| Clipped from: Lohmann |
Sea Turtles
"Turtle Positioning System" helps reptiles on fantastic voyage
"There's no off-the-shelf Speedo turtle bathing suit that we know about," laughed biologist Ken Lohmann, as he attached a soft cloth harness, or bathing suit, to a three-month-old loggerhead turtle.
About a dozen of these young turtles "work" in Lohmann's University of North Carolina (UNC) laboratory. With help from the National Science Foundation (NSF), he's learning how these and other sea turtles use the Earth's magnetic field for a journey of thousands of miles around the Atlantic Ocean.
| Clipped from: Lohmann Lab |
| Clipped from: Sea Turtle Navigation |
Orientation and Navigation of Sea Turtles
Top left: a hatchling green turtle (photo by Ken Lohmann, Univ. North Carolina
| Clipped from: Sea-Finding by Hatchling Sea Turtles |
SEA-FINDING BY HATCHLING SEA TURTLES
Given that hatchling sea turtles appear to use local visual cues to find the ocean, what environmental cues are available that might lead turtles toward the sea?
Several different possibilities are listed below.
- Towards land, the dunes and associated vegetation form a dark silhouette. Thus, the seaward horizon is LOWER than the landward horizon.
- Water reflects more light than land; thus, more ambient light is reflected from the ocean, making that region brighter.
- The beach slopes down in the direction of the water; thus, going downhill would usually lead turtles toward the sea.
- Waves breaking on the sand might provide an auditory cue that hatchlings can use to find the ocean.
| Clipped from: Wave Orientation |
ORIENTATION TO OCEAN WAVES BY SEA TURTLES
Once in the water, sea turtle hatchlings rapidly establish offshore courses that lead them away from land and directly toward the open sea. Moving quickly through coastal waters is crucial to the survival of young turtles, because fish and bird predators are abundant in nearshore waters. How do turtles maintain their orientation during this critical journey? Experiments both in the field and in the lab have revealed that, early in the offshore migration, hatchlings guide themselves seaward by swimming into waves.
| Clipped from: Magnetic Orientation |
Magnetic Orientation
Loggerhead and leatherback hatchlings are known to orient to the Earth's magnetic field, a cue that might potentially provide sea turtles with a way to maintain a heading without relying on waves. The experiments that first demonstrated that sea turtles can detect magnetic fields involved monitoring the directions that turtles swam toward under various magnetic fields in the lab. For these tests, each hatchling was placed into a nylon-Lycra harness as shown below.
Sources:
- nsf.gov - Special Report - Science Nation
- YouTube - Sea Turtles
- Lohmann Lab
- Sea Turtle Navigation
- http://www.unc.edu/depts/oceanweb/turtles/offshr.html
- Sea-Finding by Hatchling Sea Turtles
- Wave Orientation
- Magnetic Orientation
