Diversity of speed accuracy strategies benefits social insects

Bees face a difficult visual discrimination task when they must choose amongst dozens of species of flowers that differ in reward but look very similar. A speed-accuracy trade-off is often observed in humans and animals tested in analogous visual discrimination tasks [1,2]. Chittka et al. [3] showed that individual bumblebee foragers from the same colony vary in the propensity to make fast, sometimes inaccurate choices and are consistent in that propensity across situations. Unexpectedly, fast-inaccurate bees collected nectar more efficiently than slow-accurate bees [4]. Why would such behavioural variability be maintained within a colony? We suggest that behavioural variability acts to decrease variation in resource acquisition in the wild. A bet-hedging approach using a mixed group of foragers with different foraging approaches will reduce variability in nectar collection rate (NCR) because stochastic variation in forage availability is more likely to detrimentally affect a single foraging approach than multiple approaches. In turn, lower variability in NCR may help reduce the probability of extinction/colony death while overwintering [5]. Three conditions are necessary for colonies with mixed foraging strategies to outperform a colony with a single foraging strategy: first, there must be spatial or temporal heterogeneity in the distribution of rewards (we assume this to be true); second, the above heterogeneity must affect when and whether slow-accurate or fast-inaccurate strategies result in higher NCR; and third, bees must remain faithful to a particular speed-accuracy approach. Here we show that there is consistent within-colony variance between honeybee workers in their speed-accuracy approach in a flower discrimination task and that varying the proportion of rewarding flowers changes the relationship between foraging strategy and rate of nectar collection.