Paying for nectar with wingbeats: a new model of honeybee foraging.

Honeybees acquire wing damage as they age and older foraging honeybees accept lavender inflorescences with fewer flowers. These indicate the operation of some kind of optimal response, but this cannot be based on energy because energy expenditure does not change as the wings get damaged. However, wingbeat frequency increases with wing damage. A deterministic analytical model was constructed, based on the assumptions that bees have a limited total number of wingbeats that the flight motor can perform and that they maximize lifetime energy profit by conserving the number of wingbeats used in foraging. The optimal response to wing damage is to reduce the threshold number of flowers needed to accept an inflorescence. The predicted optimal gradient between wing damage (wingbeat frequency) and acceptance threshold (number of flowers on an inflorescence) was close to the observed gradient from field data. This model demonstrates that wear and tear is a significant factor in optimal foraging strategies.