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Long-term changes in adult size of green turtles at Aldabra Atoll and implications for clutch size, sexual dimorphism and growth rates
journal contribution
posted on 2022-11-24, 03:18 authored by JA Mortimer, J Appoo, B Bautil, M Betts, AJ Burt, R Chapman, JC Currie, N Doak, N Esteban, A Liljevik, JT Mahoune, C Onezia, P Pistorius, H Richards, U Samedi, CL Sanchez, W Seabrook, A Underwood, J van de Crommenacker, R von Brandis, Graeme HaysGraeme HaysAbstractAround the world, declines in the mean size of nesting sea turtles have been reported with concerns of a concomitant decrease in the reproductive output of populations. Here, we explore this possibility using long-term observations of green turtles (Chelonia mydas) at Aldabra Atoll, Seychelles. Based on > 4500 individual measurements over 21 years (1996–2016), we found the curved carapace length of nesting females declined by about 0.64 cm per decade, from 111.43 to 110.08 cm. For 391 individuals that were measured more than once with measurement interval of 2.8–19 years apart, the mean growth rate was 0.14 cm year−1. Comparisons between the size of adult females and males were based on 23 and 14 weight measurements, 107 and 33 carapace length measurements and 103 and 33 carapace width measurements, respectively, taken during 1981–1983. Adult females were larger than males, with the sexual dimorphism index, i.e. the ratio of size of the larger sex to the smaller, being 1.09 and 1.10 for carapace length and width, respectively, and 1.25 for weight. Smaller females tended to lay fewer eggs per clutch but the decrease in female mean size was accompanied by increases in numbers of turtles nesting annually, such that the estimated total numbers of eggs per year increased from 1.3 million to 2.0 million between 1996 and 2016. Therefore, a decrease in mean size of nesting females has not compromised egg production for this population.
History
Journal
Marine BiologyVolume
169Article number
123Pagination
1-10Location
Berlin, GermanyPublisher DOI
ISSN
0025-3162eISSN
1432-1793Language
EnglishPublication classification
C1 Refereed article in a scholarly journalIssue
10Publisher
SpringerUsage metrics
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Adult body sizeAssomptionBODY-SIZECarapace measurementsCARETTACHELONIA-MYDASClutch sizeCosmoledoFarquharFREQUENCYGrowth ratesINDIAN-OCEANLife Sciences & BiomedicineLOGGERHEAD TURTLESMarine & Freshwater BiologyMarine turtlesNESTING POPULATIONOSCILLATIONREPRODUCTIVE SEASONALITYScience & TechnologySEA-TURTLESWestern Indian OceanSchool of Life and Environmental SciencesFaculty of Science Engineering and Built EnvironmentEnvironmental SciencesBiological SciencesAgricultural and Veterinary Sciences
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