Amphibia: Orientation and Migration

Abstract

Most individuals of an amphibian population stay within a range of a few hundred meters around their breeding site during their whole life span, while only a low number of dispersers move considerably further distances (10–55 km depending on the species). Amphibia use at least five classes of directional information for spatial orientation, acoustic, magnetic, mechanical, olfactory, and visual cues. The sensory information is integrated into a redundant, multisensory orientation system in which single information classes are weighted according to the availability in the specific habitat. Homing to breeding sites or shelter following active or passive (experimental) displacement relies on path integration, beaconing, pilotage, compass orientation, or map-based true navigation. While the evidence for path integration is still weak in amphibians, beaconing (direct sensory contact) along acoustic or olfactory gradients emanating from the home site, as well as pilotage along fixed visual landmarks, are well-established orientation mechanisms of many species. Two independent compass systems permit steering home without direct sensory contact. The time-compensated compass processes information on celestial cues, whereas the light-dependent compass uses inclination as a magnetic cue. Map-based orientation from unfamiliar sites to home, that is, true navigation, has been demonstrated in one species, the salamander Notophthalmus viridescens . Available data suggest a magnetic nature of the map, but successful replication of experiments has not been presented yet.