Abstract:

Bees learn the location, odor, color and shape of flowers, and use these cues hierarchically to make dietary choices. If two such cues always appear together, they provide the bees with identical information about their food source. In such a situation, bees may base dietary choices on one cue and ignore the other, or they may continue to consider both cues. We studied this question by allowing bumblebees to forage on two patches of artificial flowers that differed in location, color and presence of reward in a two-phase laboratory experiment. We switched either the display color, the location, or both color and location associated with the rewarding patch between experimental phases. We tested for the effects of switches by comparing the bees' choices across treatments, and by evaluating each bee's performance before and after the change. In our analysis we characterized the different patterns of visits to empty flowers by a plot of the cumulative frequency of such visits over time. This plot enabled us to identify two regimes: ( I ) a learning regime, when new associations between reward and display cues are formed, followed by (2) a steady-state where bees make periodic visits to the empty patch. We used likelihood analysis to estimate the length of short-term memory that can account for the bees' steady-state foraging choices. The bees' performance decreased immediately following a switch in location of the rewarding patch. Switches in both reward color and location elicited a similar decrease to switches in location only. No temporary decrease in foraging performance occurred when only color of the rewarding patch was changed, and in no-change controls. The bees' flower choices at steady-state were most likely generated by a short-term memory of the last 4-6 flower visits.

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