Minutes after emerging from underground nests, hatchling green turtles
(Chelonia my das L.) enter the sea and begin a migration towards the open ocean.
To test the hypothesis that migrating hatchlings use wave cues to maintain their
seaward headings, we released turtles offshore during unusual weather conditions
when waves moved in atypical directions. Hatchlings swam into approaching
waves in all experiments, even when doing so resulted in orientation back towards
land. These data suggest that green turtle hatchlings normally maintain seaward
headings early in the offshore migration by using wave propagation direction as an
orientation cue. Because waves and swells reliably move towards shore in shallow
coastal areas, swimming into waves usually results in movement towards the open
sea.
The physiological mechanisms that underlie wave detection by sea turtle
hatchlings are not known. Calculations indicate that, at the depth at which
hatchlings swim, accelerations produced beneath typical waves and swells along
the Florida coast are sufficient to be detected by the vertebrate inner ear. We
therefore hypothesize that hatchlings determine wave direction while under water
by monitoring the sequence of horizontal and vertical accelerations that occur as
waves pass above
