Use of local visual cues for spatial orientation in terrestrial toads (Rhinella arenarum): The role of distance to a goal

Abstract

The use of environmental visual cues for navigation is an ability present in many groups of animals. The effect of spatial proximity between a visual cue and a goal on reorientation in an environment has been studied in several vertebrate groups, but never previously in amphibians. In this study we tested the use of local visual cues (beacons) to orient in an open field in the terrestrial toad Rhinella arenarum. Experiment 1 showed that animals could orient in space using two cues located near the rewarded container. Experiment 2 used only one cue placed at different distances to the goal and revealed that learning speed was affected by the proximity to the goal (the closer the cue was to the goal, the faster toads learned its location). Experiment 3 showed that the position of a cue results in a different predictive value. Animals preferred cues located closer to the goal more than those located farther away as a reference for orientation. Present results revealed, for the first time, that (i) toads can learn to orient in an open space using visual cues, and that (ii) the effect of spatial proximity between a cue and a goal, a learning phenomenon previously observed in other groups of animals such as mammals, birds, fish and invertebrates, also affects orientation in amphibians. Thus, our results suggest that toads are able to employ spatial strategies that closely parallel to those described in other vertebrate groups, supporting an early evolutionary origin for these spatial orientation skills.