Solution to 'sheepdog mystery' found in the use of two basic rules
New study reveals how canny canines manage to keep herds on the straight and narrow

The 'sheepdog mystery' that has niggled mathematical minds for years has been solved.
The puzzle is how a single dog manages to get so many selfish sheep to move so efficiently in the same direction.

Researchers fitted highly accurate GPS tracking devices into backpacks that were then placed on a trained Australian Kelpie sheepdog and on a flock of 46 female merino sheep in a five-hectare field.
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.