Long-Term Trends of Hawksbill Turtle Nest Numbers Across Key Brazilian Nesting Areas

Abstract

Hawksbill turtles are globally distributed along tropical waters and are recognized as Critically Endangered by the IUCN, with unique populations facing different challenges. As a result, while nesting populations in the Pacific are experiencing marked declines in nesting numbers, Atlantic populations show some increase, highlighting the need for regional assessments. This study assesses the nesting trends of the hawksbill turtle in two important Brazilian nesting regions: Bahia/Sergipe (BA/SE) and Rio Grande do Norte (RN), covering 29 seasons in BA/SE (1991-2019) and 17 in RN (2003-2019). During the study period an overall 7.8-fold increase in nest numbers was found in BA/SE, with pronounced increase during the first two decades, transitioning into a possible stabilization phase in the last decade. The inflection curve of the increase in nest numbers in BA/SE around 1996-1997 aligns with the maturation time required for hawksbill turtles in the Atlantic and might be a positive reflection of protection measures at nesting beaches started in 1980. RN experienced a 1.5-fold increase in nest numbers during the study period, with an observed stabilization since 2015. To further enhance conservation strategies, future research should focus on refining population estimates, improving methodologies for more accurate nest counts and including estimates of number of females. Additionally, expanding research to include in-water assessments and genetic studies will provide a more comprehensive understanding of hawksbill turtle population status. These steps are vital in a rapidly changing world where marine turtle populations face complex, cumulative, and dynamic threats.

Keywords: sea turtle, marine turtle, conservation, nesting counts, Southwest Atlantic, status