VII.l The Geomagnetic Field
and its Role in Directional Orientation
Wolfgang Wiltschko and Roswitha Wiltschko
Fachbereich Biologie der J.W.Goethe-Universitat, Zoologie, Siesmayerstrasse 70,
60054 Frankfurt a.M., Germany
Abstract
A magnetic compass has been demonstrated in vertebrates, arthropods and a nudibranch. Two different functional modes have been described: birds and marine
turtles use an inclination compass based on the inclination of the field lines, while
mammals, fishes and arthropods use a polarity compass based on their polarity.
For amphibians, both mechanisms have been described. In birds and amphibians,
magnetic compass orientation proved light-dependent, with normal responses
being observed only at the short-wavelength end of the spectrum. This suggests an
involvement of photopigments, which is in agreement with the hypothesis
assuming magnetoreception by excited-state macromolecules. The nature of the
non-light dependent primary processes of magnetoreception in turtles, mammals
and arthropods are unclear; magnetite-based mechanisms are discussed. Animals
use magnetic compass information in a wide variety of behaviors. Birds orient
their homing flights and their migration with the help of the magnetic field, newlyhatched salmon and marine turtles use a magnetic compass to reach suitable
habitats, amphibians and amphipods use it for orientation between land and water,
insects for building activities. In many of these behaviors, the animals can also use
celestial cues for locating directions. Ecological requirements determine how the
various cues interact in a given situation.
Key words Geomagnetic field, magnetic compass, magnetoreception, orientation
behavior, directional reference
1 Compass Orientation with the Help of the
Geomagnetic Field
A magnetic sense is not among the classic five senses vision, hearing, smell, touch
and taste. Man provided himself by technical means with the possibility to obtain
magnetic information; we have been making use of a magnetic compass for
navigation in exploration and seafaring for centuries. Yet the idea that animals
might use the geomagnetic field in essentially the same way for such purposes
and its Role in Directional Orientation
Wolfgang Wiltschko and Roswitha Wiltschko
Fachbereich Biologie der J.W.Goethe-Universitat, Zoologie, Siesmayerstrasse 70,
60054 Frankfurt a.M., Germany
Abstract
A magnetic compass has been demonstrated in vertebrates, arthropods and a nudibranch. Two different functional modes have been described: birds and marine
turtles use an inclination compass based on the inclination of the field lines, while
mammals, fishes and arthropods use a polarity compass based on their polarity.
For amphibians, both mechanisms have been described. In birds and amphibians,
magnetic compass orientation proved light-dependent, with normal responses
being observed only at the short-wavelength end of the spectrum. This suggests an
involvement of photopigments, which is in agreement with the hypothesis
assuming magnetoreception by excited-state macromolecules. The nature of the
non-light dependent primary processes of magnetoreception in turtles, mammals
and arthropods are unclear; magnetite-based mechanisms are discussed. Animals
use magnetic compass information in a wide variety of behaviors. Birds orient
their homing flights and their migration with the help of the magnetic field, newlyhatched salmon and marine turtles use a magnetic compass to reach suitable
habitats, amphibians and amphipods use it for orientation between land and water,
insects for building activities. In many of these behaviors, the animals can also use
celestial cues for locating directions. Ecological requirements determine how the
various cues interact in a given situation.
Key words Geomagnetic field, magnetic compass, magnetoreception, orientation
behavior, directional reference
1 Compass Orientation with the Help of the
Geomagnetic Field
A magnetic sense is not among the classic five senses vision, hearing, smell, touch
and taste. Man provided himself by technical means with the possibility to obtain
magnetic information; we have been making use of a magnetic compass for
navigation in exploration and seafaring for centuries. Yet the idea that animals
might use the geomagnetic field in essentially the same way for such purposes