Water collection and storage
The behavioural regulation of thirst, water collection and water storage in honey bee colonies.
This study examined how a honey bee colony detects and quenches its collective thirst when brood hyperthermia (>36°) is observed.
Objective and Experimental Design
This study examines how a honey bee colony regulates its collective thirst when the brood nest undergoes hyperthermia. The authors worked with two colonies housed in observation hives, with a controlled water source, and combined several experimental conditions: artificial heating of the brood nest, temporary withdrawal of water, and subsequent restoration of water access.
The researchers simultaneously monitored brood nest temperature, ventilation intensity, beard formation at the entrance, colony thirst level, the number of active water foragers, and the quantities of water collected. They also observed water forager behaviour inside the hive and analysed the sugar content of fluids in the crop of individual bees and in certain comb cells.
Main Findings
The central result is clear: water is indispensable for effective evaporative cooling of the brood nest (strong empirical evidence). When overheated colonies still had access to water, they were able to stabilise or reduce brood temperature. Conversely, as soon as the water source was withdrawn, temperature rose rapidly to critical levels despite sustained ventilation and a persistent bee beard.
The study also demonstrates that colonies have only limited water reserves (strong empirical evidence). During overheating, ventilation and partial evacuation of the hive increase almost immediately, while colony thirst and water collection rise more gradually. This lag suggests the existence of a small internal fluid buffer, sufficient to absorb a sudden spike in demand for a short period, but insufficient when access to external water is interrupted.
When water becomes available again after a period of deprivation, collection increases sharply. Water foragers resume work immediately, and brood nest temperature falls again, confirming the decisive role of water intake in colony thermoregulation.
How Water Foragers Are Activated
The study indicates that water foragers do not appear to be activated directly by brood nest heat, but by social and probably physiological signals (strong empirical evidence for the social signal, more cautious interpretation for the physiological mechanism). When a colony is short of water, bees that had previously performed this role are solicited for liquid by nestmates far more frequently. This increase in solicitations precedes or accompanies the resumption of their foraging activity.
The authors suggest that a second mechanism may be involved: heightened individual thirst in water foragers after they have redistributed the fluid from their crop. This point remains open, however, as the study does not definitively distinguish between the effect of social solicitations and that of an internal physiological signal. The overall assessment is therefore: the role of social interactions is strongly supported by the experimental observations; the precise role of individual thirst remains undetermined.
Once water is brought back to the hive, the intensity of interactions during unloading also provides reliable information about colony need: if water is rapidly accepted, demand is high; if rejections multiply, foraging activity may cease. The article thus completes the classical picture of the social regulation of water collection in honey bees.
Temporary Water Storage and Scope of the Study
The results further show that the colony can temporarily store water, or very dilute solutions, in two locations: in the crop of certain bees and in comb cells (strong empirical evidence). After heat stress, water foragers more frequently display highly dilute crop contents than other bees. In the most extreme situations, a larger proportion of the colony also appears to participate in this storage.
The authors also found, following overheating, cells containing low-sugar fluids in the brood area. This comb storage appears to be primarily transient: it is no longer observed the following morning. The data therefore suggest that the most robust water reserve is probably carried by the bees themselves, while the comb serves as a very short-term buffer.
In summary, the article shows that a honey bee colony responds to collective thirst through a finely coordinated interplay of ventilation, partial evacuation, social activation of water foragers, and temporary fluid storage. The most robust conclusion is that rapid access to a water source is an essential condition for protecting the brood nest during heat events. The question that remains open is the precise contribution of individual physiological signals to the initiation of water-foraging activity.
Source reference: Ostwald, M. M., Smith, M. L., & Seeley, T. D. (2016). The behavioral regulation of thirst, water collection and water storage in honey bee colonies. Journal of Experimental Biology, 219, 2156–2165. https://doi.org/10.1242/jeb.139824
See also:
- What water for our bees?
- Practical Guide: 1.6.3 Hyperthermia
- Varroa mite infestation affects colony thermoregulation
- Honey bee behaviour inside the hive: findings from long-term video analysis
- Entrance observations