Fig. 2. Four examples of crab responses to the approaching dummy. The four images show a bird's eye view of the mudflat at the time the dummy enters the field of view. Consecutive dummy positions are marked with black dots, and crab positions with white dots (t=240 ms). The onset of a crab's response is marked by a small white ring around the dummy's position at that point in time. Burrows are marked by large white circles. The graphs below the four images show the distance of the dummy (black dots) and of the crab (grey dots) from the crab's burrow over time. The crab's velocity towards its own burrow (cm s^-1) is shown as a continuous line at the bottom, whereby negative velocity values indicate that the crab travelled towards the burrow. Time samples during which the movements of the crabs meet the criteria for a response are marked by a black dot below the velocity trace. Further explanations can be found in the text.