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

Simple Summary Observing juvenile sea turtles at sea is challenging due to their small sizes and cryptic behaviors and is compounded by the vastness of the ocean. The first phases of sea turtle life history, commonly known as the "Lost Years", remain enigmatic and poorly understood, despite significant advances in animal ad ocean observation technologies. Our study focused on testing new prototypes of microsatellite tags and analyzing their performance on 160 juvenile sea turtles of four species in the North Atlantic. The results demonstrated that, despite challenges brought by miniaturization, the tags proved effective. However, the tracking periods were shorter than expected, limiting our ability to deeply study and understand the turtles' dispersal features. We found that tracking durations varied among species, indicating some limitations due to certain behaviors such as neritic interactions or diving activity by young sea turtles, and revealing that some of their behaviors may be too strenuous for small tags. Our findings have important implications for the bio-logging community, especially those studying marine animals such as sea turtles. Our study showcases recent technological advances and contributes to improving the effectiveness and durability of miniaturized satellite tags deployed within the marine environment. Our methodologies and findings have improved our understanding of the "Lost Years", promise to inform ongoing future technological advances and contribute to increasing the effectiveness of conservation efforts.Abstract 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.