A groundbreaking study has produced the most comprehensive estimate yet of infertility rates in an endangered wild species.
Using a decade of data, researchers from the University of Sheffield, the Zoological Society of London and the University of Auckland, New Zealand, have uncovered critical insights into the reproductive challenges facing the endangered hihi, a rare songbird native to New Zealand. -Zeeland, is confronted.
The study is the first to link small population size, sex ratio bias and reduced fertilization rates in wildlife. The research highlights the significant reproductive challenges faced by endangered species with small population sizes and distorted sex ratios.
The research team analyzed more than 4,000 eggs and assessed the fertility of nearly 1,500 eggs that failed to hatch. The findings showed that infertility is responsible for an average of 17 percent of failed outcomes in the hihi, while the majority of failed outcomes are caused by early embryo death.
The research found that embryos are most vulnerable in the first two days of their development, with no significant difference in survival rates between male and female embryos or any impact from inbreeding. Furthermore, infertility rates were observed to be higher in years when the population was smaller and the number of men exceeded the number of women, suggesting that increased stress from increased male harassment of women may play a role in these findings.
The hihi, known for high levels of female harassment by males and frequent paternity outside the pair, is an example of the reproductive challenges faced by species with skewed sex ratios. In extreme cases, females can be subjected to as many as sixteen forced copulations per hour, a behavior that is both energetically expensive and stressful, potentially contributing to reduced fertility.
By considering the impact of population size and sex ratio on fertility, conservationists can better manage the numbers and composition of animals in populations, thereby improving fertility rates.
Fay Morland, PhD student at the University of Sheffield, and lead author of the study, said: “One of our key findings is that embryo death in the very early stages of development is the most common reason eggs fail to hatch. the exact causes of failure at this stage remain unknown. These results highlight the urgent need for more research into the reproductive challenges faced by endangered species, to better understand and reduce the factors driving their risk of extinction.
Dr. Nicola Hemmings, from the University of Sheffield’s School of Biosciences, and leader of the research group that carried out the study, said: “Our research highlights the importance of understanding the factors that influence the fertility of endangered species. The links between male-biased sex ratios and lower fertility rates suggest that controlling population composition could be crucial for improving reproductive success in conservation programs.”
