Stress and the bee: the impacts of hive design and management practice on honey bees, Apis melifera L..

Daniel Cook, Caroline Hauxwell, James McGree and Althea Blackler. Corresponding author: d9.cook@hdr.qut.edu.auQueensland University of Technology (QUT), Brisbane 4000, Queensland, Australia

Figure 5. Thermal rate of change in filled and extracted honeycomb compared to ambient conditions in a simulated super.

Thermal rate of change of different states of honey comb

Figure 4. Thermal buffering effect of full honey comb verus extracted honeycomb in a simulated Langstroth 10 frame super.

Thermal buffering effect of honey in the bee colony

Figure 2. Thermal energy and time required to heat a 10 frame Langstroth super to optimal colony temperature (35°C).

Energy required to raise an empty super to colony temperature from ambient temperature

ReferencesChrousos, G. P. (2009). Stress and disorders of the stress system. Nature Reviews Endocrinology, 5(7), 374–381. http://doi.org/10.1038/nrendo.2009.106

de los Reyes, P. (2012). [Audit] The Langstroth Hive. [JPG]. Retrieved August 3, 2018 from https://mocosubmit.com/hive/

Tautz, J. (2008). The Buzz about bees, Biology of a superorganism. Springer-Verlag Berlin Heidelberg. http://doi.org/10.1007/978-3-540-78279-7

Commonly, beehives in Australia are Langstroth movable frame types, invented in 1854 for honey production. The design of these has not fundamentally changed since its invention.

Colonies of A. mellifera maintain a mean brood nest temperature of 34.5-35.5°C, critical for brood development and nectar evaporation.

Colonies invest significant energy to maintain these conditions through behavioural modification of the hive environment.

Hive inspection and honey harvesting are invasive practices requiring the partial disassembly of the beehive.

The bee-energy required to return the colony to thermal homeostasis can be described as an acute, time-limited stressor, removing worker bees from critical tasks such as cleaning, defense and foraging.

Our hypothesis is that honey harvesting and hive inspection practices create thermal stress for the hive in both micro-environment venting and removal of thermal mass (honey).

Introduction

Differences in monthly high and low mean ambient temperatures directly corolate to energy input by the bee colony to return an empty super to colony temperature (figure 3).

3) Honey acts as an effective thermal buffer in the hive providing stabilisation from external temperature changes such as weather, and internal changes such as movement of bees within the colony (figure 4).

Full honeycomb reduces the temperature rate of change by up to 75% in increasing changes and by 80% in negative changes (figure 5).

4) The results showed a drop in the top temperature sensor when the lid was removed, and a small decrease in both base and brood air temperatures.

This may indicate a possible ‘chimney effect’ of warm air rising from the colony and drawing cool air in through the bottom hive entrance.

When the hive is resealed the temperature at all sensor locations is rapidly restored.

Methods1) Langstroth honeycomb frames were weighed and centrifugally extracted to discover ratios of honey, wax and wood in the honey super.

2) Theoretical specific heat capacities and energy requirements were calculated for varying configurations of replacement honey supers, and varying environmental conditions.

3) Frames of full and extracted honey-comb were placed in a thermally controlled cabinet and cycled hrough varying diurnal temperature ranges in simulated hive environments.

4) Live beehives had custom IoT temperature sensors placed above honey frames in the honey super, and above and below the brood frames in the brood box.

1) An average Langstroth 10 frame ‘super’ of honey contains between 20-25kg (~73%) of honey and 5kg of beeswax (~19.8%).

2) A honey super maintained at 35°C will lose almost 1MJ of heat energy if allowed to cool to 20°C (ISO-1).

Extracted honeycomb requires 249kJ of heat energy to bring it to colony temperature compared to 95.5kJ for wax ‘foundation’ sheets (comb building substrate).

This equates to 64,000 bee minutes of activity (at 3.9J/min (Tautz, 2008)) for extracted comb and 24,000 bee minutes for foundation (figure 2).

However, new foundation requires construction of new wax comb requiring 339MJ of energy

Results

Hive inspection causes short term variation in colony temperature, exacerbated by a ‘chimney’ effect of the warm humid air rising from the hive pulling cool air in through the base of the hive.

Honey plays an important role in thermal stabilisation of the hive. Removal of the honey through harvesting causes a loss of colony thermal stability.

Changes in beekeeping practice, such as supering on a warm day or preheating hive components will reduce stress to bee colonies.

Conclusion

Figure 1. The Langstroth Hive. de los Reyes, P. (2012)

Hive lid

Honey Frames

Honey Super

Queen Excluder

Brood Frames

Brood Box

Landing Board / Base

Hive Stand

Inner cover

Figure 6. (Left) Colony temperature changes during a 10 minute inspection. (Right) Detailed view of inspection period

Temperature changes in the beehive due to invasive inspection procedures

Figure 3. Thermal energy required to restore colony homeostais in extracted honeycomb on mean cool and warm days.

Energy required by colony to restore hive homeostais compared to mean ambient temperature