Bluegills continuously update patch giving-up times based on foraging experience

The data from a series of patch-choice experiments with bluegill sunfish, Lepomis macrochirus, were analysed within feeding periods to describe the proximal leaving strategy bluegills use when choosing between food patches. The following hypotheses regarding strategies by which these choices are made are considered: (1) a fixed giving-up time; (2) a fixed residence time; (3) a linearly increasing giving-up time; and (4) a linearly increasing residence time. Five experiments, in which the difference in food availability between patches (tank sides) decreased from experiment to experiment, were run with eight different bluegills in each experiment. The bluegills tested did not use the fixed giving-up time rule or the fixed residence time rule to decide when to leave a patch, but did have both a longer average residence time and a longer average giving-up time in poorer environments. Within an environment, both patch residence times and giving-up times increased linearly with increasing prey encounter; the linear giving-up time rule better described bluegill behaviour than the linear residence time rule, however. This giving-up time strategy varies among individuals and yet is still robust enough to allow each individual to effectively sample and use variable food resources.