Why some females choose multiple mates to boost offspring survival

Health · Published 18 October 2026 Swipe more like this →

In short: While polygyny is common, polyandry—where one female mates with several males—offers hidden evolutionary advantages. From honeybees to tortoises, this rare mating strategy can increase genetic diversity, ensure fertilization, and even protect lineages from extinction through strategic evolutionary bet-hedging.

In the animal kingdom, mating systems are often shaped by the relative biological investments of each sex. Polygyny, where males mate with multiple females, is more prevalent because females invest heavily in large, immobile eggs, while males produce smaller, more mobile sperm. Polyandry is much rarer, occurring in approximately 1% of bird species, such as jacanas and dunnocks. However, when it does occur, it serves several critical functions. In honeybees, queens mate with multiple drones to increase the genetic diversity of the colony, which improves overall fitness and survival.

The benefits for females can be direct or indirect. Direct benefits include fertilization assurance and access to resources. Indirect benefits involve 'good genes' through sperm competition or 'cryptic female choice,' where females like the spider Pisaura mirabilis may control sperm storage from males who provide gifts. In tortoises of the family Testudinidae, females can store sperm across reproductive cycles, allowing a single clutch of eggs to have multiple paternity, which increases the genetic variability of the hatchlings.

Environmental and social dynamics also play a role. In house mice (Mus musculus domesticus), research shows that multiple paternity is strongly linked to the presence of 'roamer' males, who are twice as likely to sire offspring in multiple-sired litters compared to 'territorial' males. Research indicates that all females of the potato cyst nematode (Globodera pallida) engage in polyandry, averaging seven mates each, with this proportion staying constant despite plant resistance causing population masculinisation.

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