Hybridization is a fundamental evolutionary and ecological process with significant conservation ramifications. Sea turtle hybridization occurs at unusually high frequencies along the northeastern coast of Brazil. To better understand the process, we studied the reproductive output, migration patterns (through satellite telemetry), and isotopic niches of loggerhead turtles Caretta caretta and olive ridley turtles Lepidochelys olivacea and their hybrids. We classified 154 nesting females as loggerhead (n = 91), olive ridley (n = 38), or hybrid (n = 25) based on mitochondrial and nuclear DNA. Further, we compared nesting female morphological data and reproductive parameters (clutch size, emergence success, hatchling production, incubation period) of 405 nests among hybrids and parental species. We found no significant differences among the 3 groups when hatchling production was corrected for female body size, indicating that hybrids and parental species produce similar numbers of hatchlings per clutch. Satellite tracking of 8 post-nesting hybrid females revealed shared foraging grounds with both parental species, as well as neritic migrations between foraging and nesting areas similar to those previously reported for loggerheads and olive ridleys. Analyses of 13C and 15N isotope values (n = 69) further confirmed this pattern, as hybrid isotopic niches overlapped extensively with both parental species. Thus, given the similarities presented between hybrids and their parental species in reproductive, ecological, and behavioral characteristics, we conclude that these hybrids may persist along with other sea turtle nesting populations in the area, with research and conservation implications.
Olive ridley sea turtles display two different types of nesting behavior: in arribada (synchronous mass nesting) or solitarily. Contrarily to arribadas, little has been published about solitary nesters. This study aimed to expand the knowledge on internesting interval and site fidelity of solitary nesting olive ridleys and to test a possible development of arribada nesting behavior. Data were collected in Sergipe (Brazil) over 125 km of beach from 10°30 0 S/ 36823 0 W to 11°26 0 S/37819 0 W, between nesting seasons 2004/2005 and 2006/2007. From 962 tagged females, 173were seen renesting. The average internesting interval found was longer (22.35 ± 7.01 days) than previously described, which might relate to lower water temperatures during the internesting period. Olive ridleys at Sergipe showed high nesting site fidelity, with consecutive nesting events occurring in close proximity, non-randomly and dependently of previous events. Most of the consecutive nests were separated by 4.06-5.59 km. Development of arribada nesting behavior was not confirmed.
The states of Sergipe and Bahia comprise the main nesting beaches for olive ridley sea turtles Lepidochelys olivacea in Brazil. Between February 2014 and March 2015, 40 L. olivacea were equipped with Argos platform transmitter terminal tags. A state-space model was applied to Argos location data to investigate the animals' spatial ecology and identify areas of restricted movements (ARMs) and directional movements. The inter-nesting ARMs included the continental shelf from the south of Alagoas state to the north of Bahia, totaling 7244 km 2 (kernel density estimation, 90% isopleth) and generally extended up to 22 km from the coast or to the 50 m isobath. The post-nesting directional movements were classified as either (1) neritic north/ northeastern (N/NE) Brazil to French Guiana (n = 4 turtles), (2) neritic south/southeastern (S/SE) Brazil (n = 16), or (3) oceanic (n = 19) from Brazil to West Africa. ARMs consistent with foraging areas were identified for 24 olive ridleys: 15 along the continental shelf of SE Brazil, 2 adjacent to Ceará and Maranhão states (between the 25 and 75 m isobaths), and 7 off the African countries of Cape Verde, Senegal, Gambia, Guinea-Bissau, and Sierra Leone. The results de monstrated the complexity of olive ridley movements from northern Brazil, raised questions about connectivity, and highlighted threats such as fisheries, ports, and hydrocarbon exploration fields overlapping with, or near to, high-use areas. These results can be used as a basis for spatial management measures to protect this endangered species.
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