Collective foraging in a stingless bee: dependence on food profitability and sequence of discovery

Abstract

We examined the ability of Trigona recursa , a scent trail-laying stingless bee, to allocate foragers to the more profitable of two food sources. Imbibing time and imbibed volume of individuals were the same at feeders containing 20% or 40% w/w (weight in weight) sugar solution. However, sugar intake rate and sugar per crop load were significantly higher for the 40% solution, which was therefore more profitable. Collective foraging of two colonies was observed without interference with the recruitment process. One bee was trained to a 20% food source and another at the same time to a 40% source. Recruitment to both food sources started simultaneously. In all trials the majority of recruits landed at the 40% food source. This cannot be the result of bees comparing the two sugar concentrations because less than 1% of the recruits landed at both feeders. When we offered the 20% food source 90 min before the 40% source, the newcomers at the 40% food source never outnumbered the newcomers at the 20% source. Significantly more recruits landed at the less profitable food source. This is likely to be caused by a positive feedback resulting from the large number of bees that had already exploited the poor source and reinforced the scent trail. New recruits presumably selected the more intensively marked trail, neglecting the new and weakly marked one that would lead them to the richer food.