Bees can communicate with each other using the famous "waggle dance". With special figure-of-eight gyrations, they can accurately tell other hive-mates about the location of nectar sources. Karl von Frisch translated the waggle dance decades ago but it's just a small part of bee communication. As well as signals that tell their sisters where to find food, bees have a stop signal that silences dancers who are advertising dangerous locations.
The signal is a brief vibration at a frequency of 380 Hz (roughly middle G), that lasts just 150 milliseconds. It's not delivered very gracefully. Occasionally, the signalling bee will use a honeycomb to carry her good vibrations, but more often than not, she'll climb on top of another bee first or use a friendly headbutt. The signal is made when bees have just travelled back from a food source where they were attacked by rivals or ambush predators. And they always aim their buzzes at waggle dancers. The meaning is clear; it says, "Don't go there."
These signals were identified decades ago, but scientists originally interpreted them as a begging call, intended to cadge some food of another worker. It seems like a strange conclusion, when you consider that the signals never actually prompt workers to exchange food. Their true nature became clearer when scientists showed that playing them through speakers could stop dancers from waggling.
James Nieh from the University of California, San Diego has uncovered the meaning of these cautionary buzzes. Nieh watched workers as they arrived at crowded nectar sources. Occasionally, the crowds would get too much and the bees experienced pollinator-rage, biting and wrestling with each other. In these cases, the attacker's behaviour didn't change but the victim produced around 43 times more stop signals back at the hive and sent fewer of her fellow workers to the site of the attack.
Any sort of physical assault was enough to change their behaviour, from the attacks of other bees to a short pinch from a curious scientist. But the more dangerous the assault, the more extreme the behaviour. Fights with other bees can be off-putting but they almost never result in loss of life. On the other hand, encounters with a predator like a mantis or a crab spider are far graver perils. When Nieh simulated the strikes of these hunters by pinching worker bees with tweezers, he boosted the number of warning vibrations by 88 times.
In contrast, the smell of pheromones from a bee's sting gland suggests that other workers have been forced to defend themselves but doesn't actually involve physical contact. Accordingly, it increased the number of stop signals by just 14 times.
Surprisingly, we know very little about these sorts of off-putting signals among social insects. One of the only other examples is the Pharaoh's ant, which uses a repellent pheromone to discourage other workers from heading down fruitless paths.
Reference: Nieh, J. (2010). A Negative Feedback Signal That Is Triggered by Peril Curbs Honey Bee Recruitment Current Biology, 20 (4), 310-315 DOI: 10.1016/j.cub.2009.12.060
Image: by MakroFreak
Very cool! I'm a new beekeeper and am always looking for bits of info like this (though I'm not quite sure how I'll put it to use in my hives. :-) )
perhaps this is a very stupid question but I am just a high school student so hopefully someone might answer this without the condescension I have come to expect when asking questions on blogs.
Anyway I just find it amazing the amount of rather complex behavior that bugs like bees and ants are capable of considering they only have a couple thousand brain cells and I am curios how they know to do any of it. do bees know exactly what it is their doing, is there any kind of actual thought involved? like do they make a decision to issue that warning buzz or is it completely instinctual and automatic like me knowing to pull my hand away when I touch something burning hot without thinking about it? if it is entirely instinctual how come they warn some bees that are advertising a dangerous location and not others? And because they do that it must mean there is some degree of decision making involved, right?
Like I said just some things I don't really understand about all this. Also just have to say at the end here, I am really enjoying your blog we all had to read your guppy article (http://scienceblogs.com/notrocketscience/2010/02/evolving_guppies_shape…) for a class and I have been following this blog since. You write about a lot of really interesting stuff.
DKNY - your question is an interesting one! I'll post it up on http://www.askabiologist.org.uk to see if there are any takers.
Hi DKNY, here's a response from Dr. Michelle Pierce (posted here: http://www.askabiologist.org.uk/punbb/viewtopic.php?id=3619) who is a researcher at the School of Neurology, Neurobiology and Psychiatry in Newcastle University:
"OK, well I don't know very much about bee brains specifically, but I know a lot about brains in general and a bit about insect brains, so I will have a go at answering this.
This is a great question, and it brings up all sorts of philosophical issues about the nature of free will, and all sorts of other things that I won't go into here. The simple answer to this is that bees and other insects don't 'think' in the sense of making conscious decisions. Everything they do is pretty much a result of the way their brains are wired up. That's not to say it is innate - 'innate' suggests it is there at birth, yet even simple animals can 'learn' because their brains change over time according to the inputs they get from the environment. But what it IS, certainly, is automatic.
The important thing to remember is the difference between doing something CONSCIOUSLY and doing it UNCONSCIOUSLY. As you correctly say, humans pull their hand away from a hot stove without thinking about it - it is unconscious. And yet if you didn't know about reflexes, you might well suppose that the person was doing this on purpose by thinking 'Ow, that's hot! I'd better move my hand!'. In fact, many (even very complicated) responses can be fully automatic. You'd be surprised at some of the things you do yourself that you thought were voluntary, but that are actually generated by automatic brain activity - walking is a good example: once you get going, your spinal cord takes over, which is why you don't have to concentrate on putting one foot in front of the other. I bet you didn't know that! The difference between us and bees is that we can consciously override these automatic actions, for instance by deciding to skip instead of walk if we are in a good mood! Bees just don't have enough brain cells (we call them 'neurons') to have this degree of control, so they tend to do what they are 'programmed' to do.
You rightly say that bees do not always behave predictably and may appear to be making crude decisions, but in fact this is just a consequence of how complex their brains are. It may be hard for you or I to imagine why a bee may warn one fellow bee and not another of a danger, but you can be sure that there is a reason, and that reason lies ultimately in the way their brains are wired up. Perhaps they just don't recognise bees that are not part of their own hive? Or perhaps it depends on the context - it might be dangerous for the bee to buzz a warning if a predator is nearby, for example, so the part of the brain that senses the danger 'tells' the part that produces the warning buzz to keep quiet on this occasion? Whatever the reason, there is absolutely no reason to conclude that a bee is 'thinking' just because its behaviour isn't exactly the same each time. Complex brains produce complex responses - it stands to reason! And even tiny little bee brains are enormously complex and, as a result, often unpredictable. The bottom line is: things are not always what they seem when it comes to animal behaviour.
In fact, some people believe that free will is an illusion and that humans only THINK they have control over their own decisions. But that's another story..."