Abstract:

Newly emerged bees learn to forage more efficiently as they gain experience. We hypothesized that foraging efficiency would increase as bees gain experience during the day, but would decrease overnight, due to loss of memory. To test this hypothesis, we allowed naive bombus terretris bumblebees to forage on two clusters of artificial flowers of unequal profitabilities during three consecutive days. Nectar intake rate, percentage visitation to the more profitable cluster, probing time and time intervals between visits were computed as measures of the bees' foraging efficiency. Nectar intake rates increased significantly during the day, and decreased partially but significantly after a night. There was much variation between individual bees in nectar intake rates. The bees did not show a preference for one of the clusters at the onset of the experiment, and no consistent increase in visitation to the more profitable cluster was found during single observation days for all bees. Most individuals did not visit the higher-reward cluster exclusively by the end of the third day. However, visitation to the higher-reward cluster did increase significantly when the first day of observation was compared to the third day. Preference for the higher-reward cluster increased over the first night but decreased significantly over the second night. Probing time and inter-visit intervals decreased significantly during observation days, and increased significantly after a night. The results indicate that bees learn to approach and probe flowers faster, as they gain experience, during a foraging day, but that these skills are partially forgotten overnight. Patch preference is formed more slowly. Once formed, it is also weakened overnight. Such partial forgetting may aid the bee in reacting quickly to overnight changes in resource profitability by modifying flower choices and handling techniques.

Website