Kirschvink, Joseph L.; Winklhofer, Michael; Walker, Michael M.
Biophysics of magnetic orientation: strengthening the interface between theory and experimental design.
In: Journal of the Royal Society Interface, Vol. 7, No. 2: S179-S191
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The first demonstrations of magnetic effects on the behaviour ofmigratory birds and homing pigeons in laboratory and field experiments,respectively, provided evidence for the long-standing hypothesis thatanimals such as birds that migrate and home over long distances wouldbenefit from possession of a magnetic sense. Subsequent identificationof at least two plausible biophysical mechanisms for magnetoreception inanimals, one based on biogenic magnetite and another on radical-pairbiochemical reactions, led to major efforts over recent decades to testpredictions of the two models, as well as efforts to understand theultrastructure and function of the possible magnetoreceptor cells.Unfortunately, progress in understanding the magnetic sense has beenchallenged by: (i) the availability of a relatively small number oftechniques for analysing behavioural responses to magnetic fields byanimals; (ii) difficulty in achieving reproducible results using thetechniques; and (iii) difficulty in development and implementation ofnew techniques that might bring greater experimental power. As aconsequence, laboratory and field techniques used to study the magneticsense today remain substantially unchanged, despite the hugedevelopments in technology and instrumentation since the techniques weredeveloped in the 1950s. New methods developed for behavioural study ofthe magnetic sense over the last 30 years include the use of laboratoryconditioning techniques and tracking devices based on transmission ofradio signals to and from satellites. Here we consider methodologicaldevelopments in the study of the magnetic sense and present suggestionsfor increasing the reproducibility and ease of interpretation ofexperimental studies. We recommend that future experiments invest moreeffort in automating control of experiments and data capture, control ofstimulation and full blinding of experiments in the rare cases whereautomation is impossible. We also propose new experiments to confirmwhether or not animals can detect magnetic fields using the radical-paireffect together with an alternate hypothesis that may explain thedependence on light of responses by animals to magnetic field stimuli.