INDIVIDUAL VARIABILITY IN STATE-DEPENDENT FEEDING-BEHAVIOR IN 3-SPINED STICKLEBACKS

We studied state-dependent feeding behaviour of three-spined stickleba cks, Gasterosteus aculeatus, during several trials of sequential encou nters with 6-mm and 8-mm Asellus aquaticus prey. We used stomach fulln ess (the number of prey eaten previously) as an indicator for state, w hich we assumed to affect motivation for feeding. Dummy variable regre ssion was used to study how the per trial energy consumption, the numb er of events experienced, feeding efficiency and the average time spen t on each accepted prey depended on trial number, day and fish. A clea r individual variability was found, Feeding behaviour was strongly rel ated to the individual's recent feeding history (within a day). Legit regression models showed that the decision to accept or reject a prey encountered depended on the size of the fish as well as its state (sto mach fullness). Although limited, our results demonstrate pronounced h eterogeneity in feeding behaviour among individual fish. We discuss th is phenomenon in the broader context of population regulatory mechanis ms. (C) 1998 The Association For the Study of Animal Behaviour.