Bahia state hosts over 90% of hawksbill (Eretmochelys imbricata) nests registered in the main nesting sites monitored by Projeto Tamar-IBAMA in Brazil. The genetic diversity of this hawksbill population (n=119) was assayed through the analyses of 752 bp of the mitochondrial DNA control region in nesting females. Seven distinct haplotypes, defined by 125 polymorphic sites, were found. Most of the individuals (n=67) display four typical hawksbill haplotypes, 50 individuals display two haplotypes characteristic of the loggerhead turtle (Caretta caretta) and two individuals had a haplotype affiliated with the olive ridley (Lepidochelys olivacea). These results demonstrate hybridization between the hawksbills and two species that nest along the Bahia coast. Of special interest is the high occurrence of loggerhead  hawksbill hybrids (42%), which display loggerhead mtDNA haplotypes but are characterized morphologically as hawksbills. The true hawksbill haplotypes present only three variable sites and low genetic diversity values (h=0.358±0.069; p=0.0005±0.0001). The occurrence of several nesting individuals with identical mtDNA from another species may also suggest a long history of introgression between species producing likely F2 or further generation hybrids. Marine turtle hybrids have been previously reported, but the high frequency observed in Bahia is unprecedented. Such introgression may influence evolutionary pathways for all three species, or may introduce novel morphotypes that develop apart from the parental species. The presence of a unique hybrid swarm has profound conservation implications and will significantly influence the development and implementation of appropriate management strategies for these species.

We studied inter-and postnesting movements in the major loggerhead Caretta caretta nesting population in Brazil. Ten breeding females were satellite-tracked from nesting grounds in the state of Bahia, northeastern Brazil, for up to 1284 d. Eight females stayed in the nesting area after deployment, showing fidelity between internesting home ranges and nesting locations, even at a local scale. During postnesting movements, all of the turtles migrated to the northern coast of Brazil to individual foraging areas on the continental shelf. Distances between nesting and foraging areas reached up to 2400 km, and migration lasted from 28 to 47 d. Five females were tracked during subsequent breeding migrations to the nesting area at different remigration intervals of 2 or 3 yr. Females were also tracked during a second postnesting migration back to foraging areas, and these showed strong fidelity to foraging grounds. Movements to and from foraging grounds occurred along the shelf, clearly delineating a migratory corridor. The northern coast of Brazil, specifically the coast of the state of Ceará, is an important foraging ground for loggerheads nesting along the northern coast of Bahia.

This article presents biological data and an assessment of the conservation of the olive ridley sea turtle (Lepidochelys olivacea) population nesting in the States of Sergipe and Bahia, north-eastern Brazil, between 1991/1992 and 2002/2003. Projeto TAMAR-IBAMA (the Brazilian Sea Turtle Conservation Programme) maintains seven field stations in that region to monitor nesting activity over 339 km of beach. An increasing trend was observed in the estimated number of nests per nesting season: from 252 nests in 1991/1992 to 2606 in 2002/2003, an approximately 10-fold increase in 11 years. The available data and biological knowledge suggest that TAMAR's conservation efforts may have contributed to the significant increase in olive ridley nesting in Sergipe and Bahia; that increase is not only of regional importance, but also of significance at the western Atlantic level.

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Female sea turtles rarely have been observed foraging during the nesting season. We investigated the levels of ghrelin, leptin and other physiological and nutritional parameters in nesting hawksbill sea turtles in Brazil. We found that levels of serum leptin (appetite-suppressing protein) decreased over the nesting season, while an increasing trend was observed in ghrelin (hunger-stimulating peptide). Both findings are consistent with the prediction that post-nesting females will begin to forage after the nesting season, , either during or just after their post-nesting migration.

Data on hawksbill Eretmochelys imbricata migratory patterns are virtually unknown for nesting populations in the South Atlantic Ocean. The most significant nesting ground for hawksbills in the South Atlantic is located in Brazil, specifically in the northern state of Bahia. From February to March 2005, 15 adult female hawksbills were equipped with satellite transmitters on beaches of northern Bahia. During the internesting period, satellite-tracked hawksbills remained in the coastal waters of northern Bahia for 12 to 60 d before embarking on their postnesting migrations. Internesting areas occupied by the turtles varied between 43.1 and 447.9 km 2 . Turtles' postnesting migrations were performed mostly over the continental shelf: 5 headed south, and 8, north. Results from genetic analyses of tracked turtles showed that 6 of the individuals, characterized morphologically as hawksbills, were actually hawksbill-loggerhead hybrids. Foraging destinations of hawksbills were situated along the eastern coast of Brazil (9 to 17.5°S). Conversely, except for 1 hybrid that stayed along the eastern coast, hybrid turtles migrated to distant foraging areas located on the northern coast of Brazil (0 to 5°S). Foraging home range areas of satellite-tracked turtles ranged from 225.7 to 2192.3 km 2 , and there were no significant differences in size between areas used by hawksbills and those used by hybrids. The location of hawksbill foraging areas partially overlapped with established marine protected areas (MPAs) distributed along the main reef areas in Brazil. These results underscore the importance of strengthening MPA monitoring and enforcement to protect critical hawksbill habitats in Brazil.

In the South Atlantic Ocean, few data exist regarding the dispersal of young oceanic sea turtles. We characterized the movements of laboratory-reared yearling loggerhead turtles from Brazilian rookeries using novel telemetry techniques, testing for differences in dispersal during different periods of the sea turtle hatching season that correspond to seasonal changes in ocean currents. Oceanographic drifters deployed alongside satellite-tagged turtles allowed us to explore the mechanisms of dispersal (passive drift or active swimming). Early in the hatching season turtles transited south with strong southward currents. Late in the hatching season, when currents flowed in the opposite direction, turtles uniformly moved northwards across the Equator. However, the movement of individuals differed from what was predicted by surface currents alone. Swimming velocity inferred from track data and an ocean circulation model strongly suggest that turtles' swimming plays a role in maintaining their position within frontal zones seaward of the continental shelf. The long nesting season of adults and behaviour of post-hatchlings exposes young turtles to seasonally varying ocean conditions that lead some individuals further into the South Atlantic and others into the Northern Hemisphere. Such migratory route diversity may ultimately buffer the population against environmental changes or anthropologic threats, fostering population resiliency.

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