True navigation by an amphibian

Abstract

True navigation, also referred to as map-based homing, is the ability of an organism to return to the origin of a displacement (‘home’) without access to familiar landmarks or goal-emanating cues, and without knowledge of the displacement route. True navigation requires both a ‘map’ or geographical position sense and a compass, and has been demonstrated only in vertebrates (e.g. Walcott & Schmidt-Koenig 1973; Rodda 1984a, b, 1985). In the present study, eastern red-spotted newts, Notophthalmus viridescens, deprived of directional information during long distance displacement from their home pond were able to orient in the homeward direction, indicating that they are capable of true navigation. Homing ability appears to be well developed in the family Salamandridae. Western newts, Taricha rivularis, return to breeding sites along relatively straight paths after displacements of up to 12 km (Twitty et al. 1966). Eastern red-spotted newts exhibit homeward-directed orientation in an enclosed indoor arena after displacements of lo-50 km (Phillips 1986a, 1987; Phillips & Borland 1994). In our earlier homing studies (Phillips 1986a, 1987; Phillips & Borland 1994), male eastern newts were displaced from their home ponds to the testing facility in partially covered plastic buckets which provided access to directional cues en route that could potentially have been used to determine the direction of displacement (Phillips 1987). In the experiments reported here, male newts were deprived of visual, magnetic, olfactory and inertial directional cues during displacement from their