June 3, 2026

The perks of polyandry: mating with multiple males leads to home improvement

New research into African tree frogs reveals increased number of mates improves nest quality and survival rate of offspring

The question of why females mate with multiple males has long puzzled evolutionary biologists. A new study of African foam-nest tree frogs, led by University of Wollongong (UOW) researchers, reveals polyandry could be the key to reproductive success and a safer home for offspring.

The findings shed light on how amphibians have evolved to protect their young in challenging environments, presenting a new hypothesis for the evolution of polyandry that ties mating behaviour to the quality of nest construction.

A man holds a phone in his hand, which displays an image of African nest-foam tree frogs. Photo: Michael Gray Professor Phillip Byrne looks at images of the African foam-nest tree frogs. Photo: Michael GrayWith colleagues from Australian National University and Macquarie University, the UOW team studied the tree frog’s behaviour over a six-month breeding period. Behavioural data combined with paternity analyses revealed nests built with the help of multiple males were larger and far less likely to dry out and succumb to the hot African sun, providing greater protection for eggs. Nests built with just one male were far more likely to fall apart.

“We discovered that polyandrous matings are almost essential for offspring survival, with helping males gaining a share of paternity as reward for their assistance,” said lead author Professor Phillip Byrne, a renowned frog researcher in UOW’s School of Science.

An image of a group of African nest-foam tree frogs in their bubble-like nest in a tree. Photo: Phillip Byrne A group of African foam-nest tree frogs, building their nest. Photo: Phillip Byrne

By mating with multiple males, females secure nest building assistance from multiple males and produce bigger nests that are less likely to fail, increasing the chance that their offspring survive. Published in Evolution, the findings suggest nest-building species provide an insight into how polyandry evolved across the animal kingdom. The research challenges the idea that reproduction is always a fierce contest between males.

“Unlike most other animals where males fight to gain the attention of females, the amorous frogs displayed almost no aggression towards each other,” Professor Byrne said.

“Reproduction is more of a coordinated activity than a brutal competition. This pattern may have evolved because any antagonistic behaviours that compromise nest construction would be detrimental to both sexes. It is a remarkable case of reproduce harmoniously or the house collapses and no-one wins.”

Professor Phillip Byrne stands in front of a group of trees on UOW's Wollongong Campus. Photo: Michael Gray Professor Phillip Byrne at UOW's Wollongong Campus. Photo: Michael Gray

The research team highlighted the significance of this finding; nest building is common in nature, and many nest building species are known to have multiple paternity, with anecdotal evidence for various forms of direct or indirect male assistance.

Professor Byrne predicts studying these systems may reveal that nesting-assistance explains the evolution of polyandry in a large diversity of animals, shedding new light on why females seek matings with multiple males.

About the research

‘“Nesting assistance”: a new hypothesis for the evolution of polyandry and a test in the African foam-nesting treefrog’, by Phillip G Byrne, Martin J Whiting, Aimee J Silla, and J Scott Keogh, was published in Evolution: https://doi.org/10.1093/evolut/qpag071

The perks of polyandry: mating with multiple males leads to home improvement

The perks of polyandry: mating with multiple males leads to home improvement

About the research

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