Trapline foraging by bumble bees: III. Temporal patterns of visitation andforaging success at single plants

We analyzed the temporal structure of visitation by bumble bee workers to a single Penstemon strictus plant growing in an array of conspecifics. When tested against a null distribution using a randomization model, the observe d pattern of arrivals for the whole group of bees was random, but departure s were clustered in time. Certain individuals visited the plant repeatedly and frequently throughout the day. These showed significantly regular arriv al and departure schedules, which were likely produced by traplining. We ex plored whether these more frequent and regular foragers gained a higher rew ard than random or incidental plant visitors. Using an analytical model, Po ssingham predicted that a dominating forager that visited a simple, renewin g resource in a regular pattern would garner higher and less variable rewar ds than random visitors. Inspired by these results, but interested in plant -level visitation, we constructed a simulation model of resource dynamics f or a multiflowered plant with high visitation. The model incorporates the o bserved visitation schedules of all bees and independent reward dynamics fo r each flower on the plant. We calculated the rewards that observed bees wo uld have collected given a range of resource-renewal parameters. More frequ ent visitors did not return to the plant when whole-plant resource levels w ere higher, but these visitors did get greater rewards. Their increased rew ard resulted from greater foraging efficiency, primarily through selecting (on average) more rewarding flowers than those selected by less frequent, r andom visitors.