Innate preference for magnetic compass direction in the Alpine newt, Triturus alpestris (Salamandridae, Urodela)?

Abstract

Magnetic compass orientation was first discovered for migrating/homing birds in which all individuals of a population or species prefer a predictable magnetic direction during a particular migratory situation. If all other sensory cues are absent, the Earth’s magnetic field may serve as a reference for other orientation mechanisms. It will be demonstrated that alpine newts (Triturus alpestris, Salamandridae) spontaneously align according to the natural or the deviated magnetic field lines of the Earth. They are able to do this in the dark and by apparently seeking to maintain a specific angle with respect to the magnetic field vector. When the horizontal component of the magnetic vector was eliminated, animals became disoriented, and orientation became random. We infer that the animals observed had learned to prefer a particular magnetic direction following environmental/geographical cues. Alternatively, the magnetic directional alignments are innate as, e.g. in migrating birds, but these may be modified/altered according to season, age, hormonal status, and environmental factors such as “landmarks”, light-, sound-, or olfactory cues. Numerous observations of the aligning showed that the preference for a certain magnetic compass direction/axis was not only individual but also specific for the population-subgroups tested. Specimens roughly preferred magnetic directions close to east or west. However, the larvae were able to learn to align to obviously attractive hiding spots (tubes) that were provided in a direction that deviated with respect to the first magnetic preference. The new conditioned alignments were, again, referred to magnetically by the animals and remained stable, even if the hiding tubes were absent. Animals preferred that direction until, eventually, a new directional cue became attractive.