![]() ![]() ![]() While all these approaches have produced major advances in our knowledge, they all provide only integrated measures of processes occurring during migration and do not reveal any intricacies of temporal patterns within migration. These deep dives may have evolved to reduce silhouetting against the surface, which would make turtles more susceptible to visual predators such as large sharks. These results suggest that green turtles crossing the Atlantic do not behave invariantly, but instead alternate between periods of travelling just beneath the surface and diving deeper. TDRs revealed that much of the time was spent conducting short (2–4 min), shallow (approximately 0.9–1.5 m) dives, consistent with predictions for optimisation of near-surface travelling, while long (typically 20–30 min), deep (typically 10–20 m) dives had a distinctive profile found in other marine reptiles. Satellite telemetry revealed that most submergences were short (20 min), particularly at night. ![]() Satellite telemetry was used to record the submergence duration of green turtles ( Chelonia mydas) as they migrated from Ascension Island to Brazil ( N=12 individuals) while time/depth recorders (TDRs) were used to examine the depth distribution and dive profiles of individuals returning to Ascension Island to nest after experimental displacement ( N=5 individuals). ![]()
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