Satellite tracking of hawksbill turtles Eretmochelys imbricata nesting in northern Bahia, Brazil: turtle movements and foraging destinations

Abstract

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.

Evaluating the importance of Marine Protected Areas for the conservation of hawksbill turtles Eretmochelys imbricata nesting in the Dominican Republic

“…Core activity areas occurred in shallow waters (< 200 m) and were associated with coral reefs. Our results support previously described hawksbill internesting spatial behaviour observed in other internesting areas throughout the Caribbean (van Dam et al 2008, Marcovaldi et al 2012, Walcott et al 2012). Although we did not record diving depth, it appears turtles were likely to have been making shallow dives; indeed, hawksbill turtles probably exhibit shallow diving behaviour throughout the year (Storch et al 2005, Blumenthal et al 2009).…”

“…Numerous studies have suggested the key role of this species in maintaining the structure, ecology and evolution of coral reefs (León & Bjorndal 2002, Bjorndal & Jackson 2003. During the nesting season, which usually spans several months, females return repeatedly to the same beach to lay a variable number of clutches (Allen et al 2010, Marcovaldi et al 2012, Walcott et al 2012, Phillips et al 2013, similar to that documented for other marine turtle species. However, some populations of marine turtles remain within 100 m of the nesting beaches between nesting attempts (green turtles Chelonia mydas on Ascension Island; Hays et al 1999), while others may travel up to 100 km from the nesting beach to alternative sites (loggerhead turtles Caretta caretta in Greece; Schofield et al 2010).…”

Nuclear markers reveal a complex introgression pattern among marine turtle species on the Brazilian coast

“…The observation of hybrids introgressed with either parental species raises the possibility that hybrid individuals could display behavioural differences which could lead to divergent mating preferences, some tending to mate with E. imbricata and others with C. caretta . This behavioural difference was already observed among some of these hybrids found along the Brazilian coast where individuals exhibited different pattern of migrations in relation to either parental species (Marcovaldi et al. 2012, see details below).…”

Paper-efficient multi-species conservation and management are not always field-effective: The status and future of Western Indian Ocean leatherbacks

“…Their internesting loops tend to be more like directional trajectories that can extend well offshore, typical of what might be expected for a pelagic drifter, and consequently are associated with much longer tracks and faster swimming speeds than those observed for loggerheads. Given these vast differences in behaviour and resulting internesting home ranges, loggerheads, and other hard-shell turtles (Maxwell et al, 2011;Blanco et al, 2013;Marcovaldi et al, 2012), are much easier to encompass in MPAs during this critical life history stage than are leatherbacks (Witt et al, 2008).…”