Fig. 1. (A–C) Three examples of natural foraging paths, digitized at 1 frame s^-1. (Ai–Ci) Positions of transverse body axis of fiddler crab, with the arrow pointing toward the `homeward' side, as seen in the boxed inset in Ai, for each digitized frame. The boxed inset also shows the convention for egocentric directions used throughout this paper. Numbers correspond to elapsed time (s). The center of the carapace is connected between frames. The burrow is the large open circle. Scale bars in Bi apply to Ai–Ci. The small gray circles in Ai adjacent to the burrow represent calculated burrow positions for each digitized step, assuming the burrow entrance were to lie directly in line with the crab's transverse axis on its the homeward side (see Results for details). Open inset in Ai is a diagrammatic representation of the orientation error (see below). The hatched solid area in Ci is the base of a mangrove sapling. (Aii–Cii) Orientation error (degrees), defined as bearing minus orientation (inset in Ai), over time (s). The double-headed arrow in Cii indicates the time when the burrow was blocked from view by a mangrove sapling. (Aiii–Ciii) Frequency histogram showing the distribution of orientation errors in 1° bins, with an ideal normal probability density function overlaid (solid line).