THE ROLE OF LEARNING AND MEMORY IN THE FEEDING-BEHAVIOR OF THE 15-SPINED STICKLEBACK, SPINACHIA-SPINACHIA L

As a result of experience, fifteen-spined sticklebacks began to attack Gammarus and Artemia more efficiently. This was caused by changes in reaction distance, speed of attack, handling time and success in apprehending and handling prey. How quickly foraging efficiency improved depended on the type of prey. Handling times for Artemia decreased more than those for Gammarus; attack and handling efficiency increased correspondingly. Sticklebacks feeding on Artemia also had shorter and less complex foraging sequences. The fish learned about the characteristics of prey items. Gammarus, whose legs lay head-to-tail, were most easily swallowed head-on, and foragers modified their behaviour accordingly. When two types of prey were presented alternately, individuals improved their foraging skills less effectively and handling times decreased less than when on pure diets. Foragers did not retain learned foraging skills indefinitely and became less efficient at dealing with specific prey when these were encountered less frequently. Handling times for prey offered in trials separated by 8 days were similar to those of naive fish. By decreasing handling time, learning increased the profitability (yield of energy/time) of specific prey. Gammarus could thus become more profitable than Artemia, if it predominated in the diet for several feeding bouts, and vice versa. © 1991 The Association for the Study of Animal Behaviour.