As a young stallion matures, he becomes an increasing threat to the the dominant males. The herd stallion will position himself between his harem of mares and the younger male, and any advancement of the junior horse too close to the mares will be instantly confronted.

Here, a four year old pinto stallion watches a herd of mares and the older stallion feeding across a ravine. He was chased away immediately after this image was taken, only to return and watch again.