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Longitude perception and bicoordinate magnetic maps in sea turtles
Nathan F Putman1, Courtney S Endres, Catherine M F Lohmann
1Department of Biology, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA. nathan.putman@gmail.com
Current Biology : CB
|March 1, 2011
Summary
Loggerhead sea turtles use Earth's magnetic field for navigation, sensing both latitude and longitude. This study reveals how these migratory animals can determine their east-west position, a crucial finding for understanding animal navigation.
Area of Science:
- Animal behavior and navigation
- Geophysics and geomagnetism
- Marine biology and conservation
Background:
- Long-distance animal migration often requires awareness of geographic coordinates, including latitude and longitude.
- While magnetic cues are known to help some species determine latitude, the mechanism for perceiving longitude remains largely unknown.
- Traditional magnetic parameters show greater variation along north-south axes, making them seemingly unsuitable for determining east-west positions.
Purpose of the Study:
- To investigate whether hatchling loggerhead sea turtles can perceive longitudinal information using magnetic cues.
- To determine if loggerhead sea turtles utilize a bicoordinate magnetic map for navigation, integrating both latitudinal and longitudinal data.
- To provide the first evidence of an animal encoding longitude into its magnetic positioning system.
Main Methods:
- Exposing hatchling loggerhead sea turtles (Caretta caretta) from Florida to simulated magnetic fields.
- These magnetic fields mimicked conditions found at two distinct locations with identical latitudes but differing longitudes across the Atlantic Ocean.
- Observing and analyzing the swimming directions of the turtles in response to the different magnetic field stimuli.
Main Results:
- Turtles exhibited distinct swimming responses when exposed to magnetic fields from different longitudinal locations.
- The observed swimming directions were consistent with movements that would advance the turtles along their natural migratory routes.
- This indicates that loggerhead sea turtles can differentiate between magnetic signatures associated with different longitudes.
Conclusions:
- The study provides the first demonstration that longitude can be encoded within the magnetic navigation system of a migratory animal.
- Loggerhead sea turtles possess a sophisticated navigational system that likely uses Earth's magnetic field as a bicoordinate map.
- This magnetic map allows turtles to extract both latitudinal and longitudinal information, enabling precise navigation over long distances.
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