Demystifying the “Lost Years”

Research into the early years of a sea turtle after it emerges from the nest and swims into the ocean has always been difficult. Because of their small size, they cannot be reliably monitored through aerial surveys. Also, until recently, making satellite tags that are small and lightweight for juveniles yet rugged enough for ocean environments has also been a challenge. That’s why this early stage of a sea turtle’s life cycle has commonly been referred to as the “lost years” because there has been little scientific data on their movements and habitat use.

For many years, it’s been assumed that the hatchlings of several species of sea turtle spend the first few years of their lives drifting with the ocean currents. Now, new research of wild-caught juveniles in the Gulf of Mexico has provided evidence which contradicts the long-held assumptions about the early lives of sea turtles. In “New insights on sea turtle behavior during the ‘lost years’”, authors Katrina Phillips (UCF Marine Turtle Research Group (MTRG)), Nathan Putman (LGL Ecological Research Associates), and Kate Mansfield (UCF MTRG) tracked 79 green, 26 Kemp’s ridley, 5 loggerhead and 4 hawksbill juveniles using satellite tags. After analyzing the data collected between 2011 and 2022, they discovered that the young sea turtles actively swim (not just drift) and move from the open ocean (over 200 meters deep) to shallower continental shelf waters (less than 200 meters).

Based on their findings, the authors recommend that sea turtle life-stage terminology be changed from place-based to behavioral definitions. So, instead of calling a sea turtle’s early years as an “oceanic stage,” they suggest renaming it a “dispersal stage.” Additionally, this research shows that the West Florida Shelf is an important habitat for juveniles in the Gulf of Mexico which may require updates to conservation management strategies for that area.

Included in this new study is the largest set of data on the behavior of wild-caught juveniles. It also includes the first satellite tracks for wild-caught hawksbill and loggerhead juveniles. Furthermore, since this study focused on juvenile sea turtles in the Gulf of Mexico, the authors recommended that additional research is needed to better understand how young sea turtles navigate the currents in different ocean bodies.

Sources:

• AP News: “Scientists solve the mystery of sea turtles’ ‘lost years’”
• Proceedings of the Royal Society B: “New insights on sea turtle behavior during the ‘lost years’”