Sheep have a natural instinct to copy everything their neighbors do.

Sheep movements are governed by a simple rule: stay close to your neighbor and move when they move. Researchers used GPS tracking in a 2015 study to confirm this behavior. This social copying helps the flock act as one large unit.Sheep have eyes on the sides of their heads. This gives them a wide field of vision between 270 and 320 degrees. They can see almost everything around them without turning their heads. This helps them monitor every movement in the flock at all times.When a predator appears, sheep use a strategy called the selfish herd. Each sheep tries to move toward the center of the group. This creates a tight, swirling mass of animals. Being in the middle makes it harder for a predator to catch an individual sheep.Humans have raised sheep for about 10,000 years. This process has made sheep very dependent on each other. A sheep left alone will have a large increase in cortisol. Cortisol is a hormone that shows the animal is under high stress.The instinct to follow is so strong that it can cause mistakes. If a lead sheep jumps over a shadow, the sheep behind it will jump at that same spot. They jump even if there is nothing there to clear. This predictable nature allows one person and a dog to move thousands of sheep at once.