Why are some bees aggressive?

‘Angry as a bee’ is a phrase commonly used in Swedish to describe a person who is extremely irate or furious. Although I sometimes use it myself, this idiom has long bemused and perplexed me, especially since becoming a beekeeper. Because even though bees are in possession of a sting and the accompanying venom to inflict serious pain, they are not creatures who are inherently aggressive or angry. But why then do we sometimes think honey bees are aggressive or angry?

Roman mythology tells the story about how the honeybee acquired her sting. It describes how the queen bee asked Jupiter for a sting in order to defend against humans stealing honey from her defenceless colony. Jupiter granted her wish. But as he loved humans and did not want to inflict unnecessary pain on them, he added that if a bee used her sting, she would also die. Evolutionists may argue that this is not what actually happened. However, the fact remains that to the bee, the sting is a double-edged sword. It is a very effective defence mechanism, but one that should only be used when absolutely necessary to defend the survival of the colony as it leads to the inevitable death of the bee herself.

In this blog article, we will look at the different reasons why bees show aggressive or defensive behaviour. And how to best deal with it. Read also: Bee stings, reactions and immunity – a beginner’s guide

What is aggression in bees?

When we talk about angry bees or aggressive colonies, we often talk about bees who display behaviour such as meeting, following, stinging, pouring out of the hive at inspections and charging at us. To us, and others around us, our families, and neighbours, this feels like aggression. After all, the bees are after us, and when they get us, it hurts. We feel under attack and try to defend ourselves by swatting, running, flailing, or barricading ourselves in the garden shed. Conversely, if we look at the scenario from the bees’ perspective, we will see that it is not seldom us, the beekeepers, who are the aggressors. Their behaviour is merely a defensive one. But because of the sting and venom and the pain it causes us, we often call it aggressive instead of defensive behaviour.

One might argue that it is simply semantics, different ways of describing the same behaviour, but in calling bees angry or aggressive, we are doing them a disservice. It also does not help in identifying the root cause or causes of their behaviour. Certainly, there are times when bees display aggressive behaviour. I will not pretend that I too have not encountered the notorious Kamikaze bee who fly straight at you and bury her stinger in you without warning. However, far more common than aggression, are bees that are defensive, agitated, disturbed, hungry, frightened, alarmed, stressed or restless. In dealing with a colony that appears aggressive, we must first figure out why they are acting or reacting the way they are. Only then can we deal with them appropriately.

Alarm pheromone

It is often said that the first sting causes the most damage. This is not because the sting itself is necessarily more painful than others, but because when a bee stings, she releases an alarm pheromone which alerts other bees and causes them to behave defensively and sting. Honeybees are known to have two alarm pheromones, both of which are highly volatile for maximum effect.

The main alarm pheromone is released by the Koschevnikov gland, which is located near the sting. It releases a pheromone consisting of a large number of chemical compounds. It also smells like bananas, which has given rise to the advice not to eat bananas before working with bees!

When the pheromone is released, it will attract other bees to the location. The more bees join in, the more pheromones are released attracting even more bees. This is how situations can escalate very quickly, and the reason why dealing with overly aggressive or defensive bees becomes so difficult.  

Temporarily cross bees

The Roman story described very well how a colony’s ability to defend itself is absolutely essential for its survival. What it failed to mention though, is that most aggressive or defensive behaviour is temporary, and that in many cases, it is possible to intervene to lessen hostile behaviours. It is useful to make a distinction between temporarily cross bees or colonies and permanently or increasingly aggressive colonies.

The temporary behaviour is linked to the cyclical nature of the seasons and the life of the honeybee as well as external factors. Permanent or increasing aggression is linked largely to genetics, but also in some cases the location of the hive. It is sometimes a combination of two or more factors that causes the bees to become feisty.

Reasons for aggressive & defensive bee behaviour

Weather

Changes in weather can make some bees very tetchy. Especially if it is thundery, overcast, raining or there is a weather front approaching. A combination of high temperatures and high humidity is usually worst. Handling tip: leave colonies alone if possible and return when the conditions have improved.

