Foraging Mechanisms and the Currency for Models of Energy Maximization in Bumble Bees (Hymenoptera: Apidae: Bombus occidentalis)
[Futtersuche-Mechanismen und Verhaltensmuster der Energie-Maximierung bei Hummeln (Hymenoptera: Apidae: Bombus occidentalis)]
Taneyhill, D. E
Experiments were performed with bumble bees (Bombus occidentalis Greene 1858) in order to resolve a debate over whether the proper currency for models of their foraging behavior should be the long-term or short-term rate of energy gain. Individual worker bees foraged in a flight box containing 50 blue and 50 yellow artificial flowers filled with various amounts of sucrose solution. In an initial experiment, bees visited more than 84% on average, after 150 flower visits, of the color that contained more sucrose (3 vs 1 μL). In two subsequent experiments the volume of sucrose in one color of flowers was constant, while the amount in the other color was variable, with equal 3 μL means for both. After approximately 150 total visits, the proportions visited by most individuals were approximately equal for both types. The final proportions were consistent with long–term rate maximization being the proper currency. To explain the results, I present a model based on the Rescorla–Wagner mechanism of classical conditioning. The change in associative strength between stimulus and reward after each flower encounter is assumed to be an increasing and decelerating function of nectar reward. The model predicts that foragers sampling both a constant and a variable reward type may appear risk averse in the short term, but close to risk indifferent in the long term.