Sheepdog Strategy

Herding a small group of “noisy” sheep holds hints for computer algorithms

- Rohini Subrahmanyam

Sheepdog trials put trained dogs to work herding small groups of sheep.

WATCHING HOURS of “sheepdog YouTube”—competitions where trained dogs shepherd a small number of unpredictable sheep—gave scientists a key insight into how to control chaotic swarms. The trick, they write in Science Advances, is to exploit the sheep’s indecisiveness.

Sheepdogs routinely steer and split groups of 50 or more sheep. But in the century-old tradition of sheepdog trials, dogs display their skills by controlling only four or five. Such a small flock is inherently “noisier”—less predictable—and harder to manage than a large herd. Without the safety of numbers, their individual personalities can drive them to frequently switch between “Flee the dog!” and “Keep calm and follow the others.” How do sheepdogs successfully steer small groups of erratic sheep?