Use of a Magnetic Compass for Nocturnal Homing Orientation in the Palmate Newt, Lissotriton helveticus

摘要

Previous studies have shown that migrating palmate newts (Lissotriton helveticus) can rely on acoustic cues for orientation to breeding ponds. Nonetheless, although acoustic cues are reliable over relatively short distances, they are unlikely to account for the long-distance homing demonstrated in several other species of newts. Most individuals of L. helveticus migrate only a few hundred meters (Diego-Rasilla, F. J. & Luengo, R. M. 2007: Acoustic orientation in the palmate newt, Lissotriton helveticus. Behav. Ecol. Sociobiol. 61, 1329--1335), raising the possibility that this species may only utilize short-distance cues (Joly, P. & Miaud, C. 1993: How does a newt find its pond? The role of chemical cues in migrating newts (Triturus alpestris). Ethol. Ecol. Evol. 5, 447--455; Russell, A. P., Bauer, A. M. & Johnson, M. K. 2005: Migration of amphibians and reptiles: an overview of patterns and orientation mechanisms in relation to life history strategies. In: Migration of Organisms (Elewa, M. T., ed). Springer-Verlag, Berlin Heidelberg, pp. 151--203; Sinsch, U. 2006: Orientation and navigation in Amphibia. Mar. Freshw. Behav. Phy. 39, 65--71). Therefore, experiments were carried out to investigate the use of the geomagnetic field in the nocturnal homing orientation of L. helveticus. Tests were carried out at night in an outdoor circular arena, under total overcast sky that prevented access to celestial compass cues. Individual newts were tested in one of four symmetrical alignments of an earth-strength magnetic field. We studied the orientation behaviour of newts from two breeding ponds located 9.05 km west-southwest and 19 km east-northeast of the testing site. The distribution of magnetic bearings from both groups of newts exhibited significant orientation in the homeward direction. These findings indicate that palmate newts are capable of long-distance homing and are able to orient in the homeward direction at night using the magnetic compass as the sole source of directional (i.e., compass) information.