There is the riddle of the Bermuda Triangle. The unresolved identity of Jack the Ripper. The enigma of how the universe developed beyond a quark-gluon soup following the Big Bang. And then there is the sheepdog mystery.
A puzzle that has niggled mathematical minds for years, the mystery is this: how does a single dog get so many selfish sheep to move so efficiently in the same direction?
The answer may perhaps be that sheepdogs cleverly follow a simple rulebook, according to a journal published by Britain’s prestigious Royal Society.
Researchers fitted highly accurate GPS tracking devices into backpacks that were placed on a trained Australian Kelpie sheepdog and on a flock of 46 female merino sheep in a five-hectare field — an area roughly equal to about seven football fields.
They then used the GPS data to build a computer model of what prompted the dog to move, and how it responded. Sheep cohesiveness is the big clue. The dog’s first rule is to bind the sheep together by weaving around side-to-side at their backs, and once this has been achieved, it drives the group forward.
“It basically sees white, fluffy things in front of it,” said Andrew King of Swansea University in Wales. “If the dog sees gaps between the sheep, or the gaps are getting bigger, the dog needs to bring them together.”
Daniel Stroembom of Uppsala University in Sweden explained, “At every step in the model, the dog decides if the herd is cohesive enough or not.
“If not cohesive, it will make it cohesive, but if it’s already cohesive, the dog will push the herd towards the target.” Single sheepdogs can successfully herd flocks of 80 or more sheep in their everyday work and in competitive herding trials.
“There are numerous applications for this knowledge, such as crowd control, cleaning up the environment, herding of livestock and collective or guiding groups of exploring robots,” said King.