Uncovering loggerhead (
            <i>Caretta caretta</i>
            ) navigation strategy in the open ocean through the consideration of their diving behaviour

Laforge, Antoine; Gaspar, Philippe; Barat, Anne; Boyer, Julien Temple; Candela, Tony; Bourjea, Jérôme; Ciccione, Stéphane; Dalleau, Mayeul; Ballorain, Katia; Monsinjon, Jonathan R.; Bousquet, Olivier

doi:10.1098/rsif.2023.0383

Cited by 3 publications

(1 citation statement)

References 63 publications

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“…Today, these technologies have become a fundamental tool for studying the movement and spatial ecology of marine species [ 5 ], with thousands of devices deployed each year [ 6 ]. They allow for relatively accurate long-term tracking of marine animal migrations and can provide insights into a variety of other knowledge gaps, including habitat use at the scale of entire oceans [ 7 ], navigation mechanisms [ 8 , 9 , 10 ], and faced threats and risks [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

Novel Microsatellite Tags Hold Promise for Illuminating the Lost Years in Four Sea Turtle Species

Candela,

Wyneken,

Leijen

et al. 2024

Animals

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After hatching, sea turtles leave the nest and disperse into the ocean. Many years later, they return to their natal coastlines. The period between their leaving and their returning to natal areas, known as the “Lost Years”, is poorly understood. Satellite tracking studies aimed at studying the “Lost Years” are challenging due to the small size and prolonged dispersal phases of young individuals. Here, we summarize preliminary findings about the performance of prototype microsatellite tags deployed over a three-year period on 160 neonate to small juvenile sea turtles from four species released in the North Atlantic Ocean. We provide an overview of results analyzing tag performance with metrics to investigate transmission characteristics and causes of tag failure. Our results reveal that, despite certain unfavorable transmission features, overall tag performance was satisfactory. However, most track durations were shorter than those observed on individuals of similar size in other studies and did not allow for detailed analyses of trajectories and turtle behavior. Our study further suggests that tracking durations are correlated with the targeted species, highlighting a lack of robustness against some neritic behaviors. Unprecedented diving data obtained for neonate sea turtles in this study suggest that the vertical behaviors of early juveniles are already too strenuous for these miniaturized tags. Our findings will help to inform the biologging research community, showcasing recent technological advances for the species and life stages within our study.

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Section: Introductionmentioning

confidence: 99%

Novel Microsatellite Tags Hold Promise for Illuminating the Lost Years in Four Sea Turtle Species

Candela,

Wyneken,

Leijen

et al. 2024

Animals

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Uncovering loggerhead ( Caretta caretta ) navigation strategy in the open ocean through the consideration of their diving behaviour

Laforge,

Gaspar,

Barat

et al. 2023

J. R. Soc. Interface.

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While scientists have been monitoring the movements and diving behaviour of sea turtles using Argos platform terminal transmitters for decades, the precise navigational mechanisms used by these animals remain an open question. Until now, active swimming motion has been derived from total motion by subtracting surface or subsurface modelled ocean currents, following the approximation of a quasi-two-dimensional surface layer migration. This study, based on tracking and diving data collected from 25 late-juvenile loggerhead turtles released from Reunion Island during their pre-reproductive migration, demonstrates the importance of considering the subsurface presence of the animals. Using a piecewise constant heading model, we investigate navigation strategy using daily time-at-depth distributions and three-dimensional currents to calculate swimming velocity. Our results are consistent with a map and compass strategy in which swimming movements follow straight courses at a stable swimming speed (approx. 0.5 m s −1 ), intermittently segmented by course corrections. This strategy, previously hypothesized for post-nesting green and hawksbill turtles, had never been observed in juvenile loggerheads. These results confirm a common open-ocean navigation mechanism across ages and species and highlight the importance of considering diving behaviour in most studies of sea turtle spatial ecology.

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Post-nesting migrations of green turtles from Aldabra Atoll, Seychelles: satellite tracking, flipper tag returns and marine protected areas

Richards,

Sanchez,

Haupt

et al. 2024

Endang. Species. Res.

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To effectively implement protective measures for migratory species such as marine turtles, knowledge of their breeding grounds, foraging areas, migratory pathways and possible threats encountered is required. Aldabra Atoll, a UNESCO World Heritage site in Seychelles, hosts and protects one of the largest nesting populations of green turtles Chelonia mydas in the Western Indian Ocean. We satellite tracked 21 post-nesting green turtles during 2011-2014 (n = 8) and in 2022 (n = 13). Nineteen turtles were tracked beyond Aldabra and took 8-49 d to reach their final recorded locations, travelling 743-2552 km along distinct routes, each taking a unique path to widely dispersed coastal sites in Tanzania, Madagascar, Somalia, Kenya, Mozambique and Seychelles, highlighting the connectivity of the region through one large rookery. When compared to the locations of 54 international flipper tag returns from Aldabra females recorded since the 1980s, there was consistency in the use of Tanzania, Kenya, Mozambique, Somalia and Madagascar as foraging destination countries for Aldabra turtles. However, satellite tracking expanded the countries used as foraging sites to include Seychelles and elevated the relative importance of remote sites for which fishermen were unlikely to report intercepted flipper tags—especially Somalia, northern Madagascar and distant offshore foraging habitat within Seychelles. The end points for >40% of the turtles were within or nearby marine protected areas (MPAs) in Madagascar, Mozambique, Tanzania and Seychelles, 5 (26.3%) within MPAs and 3 (15.8%) <25 km away from MPAs. Eleven (57.9%) turtles travelled through MPAs after leaving the Aldabra protected zone. There is further opportunity to increase the protection and connectivity of foraging areas by expanding existing MPAs. Identifying foraging hot spots within the region by pooling data from other important breeding grounds should be a priority to focus conservation efforts on migratory corridors and the status and state of those foraging areas.

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Uncovering loggerhead ( Caretta caretta ) navigation strategy in the open ocean through the consideration of their diving behaviour

Cited by 3 publications

References 63 publications

Novel Microsatellite Tags Hold Promise for Illuminating the Lost Years in Four Sea Turtle Species

Novel Microsatellite Tags Hold Promise for Illuminating the Lost Years in Four Sea Turtle Species

Uncovering loggerhead ( Caretta caretta ) navigation strategy in the open ocean through the consideration of their diving behaviour

Post-nesting migrations of green turtles from Aldabra Atoll, Seychelles: satellite tracking, flipper tag returns and marine protected areas

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