Magnetic navigation behavior and the oceanic ecology of young loggerhead sea turtles

Abstract

During long-distance migrations, animals navigate using a variety of sensory cues, mechanisms and strategies. Although guidance mechanisms are usually studied under controlled laboratory conditions, such methods seldom allow for navigation behavior to be examined in an environmental context. Similarly, although realistic environmental models are often used to investigate the ecological implications of animal movement, explicit consideration of navigation mechanisms in such models is rare. Here, we used an interdisciplinary approach in which we first conducted lab-based experiments to determine how hatchling loggerhead sea turtles (Caretta caretta) respond to magnetic fields that exist at five widely separated locations along their migratory route, and then studied the consequences of the observed behavior by simulating it within an ocean circulation model. Magnetic fields associated with two geographic regions that pose risks to young turtles (due to cold wintertime temperatures or potential displacement from the migratory route) elicited oriented swimming, whereas fields from three locations where surface currents and temperature pose no such risk did not. Additionally, at locations with fields that elicited oriented swimming, simulations indicate that the observed behavior greatly increases the likelihood of turtles advancing along the migratory pathway. Our findings suggest that the magnetic navigation behavior of sea turtles is intimately tied to their oceanic ecology and is shaped by a complex interplay between ocean circulation and geomagnetic dynamics.

DNA and dispersal models highlight constrained connectivity in a migratory marine megavertebrate

“…Limited temporal variation, however, contrasts with observed ocean current variability. Recent modeling studies suggest that directional swimming can significantly dampen effects of variable ocean currents on animal trajectories (Putman et al ), further supporting our hypothesis that swimming behavior is responsible for discordance between genetic and ocean modeling connectivity estimates.…”

“…Newly available and state‐of‐the‐art bioinformatic tools are uncovering fundamental and previously obscured aspects of population structure, history, and spatial distribution. High‐resolution ocean circulation models and advanced experiments have shed light on mysteries of marine animal movements, including geomagnetic orientation by salmon and sea turtles (Putman et al , , ), and larval retention in reef fishes despite the potential for extensive dispersal (Cowen et al , Staaterman and Paris ). The genomics field is booming as cutting‐edge technology enables faster and expanded gene sequencing at lower cost.…”

“…The classic hypothesis is that small turtles drift with the currents for several years before recruiting to coastal feeding grounds, or FGs (Carr ). Recently, high resolution ocean circulation models have begun to simulate the movements of ‘lost years’ turtles under a range of behavioral scenarios, many of which question the preponderance of passive drift (Gaspar et al , Putman et al , , , Putman and He , Putman and Naro‐Maciel , Naro‐Maciel et al , Putman and Mansfield ). A case study from Palmyra Atoll (Central Pacific), for example, revealed pronounced differences between genetic and ocean connectivity estimates, suggesting that many pelagic turtles were retained in the Eastern Pacific (Naro‐Maciel et al ).…”

Does behaviour affect the dispersal of flatback post-hatchlings in the Great Barrier Reef?

“…The use of sound or olfactory cues remains unknown. Thus, our understanding of the early dispersal of flatback turtles would be greatly enhanced by experimentally testing the orientation of hatchlings as a response to wind-driven waves, smell/sound plumes or magnetic fields [33,80,83], or directly tracking neonates with satellite or acoustic tags [18]. …”

Paper-efficient multi-species conservation and management are not always field-effective: The status and future of Western Indian Ocean leatherbacks

“…It would also mean that the prevailing currents during hatching could determine the relative proportion of animals that would ultimately be pelagic drifters that could be more susceptible to capture in offshore fisheries, a threat which has the potential to collapse entire populations (Spotila et al, 2000). We also acknowledge, however, that there may be an additional genetic role that may predetermine whether hatchlings are coastal clingers or ocean rovers, e.g., some form of inherited navigation and/or response to geomagnetic fields (Putman et al, 2015).…”