Honey bee colonies maintain CO 2 and temperature regimes in spite of change in hive ventilation characteristics

CO 2 , a byproduct of respiration, is toxic at high concentrations so regulation of CO 2 within the honey bee hive is an important colony function. In this study, we measured hive CO 2 concentrations at 1-s intervals while ventilation characteristics of the hive were changed every few days, and we analyzed the data for effects of increased ventilation on colony behavior and thermoregulation. Average CO 2 concentrations were significantly higher, by > 200 ppm, when hives had screened bottom boards (higher ventilation) compared to hives with solid bottom boards (lower ventilation) at the same time. Daily CO 2 concentration amplitudes, hourly temperature, daily temperature amplitudes, nor hourly hive weight changes were not significantly affected by the changes in hive ventilation. In a second experiment, we found average CO 2 concentrations at the top center of the upper hive box, on top of the frames, were significantly lower than concentrations at the center of a solid bottom board underneath frames, which was expected due to the higher density of CO 2 relative to air. Bee colonies have been reported to cycle air, with shorter periods of 20 to 150 s and longer periods of 42–80 min, but a periodogram analysis of the CO 2 concentration data found no evidence of important CO 2 cycle periods other than a strong 24-h period. Bee colonies maintained strong daily cycles of CO 2 concentration, with average maximum concentrations > 11,000 ppm, even in conditions of increased ventilation, indicating that managing CO2 concentration is a complex colony behavior.