Data Availability.xlsx

Sea turtles exhibit highly migratory behavior and spend most of their life in oceanic habitats, complicating the study regarding their life cycle. Sea turtle research predominantly focuses on nesting females, relying on nest counts and mark-recapture data, while male behavior is poorly understudied. Previous studies have investigated their reproductive behavior by analyzing the genotypes of females and hatchlings to indirectly access male genotypes and understand the level of multiple paternity within populations. We aimed to test the presence of multiple paternity in nests of loggerhead turtles (Caretta caretta) for the first time in Brazil. We sampled 42 females and up to 20 hatchlings per clutch during the 2017/18 – 2019/20 nesting seasons and genotyped four highly species-specific polymorphic microsatellite markers (nDNA). We performed a parentage test to reconstruct the paternal genotypes to determine the rates of multiple paternity within clutches. Multiple male contributions were found in 72.09% of the clutches, ranging from 1 to 6 males. Seven out of 88 males (7.95%) sired clutches from multiple females. Some males contributed to more than one clutch within and across breeding seasons. The breeding sex ratio (BSR) was 2.09 males for each female. Although multiple paternity is commonly found among sea turtles, this is the first study describing polyandry for loggerheads in Brazil and the first evidence of polygyny in loggerheads anywhere. This work provides a database for future studies in Brazil, especially considering the BSR of the Southwest Atlantic subpopulation. Such information is crucial to develop management strategies for this vulnerable population.
Ethical statement:
This study was performed under the Biodiversity Authorization and Information System license from Chico Mendes Biodiversity Institute (SISBIO/ICMBio), number #6069-1. The study was approved by the Ethics Committee on the Use of Animals (CEUA) of the Federal University of Espírito Santo (UFES), number #07/2019. When obtaining a tissue sample for genetic analyses, sampling of loggerhead turtles was performed by minimizing animal suffering. We also obtained permission from the Sistema Nacional de Gestão do Patrimônio Genético e do Conhecimento Tradicional Associado (SisGen) on the number #A32C980.