Orientation
and Navigation of Sea Turtles
Long-distance
migrations
of animals represent one of the great wonders of the natural world. In the marine environment, migratory movements
sometimes reach astonishing extremes: for example, some sea turtles,
salmon,
sharks, and elephant seals travel distances that exceed the width of
oceans
before returning to their home areas to reproduce.
How animals find their way during such migrations has remained a
central mystery of sensory and behavioral biology.
Sea
turtles are among the most impressive navigators
in the animal kingdom. As hatchlings, turtles that have never before
been in
the ocean are able to establish unerring courses towards the open sea
and then
maintain their headings after swimming beyond sight of land.
Young
turtles follow complex migratory pathways that often lead across
enormous
expanses of seemingly featureless ocean. After completing their years
in the
open sea, juvenile turtles take up residence in coastal feeding grounds
and
show great fidelity to their feeding sites, homing back to specific
locations
after long migrations and experimental displacements. Similar
navigational abilities exist in adult turtles, which migrate
considerable
distances between specific feeding areas and nesting beaches.
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Top left: a hatchling green
turtle (photo by Ken Lohmann, Univ. North |
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The longest and most spectacular
migrations are
made by young loggerhead turtles. The journey begins when the
hatchlings, each
no bigger than a child's hand, dig their way out of their underground
nests on
the beach and enter the sea. During the vast migration that follows,
turtles
travel for a period of years along migratory routes that span entire
oceans.
Young loggerheads in the
How can young sea turtles with no prior migratory experience guide
themselves
across an entire ocean and back? Considerable progress has been made
toward
understanding how young loggerheads in the
Hatchlings embark on an impressive
transoceanic migration, but they do not navigate to targets more
specific than
broad oceanic regions. In contrast, older turtles acquire an
ability to
pinpoint specific geographic locations such as feeding areas and
nesting
beaches. Recent experiments have demonstrated that sea turtles
possess a remarkable ability to exploit positional information in the
Earth's
magnetic field as a kind of navigational map that can be used to guide
movements toward
specific goals. To
learn about this research, follow the magnetic
map links.
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Much of the research presented in these web pages was made possible by grants from the National Science Foundation. |
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Last revised 24 September 2010