Does the Homing Accuracy of Intertidal Chitons Rely on Active Trail Following? A Simulation Approach

The role of trail following in the homing of three Acanthopleura chitons was investigated using a Monte Carlo simulation model. Four different sets of simulations were performed to assess: (1) the importance of an active mechanism of trail following in producing trail overlap and allowing the animals to home; (2) its importance in the different segments of the excursions; (3) the range of probability values associated with trail following behaviour, yielding a homing performance not different from the empirical one; and finally, (4) if trail following can be replaced, as a homing mechanism, by a tactic behaviour. mparison between simulated and empirical data shows that the degree of trail overlap and homing performance shown in the field by Acanthopleura gemmata and Acanthopleura brevispinosa rely on an active mechanism of trail following which begins to be important about midway in each foraging excursion, while the low trail overlap and homing performance of Acanthopleura granulata are due entirely to chance coincidence of different path segments. Specific simulations show that a homing performance similar to that observed in the field can be obtained only within a narrow range of probability values of beginning and ending trail following. Moreover the results of simulations also show that in A. gemmata and A. brevispinosa a strong homeward taxis during the return phase does not efficiently replace trail following.