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“It is said that smoke calms honeybees”

We would like to tell you about the remarkable people behind the South African honeybee conservation group Ujubee and share with you their latest findings on a behaviour of the honeybee that serves to immensely enhance our understanding of colony responses. More than that, their findings serve to do away with one of the much touted explanations for the bees’ response to smoke introduced to their hives by the beekeeper. It behoves us as responsible beekeepers to ensure that our interactions with the bee are guided by true insight into the nature of the bee in the wild as opposed to drawing conclusions from what is seen of the creature in captivity.

We are grateful to Ujubee for sharing with us the results of their latest research project. Karin Sternberg, Jenny Cullinan and Dr. Geoff Tribe devote themselves with selfless abandon to researching, observing and recording the behaviour and life expressions of the South African honeybee Apis mellifera capensis. Their work is an exemplary celebration of the honeybee in the wild and encompasses also artistic expression of the inspiration they find in the Bee. Jenny Cullinan’s works of art are a beautiful testimony to her love for the wild bee.

More recently the intrepid Ujubee team have been collaborating with members of Würzburg University’s HOBOS group to research the responses of honeybees to fire and smoke. Geoff Tribe, Karin Sternberg and Jenny Cullinan tell the exciting story of their exploits:

The perception that honeybees can escape an approaching wildfire by absconding in advance of the fire is so well entrenched that no thought appears to have been given to see that it is an utter fallacy. Entire apiaries in the Western Cape have been utterly consumed by fire on a fairly regular basis over the years with not a single swarm issuing from them as the fire bears down on the apiary.

The reason for such thinking is as a result of the well-known behaviour of bees to imbibe honey when a reproductive swarm departs the hive or the colony absconds. This honey stored in the bodies of workers tides the bees over the period in which they found a new colony by creating combs in which to rear brood. Thus the reasoning that follows is that in responding to smoke by imbibing honey the honey bees are preparing to abscond.

However, a gravid queen is too heavy to fly and honey bees rarely abscond if brood is present. Thus for a swarm to issue from a hive takes preparation in advance – which is impossible with the sudden arrival of a fire. Pheromones are crucial in coordinating such a swarm and smoke disrupts and smothers such chemical communication – which in the case of a beekeeper using a smoker, disrupts the alarm pheromone which targets concentrated attack on the perpetrator who is disrupting the hive.

Reaction of wild colonies of honeybees to fire

Such questions regarding the behaviour of honeybees to fire were raised after the devastating wildfire in the Cape Point section of Table Mountain National Park on 4 March 2015 which incinerated 988 ha of fynbos before it was brought under control. How many of the wild honeybee swarms in this burnt area had survived the fire? We realized then that the swiftness of the fire alone would have ensured that no colony could have escaped in advance of the fire. The question then arose as to why the bees always respond to fire by imbibing honey when there is no intention to abscond? An analysis of the 17 nests within the fire zone supplied an explanation.

The fynbos vegetation is adapted to fire which is essential for its maintenance and which occurs at intervals of 15 to 25 years. Analysis of the wild honeybee nests throughout Cape Point revealed that 78% were located under rock outcrops, within clefts in rocks or in cliff faces; 11% were directly in the ground; 8% in cavities in trees and 3% within the intertwined branches of bushes. Of these nests, 68% had their openings entirely enclosed in propolis with small openings within this propolis wall serving as entrances to the nest.

Honeybee colonies within the burnt area

Within the burnt area were 17 wild nests of which 13 were situated under the bases of boulders and 4 in clefts within boulders. Propolis walls enclosed all these nests, of which two walls and adjacent combs had been totally destroyed by the fire and two walls partially destroyed. However, all these colonies survived the fire. The response of the bees to fire was to imbibe honey and retreat to the deepest recess of the cavity.

