Polyandry in nature

In behavioral ecology, polyandry is a class of mating system where one female mates with several males in a breeding season. Polyandry is often compared to the polygyny system based on the cost and benefits incurred by members of each sex. Polygyny is where one male mates with several females in a breeding season (e.g., lions, deer, some primates, and many systems where there is an alpha male). A common example of polyandrous mating can be found in the field cricket (Gryllus bimaculatus) of the invertebrate order Orthoptera (containing crickets, grasshoppers, and groundhoppers). Polyandrous behavior is also prominent in many other insect species, including the red flour beetle and the species of spider Stegodyphus lineatus. Polyandry also occurs in some primates such as marmosets, mammal groups, the marsupial genus' Antechinus and bandicoots, around 1% of all bird species, such as jacanas and dunnocks, insects such as honeybees, and fish such as pipefish.

Among the whales, polyandrous behavior has been noted among the bowhead,harbour porpoise (Phocoena phocoena), and humpback whales.

It is theorized that polyandry is more prevalent in organisms where incompatibility is more costly, and where this incompatibility is more likely. The former is especially true in viviparous organisms. Where the cost of having a low-quality father is significant, although, an organism is less likely to be polyandrous.

The adaptive significance of polyandry in animals is controversial. Polyandry has direct benefits for females allowing fertilization assurance, provision of resources, and parental care for their offspring.House mice (Mus musculus musculus) have shown indirect, genetic benefits, where females have increased offspring survival through multiple mating, showing that practicing polyandry mating results in an increase in offspring viability. In a meta analysis, including 10 different orders of insects, polyandry increased the production of eggs by females specifically in Lepidopterans and Orthopterans. Indirect benefits of mating for females can be gained through sperm competition to attain "good genes", cryptic female choice, increased genetic quality, and genetic diversity. Females spiders (Pisaura mirabilis) store more sperm from gift-giving males suggesting that sperm storage is under female control through cryptic sperm choice. The increase in sperm storage from the gift giving males might allow females to produce "sexy sons" that also give gifts and increase the fitness of offspring. Sperm storage and fertilization success increased with copulation duration, suggesting an advantage in sperm competition.

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