Honey bee drones are synchronously hyperactive inside the nest

Abstract

Eusocial insects operate as an integrated collective with tasks allocated among individuals. This applies also to reproduction, through coordinated mating flights between male and female reproductives. While in some species male sexuals take only a single mating flight and never return, in the western honey bee, Apis mellifera, the male sexuals (drones) live in the colony throughout their lives. Prior research has focused almost exclusively on drone behaviour outside the nest (mating flights), while ignoring the majority of their life, which is spent inside the nest. To understand the in-nest behaviour of drones across their lives, we used the BeesBook tracking system to track 192 individually marked drones continuously for over 20 days, to examine how drones moved and spent time in the nest. In agreement with previous work, we found that drones spend most of their time immobile at the nest periphery. However, we also observed that drones have periods of in-nest hyperactivity, during which they become the most active individuals in the entire colony. This in-nest hyperactivity develops in drones after age 7 days, occurs daily in the afternoon and coincides with drones taking outside trips. We found strong synchronization across the drones in the start/end of activity, such that the drones in the colony exhibited a ‘shared activation period’. The duration of the shared activation period depended on the weather; when conditions were suitable for mating flights, the activation period was extended. At the individual level, activation order changed from day to day, suggesting that both the external influence of weather conditions as well as exchange of social information influenced individual activation. Using an accumulation-to-threshold model of drone activation, we show that simulations using social information match experimental observations. These results provide new insight into the in-nest behaviour of drones and how their behaviour reflects their role as the male gametes of the colony.