Maternal behavior is that behavior exhibited by mothers towards their young which is presumed to aid the young in their survival growth and development, both physically and behaviorally. Maternal behavior is a characteristic of mammals that the females suckle their young from specially developed mammary glands, which produce mild sufficiently nutrition to sustain the young during the early stage of life. It is therefore, appropriate to restrict the term "maternal behavior" to females and to use the general heading "parental behavior" when considering other animals (birds like pigeons). Maternal behavior has two phases: 1) general motivation to approach and nurse a neonate and 2) specific identification of the neonate as one' s own. General maternal behavior is triggered by the events of parturition especially the fall in estrogen and progesterone and the appearance of a foal - like creature - small, wet, uncoordinated, with a foreshortened face and a high pitched neigh. Signaling a critical period during which the odor of the neonate encountered will be learned . Subsequently all other neonates will be rejected. The sense she uses is probably not from the main olfactory system, but from the vomeronasal organ. In sheep, blockage of the entrance to the vomeronasal organ results in promiscuous ewes who will allow lambs other than their own to suckle. The same is probably true of horses.