Some mammals invest a large amount of energy into gestation which decreases the energy and investment needed from the mother post-parturition (Carter, 1974). The less developed the offspring are at birth the more maternal care is needed.
There are two major types of offspring among mammals specifically the eutherians. Eutherians include those mammals that have placentas during pregnancy. They also have long gestation periods that increase development before birth (Nelson, 2000). The first type of offspring is altrical. Examples of altrical mammals are mice, rats, pigs, cats, and dogs. Their offspring are born almost completely helpless being both deaf and blind and deficient in both motor control and temperature regulation (most species born naked-lacking hair/fur). They require a large amount of care from their mother. Some of the maternal behaviors exhibited by mothers with altrical offspring are nursing and suckling as well as building and maintaining a warm nest, licking offspring to stimulate urination and defecation, and usually aggression towards intruders (Kendrick et al., 1997). .
The second type of offspring that mammals give birth to is precocial. Ungulates are the major group that gives birth to precocial offspring and they include sheep, deer, goats, horses, and cattle. Precocial offspring are usually grazing animals that live in large social groups. When born they have relatively mature motor systems, and they can maintain their own body temperature (most species born with hair/fur). This self-regulation of temperature and mature motor systems are needed due to the fact that they do not have nests and are constantly relocating. They require less maternal care and investment than altrical infants do. Offspring recognition is very important and a strong mother infant bond is usually formed very early. This is necessary for the mother to be able to recognize her own infants among the hundreds that may be born at around the same time.