HOW DOES A NEWT FIND ITS POND - THE ROLE OF CHEMICAL CUES IN MIGRATING NEWTS (TRITURUS-ALPESTRIS)

The hypothesis that newt orientation during breeding migration is base d on a course reversal mechanism has been tested in Triturus alpestris , by experimental displacements in the field. Two migratory directions were determined by the position of the newt captures at a forest edge fence. According to their migratory direction, the newts were then tr ansferred to two arenas, located underbush on the pond side opposite t o the migratory direction. The results show clearly that orientation d uring at least a large part of the migratory movement can be explained by a more simple mechanism based on goal-emanating cues. In order to modify the emission of odour from the pond, it was covered by an opaqu e tarpaulin. When the pond was covered, orientation shifted in the two arenas, the newts heading in another direction than that of the pond, suggesting that the odour of the pond acted as the main cue in orient ation. Laboratory experiments giving a choice between water from diffe rent origins reinforced this hypothesis. By recognizing water from the ir own pond compared with water from a pond inhabited by another popul ation, newts showed specificity of response to the odour of a particul ar site. These data are compared with those from the literature on ori entation mechanisms in urodeles.