘feminization’ of sea turtle populations, which have temperature-dependent sex determination. In July and October 2021, we conducted surveys using a drone (also referred to as an unmanned aerial vehicle or UAV) and shore-based observations to assess the operational sex ratio (OSR) (number of males and females in breeding condition) for green turtles (Chelonia mydas) in the southern Great Barrier Reef, Australia (23.44 °S, 151.92 °E). Using drone-imagery, the length:width (L:W) ratio of a turtle’s head was used to distinguish loggerhead turtles (Caretta caretta) from green turtles, and the L:W of the carapace was used to distinguish juveniles from adult-sized green turtles. The first breeding pair was observed in shore-based surveys on 14 September 2021 and the number of mating turtles then increased to a peak on 4 October, about 8 weeks before the peak in nesting. A total of 94 km of drone transects with associated video footage was analysed. In October, at the peak of the mating season, the ratio of adult turtles displaying breeding behaviours near the island was 0.51 female (95% CI ± 0.17), supporting previous conclusions that despite the female-biased (> 80%) hatchling sex ratio, this population likely has a fairly balanced OSR. These findings are likely explained by males breeding 2–3 times more frequently than females, which helps mitigate female-biased hatchling sex ratios. Assessing the OSR of populations with extreme female hatchling bias may help to inform whether intervention is needed to increase male hatchling production.
History
Journal
Marine BiologyVolume
169Article number
152Pagination
1-11Location
Berlin, GermanyPublisher DOI
ISSN
0025-3162eISSN
1432-1793Language
EnglishPublication classification
C1 Refereed article in a scholarly journalIssue
12Publisher
SpringerUsage metrics
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No categories selectedKeywords
ABUNDANCEAerial surveyBreeding sex ratioCARETTA-CARETTAClimate changeFEMINIZATIONGREAT-BARRIER-REEFGREEN TURTLESHeron IslandHERON ISLANDLife Sciences & BiomedicineMarine & Freshwater BiologyMigrationNESTPATERNAL GENOTYPESRemote sensingScience & TechnologyTEMPERATURESTURTLES CHELONIA-MYDASSchool of Life and Environmental SciencesFaculty of Science Engineering and Built EnvironmentEnvironmental SciencesBiological SciencesAgricultural and Veterinary Sciences
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