Meeting Abstract
Sea turtles and salmon are iconic long-distance ocean migrants with extraordinary navigational abilities. Both groups of animals have been hypothesized to complete long-distance reproductive migrations by sequentially using two different suites of mechanisms, each of which functions over a different spatial scale. For salmon, evidence indicates that magnetic cues guide fish into the vicinity of their home rivers, after which olfactory cues lead them upstream to the spawning grounds. For sea turtles, individuals that nest on continental coastlines may be able to reach nesting areas using magnetic cues alone, but for those that nest on small, remote islands, the gradual change in Earth’s magnetic field probably precludes relying exclusively on magnetic navigation. An interesting example involves green turtles that nest on Ascension Island, a tiny land mass located 2000 km from the turtles’ foraging grounds along the coast of Brazil. One possibility is that turtles use magnetic cues to arrive in the vicinity of the island, then use olfactory cues to pinpoint its location. To investigate, we used oceanic, atmospheric, and geomagnetic models to assess whether magnetic and chemical cues might plausibly be used by turtles to locate Ascension Island. Results suggest that either cue alone is unlikely to enable turtles to reach the island, but using the two together can potentially provide a successful navigational strategy. These findings are consistent with the hypothesis that sea turtles, and perhaps other marine animals, use a multi-modal navigational strategy when migrating long distances to remote islands.
