How does resource-defense polygyny give some males access to multiple females?

In the context of zoology, resource-defense polygyny is a mating system where males gain access to multiple females by defending specific, clumped resources that those females require.1

This system relies on the spatial distribution of essential resources, such as food or nesting sites. When these resources are clumped rather than spread out, they become economically defendable, meaning the benefits of restricting access to them outweigh the costs of defense. Because females are attracted to these high-quality resources, a male that successfully monopolizes a territory containing them effectively gains exclusive or primary access to the fertile females that visit or reside within that area.12

It is important to clarify that this mating system is not caused by an imbalance in the sex ratio of a population. While some polygynous species may exhibit an adult sex ratio skewed toward females, research has demonstrated that the ratio of males to females is typically 50:50 at birth. Instead, the observed imbalance is a consequence of the polygynous relationship itself, as the intense competition and sexual selection pressures associated with these systems often result in higher mortality rates for males.3