Effects of weather and colony size on water collection in honey bee, Apis mellifera, colonies

Honey bee, Apis mellifera , colonies collect water primarily for thermoregulation and larval food production. Although the mechanism underlying the regulation of water collection in honey bees is fairly well understood, less is known about the water requirements at the colony level and the factors that drive them. Therefore, in this study, daily colony water collection was measured using waterers under semifield conditions in spring, summer and autumn, to investigate the effects of weather and colony size on it. Results showed that daily colony water collection increased sharply above a daily mean temperature threshold of 22.3 °C or a daily maximum temperature of 31.5 °C. Based on previous studies, this increase in water collection was likely caused by the needs of brood thermoregulation. Investigating the effects of weather and colony size on daily water collection below and above the temperature threshold that triggers an increase in water collection, we found that the number of adult bees in the colony accounted for just over 40% of the observed variance in daily colony water collection in both conditions. In addition, temperature accounted for 23% of the observed variance in daily colony water collection above the temperature threshold, while the number of open brood cells accounted for 19% of the observed variance below this threshold. Finally, colony size affected the proportion of water foragers, which decreased with the increase of the number of bees before stabilizing at around 13 000 bees. This result indicates that water foraging specialization is dependent on colony size. Our results could help beekeepers in managing colony water supply in apiaries, especially in the face of increasing concurrent heat waves and droughts caused by climate change. • Daily colony water collection under semifield conditions in a tunnel was recorded. • Up to 1.4 litres of water was collected daily. • Daily colony water collection increased sharply from 31.5 °C. • Number of bees explained 40% of the observed variance in daily water collection. • Colony size affected the proportion of water foragers.