IBN-9729195 PI: Klimley There is controversy over how animals might sense features of the earth's magnetic field for information useful in homing and migration behavior. Most work has focused on a magnetic compass sense, with as yet unproven sensory mechanisms. It has been known for decades that sharks and rays and many bony fish have specialized sensory organs for detecting weakly electric fields in the environment, and similarly noted that this sensitivity could be used for magnetoreception by detecting the small electrical signal induced by magnetic fields as the animal swims through them. This project builds on some prior behavioral work with sharks in the open ocean, and proposes an alternative to the usual hypothesis of detecting the compass-oriented vector of earth's magnetic field. Instead, it may be that sharks and rays detect the small changes in local magnetic topography of the bottom over which they swim and use it as a guiding map. This Small Grant for Exploratory Research tests this novel hypothesis by a behavioral experiment under controlled laboratory conditions, using a simple Y-maze and artificial magnetic fields to see whether bat rays can be trained to show detection of local magnetic topography. There is a risk is that the results will not show the required sensitivity, and that the challenge to the present dogma fails. However, the impact of this work on both sensory neuroscience and neuroethology is likely to be high in this controversial area, because the results will demonstrate whether or not a topographic magnetosensory capability can be distinguished from demonstrations of compass-oriented sensing of magnetic fields, or responses to local electrosensory stimuli. There also is a payoff in the potential for development of electronic navigation aids.
