Good Flocking Behavior Is An Answer To The Big Bad Wolf

Good flocking behavior is the herd animal’s answer to the predator out there, whether it is wildebeests and a lion, or homeowners and a banker. Sticking together won’t fight off the threat, but you have a better chance of being available for appointments tomorrow.

King et al in the current issue of Current Biology tried to quantify good flocking behavior using an unsuspecting group of 46 sheep with an Australian sheep dog standing in for the big bad wolf (1,2). This was going to be a set of quantitative experiments so each sheep was fitted with a gps system so that its precise position could be plotted as a function of time. The sheep dog was also fitted up with a gps system so any sneaking moves would be fully recorded.

The result was that as the dog appeared in its role of the villain, the individual sheep made haste to find the center of the flock. Of course, each sheep could not be at the center simultaneously, so there was a deal of milling around as they showed good flocking behavior with the idea that inside the group meant that you were less likely to feel sharp teeth than if you were outside.

With eager mathematicians amongst the observers, and a plethora of numerical data showing sheep coordinates as a function of time, meant that the apparent chaos of such flocking behavior could be reduced to the simplicity of a first order differential equation. This wonder of simplicity expresses the rate that the cohesion of the flock changes with time once the dog gets within a critical distance.

With these sheep and this Australian with gnashing teeth, 60 meters was felt to be close enough to move into good flocking behavior. By the third trial, the sheep were pretty close together before the dog appeared.  I guess that they had a suspicion that it hadn’t left for the Heathrow to Sydney flight.


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