The reproductive strategy for promiscuous species seems to be the spreading of sperm widely and abundantly. Polygyny describes a situation in which a single male mates with multiple females. Some scientists have even placed Homo sapiens in this category by citing studies of human culture in which four in five societies practice polygyny. Researchers observe that these different strategies are revealed in the size of an animal's testes. Chimpanzees and gorillas provide a nice example.
Chimps are promiscuous, and gorillas are polygynous.
The chimps have larger testes because it is important for them to have sex with many females and spread their seed. They are not committed to any one female, and they have no assurance of the survival of their children because they are not obligated to care for any particular one. Gorillas, on the other hand, are committed to a group of females. They devote less energy to spreading their genes and more to protecting their territory and providing for their females and their children. These same ratios are noted in butterflies, frogs, and many others.