10.4 Polygyny

Polygyny is, in many ways, similar to polyandry. Like polyandry, the term polygyny uses the prefix “poly-” but with the addition of the root word “gyn,” meaning female (think of the prefix in “gynecologist”). In this system, one male mates with multiple females. It is more common than polyandry, being found in many mammals, birds, insects, and beyond.

Environments in which this mating system arises also tend to require parental care that is manageable by one individual, in this case the females. Because the females of this species invest so much energy into both parental care and gamete production, the males will often defend females from other males through fights or territorial displays, ensuring that they can reproduce with many females. This prevents many males of the species from being able to reproduce, but does allow nearly all females to do so—the opposite of polyandry.

Additionally, only the males with the “best” genetic quality, or those who are better at attracting and defending their mates, produce the majority of the offspring. In exchange for raising offspring, the males of these species will often present females with nuptial gifts such as food, resources, or a spot within a defensible territory with other females.

Polygynous Gorillas

Gorillas, being such a close relative of our own species, have been well-studied to understand their behaviors and the differences between our species. They are well known for their polygynous behaviors, forming groups in which a single male, often referred to as the silverback, protects a group of females and their offspring, the vast majority of which are closely related to the silverback. Such groups of one male defending many females are often called “harems.” Other males form bachelor groups and attempt to mate with females away from the watchful eye of the silverback.

Females choose their mates, often based on how abundant the resources are that a male controls. The males who are strong and able to defend a larger territory often have more females choose them, but younger and weaker males still often gather control over a small territory with a few females. These males are less competitive, but with time and experience, some will eventually become the iconic silverbacks we are familiar with.

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