Central place foraging by an ant (Cataglyphis bicolor Fab.): a model of searching

A computer model of the searching activity of Cataglyphis bicolor (Fab.), based on quantitative data obtained in the field in Greece, was investigated. This ant searches for individual items of food (mainly dead arthropods) in the open on flat ground, on which its paths can be followed and mapped. The model was based on an analogy with molecular diffusion from a centre, suggested by the fact that the average distance of ants from the nest increased in proportion to the square root of time, up to a distance more than half the radius of a circle enclosing 90% of the search area. Actual behaviour was well described by a model in which individual ants went out for the first time to search in a direction determined at random. Subsequently they went out in a straight line in a direction and to a distance related to that of the previous find before commencing a semi-random search, on a path consisting of straight portions branching at random angles, with restriction on turns in a backward direction. Individual real ants search in restricted areas, commonly sectors centred on the nest. This behaviour was reproduced in the model as were quantitative aspects of the nest behaviour. Communication between individuals was not required in the model.