Fig. 3. Three-dimensional search density distributions of individually tracked desert ants searching for the nest located within a four-cylinder landmark square array. The fictive positions of the nest are depicted by open arrows. Data are given separately for the first and the second 1.5-min recording periods in the upper and lower graphs, respectively. The ants were released in four different compass directions relative to the landmark square (NW, NE, SW, SE). The four cylindrical landmarks are positioned in each of the four corners of the search density square. N=16 (NW), N=18 (NE), N=20 (SW) and N=22 (SE) ants. The same data are presented in Fig. 2 for the entire 3-min recording periods.