Geomagnetic Position Fixing

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NON-TECHNICAL SUMMARY Phillips, John IBN-9507826 Dr. Phillips' research will investigate the use of the earth's magnetic field to determine geographic position. Previous studies of migratory/homing orientation have provided evidence for the involvement of a specialized magnetoreception mechanism in the "map" component of homing, and for effects of small changes in magnetic inclination or intensity on migratory/homing orientation. Studies of map-based homing (i.e., true navigation) will be carried out under controlled laboratory conditions where the response to manipulation of individual parameters of the magnetic field can be investigated. Two forms of orientation that involve the earth's magnetic field will be studied, i.e., magnetic compass orientation (requiring only compass information) and long-distance homing or true navigation (requiring both map and compass information). This will make it possible to distinguish effects of experimental manipulations on the map or geographic-position sense from effects on the compass. In addition, a graphical model of bicoordinate navigation developed for this work will be used to estimate the local gradients of magnetic field parameters in the vicinity of the animal's home from their behavioral responses to experimental manipulation of these parameters. These estimates can then be compared with future measured values of geographic variation in the magnetic field. Dr. Phillips' research will provide information about the sensitivity of biological systems to weak magnetic fields which will contribute to the current debate concerning possible effects of artificial sources of EMF (power lines, electrical appliances, etc.) on human health.