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ESR 51:59-72 (2023)  -  DOI:

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

Jaime Restrepo1,2, Emily G. Webster3, Iván Ramos1, Roldán A. Valverde1,4,*

1Sea Turtle Conservancy, 4581 NW 6th St, Suite A, Gainesville, FL 32609, USA
2School of Earth and Environmental Sciences, University of Queensland, Brisbane, Queensland 4072, Australia
3College of Science and Engineering, James Cook University, Townsville, Queensland 4811, Australia
4Southeastern Louisiana University, Hammond, LA 70402, USA
*Corresponding author:

ABSTRACT: Trends in abundance of different life stages present important opportunities to manage 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 modelled 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.

KEY WORDS: Sea turtles · Chelonia mydas · Atlantic · Caribbean · Long-term assessment · Population decline · Spatial distribution · Nesting trend

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Cite this article as: Restrepo J, Webster EG, Ramos I, Valverde RA (2023) Recent decline of green turtle Chelonia mydas nesting trend at Tortuguero, Costa Rica. Endang Species Res 51:59-72.

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