Anim. Behav., 1994,47,501-513 Bluegills continuously update patch giving-up times based on foraging experience

Abstract. The data from a series of patch-choice experiments with bluegill sunfish, Lepomis mucrochirus, 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: (I) 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 Over 25 years ago, MacArthur & Pianka (1966) suggested strategies animals may use when exploit ing prey in patchy environments. Since that time, many new and more complex theories related to optimal foraging have been described (for recent reviews see Pyke 1984; Stephens & Krebs 1986). More recently, theoretical ecologists have described the more proximal mechanisms animals might use to decide when to leave a patch (e.g. Kreb