Northeast Brazil shows highest hawksbill turtle nesting density in the South Atlantic

Abstract

To date, hawksbill turtle Eretmochelys imbricata nesting in Brazil has been estimated by recording clutch numbers. To better address conservation assessments and more reliably estimate the number of females, the Projeto TAMAR-ICMBio initiated a mark and recapture program of nesting females to gather data on critical parameters such as clutch frequency and remigration interval. The study area on the southern coast of Rio Grande do Norte was divided into 2 data-recording efforts: index (IA) and protected (PA) areas. Overall, 243 nesting hawksbill turtles were tagged along 42 km of nesting beach; 153 of these were within the 4 km area of intensive tagging. We estimated a remigration interval of 2.1 yr and a clutch frequency of between 2.3 and 2.6 clutches per female. Furthermore, the number of active breeding females was estimated to be between 705 and 791. The average number of clutches per kilometer was 21.1 in the IA and 20.7 in the PA (although some sections were as high as 37.5 and 48.5 nests km-1, respectively). This represents the highest density of hawksbill clutches per kilometer found so far for the South Atlantic, and highlights the importance of southern Rio Grande do Norte for the conservation of the Critically Endangered hawksbill turtle.