Are Animal Maps Magnetic?

Open-Sea Migration of Magnetically Disturbed Sea Turtles

“…Walker et al, 1997). This hypothesis, suggested in its original form long ago (Viguier, 1882;Gould, 1985), faces a burden of theoretical problems (Wiltschko and Wiltschko, 1995;Wallraff, 1999) and has received very little support from the many experiments prompted by the enthusiasm for the findings demonstrating magnetic orientation (but not navigation) in many animals (Wiltschko and Wiltschko, 1995;Åkesson and Alerstam, 1998). The second assumption is that the oceans are featureless voids with few navigational cues, a view that has led to a disregard for the many types of information that can be conveyed to navigators by the physical and chemical features of the oceanic environment, especially those provided by winds and currents.…”

Foreword to papers on magnetic sensitivity in birds

“…The total intensity of the earth's field varies geographically between about 0.25 and 0.65 G, and in temperate latitudes the horizontal component is on the order of 0.25 G. The earth's field varies in time, with short-term variations in magnetic storms commonly on the order of a few hundred gamma, where I gamma = 11100,000 G. The earth's field also varies over short distances due to deposits of iron, and these variations are also on the order of 1/1,000 of the earth's field. Magnetic storms and magnetic anomalies have been reported to affect the orientation of birds, as reviewed by Able (1980), Gould (1985), and Keeton (1974). These reported effects imply sensitivity not only to the earth's overall field of roughly 0.5 G but to variations over time and space of less than 0.1 %.…”

The magnetic and electric fields induced by superparamagnetic magnetite in honeybees

“…Correlation could be associatively learned, such that with an overcast sky the magnetic input alone may be enough for determining the position of the sun or, vice versa, the visual input alone may be enough for orientation. Pigeons with mounted magnets (which compensate the external magnetic field) orient normally on sunny days (Gould 1985).…”

“…Without an external magnetic field the magnetization of SPM magnetite is zero, in an external field it is larger than that of paramagnetic material. SD crystals are believed to determine a compass sense, SPM crystals a learned navigational map sense of magnetic intensity This paper is dedicated to the memory of the late Prof. Dr. W. Reichardt, an outstanding scientist and personality, who will be greatly missed by all who knew him and his work gradients (Gould 1985) (i.e. learning the recognition of magnetic gradients in their environment).…”