Bees differentiate sucrose solution from water at a distance

Abstract

AbstractHow we treat animals is strongly influenced by our understanding of their cognitive abilities, and thus accurately assessing cognitive abilities has large ethical and policy implications. Bees have become perhaps the most important model group for studying complex cognition in invertebrates, and show a broad variety of impressive cognitive abilities. Most cognition experiments employ a training procedure in which the animal is required to associate a characteristic of a “flower” (neutral stimulus) to a sucrose solution (positive stimulus) over multiple foraging bouts. We hypothesized, however, that sucrose solution may appear different from water to the bee sensorium, especially their visual system, rendering it superfluous for the bee to learn the intended experimental cues. To test this hypothesis, we presented bumblebees simultaneously with 1.6M sucrose and water on artificial flowers, each flower carrying both liquids. The solutions were presented in three different manners, so as to identify the most likely recognition mechanism: 1) in drop form, providing spectral information as well as visible viscosity information; 2) inside cotton-plugged centrifuge tube, to reduce visual information and remove viscosity information; and 3) soaked on raised cigarette filters, to enhance visibility while removing the viscosity information. The bumblebees chose to contact the sucrose solution significantly more often in all three condition, confirming their ability to discriminate sucrose from water at a distance without the use of any other cues. Spectral differences between sucrose and water are the most likely mechanism for this differentiation. These results may have large implication for the design of training procedures, as the presence of an alternative, natural cue may mask the learning of challenging tasks and increase false negative rates. Importantly, the realization that bees can distinguish sucrose from water at a distance may force us to re-examine much of the literature and unpublished ‘negative results’ on bee cognition and learning, weakening some claims, but strengthening others.