Fynbos fires are not exceptionally intense but flames tend to be high (2 to 5m) and of short

duration where temperatures may reach 550 °C for only 10 seconds. Experimental fires in the fynbos spread at a rate of 0.04 to 0.89msˉ¹. Once the fire has passed, the landscape is filled with powdery grey sand and the blackened skeletons of the larger shrubs. It is this devastation of their environment which the bees encounter after the fire has passed where neither nectar nor pollen is available to them. This is when the imbibed honey is essential to tide them over this dearth period which is about 2 to 3 weeks long before the fire-loving ephemerals sprout from underground bulbs or rhizomes and flower in profusion, having been relieved of competition from other plants. However, the surviving swarms were considerably weakened because of the suspension of foraging which was possibly followed by the eating of existing eggs and larvae which could not be reared further due to such a lack of food.

Firmly established, innate behaviour

The response of honeybees to smoke by imbibing honey which tends to make them less inclined to sting, coupled with the masking of their alarm pheromone is a godsend to beekeepers in their manipulation of hives in extensive apiaries. This behaviour is innate and firmly established. That all honeybees of the genus Apis respond in a similar way by imbibing honey in the presence of smoke indicates an evolution in a fire-prone ecology.

Original publication: Tribe, G., Tautz, J., Sternberg, K. and Cullinan, J. 2017. Firewalls in bee nests – survival value of propolis walls of wild Cape honeybee (Apis mellifera capensis). Sci. Nat. 104:29.

DOI 10.1007/s00114-017-1449-5.

Acknowledgment: The permission granted by SANParks to locate and analyse the nesting sites of honeybees in the Table Mountain National Park is gratefully acknowledged.

Here are Jürgen Tautz’s comments on the project:

Honeybees build firewalls

No piece of equipment is more frequently used by a beekeeper than a bellows attached to a tin burner, better known as a smoker. When a beekeeper inspects his hive he uses thick puffs of smoke to deter the bees from defending their nest. It is said that smoke calms honeybees.

Is this so? What is behind this statement?

The localities most often chosen by honeybees in which to construct their nests are hollows in trees. In such forested areas, fires are commonplace and are an integral part of forest ecology. Where there is fire, there is smoke. In response to smoke, bees imbibe honey and retreat into the furthest recess of their nest cavity. The most widely touted reason for this behaviour is that the bees imbibe honey in preparation to abscond or flee should the fire become too much of a threat.

But is this true?

There are many reasons to consider this with scepticism. Firstly, the gravid queen is unable to fly; without the queen and the brood, most bee colonies would be unable to survive. The presence of smoke disrupts all chemical communication necessary to coordinate swarming and the warning period is too short. There is not a single recorded observation of entire colonies absconding in the face of a fire. But there are countless tales of entire apiaries regularly lost as a result of runaway fires.

One could speculate that the consumption of honey by bees increases the volume of their bodies which has the physical-thermal advantage of slowing down the absorption of heat, or that the bee is able to release heat through expending hot honey. This is pure speculation, but both assumptions could be tested experimentally.

With certainty and under specific circumstances, bees build firewalls of propolis behind

which they can survive fire. Recently this was shown (Tribe et al. 2017) for the South African honeybee race, Apis mellifera capensis. The Cape bee is endemic to the winter rainfall region of South Africa where the fynbos (heathland) vegetation is adapted to fire which is essential for its maintenance and which occurs naturally at intervals of 15 to 25 years. Most vegetation is knee-height and devoid of indigenous trees so most of the honeybee nests are located under rock outcrops, within clefts in rocks or in cliff faces, or directly within the ground. Wild fires in fynbos are fast and hot reaching temperatures of 550°C and lasting barely a few minutes. Unprotected colonies could not survive such intensities. The circumstances of these bees require a remarkable solution to protect them from probable death in the face of runaway fires. They build protective walls of propolis, with an average diameter of 20cm and a thickness of up to several centimetres. These firewalls entirely enclose the nest openings, with entrances to their comb restricted to several small openings within the propolis wall. Behind such walls most of the colonies are able to survive wild fires, another example of the incredible genius which exists in nature.

Photo credits Karin Sternberg

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