Honey bee colonies maintain CO2 and temperature regimes in spite of change in hive ventilation characteristics

Authors: Meikle, William; BARG, A. - Tufts University; Weiss, Milagra

Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/2022
Publication Date: 8/18/2022
Citation: Meikle, W.G., Barg, A., Weiss, M. 2022. Honey bee colonies maintain CO2 and temperature regimes in spite of change in hive ventilation characteristics. Apidologie. 53. Article 51. https://doi.org/10.1007/s13592-022-00954-1.
DOI: https://doi.org/10.1007/s13592-022-00954-1

Interpretive Summary: Honey bee colonies need to maintain certain conditions within the bee hive for the colony to thrive. That bee colonies warm the inside of the hive, particularly near the larval bees, is well known. Because bee colonies live in a confined space, bees must also ventilate the hive to get rid of CO2. Researchers have found large swings in the concentration of CO2 within hives during the day. Whether high concentrations are a by-product due to bees simply ventilating less and allowing CO2 to build up, or whether the peaks are actually something the bees want, is not clear. One way to test that is to increase ventilation in the hive and see if bees take advantage of that to lower CO2. We put screened bottom boards under half of the hives, allowing CO2, which is heavier than air, to sink down and out from the hive. We found that average CO2 concentration increased when ventilation increased, which suggests bee colonies desire the CO2 peaks. We also put a sensor near the entrance to see if the bee colony brought in air every 20-150 seconds (like breathing) but we found no such air cycles.

Technical Abstract: CO2, a byproduct of respiration, is toxic at high concentrations so regulation of CO2 within the honey bee hive is an important colony function. In this study, we measured hive CO2 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 CO2 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 CO2 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 CO2 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 CO2 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 CO2 concentration data found no evidence of important CO2 cycle periods other than a strong 24-h period. Bee colonies maintained strong daily cycles of CO2 concentration, with average maximum concentrations'>'11,000 ppm, even in conditions of increased ventilation, indicating that managing CO2 concentration is a complex colony behavior.