| Popis: |
To ensure the optimal development of brood, a honeybee colony needs to maintain its temperature within a certain range of values (thermoregulation), regardless of environmental changes in biotic and abiotic factors. While the set of behavioural and physiological responses implemented by honeybees to regulate the brood temperature has been well studied, less is known about the factors that may influence the efficiency of this thermoregulation. Based on the response threshold model of task allocation, increased colony homeostasis should be driven by increases in group size. We therefore determined whether colony size (number of adult bees and amount of brood), positively influenced the efficiency of thermoregulation that we measured via two criteria: (i) the precision of the temperature close to its brood optimum, and (ii) the stability of the temperature around this optimum value. Finally, within the applied perspective of honeybee colony monitoring, we assessed whether the efficiency of thermoregulation could be used as a proxy of colony size. For that purpose, we followed 29 honeybee colonies over two years, measured both brood and adult population size regularly over the beekeeping season, and monitored the in-hive temperature over the 24 hours preceding the inspections of these colonies. We then studied the effect of the size of the colony (number of adult bees and number of brood cells), as well as meteorological variables, on the efficiency of thermoregulation (mean and stability of brood temperature, i.e. between 32 and 36°C). In addition to a clear link with meteorological conditions, we found that the mean brood temperature and the stability of this temperature were both positively linked to the size of colonies. The mean brood temperature was more dependent on the amount of the brood, while its stability was more dependent on the number of bees. However, these relationships between colony size and thermoregulation were too weak for clearly discriminating colony population size based solely on the brood thermoregulatory efficiency. This demonstrates an extremely high flexibility and efficiency of honeybee colonies to thermoregulate the brood regardless of the amount of brood and the group size. |
