Mate Choice - Male Mate Choice/Sex Role Reversal

Male Mate Choice/Sex Role Reversal

In species where mating biases exist, females are typically the choosy sex because they provide a greater parental investment than males. However, there are some examples of sex role reversals where females must compete with each other for mating opportunities with males. Species that exhibit parental care after the birth of their offspring have the potential to overcome the sex differences in parental investment (the amount of energy that each parent contributes per offspring) and lead to a reversal in sex roles. The following are examples of male mate choice (sex role reversal) across several taxa.

• Fish: Male fish typically display high levels of parental care (see pipefish, Scissortail sergeant, and seahorses). This is because females will deposit their eggs in a special brooding pouch that the male possesses. She doesn't participate in parental care after this event. The male then has the burden of raising the offspring on his own which requires energy and time. Thus, males in these species must choose among competitive females for mating opportunities. Surveys across multiple species of pipefish suggest that the sex differences in the level of parental care may not be the only reason for the reversal. Mating systems (e. i. monogamy and polygamy) might also heavily influence the appearance of male mate choice.
• Amphibian: Male poison-arrow frogs (Dendrobates auratus) take on a very active parenting role. Females are lured by the males to rearing sites where they deposit their eggs. The male fertilizes these eggs and accepts the burden of defending and caring for the young until they are independent. Because the male contributes a higher level of parental investment, females must compete for opportunities to leave their eggs with the limited available males.
• Bird: Bird species are typically biparental in care, and may also be maternal like the Guianan Cock-of-the-rocks, however the reverse may also hold true. Male wattled jacanas provide all parental care after the eggs have been laid by the females. This means that the males must incubate the eggs and defend the nest for an extended period of time. Since males invest much more time and energy into the offspring, females are very competitive for the right to lay their eggs in an established nest.
• Mammal: There are no confirmed cases of sex role reversed mammals but female spotted hyenas have peculiar anatomy and behavior that has warranted much attention. Female spotted hyenas are much more aggressive than males due to their high levels of androgens during development. The increased male hormones during development contribute to an enlarged pseudopenis that is involved in mating and birth. Although the anatomical and behavioral roles differ from accepted norms, spotted hyenas are not sex role reversed because the females do not compete with each other for mates.