A Game of Hives: native bees at war
Who would have guessed that Australian backyards might be a battlefield for bees?
Or that these deadly skirmishes can involve aerial battles lasting days, thousands of fatalities on both the attacking and defending sides, ousting of the helpless from the hive by the attackers and eventual overthrow of the resident queen, with the victor’s queen then being installed in her place.
A cluster of dead native bees found on the ground in a Brisbane backyard was enough to entice a group of scientists into a deeper investigation of this unusual behaviour of the Australian native bee species, Tetragonula carbonaria.
Their study of the backyard colony, published in The American Naturalist, led to the surprising discovery that the T. carbonaria study colony was not only being attacked by neighbouring colonies of its own species but also by a closely related species, T. hockingsi.
While the T. carbonaria species was known to engage in battles between neighbouring colonies prior to this work, this study provided the first evidence of fatal fighting between different species.
Fighting to the death
Fighting to the death or ‘fatal fighting’ is relatively rare in nature. Evolutionary biologists propose that this is because species have evolved different ways to assess strength and fighting ability that doesn’t involve the loss of the individual.
In species where fighting does escalate to death, scientific theory predicts the risk of death is outweighed by the benefits being obtained, such as fighting for scarce food resources, mates or nest sites.
Fatal fighting has been well studied in ants with beneficial outcomes including slave-making, raiding of nest supplies and gaining access to new food sites.
In the case of the T. carbonaria, the researchers hypothesised that the fighting swarms were most likely attempts at taking over neighbouring hives—that is, the nest location, nesting materials and stored resources.
To test their hypothesis, they made regular observations on the ‘study’ hive in the backyard and collected the dead bees after fights for analysis. Using modern molecular techniques they were able to track which group of bees were attacking and which were defending. It was this analysis that led to the surprising discovery that the attacking bees were in fact a separate species.
Following a succession of attacks by the same T. hockingsi colony over a four-month period, the defending T. carbonaria colony was defeated and the hive usurped, with the winning colony installing a new queen.
The war rages on
To ensure that what had occurred at the study hive was not a one-off event, the research team monitored the colonies of over 260 commercial T. carbonaria hives over a five-year period, recording any changes in species through changes in hive architecture (see note).
[NOTE: T. carbonaria has a brood chamber, in which cells are even and connected by their walls to adjacent cells at the same height—see the spiral-like chamber in the image top of page. The T. hockingsi brood chamber takes on a less organised appearance, being an irregular lattice comprised of clumps of around ten cells connected by vertical pillars—see image below.]
They found evidence of 46 interspecies hive changes (via the change in hive architecture) during the five year period, which were most likely to be usurpation events.
There is still much to be learnt about these small creatures, such as what instigates the attacks, how and when the invading queen enters the nest, and whether the young in the usurped hive are spared and reared as slaves, or killed outright.
For Australian native bees, it is thought that the capture of a fully provisioned nest (including ‘propolis’, pollen and honey stores) is a sufficiently large benefit that it outweighs the loss of so many lives.
As the researchers note, this is an excellent example of how little we actually know about small stingless bees, which can be excellent and resilient alternative pollinators to declining honey bee populations.
Cunningham JP, Hereward JP, Heard T, De Barro PJ, West SA. 2014. Bees at War: Interspecific Battles and Nest Usurpation in Stingless Bees. Am. Nat., 184(6).
September 15, 2015 at 11:36 pm
Very interesting research. We have a hive of T. carbonaria and there has be a great deal of activity by a neighboring colony of similar species for the past 4 months. We’ve noticed eggs being removed and larvae recently. The amount of activity gives us hope that we will end up with a large hive.
October 19, 2015 at 3:28 pm
We have had a hive in the besser block wall at the front of the house for over 18 months and have tried unsuccessfully to move it into another place. We will keep trying that one. But, my question is about behaviour. We thought they were swarming but they don’t go anywhere (been doing this for days)they just appear to be involved in ‘fatal fighting’ with hundreds dead on the ground. It appears that they are all the same type of bee. Any ideas as to why they do this?
October 22, 2015 at 9:59 pm
The behaviour that you have described is not uncommon for Tetragonula bees. We call them fighting swarms and they involve bees from the defending hive and another attacking colony. The attacking colony is attempting to take over the defending one by installing their own queen. Colonies do not die out as a result of fighting and in fact may be strengthened by it. It happens between nests of the same species and also between species, e.g. between carbonaria and hockingsi. There is strong scientific evidence that the genetics of the colony can change from the attacking after a fighting swarm. There is not a lot you can do about it, except watch the spectacle. It may continue for a few weeks. Certainly let me know if the hive appears to have died out at the end of it, but I doubt this will happen. If you want to read more, See: http://www.aussiebee.com.au/abol-013.html.
June 18, 2018 at 6:27 pm
3 weeks ago both of my carb hives were overtaken by hockingsi. I watched their behaviour closely on the final takeover, as they were removing unborn from the nest including the queen. The queen was torn in half. They did not keep any unborn. I was suprised as I had been told that hockingsi were not naturally in my area of Brassall, Ipswich. I have since found the giant nest in a neighbouring yard. The neighbour said the bees were there before the house was built.
June 18, 2018 at 6:31 pm
I would appreciate any pearls of wisdom as I have only had hives for 12 months, thanking you.