New insights on sea turtle behavior during the ‘lost years’

Several marine turtle species spend their first years of life in oceanic
habitats. This early life stage is referred to as the “lost years” due to
the difficulty of accessing individuals for study offshore. We satellite
tracked 114 wild-caught juvenile turtles (straight carapace lengths
12.3-29.9 cm) from the Gulf of Mexico between 2011-2022 to investigate
“lost years” movements with respect to traditional definitions assigned to
the life stage. Satellite-tracked turtles included 79 green turtles
(Chelonia mydas), 26 Kemp’s ridleys (Lepidochelys kempii), 5 loggerheads
(Caretta caretta), and 4 hawksbills (Eretmochelys imbricata). Many tracked
turtles transited between oceanic (>200 m depth) and neritic waters
(<200 m depth), challenging the assumption that this life stage is
exclusively found in oceanic habitats. Turtle movements differed
from oceanographic surface drifters, providing further evidence that sea
turtles of this life stage do not exclusively drift with currents. We
recommend redefining the “oceanic stage“ as a “dispersal stage“ to better
reflect their behavior and habitat plasticity. Our findings establish the
West Florida Shelf as a high-use area, particularly among green turtles
and Kemp’s ridleys. The northeastern Gulf of Mexico is an important region
for these species of conservation concern.