Oxytocin serves several functions in the body including control over uterine contractions, cervical softening, and penile erection in the male. Other oxytocin-receptive nerves act in the modulation of pain as well. Vasopressin typically is known for action in the cerebral cortex aiding in memory. These endorphin studies have centered on the vole, a tiny mouse-like rodent that lives in the Midwest United States. Two species of voles, although similar in most respects, differ greatly in terms of mating habits.
Prairie voles are extremely monogamous.
A pair will share the same burrow-nest, cooperate in raising young, show distress if separated, and spend most of their lives side by side. Even if one of the pair dies, the other rarely finds another mate. The counterpart to the prairie vole is the montane vole. The mountainous rodent is promiscuous, only maternally parental, and appears to be ambivalent to isolation. Initial investigations showed that prairie vole females did not form a bond with a male until after mating.