Bumble bee nest thermoregulation: a field study

Careful control of brood temperature is important for successful colony development in social insects. Six bumble bee colonies of six common Central European species (<i>B. hypnorum</i>, <i>B. hortorum</i>, <i>B. argillaceus</i>, <i>B. pascuorum</i>, <i>B. humilis</i>, <i>B. sylvarum</i>) were continuously monitored for several weeks. We recorded the brood temperature as well as the air temperature in the nest and outside once per minute using a homemade electronic setup. Two colonies succeeded in producing new queens and males during the measurement period while the other four colonies were attacked by parasites at some point during the equilibrium stage. We discuss the nest thermoregulation in view of species and the number of workers in the colony. The results show that the strongest colonies were able to maintain very stable brood temperature over longer periods (standard deviations below 0.5 °C), which is in agreement with previous studies. Colonies with 25 or more workers typically kept the standard deviation below 1 °C. There are two main contributions to the paper. First, we discuss the applicability of a multi-sensor monitoring setup for an outdoor study. Second, due to fast temperature sampling, we were able to observe different thermoregulation strategies that colonies may apply, including keeping the temperature above 31 °C at night and letting it rise during the day in <i>B. argillaceus</i> and short heating cycles in <i>B. sylvarum</i>.

对于社会性昆虫而言，精准调控育幼巢温对蜂群的成功发育至关重要。本研究针对6种中欧常见熊蜂（*B. hypnorum*、*B. hortorum*、*B. argillaceus*、*B. pascuorum*、*B. humilis*、*B. sylvarum*）的6个蜂群开展了数周的连续监测。我们采用自制电子监测装置，以每分钟1次的频率同步记录育幼区温度、巢内空气温度与外界环境温度。监测期间，共有2个蜂群成功繁育出新蜂王与雄蜂，其余4个蜂群则在平衡阶段先后遭到寄生虫侵袭。本研究结合物种差异与蜂群工蜂数量，探讨了熊蜂的巢温调控机制。研究结果显示，群势最强的蜂群可在较长周期内维持极为稳定的育幼巢温（标准差低于0.5℃），该结论与既往研究结果一致；工蜂数量≥25的蜂群，其巢温标准差通常可控制在1℃以内。本研究的两项核心贡献如下：其一，探讨了多传感器监测装置在野外研究中的适用性；其二，得益于高频温度采样，我们得以观测到不同蜂群所采用的差异化温调策略，包括*B. argillaceus*蜂群夜间维持巢温高于31℃、日间提升巢温，以及*B. sylvarum*蜂群采用的短时加热循环模式。