How does mate choice differ from competition between members of the same sex?

In the context of sexual selection, mate choice and competition between members of the same sex represent two distinct strategies for increasing reproductive success, often categorized as intersexual and intrasexual selection, respectively.1

Competition Between Members of the Same Sex (Intrasexual Selection)

This form of competition typically involves members of one sex—most commonly males—vying for access to the opposite sex. It favors traits that enhance fighting ability, such as increased size, strength, and the development of weapons like horns or antlers. These physical attributes allow individuals to dominate rivals, defend territories, or secure harems. Additionally, this competition can extend to post-mating behaviors, such as sperm competition, where males employ strategies like mate-guarding or physical removal of a competitor's sperm to ensure their own paternity.213456

Mate Choice (Intersexual Selection)

In contrast, mate choice involves one sex—usually the female—exercising discrimination when forming partnerships. Because females often invest more in offspring (e.g., producing large, nutrient-rich eggs), they are typically more selective. They may choose mates based on:2354
* Direct Benefits: Selecting males that provide resources, such as food or protection, which directly improve the female's or offspring's survival.54
* Good Genes: Choosing males with elaborate displays or ornaments that serve as honest indicators of genetic quality and health.534
* Runaway Selection: Preferring traits that are attractive, even if they are arbitrary, which can lead to the evolutionary exaggeration of those characteristics over generations.534

While competition focuses on overcoming rivals to gain access to mates, mate choice focuses on the active selection of partners based on traits that signal fitness or provide tangible benefits.21