Fig. 11. The parameters that influence a crab's decision of when to initiate its response to the approaching dummy. (A) The influence of crab-burrow distance on the dummy-burrow distance at the time of the response. The data set has been split according to the track's distance from the crab's burrow: small burrow track distances of 20 cm are shown as open circles, and the corresponding model fit (track distance = 10 cm) as a dotted line. Larger track distances of >20 cm and the model fit for a track distance of 20 cm are shown as filled dots and a solid line, respectively. (B) Response distance and the direction of approach of the dummy. The response distance is only slightly influenced by different track angles. The solid lines show the direction of dummy paths, and the large circles mark dummy positions at the time of response as fitted by the statistical model. The fitted response distance is shown for each of the nine approach directions (track angle) and the two values of crab side (see Fig. 6). Increasing track angles are shown in progressively lighter greys. Fitted values were calculated at the mean of all other parameters in the statistical model. The mean crab-burrow distance is 23.4 cm. Solid and dotted circles represent the mean response distance ± 2 S.E.M. (C) The effect of repeated dummy presentations on the response distance. The dotted line shows the mean response distances over successive dummy presentations. The grey dots joined by a solid black line show the model fits for the six categories of presentation repeat. The grey bars at the bottom of the panel show the number of experiments (crabs) contributing to each estimate. The two shades of grey indicate which presentation repeats correspond to the six categories of the variable presentation repeat used in the statistical modelling.

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