Satellite Tracking the Sea Turtle "Lost Years"

Using small, solar-powered satellite tags and novel tag attachment methods, we satellite tracked 17 neonate loggerhead sea turtles from their natal beaches in the western Atlantic. Young loggerheads are known to associate with epipelagic Sargassum for food and shelter; however, the thermal benefits of associating with surface habitats have not been considered. The first satellite tracks of neonate loggerheads in the Atlantic revealed a thermal disconnect between predicted (satellite- and model-derived) sea surface temperatures and ambient temperatures recorded by the satellite transmitters. Tag charge rates and Argos location accuracy codes both suggest that these neonate turtles spent most of their time at the sea surface. We measured the solar reflectivity of satellite tags, turtle shells, Sargassum spp. specimens, and seawater to determine whether the observed difference between ambient and predicted temperatures could be explained by differences in solar reflectivity among these different materials. Our results show that the average 6 degree C difference is likely due to surface-based habitat use and solar absorption. This surface-based habitat selection provides oceanic stage turtles with a thermal refuge that promotes growth and temperature-dependent processes such as feeding, suggesting an evolutionary mechanism that supports the survival of young, heterothermic reptiles in the open ocean.