Offspring are very vulnerable and inexperienced at birth and during the early stages of infancy therefore, maternal behavior is an integral part of an infant's survival. They promote and assure an infant's growth and development with out that death of the infant is almost always seen (Pryce et al., 1994). Maternal behavior as defined in Nelson (2000) is "any behavior that contributes directly to the survival of fertilized eggs or offspring that have left the body of the female." Maternal investment is "the extent to which parents compromise their ability to produce additional offspring in order to assist current offspring." Maternal behavior and investment can differ both within and among species. It can differ in the time spent providing care as well as the quality of care. The differences are due to the animal's habitat as well as the developmental status of their young at birth (Kendrick et al., 1997). In a way it is the quality of the care given to the infant that is most important. Quality of care varies with the amount of direct mother-infant contact and the extent to which the mother provides the infant with carriage, warmth, security, stimulation, and protection (Pryce et al., 1994). If the mother provides care but it is inadequate her offspring may die. Female mammals are unique in that they provide food for their offspring by the milk that is secreted by their mammary glands (Nelson, 2000). This decreases the amount of time the mother has to leave the infants unattended, thus allowing her to stay close to the offspring and provide more direct mother-infant contact.
Litter size, gestation period, intensity and length of care of the young all add up to the total reproductive effort (Nelson, 2000). This seems to correlate with the extent of maternal care given. Litter size is a large determinant of quality of care and individual offspring. Quality of care tends to increase with decreasing litter size.