Title: Direct Evidence of Swimming Demonstrates Active Dispersal in the Sea Turtle “Lost Years”
Abstract: Although oceanic dispersal in larval and juvenile marine animals is widely studied, the relative contributions of swimming behavior and ocean currents to movements and distribution are poorly understood [1Largier J. Considerations in estimating larval dispersal distances from oceanographic data.Ecol. Appl. 2003; 13: S71-S89Crossref Google Scholar, 2Hill A.E. A mechanism for horizontal zooplankton transport by vertical migration in tidal currents.Mar. Biol. 1991; 111: 485-492Crossref Scopus (70) Google Scholar, 3Staaterman E. Paris C.B. Helgers J. Orientation behavior in fish larvae: a missing piece to Hjort’s critical period hypothesis.J. Theor. Biol. 2012; 304: 188-196Crossref PubMed Scopus (88) Google Scholar, 4Young C.M. He R. Emlet R.B. Li Y. Qian H. Arellano S.M. Van Gaest A. Bennett K.C. Wolf M. Smart T.I. Rice M.E. Dispersal of deep-sea larvae from the intra-American seas: simulations of trajectories using ocean models.Integr. Comp. 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Here, we use an experimental approach designed to directly test the passive-migration hypothesis by deploying pairs of surface drifters alongside small green (Chelonia mydas) and Kemp’s ridley (Lepidochelys kempii) wild-caught turtles, tracking their movements via satellite telemetry. We conclusively demonstrate that these turtles do not behave as passive drifters. In nearly all cases, drifter trajectories were uncharacteristic of turtle trajectories. Species-specific and location-dependent oriented swimming behavior, inferred by subtracting track velocity from modeled ocean velocity, contributed substantially to individual movement and distribution. These findings highlight the importance of in situ observations for depicting the dispersal of weakly swimming animals. Such observations, paired with information on the mechanisms of orientation, will likely allow for more accurate predictions of the ecological and evolutionary processes shaped by animal movement.