Lactation of suckling by the baby. The milk ejection reflex (also called let-down reflex) is not always consistent, especially at first. Once a woman is conditioned to nursing, let-down can be triggered by a variety of stimuli, including the sound of any baby. Even thinking about breastfeeding can stimulate this reflex, causing unwanted leakage, or both breasts may give out milk when an infant is feeding from one breast. However, this and other problems often settle after two weeks of feeding. Stress or anxiety can cause difficulties with breastfeeding. The release of the hormone oxytocin leads to the "milk ejection" or
Social monogamy in mammalian species advantages, however, do not describe why monogamy, and not polygyny, has evolved in the species mentioned above. Some possible conditions which may account for cases of monogamous behavior in mammalian species may have to do with: There are several hypotheses for the evolution of mammalian monogamy that have been extensively studied. While some of these hypotheses apply to a majority of monogamous species, other apply to a very limited number of them. Vasopressin, a hormone that induces a male prairie vole ("Microtus ochrogasters") to mate with one female and stay by her side in order to protect her, has been