Changes in the metabolic rate of the foraging honeybee: effect of the carried weight or of the reward rate?

MOFFATT LUCIANO

JOURNAL OF COMPARATIVE PHYSIOLOGY A-SENSORY NEURAL AND BEHAVIORAL PHYSIOLOGY

Springer-Verlag

Lugar: Berlin Heidelberg ; Año: 2000 vol. 186 p. 299 - 306

0340-7594

The metabolic rate of free flying honeybees (Apis mellifera ligustica) foraging on a multiple automatic feeder was measured in complete absence of per- turbation. Each time the sucrose flow rate was doubled, the metabolic rate increased by 18.2 ± 2.0% (14.7 µl CO2 min-1) and final crop load by 25.1 ± 2.4% (7.04 µl). The possibility that the heavier load carried by the bees caused the increase in the metabolic rate was analyzed in detail. It was found that, for the same weight in the crop, the metabolic rate increased with the in- creasing reward rate. Therefore, a factor other than the carried weight might account for this increase: a moti- vational drive, whose intensity may depend on the re- ward rate at the food source. Although at higher reward rates metabolic rate increased during the visit, at lower reward rates it remained constant, suggesting that the effect of the carried weight on the metabolic rate might be controlled by this motivational drive. The hypothesis that honeybees maximize individual efficiency by re- ducing their crop load loses support, as foraging costs are not determined by the carried weight. The functional meaning of the reduction in crop load would be to in- crease the informational exchange at the hive.