Dispersal patterns of male loggerhead turtles Caretta caretta from a high-latitude summer foraging ground in the North Pacific

Knowledge of the spatiotemporal distribution of sea turtles has been biased toward adult females because males are less accessible for research. Male loggerhead turtles Caretta caretta in the North Pacific are particularly understudied. A recent study found a male-biased sex ratio in this species at a high-latitude, summer-restricted foraging ground (39°N) in the Sanriku coastal area, northeastern Japan. To describe the movement patterns of males, we satellite-tracked 16 juvenile- and adult-sized males and putative males (straight carapace length: 56.3-88.9 cm) released from the Sanriku coastal area between 2009 and 2017. All turtles moved into low-latitude habitats around 30°N in winter and remained mainly in waters south of 35°N until April. Subsequently, turtles tracked until the following summer (n = 6) began northward migration during May and June, and remained in high-latitude coastal and oceanic habitats (37-42°N) in summer. These results suggest that males may benefit from the nutrient-rich, high-latitude foraging grounds, including the Sanriku coastal area, regardless of their growth stage or reproductive status. Our study highlights the importance of comparative studies for understanding the significance of high-latitude foraging grounds for male loggerhead turtles across the North Pacific population.