Final answer:
In monogamous systems, males stay with females to prevent other males from mating with them and to help raise offspring.
Step-by-step explanation:
In monogamous systems, one male and one female are paired for at least one breeding season. This behavior is advantageous in such situations where mates are scarce and difficult to find. The male stays with the female to prevent other males from mating with her, which is known as the "mate-guarding hypothesis". Another explanation is the "male-assistance hypothesis", where males that remain with a female to help guard and rear their young will have more and healthier offspring.