During travel, groups are led by the dominant female and her foal who are followed by other females in order of rank. The stallion is the rear guard when the family flees from a predator. Members recognize each other primarily by sight, but also by voice and smell. The female guards her baby from other members of the herd when it is first born, perhaps giving it time to learn her pattern of stripes. There is much discussion about the adaptive value of stripes. One theory is that all those black and white stripes break up the shape and make it less recognizable as prey; another is that the stripes of a herd exploding in all directions make it difficult for a predator to focus on one animal. An interesting note is that a newborn zebra has brown, not black stripes.