Abstract of my talk at the VIth European Conference on Behavioural Biology 2012, Essen, Germany.
Evening acquisition of map information by the Alpine newt (Mesotriton alpestris)
Francisco J. Diego-Rasilla1, John B. Phillips2
1Departamento de Biología Animal, Universidad de Salamanca, Campus Miguel de Unamuno, Edificio de Farmacia 5ª planta, 37007 Salamanca, Spain,
2 Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061-0406, USA
Alpine newts show a remarkable ability to use the earth’s magnetic field to determine the home direction after being displaced far beyond their normal range of movement. To ‘fix‘ their location at an unfamiliar site, newts must detect the spatial variation in the geomagnetic field. However, this variation is extremely weak, and for animals like newts that home over short distances (< 5 km), short-term daily variation in the geo-magnetic field tends to be larger than the spatial variation a newt encounters as it moves about its home range. Here we address the question of whether newts can minimize the impact of daily variation in the magnetic field by taking map readings at times of day when temporal variation in the magnetic field is minimal. At approximately 20-30 minutes on the dark side of dawn and dusk during ‘civil twilight’ magnetic intensity reaches daily maximum values that are nearly identical. Obtaining magnetic measurements at these two times of day could provide newts with independent map readings that minimize the effect of the regular daily variation, while a comparison between these two times of day could be used to filter out unreliable map measurements obtained during periods of magnetic storm activity. We investigated whether newts obtain magnetic map measurements at one or both of these times of day, or else during the night. We found that exposure to magnetic and celestial cues for 30 to 45 minutes after sunset is necessary and sufficient for homeward orientation, whereas newts given access to these cues outside of this time window fail to orient in the homeward direction.
Keywords: homing, magnetic field, magnetoreception, map, newt, orientation