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Large-scale movements in the oceanic environment identify important foraging areas for loggerheads in central Mediterranean Sea
Full text linkLoggerhead sea turtles (Caretta caretta) are known to display a wide range of movement patterns during the different stages of their life cycle, but empirical information to document this extensive behavioural plasticity is still limited. This is especially true for large, adult-sized individuals, that are thought to mainly forage in neritic areas. In the present paper, eight adult-sized loggerhead turtles were tracked using satellite telemetry to identify the location of their foraging grounds in the seas along the western coast of the Italian peninsula. Tracked turtles mostly stayed in the region between the Italian peninsula and the islands of Sicily and Sardinia, that was reached following quick, directed movements by the turtles from a release site to the north. In this area, two turtles took up residence in spatially limited neritic sites along the coast, while the remaining six alternated circumscribed coastal stays with long-distance, circuitous movements in the oceanic environment. An utilization distribution analysis clearly identified an area, mostly comprising oceanic waters, that was continuously used by turtles in different seasons and years. The present results contribute to the still-limited knowledge of the spatial ecology of loggerheads frequenting the Western Mediterranean Sea and highlight the presence of a potentially important oceanic region in the Southern Tyrrhenian Sea where adult-sized turtles forage for extended periods. These findings increase our knowledge of complex life history traits of loggerhead turtles and provide important information to be considered for evidence-based conservation measures
Long-distance displacement experiments on migrating loggerhead sea turtles (Caretta caretta)
No full textMovements of three loggerhead sea turtles in Tuscany waters
No full textThe coastal waters along Tuscany (Central Italy)
are thought to represent a good foraging ground for loggerhead
turtles (Caretta caretta), especially, but not only, during the
juvenile phase. We describe the movements of three juvenile
loggerheads released along the Tuscany coast after having been
accidentally caught by fishermen and rehabilitated by recovery
centres of the region. The turtles were tracked by satellite for
20-125 days, displaying two main movement patterns. Two
turtles remained in neritic coastal waters for the whole duration
of tracking, while the third one moved north soon after
release, reaching the northern Ligurian Sea with an open-sea
route. These findings show that loggerheads can use Tuscany
waters both as a profitable long-term foraging site and as a
transit area during their movements towards other destinations
Living between widely separated areas: Long-term monitoring of Mediterranean loggerhead turtles sheds light on cryptic aspects of females spatial ecology
Full text linkOver the last decades, satellite tracking techniques have substantially advanced our understanding of sea turtle spatial behaviour, especially for the post-nesting migrations of females. Substantial gaps remains in our knowledge of the turtle behaviour during the remaining inter-reproductive period, that spans over 2–3 years. We report the results of a prolonged tracking experiment on loggerhead turtles nesting along the Ionian Calabria, the main breeding ground in Italy. Argos satellite transmitters were deployed on eight females, a sample representing a substantial fraction of the overall population (20–25 nesting females). All turtles but one were tracked for > 300 days (range: 313–1523 days), revealing their spatial behaviour during a complete reproductive cycle and providing novel information on a number of poorly-known aspects of loggerhead spatial ecology: i) the post-nesting migratory strategy resulted in accordance with that of most adult loggerheads tracked so far, as the nine routes of six turtles were directed towards specific sites all located in the Tunisian continental shelf, a main foraging area for Mediterranean turtles; ii) the pre-breeding migratory routes were rather variable, likely deriving from different navigational strategies adopted by migrating turtles, and their temporal pattern indicates that mating occurred away from the nesting area; iii) the 10 inter-nesting movements of four turtles revealed unusual long-distance loops mostly in oceanic waters (median of maximum distance from nesting location: 145.5 km); iv) while at the foraging grounds, four turtles occupied distinct areas during summer and winter, making directed movements between the two sites, seasonal core areas were separated and their size was larger in winter than in summer (median: 498 km2 vs. 258 km2); v) individual females displayed an high fidelity to both sites in successive years. These findings further highlight the plasticity in loggerhead spatial behaviour and the importance of the Central Mediterranean and of the Tunisian shelf for loggerhead conservation
Influence of ocean currents on long-distance movement of leatherback sea turtles in the Southwest Indian Ocean
No full textProlonged stays in coastal areas of loggerhead turtle (Caretta caretta) in the Tuscany sea
No full text
Influence of oceanic factors on long-distance movements of loggerhead sea turtles displaced in the southwest Indian Ocean
No full textThe routes of five satellite-tracked loggerhead turtles (Caretta caretta), subjected to an experimental translocation away from their usual migratory routes, have been analysed in relation to the concurrent oceanographic conditions. Remote sensing data on sea surface temperature and height anomalies, as well as trajectories of surface drifters were used, to get simultaneous information on the currents encountered by the turtles during their long-range oceanic movements. Turtles mostly turned out to move in the same direction as the main currents, and their routes were often influenced by circulation features they encountered. A comparison between turtle ground speeds with that of drifters shows that in several instances, the turtles did not drift passively with the currents but contributed actively to the overall movement. Two turtles embarked on an oceanic crossing, probably induced by seasonal changes in surface temperatures, a crossing that was largely determined by the main currents existing in the area
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