Because sexual behavior has such direct impact on reproductive success, sociobiologists have given a good deal of thought to the evolutionary significance of various forms of sexual behavior. In many species, males and females may have different strategies for reproductive success. Females devote an enormous amount of time and energy to bearing and raising their young. The more complex the species, the more this is the case.

For example, humans, chimpanzees, and dogs provide much more maternal care than turtles do. Therefore it is in the evolutionary interest of many females to be highly selective in their choice of mates and to seek males that can contribute to care of the young. Males, on the other hand, do not bear young and are not physically bound to the care of the young. They can develop a wide array of successful reproductive strategies. They can inseminate a large number of females but give little resources to the care of their offspring (e.g., buffalo, wildebeests), or they can inseminate fewer females, have more offspring with them and give much more time and energy to the care of their young (e.g., trumpeter swans, gibbons). Some males (e.g., gorillas, fur seals) compete for exclusive access to a group of females, devoting considerable energy to protecting their harems from encroachment from rival males.