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Behavioral titration of a magnetic map coordinate
John B Phillips1, Michael J Freake, Janette H Fischer
1Department of Biology, Indiana University, Bloomington, IN 47405, USA. jphillip@vt.edu
Summary
Eastern red-spotted newts use geomagnetic inclination for navigation. Small changes in magnetic inclination near their home value significantly impact homing orientation, supporting the magnetic map hypothesis.
Area of Science:
- Zoology
- Geophysics
- Animal Behavior
Background:
- The eastern red-spotted newt (Notophthalmus viridescens) exhibits homing behavior.
- Spatial variation in Earth's geomagnetic field inclination is a potential factor in animal navigation.
Purpose of the Study:
- To investigate the role of geomagnetic field inclination in the homing orientation of newts.
- To test predictions of the magnetic map hypothesis regarding magnetic inclination sensitivity.
Main Methods:
- Exposing newts to controlled, small changes in magnetic inclination.
- Observing and analyzing changes in homing orientation direction.
Main Results:
- The most significant effects on homing orientation occurred at magnetic inclination values close to the newts' 'home value'.
- Newts reversed their homing direction within a narrow range of 0.5 degrees of inclination change around the home value.
Conclusions:
- Geomagnetic inclination, or its components (vertical/horizontal intensity), is likely used by newts to derive navigational map information.
- Findings provide strong evidence supporting the magnetic map hypothesis in this species.