Study Reveals Gender Imbalance in Zoo Births Threatens Conservation Efforts

A new analysis out in the journal Scientific Reports lays bare some shocking trends in birth sex ratios among zoo animals. If unaddressed, these trends may put the efforts to save endangered species at risk. Oscar Miranda from the University of Debrecen in Hungary led a team of researchers that looked at more than 2.6…

Lisa Wong Avatar

By

Study Reveals Gender Imbalance in Zoo Births Threatens Conservation Efforts

A new analysis out in the journal Scientific Reports lays bare some shocking trends in birth sex ratios among zoo animals. If unaddressed, these trends may put the efforts to save endangered species at risk. Oscar Miranda from the University of Debrecen in Hungary led a team of researchers that looked at more than 2.6 million birth records. Specifically, they looked at 450+ species of birds and mammals from other zoos. This study, which included 30 endangered species such as Asian elephants, tigers, and pygmy hippos, highlights critical issues that zoos must address to ensure the survival of these vulnerable populations.

Miranda will be starting his Ph.D. this September at the Milner Centre for Evolution, University of Bath. He urges that these findings identify a clear need for zoos to monitor the proportion of males to females that are produced in captivity. These ratios become very important when trying to plan breeding programs and conservation projects, he notes.

Disturbing Findings on Birth Sex Ratios

Our research revealed widespread extremely-biased BSRs across these critically endangered, keystone, species. One such finding came from researchers who found a male bias in the Asian elephant. Lions usually have a 50-50 split between male and female cubs. Remarkably, cheetahs favored male offspring as opposed to tigers, which were biased toward producing female births. What these findings demonstrate is that even well-meaning and reputable zoos can inadvertently produce sex imbalances. This mismatch jeopardizes the long-term sustainability of these species.

“This is the largest study of birth sex ratios in zoo animals, giving us a much better understanding of the factors that shape sex ratio variation in different species,” said Oscar Miranda.

The implications of these biases are significant. A male or female bias in populations of some species can pose significant reproductive issues. This result threatens to erode genetic diversity, which is critical for ensuring long-term population health.

The Need for Collaboration Among Zoos

Professor Tamás Székely works jointly with the Milner Centre for Evolution and the Department of Life Sciences, University of Bath. He distills the importance of the collaboration between zoos to achieving their collective purposes more than ever. To manage these conservation and breeding programs effectively, he says, they need to share data on animal populations.

Our research illustrates the need for inter-zoo collaboration. By making their data on their animals public, they have all the pieces they need to successfully coordinate the conservation and breeding of endangered species. Professor Székely stated.

By fostering cooperation and transparency among institutions, zoos can work together to address the challenges presented by skewed birth sex ratios. By sharing this kind of information, zoos and aquariums can make better-informed decisions about their breeding plans and support their commitment to keeping endangered species alive and healthy.

Implications for Future Conservation Strategies

The results are making a big splash in the conservation world. What has slowly started to emerge is an understanding that zoos should reconsider how they breed. For numerous species, ensuring even birth sex ratios is important to avoiding declining populations and extinction. Importantly, it increases genetic diversity, a key factor in any population’s ability to adapt and bounce back from threats.

Oscar Miranda noted, “Our findings show that even well-managed zoos may be silently accumulating sex biases that threaten the survival of endangered species.” This shot across the bow is a call to arms for all institutions serious about conserving wildlife.