Exploration Effort in Foraging Bees Is Enhanced by Clustering of Food Resources

Tamar Keasar, Uzi Motro & Avi Shmida

Foraging can be viewed as a dual activity: a food-collection process, and an exploration process, which enables foragers to collect information on food resources. Exploration of food sources may involve patch sampling, as well as sampling of various food sources within heterogeneous patches. The present study aimed to quantify exploration effort in relation to the spatial distribution of the food sources. Exploration effort was measured in two-stage laboratory experiments on naive bumblebees, Bombus terrestris (L.). In the first stage the bees were allowed to forage on three types of color-distinct artificial flowers. In the second stage a new type of artificial flowers ("exploratory flowers"), which were non-rewarding, was added. The four types of artificial flowers were either arranged in spatially distinct clusters or randomly intermingled. Two reward schedules were used in each spatial arrangement: constant refilling of visited flowers and probabilistic refilling. The bees' visit to the exploratory flowers were recorded as a measure of exploratory activity, and were related to their previous foraging experience. Bees which experienced a probabilistic reward schedule explored more than bees from the constant-reward treatments. Bees which foraged on clustered flowers directed a larger proportion of their flights to exploratory flowers, and made more visits to these flowers, than bees that foraged on intermingled flowers. This tendency was obtained both in the probabilistic and in the constant reward schedules. The results suggest that bees allocate more effort to the exploration of novel feeding patches than to the exploration of new food types within a known patch.

November, 1996
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