Recent decline of green turtle Chelonia mydas nesting trend at Tortuguero, Costa Rica

Restrepo, Jaime, Webster, Emily G., Ramos, Iván, and Valverde, Roldán A. (2023) Recent decline of green turtle Chelonia mydas nesting trend at Tortuguero, Costa Rica. Endangered Species Research, 51. pp. 59-72.

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Abstract

Trends in abundance of different life stages present important opportunities to man-age the conservation of threatened species. For marine turtles, most trend assessments are based on long-term monitoring of nesting aggregations, which provides critical information on rookery dynamics across years. Tortuguero, Costa Rica, is the largest nesting colony of the green turtle Chelonia mydas in the Atlantic. Here we present an updated trend in annual clutch abundance spanning over 50 yr of monitoring at Tortuguero. We conducted weekly censuses recording clutch counts and used a generalized additive model (GAM) fitted for each monitored nesting season separately to predict daily tallies. We estimated annual clutch count as the sum of these. We mod-elled the long-term trend in annual clutch numbers with a Bayesian GAM with a cubic regression spline basis, fit to estimated annual clutch counts for 1971-2021. Finally, we examined spatio-temporal patterns in clutch counts along the beach by fitting a GAM with a 2-dimensional spline. Clutch estimates varied across years (78 695 ± 6727 [mean ± SE], range: 7004-186 640 clutches per year), but increased steadily over the first 37 yr. However, growth slowed gradually from 2000 to 2008, when the curve began to trend downwards. Tortuguero remains the largest aggregation of nesting green turtles within the Caribbean. Phenomena occurring across the population’s range and at several life history stages influence Tortuguero’s nesting trend. Thus, a decreasing trend at Tortuguero may be a warning sign for the Greater Caribbean green turtle metapopulation.

Item ID: 79562
Item Type: Article (Research - C1)
ISSN: 1613-4796
Keywords: Atlantic, Caribbean, Chelonia mydas, Long-term assessment, Nesting trend, Population decline, Sea turtles, Spatial distribution
Copyright Information: © The authors 2023. Open Access under Creative Commons by Attribution Licence. Use, distribution and reproduction are unrestricted. Authors and original publication must be credited.
Date Deposited: 30 Jan 2024 00:03
FoR Codes: 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 100%
SEO Codes: 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280102 Expanding knowledge in the biological sciences @ 100%
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