Should I stay or should I go: honeybee drifting behaviour as a function of parasitism

Nest drifting is often observed in honeybees (Apis mellifera) and can be detrimental to neighbouring colonies because it has the potential to increase disease transmission. However, the characteristics of drifting behaviour over a honeybee's lifetime and the influence of parasitism on this phenomenon have been insufficiently investigated. Using optical bee counters, we tracked the drifting behaviour of workers that were either infected with the parasite Nosema ceranae or uninfected. Approximately 10 % of the tracked bees drifted into a foreign colony. The drifting prevalence was influenced by the colony's location in space but not by N. ceranae parasitism. However, the number and duration of drifts changed over the lifetime of the bees and the season, and parasitism had an effect on drifters, with Nosema-infected bees performing more but shorter drifts. This phenomenon was more pronounced in old bees (+62 and -15 % for the number and duration of drifts, respectively) and could potentially be explained by the energetic stress induced by the parasite. In conclusion, combining a detailed analysis of drifting behaviour with the actual risk of newly established disease in colonies will benefit our knowledge of bee epidemiology.