Skip to main content
. 2011 Aug 15;108(37):E718–E724. doi: 10.1073/pnas.1107365108

Fig. 3.

Fig. 3.

Bat navigation relies primarily but not exclusively on distal visual landmarks. (A) Line-of-sight calculations: large black polygon represents the visually familiar area, as seen from the highest recorded altitude of bats’ flights (643 m above ground level); small gray polygon represents the familiar area physically visited by foraging bats (Methods). Red squares mark locations seen both from the familiar area (near cave) and from release site R1 (at the highest recorded flight altitude of 115 m). Blue squares represent the same for release site R3 (at the highest flight altitude of 74 m). Note absence of green squares, indicating that bats released within the crater (R2), flying at the highest recorded altitude of 101 m, could not see any familiar visual landmarks. (B) Example of bat 259, released inside the crater; note the tortuous disoriented flight: this bat flew 33.9 km before it left the crater and turned northeast, then northwest toward the familiar area. View from the northeast. (C) Homing flight of two bats (bats 259 and 274, green lines) released inside the crater and two bats (bats 317 and 318, blue lines) released high on the crater rim; light-gray polygon represents the familiar area of the bats. Note that bats released at the crater rim flew north much straighter than bats released inside the crater. (D) Population data showing cumulative straightness index as function of distance from the release site; the four colors represent bats released at the four different release locations (cave, R1, R2, and R3); dotted lines represent median ± SE of the median; shown are only the distances with data from at least three bats. Note the substantially lower cumulative straightness index for within-crater releases (green), indicating strong disorientation when distal landmarks are not visible. (E) Polar display of bats’ vanishing bearings (green circles) and the direction of the bats’ exit points from the crater (triangles) after release at point R2 (inside crater). Green solid and dotted lines represent average directions of the circles and triangles, respectively; black line represents homeward direction (to cave).