Monogamy

Monogamy, or should I say the lack of it, has been in the news a lot recently: John Edwards, Tiger Woods, and now Jesse James. Say what you will about how monogamy works, or doesn’t work in humans, but it is relatively rare in the animal kingdom. Less than five percent of mammalian species mate for life.

Biologists recognize several types of mating systems, ranging from monogamy to promiscuity. Why, for example, are deer polygamous while Canada geese mate for life? The vast majority of animal species do not even form pair bonds.

The ultimate objective of a species is to reproduce. The alternative of course is extinction. So the drive to survive and reproduce is strong. As a result, due to a variety of factors, different mating systems have evolved.

Monogamy is a reference to the formation of a pair bond between one male and one female that lasts long enough to rear their young, or perhaps for life, or as long as both individuals are alive. Biologists have even defined different levels of monogamy. One example is seasonal monogamy which occurs in most of our migratory birds, where they pair up during the breeding season but separate during the remainder of the year. The following year they may select a different mate.

Something like 90% of bird species are monogamous, largely because the incubating and feeding of helpless young takes a tremendous parental investment. One parent simply isn’t enough. But, things are not always as they appear, and scientists have discovered that trysts can be quite common in some of these species. Those bird species that produce precocial young such as pheasants are more polygamous.

In mammals, rearing the young is obviously a function of nursing. As a result, the male contribution to the rearing of offspring may be somewhat limited. So monogamy may not provide much of an advantage in mammals. However, in situations where the offspring have an extended period of dependence on parental care, the father may significantly improve the changes of the offspring surviving. That may be exemplified by humans, although as we all know, the system does not always work that way.

Chuck Lura

Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Minot State University-Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.