Distant Landmark Objects Are Not Crucial for Learning the Goal Location in a Maze by Adult Common Toads ( L.)

Amphibians are known to be capable of using both proximal and distant visual landmarks for orientation during the summer period, but their relative importance for amphibians remains almost unstudied. The present research tests the significance of distant landmarks in the case of the Common toad, . Rectangular mazes consisting of one central and 4 side rooms were used for experiments. Various objects that could be used as orientational cues (proximal landmarks) were placed on the floor of the central room, while distant landmarks were positioned on screens outside the maze (a cardboard figure 155 × 30 cm in size). The experiment consisted of two consecutive trials, each lasting 4 h. During the first trial, the animal learnt the location of one of the four rooms of the rectangular maze (160 × 96 cm) that contained attractive “resources” (container with moving prey, water source and shelter). The first trial of the experiment was followed by a 30 min break. During the break, the “resources” were removed from the maze and all four side rooms were left empty, but the location of the distant landmark was changed 180° relative to the maze (proximal landmarks were left in the same place). According to our hypothesis, if the animal uses a distant landmark to learn the location of the target room, in the second trial it will spend more time and travel a greater distance in the room located diagonally to the “resource” room. However, if the distant landmark is not the primary one used to find the target room, the amphibian would visit the room that earlier contained the “resources” more often like in the first trial. A total of 20 adult common toads were tested individually. In this experimental situation, the toads successfully found the room, where the “resources” were previously located, 30 min following the first trial. Thus, our distant visual landmark was not used by common toads as a primary one to learn the location of the target room, but changing the location of this landmark resulted in increased locomotor activities in the second trial.