Final answer:
Females cannibalize males during copulation to provide necessary nutrients for egg development, especially when energy availability is low. Other mating systems like monogamy can be based on mate guarding, male assistance, and female enforcement.
Step-by-step explanation:
The observation that females cannibalize males during copulation is seen in certain species and has led to several hypotheses about its evolutionary benefits. One such hypothesis is the hungry lover hypothesis, which posits that female cannibalism of males provides necessary nutrients that support the development of her eggs. This may occur particularly in environments where energy availability is low and females must prioritize their own survival over reproduction.
Furthermore, polyandrous mating systems, where a female mates with multiple males, are more rare compared to polygynous systems. The key reason is that females typically invest more energy into offspring production and development, making the energy provided by male cannibalism significant for egg development and overall reproductive success.
Contrary to the focus of the question, other mating systems, such as monogamous systems, exist where males and females pair for at least one breeding season, or even life, as observed in the gray wolf. The advantage of such systems is hypothesized to be based on factors such as mate guarding, male assistance, and female enforcement, rather than cannibalism.