Navigation of Sea Turtles - PowerPoint PPT Presentation

1 / 16
About This Presentation

Navigation of Sea Turtles


Special adaptations for life at the sea -large shells for protection ... A turtle usually spends about 5 to 7 years circling the Sargasso Sea. ... – PowerPoint PPT presentation

Number of Views:389
Avg rating:3.0/5.0
Slides: 17
Provided by: earlyacti


Transcript and Presenter's Notes

Title: Navigation of Sea Turtles

Navigation of Sea Turtles
  • Christina Ryder
  • Herpetology
  • January 24, 2003

A Little bit about sea turtles
  • from the families Chelonidae Dermochelyidae
  • - caretta caretta (loggerhead sea turtle)
  • -chelonia mydas (green sea turtle)
  • -eretmochelys imbricata (hawksbill sea
  • -dermochelys coriacea (leatherback sea
  • -lepidochelys kempi (Kemps ridley sea turtle)

  • Loggerhead sea turtle
  • Green sea turtle?

Hawksbill sea turtle ?
?Leatherback sea turtle Kemps ridley sea turtle?
and a little more
  • Special adaptations for life at the sea
  • -large shells for protection
  • -tough keratinous beak to bite
  • -modification of limbs to flippers for

The great journey
from the beginning
  • Hatchlings must leave the nest to safely get to
    the sea to find food, shelter, and warm water

So how do they do it?
  • They must rely on the reflection of the moon and
    stars on the ocean, the downward slope of the
    beach, and the lack of vegetation to get them to
    the sea

Then, Its off to the Gulf Stream
  • Once in the water, the baby turtles must find the
    current of the North Atlantic gyre. For as long
    as possible, the turtle swims against the waves,
    away from the coast. They also use the direction
    of the waves to set their compasses for future

Staying in the gyre
  • For the rest of its life, except time to lay
    eggs, the turtle will remain in the gyre, relying
    on the waters to provide food and warmth.
  • A turtle usually spends about 5 to 7 years
    circling the Sargasso Sea.
  • Getting off-course is deadly. The turtle must
    turn south or else the current will carry him or
    her to the frigid waters of England.

So, how do they do it?
  • By using their internal compass and magnetic
    inclinations to sense the angles created by the
    magnetic field.
  • By sensing the slight change of angle, the turtle
    is able to make the correct turns to follow the
    current to stay alive.
  • 57? ? Florida beach
  • 60?? Gulf of Portugal

So, how does it work?
  • The earth has a magnetic field best described as
    lines of magnetic force that flow around the
    planet from the magnetic South Pole to the North
  • Turtles brains contain the magnetic mineral
    magnetite used for detection and orientation.

And then they return
  • When the female is mature and is ready to lay
    eggs, she returns to the very beach at which she
    was hatched.
  • She digs a hole, lays her eggs, and then returns
    to the ocean.

How does she get there?
  • By swimming , of course!

But how does she know where to go?
  • In addition to a sense of direction and guidance
    by their magnetic inclinations, sea turtles have
    map-sense. (They remember the relativeness of
    one location to another.)

and the whole journey starts over again
  • the loggerhead migration picture mow looks like
    this Hatchlings emerge from their beachfront
    nests at night and head toward the bright light
    coming off the ocean, setting their magnetic
    compasses. Once in the water, they swim directly
    into the waves. Swimming into the waves keeps
    the youngsters heading away from the coast. When
    they hit the Gulf Stream, they ride the current,
    relying on their magnetic inclination compasses
    to tell them when to turn and head south for the
    Sargasso Sea. Then, in late adolescence, they
    find the magnetic inclination angle of the
    Florida beaches and ride it home.

-according to Kenneth Lohmann
  • Reptiles and Amphibians. Roger Conant/ Joseph
    T. Collins ed. Houghton Mifflin Company, 1998.
  • Sea Turtles Master Migration with Magnetic
    Memories. Science. April 29, 1994 v264 n5159
Write a Comment
User Comments (0)