In this model, sheep wander randomly while shepherds circulate trying to herd them. The shepherds follow a set of simple rules. Each shepherd starts wandering randomly. If it bumps into a sheep, it picks the sheep up and continues to wander randomly. When it bumps into another sheep, it finds a nearby empty space, puts its sheep down, and looks for another one. Whether or not the sheep eventually end up herded and in a single pile depends on the number of shepherds and how fast they move compared to the sheep. This project is an extension of the model of termites gathering wood chips into piles (see "Termites").
For detailed instructions on using the program, take a look at the info window from the Shepherds model.
Click on one of the pictures to see a quicktime movie of the model: