Why do males often have higher mortality rates than females in polygynous species?

In the context of Darwinian medicine, the higher mortality rates observed in males of polygynous species are primarily a consequence of sexual selection.

In these species, natural selection shapes bodies to maximize reproductive success rather than longevity or health. Because a single male can fertilize multiple females, the reproductive potential of an individual male is often less constrained by time and resources than that of a female. Consequently, males often engage in intense competition to secure mates, which frequently leads to increased size, aggressiveness, and the development of conspicuous, cumbersome physical traits that can increase vulnerability to predators or injury.123

Furthermore, because an incremental investment in bodily protection and repair yields greater reproductive fitness for females than for males in polygynous systems, males are often "expendable" in an evolutionary sense. This trade-off results in males prioritizing competitive prowess over long-term survival, contributing to higher mortality rates compared to females.23