Overview
Research on spotted hyenas suggests a unique pattern of reproductive success compared to many other mammals. While male mammals typically show greater reproductive inequality, meaning a wider range in the number of offspring produced, the inverse is observed in spotted hyenas. Here, females exhibit greater reproductive inequality than males.
Research Context
In many mammalian species, established biological patterns indicate that males generally possess greater physical strength and display more competitive behaviors than females. Concurrently, males often demonstrate higher levels of reproductive inequality compared to females. This inequality can manifest as a significant difference in the number of offspring an individual produces over its lifetime. Spotted hyenas present a departure from this common mammalian characteristic. The species provides a context where reproductive inequality is more pronounced among females than among males.
Findings
The observed reversal in reproductive inequality in spotted hyenas, where females experience greater disparity in offspring production than males, stems from specific social dynamics. Female spotted hyenas are found to transmit their social rank to their offspring. This transmission of social rank includes the associated advantages, such as preferential access to food resources. In contrast, male spotted hyenas do not pass on such social benefits to their progeny.
The mechanism behind this finding is directly linked to the intergenerational transfer of social standing. The high-ranking female’s offspring, particularly female offspring, inherit the mother's social position. This inherited rank subsequently provides consistent advantages, such as better nutritional intake due to priority access to food. Such advantages directly impact the reproductive success of these females, widening the gap between high-ranking and low-ranking females in terms of the number of offspring they can successfully produce. Without a similar mechanism for males, their reproductive success shows less variation.