The Effect of Shadow Flicker on Horses

Shadow flicker is a phenomenon caused by the rotating blades of wind turbines. Because horses are prey animals, their response to any unknown or frightening situation is the "flight not fight" instinct. Although shadow flicker is not common in the U.S., any situation where the horse can see rapid unexplained movement is frightening and provokes the flight response.

  1. About Shadow Flicker

    • Shadow flicker occurs when the rotating blades of wind turbines cast a flickering shadow on stationary objects such as houses. The phenomenon relies on several factors, including latitude, the direction of the wind and the height of the sun. Under normal conditions, shadow flicker is rarely seen in the U.S. except in Alaska. At all other U.S. latitudes, the sun isn't at a sufficiently low angle in the sky. If any flicker occurs at all, it's generally limited to a few hours over a year.

    How Horses See

    • Because it's a prey animal, a horse's eyes are set on each side of its head, giving it a wide circle of vision. Its vision extends almost 360 degrees, with blind spots directly in front, directly behind and under its chin. This wide field of view allows the horse to spot predators, and it's extremely sensitive to movement on the edges of its peripheral vision. Normally, the horse's view behind is monocular, using one eye only. If threatened, it will raise its head to bring both eyes into play -- binocular vision -- to assess the danger.

    Shadow Flicker and Horses

    • Horses are very sensitive to movement and could easily be frightened by the flickering shadows of a wind turbine. The first instinct of a frightened horse is to run, which can be dangerous for the rider. Most well-trained horses obey their flight instinct, then allow the rider to pull them up when they realize that the danger isn't getting any closer. However, nervous or inexperienced horses will resist a rider's attempts to stop them, and may even throw the rider off if they become frightened enough.

    Avoiding the Danger

    • According to the American Wind Energy Association, shadow flicker is negligible in U.S. latitudes. If your farm borders wind turbines, the effect of shadow flicker can be disrupted by planting trees between horse fields and turbines. Remember that horses may also become frightened by the noise of turbines, or the unusual sight. When riding a young or inexperienced horse near something new, always try to have an older horse along as company, and make sure you wear a helmet.