Researchers at the University of Debrecen, in collaboration with international experts, have uncovered critical risks in zoo breeding linked to distorted birth sex ratios. The study, published in Scientific Reports, analyzed data from more than 2.6 million birds and mammals across 453 species. Findings reveal significant imbalances: while bird populations remained relatively balanced, mammal births often showed skewed ratios, with males overrepresented in primates and females in ungulates and marsupials.
Disturbances in sex ratios pose major threats to conservation, increasing risks of inbreeding, aggression, and reduced reproductive success. Particularly endangered species such as tigers, pygmy hippopotamuses, and Asian elephants were found to exhibit distortions that could undermine reintroduction efforts.
“Our research highlights how even small disruptions in sex ratios can jeopardize long-term survival,” said first author Miranda Oscar G. Co-author Professor Tamás Székely emphasized that such imbalances could compromise global conservation programs.
The study concludes that evolutionary traits, such as mating systems in mammals and brood size in birds, play a central role in determining sex ratios. The findings provide valuable guidance for zoos to better manage breeding programs and safeguard species survival.
Source: University of Debrecen
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