The mating pattern in which an animal maintains a single sexual partner is known as animal monogamy. All other forms of sexual relationships make perfect sense from an evolutionary standpoint. A polyandrous female gains feeding territory and protection of her young as well as a larger gene pool for her young. Polygynous males can spread their genetic information more effectively by impregnating many females during the mating season instead of just one.

Animals who exhibit monogamous relationships do so because it increases their ability to survive and hence their reproductive success. For this to be true then both mates must benefit from the relationship, and the number of young who are born and survive must be larger than the number who would survive had the pair not been monogamous. In altricial birds constant parental care is required to feed and protect young. Two parents means that a larger brood can be reared. If a female had to search for food and leave the nest unguarded, the chance of her young being attacked would greatly increased. Furthermore she may not be able to collect enough food for her large brood, and so would have to raise fewer young and hence be less reproductively successful. Another situation that requires a male to stay with just one female is mate guarding. This occurs when the ratio of males to females is very high. The male must stay with his mate in order to guard her so that another male will not impregnate her. In this case because the number of available females is so low the male would probably not be able to participate effectively in polygyny anyway. Another example of monogamy increasing reproductive success is in the cave dwelling oilbirds. The temperature in the cave is always low and the female must continually nest in order to keep her eggs warm. This behavior ensures that the eggs remain warm but leaves no time to gather food. In this case the male is also integral to the survival of his young. He seals the female in the nest and delivers food to her all throughout their clutches gestation.

Mammals display very little monogamy as a group. In most cases very little parental care is required of the males. The females produce milk and in many cases give birth to precocial young. Hence it is surprising to find monogamous mammals, but some do exist. For instance the male Djungarian hamster actually helps deliver his young. He pulls the birthing baby out of the female’s birth canal and clears its air passage. In studies where the male is removed before labor the young do not survive. This is yet another situation where male presence increases reproductive output. Another example of mammalian monogamy is apparent in primates. The male’s main function in this instance is to protect young from infanticide by other males. However, there is no connection between male mammals that offer parental care and monogamy. In many cases when a male offers parental care he is polygynous.

So the age-old question of whether or not monogamy is a natural occurrence in humans can be argued either way. If a male can effectively care for several families perhaps he need not be monogamous. Also it has been extensively demonstrated that females do not require a male to successfully raise offspring. However a male female bond is definitely formed when caring for children. Is this a new development of human interaction or an evolutionary trait that has lead to monogamy? With the divorce rate at 50% the statistics for successful marriages in the United States also offer no definitive answer. Leaving us to do what we are so well known for in the animal kingdom: make an informed decision.