Lack of food/protecting stores

Increased hostility can also be experienced during nectar dearth or as a flow is coming to an end. This is particularly poignant when bees have been working a single crop such as oilseed rape and a lot of the forager bees are idle in the hive causing congestion. If it happens to coincide with the honey being removed it is often worse. Handling tip: this state is temporary. Check stores and feed if necessary. Reduce entrance if colony is at risk of being robbed. Check for robbing behaviour. Increased congestion can lead to swarming preparations in the spring so be prepared.

Bees can also get increasingly defensive if stores are low. They might be at an increased risk of robbing which places the whole colony in a state of alert. Handling tip: Check stores and feed if necessary. Reduce entrance if colony is at risk of being robbed. Check for robbing behaviour.

Bees feeling under threat

Defensive behaviour is usually linked with bees feeling under threat or unsafe. They may be defending stores, trying to fight off bees and wasps, under attack from other predators (beekeeper included). In many colonies you will also notice defensive behaviour increasing as the colony expands. The extent of which varies from colony to colony. Handling tip: Reduce handling while this phase passes. Reduce entrances and make sure the entrance does not overlook where people or animals are moving around. Constant movement puts the guard bees on high alert, and they will fly out to investigate. Place hives such that drifting is at a minimum, as this can also agitate the guard bees.

If bees are unruly and difficult to handle, or have a sudden change in temperament, this behaviour is often linked to the state of the queen. It can signal an impending change of queen as in swarm preparations or queenlessness. A thorough inspection will be necessary, and steps taken to remedy the situation. I.e., swarm manipulations or inserting a test frame.

Poor handling skills

Poor handling skills by the beekeeper can make bees very agitated. If we are clumsy, dropping things, rolling bees, using too much or too little smoke or inspecting or manipulating our colonies too often or for too long, the bees will usually rear up. We also know that the bees react to smells. Hence, if the beekeeper uses perfume or has a lot of residual alarm pheromone on the beekeeping suit, the bees can react to this as well. Handling tip: The only remedy here is experience. Inspect colonies when necessary and to try to handle your bees calmly and purposefully. Do inspections when most forager bees are out, and the weather is amenable. Wear a light coloured suit, wash it regularly and use your smoker properly.

Calm bees are a dream to handle and make beekeeping a very enjoyable hobby

Permanently or increasingly aggressive bees

Hive placement

The positioning of the hive could be responsible for hostile behaviour. The bees can become agitated if the hive is placed in a vulnerable location, if there is a heavy canopy over head or dense vegetation surrounding it. Beekeeping tip: clear the apiary of excessive vegetation or move the colony.

F2 Aggression

If all else has been ruled out, the aggression or overly defensive behaviour of a colony could be genetic.  F2 aggression is a term commonly used to describe an increase in aggression that occurs in the offspring of the daughters and grand-daughters of pure bred queens. Most beekeepers will have bought queens at some stage. However, it is fair to presume that most of our queens have mated in the locality around their apiary. They will have mated with drones from a number of different colonies and sometimes also different strains of honeybee. Because of this genetic diversity, it is not surprising that the temperament will vary from colony to colony, and that some bees are more difficult to handle.

When requeening an aggressive colony, you will often see an improvement even before the bees from the old queen have died off and been replaced by the progeny of the new queen. It is therefore argued that not only is aggression genetic, it also is affected by the temperament of the queen.

It is important to keep records of the temperament of your colonies, and not to breed from the ones showing undesirable traits. Read more about keeping Hive records here: Hive records. It’s also advisable to cull overly aggressive colonies (replace the queen, not euthanize the colony). Also consider culling drones from worst ones. Allowing drones from aggressive colonies to mate is irresponsible and will only prolong the problem for both yourself and surrounding beekeepers. If you are in an area with breeding programs or a conservation area, avail of the resources at hand.

If you enjoyed reading this article, you might find my article How to deal with aggressive bees interesting.

Happy beekeeping!

/Hanna

Hanna Bäckmo