The waggle dance, and what it tells you about your forage

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This one is here because it is useful, not only because it is clever. A colony that has to fly further is telling you something about the ground around your hives, and the dance is where it says so.

What the dance actually is

A forager who has found something worth having walks a figure of eight on the comb. The middle stroke of the eight is the waggle run. She moves forward in a fairly straight line while shaking her body from side to side. Then she loops back to the start and does it again. 2

Three parts, and only one of them is the message.

• The waggle run carries everything. How long that one straight stroke lasts, and which way it points, is the whole of what the other bees are given.
• The return loop is just getting back. Its length is not where the information is.
• She alternates. One loop swings round to the left, the next to the right, which closes the eight and lets her repeat the same stroke over and over. The swing during the run itself is fast, about 13 Hz, and it is one of the steadiest things about the performance. 3

Direction is the angle off vertical

She is on vertical comb, in the dark, so she cannot point at anything. Instead she uses the one direction a hive always has, which is up.

Straight up the comb means fly towards the sun. A run 40 degrees left of vertical means fly 40 degrees left of the sun. Straight down means fly away from it. 10

Put plainly, she is substituting gravity for the sun. Outside she holds a course against the sun’s azimuth, which is its compass bearing rather than its height. On the comb she holds the same angle against gravity, and the bees behind her turn it back again.

The sun moves, so the dance moves

The sun’s bearing shifts all day. A field that is dead into the sun at nine in the morning is well off to one side by five. No fixed angle can keep meaning the same place.

It does not have to. The dance is turned as the day goes on, so a run for the same site sits at a different angle in the evening than it did that morning. 4 That correction is happening inside a dark box. She cannot see the sun while she dances. What she works from is a learned course for it, held in memory. 10

The neat proof of that is a cloudy day. Overcast does not stop a colony working a familiar patch, and it does not stop the dances pointing the right way either. The bees have learned where the sun sits relative to the landmarks they already know, so they can pull the correct angle out of memory with nothing showing in the sky.

Distance is in the length of the run

The longer the waggle run lasts, the further away the food is. The return loop lengthens with distance too, but it is variable and carries little of the signal, so it is the waggle phase that gets timed. Bees trained to feeders between 100 m and 1.7 km stretched their runs more than fivefold. 5

• About 0.41 seconds at 100 m. That is a mean, and the spread around it is 0.10 seconds, so short runs are noisy.
• About 2.20 seconds at 1.7 km.
• The line bends. Inside roughly a kilometre the run grows by about 1.4 seconds per extra kilometre. Beyond that it grows by about 0.67 seconds per kilometre.

So inside the first kilometre it is near 140 milliseconds of waggle for each extra 100 m. Further out it is nearer 70. The scale is stretched close in and squeezed at range, and both figures are ballpark. The next section is why.

Why nobody can give you one number

Popular writing about the dance loves a clean conversion. There is not one, for three separate reasons.

• Species and subspecies differ. The slope of that distance curve varies across the genus, and it tracks how far each kind normally flies. A short usual range goes with a steep curve, and a long one with a shallow curve. 6 The figures above came from Carniolan bees, which may not be what is in your hive. 5
• Individual bees differ. Every marked bee trained to a feeder of known distance turned out to have her own calibration, differing in both slope and intercept. A dancer and a recruit can be out by as much as 50 per cent on distance. 7
• The measurement is visual. What she is timing is not effort or air miles but the flow of the ground past her eyes. 8

That last one is why anyone mapping forage this way calibrates their own bees over their own ground, rather than borrowing a curve. 12 Every figure above is a local answer.

The round dance is not a second dance

Most introductions give you two dances. A round dance for food close to the hive, with no direction in it, and a waggle dance for food further out. Tidy, and not quite true.

Foragers trained to ten distances from 10 m out to 500 m put a waggle phase in every dance. 9 Close in the run is very short and the two loops swing so far round that the figure reads as a circle. Nothing has switched. The signal has been squashed, and it still has a direction in it.

A round dance makes better sense read as a waggle dance with a very short distance in it. 10 So where you see a number quoted for the changeover, treat it as a convention rather than a boundary.

The bees following her

Followers crowd round the dancer, most of them alongside her, and reach out to touch her with their antennae. Her wings beat at roughly 265 Hz while she waggles, and that carries through the wax. Empty comb passes it on better than capped brood, and dancers on open comb recruit about three times as many nestmates. 2

No single run is exact either. Successive runs in one dance scatter by about 10 to 15 degrees either side of that bee’s own mean direction, so a follower is averaging a spread. What she comes away with is less than most people assume.

• A bearing and a distance, roughly. Not a fix.
• No picture and no landmark. She has to go out and find the thing herself.
• No guarantee. Following a dance is the start of a search, not the end of one.

That last point is not guesswork. Riley and colleagues put transponders on recruits and tracked whole flight paths by harmonic radar. 11 It is the first real measure of how well a bee turns a dance into a flight. Most recruits flew straight out along the line they had been given, then spent a long time hunting about at the end of it. The dance gets a bee to the right field. It does not put her on the flower.

Von Frisch, and the argument that followed

Karl von Frisch worked out what the dance meant. He shared the 1973 Nobel Prize in Physiology or Medicine with Konrad Lorenz and Nikolaas Tinbergen, a third each, for their work on animal behaviour. 1

It was not accepted quietly. From the 1960s Adrian Wenner and Patrick Wells argued that recruits were not reading a message at all. Scent on the dancer and scent at the flowers, they said, was enough to explain how new bees turned up in the right place. 10 The objection was fair. Odour does matter, and nobody had ever watched a recruit fly.

Experiment after experiment then went against the odour-only account, and most researchers had settled the question well before the radar arrived. What the radar added was the flight itself. Follow the whole path of a bee who has had nothing but a dance to go on, and the question answers itself. 11

What it says about your forage

Here is the part that matters if you keep records. The dance is the colony measuring, in flight time, how hard it is to find food where you have put them.

Couvillon, Schürch and Ratnieks decoded more than five thousand dances at a Sussex site over two years and used them for exactly that. Mean distances came out near 493 m in spring, 2,156 m in summer and 1,275 m in autumn, so high summer was the hard season rather than spring. 12 Choosing and laying out an apiary covers what that means for siting.

The National Bee Unit comes at it from the other end. Forage varies by place, by year and through the season. April and May are a key stretch, because brood rearing picks up just as the spring flowers come out. Parts of the country then run lean in June, the June gap, though it does not come every year. Learn what is in flower near you, and when. 13 A colony flying further in June than it did in May is one way of watching that gap arrive.