Coastweek website



Rhinos “correct” sex imbalances in offspring: New Zealand-led study

WELLINGTON (Xinhua) -- African rhinos have the ability to change the sex of their offspring to avoid gender imbalances and to curb severe competition for breeding, according to a New Zealand-led study out Tuesday.

The study provided the first experimental evidence in the wild that unbalanced population sex ratios could result in a response by parents to “correct” the imbalance, said study leader Associate Professor Wayne Linklater, of Victoria University.

“This is called a homeostatic sex allocation (HSA) response—a biological theory first proposed in 1930,” Linklater said in a statement.

“Almost all population models assume birth sex ratio is fixed. Our evidence indicates that this may not be the case.”

The research team, including scientists from South Africa and Namibia, examined 24 years of rhinoceros data, gathered during the course of 45 reintroductions of the animals across southern Africa.

Sex bias was especially important in rhinoceros populations due to their critically low numbers, said Linklater.

“But because of the evidence of HSA, we need not be so concerned about that misbalance, because parents appear able to ‘correct’ it when they breed,” he said.

“HSA has an especially strong effect when the gender imbalance is very large. In fact, the further it is from an even-sex ratio, the stronger the response is by parents.”

Populations where HSA was possible would be more resilient.

“Their small populations will have improved establishment and greater viability. Such species will populate habitats faster, and be less susceptible to random demographic processes and genetic drift,” he said.

Explaining the allocation of resources by parents among male and female offspring was a leading issue in evolutionary biology.

“Extreme sex ratios commonly occur, so the incidence of HSA will significantly impact our understanding of a range of ecological processes including invasion biology and conservation management,” he said.

Linklater planned further research into how an HSA response worked in Australian brushtail possums.

“Possums are ideal subjects for such a study because their offspring are born into the marsupial pouch at an extraordinarily young age—very early in development—and so can be studied in great detail,” he said.

“Possums are also invasive mammals in New Zealand. Understanding their reproductive processes can provide new ways of managing population numbers.” 

Remember: you read it first at !


Please contact

MOMBASA - GULSHAN JIVRAJ, Mobile: 0722 775164 Tel: (+254) (41) 2230130 /
Wireless: 020 3549187 e-mail:

NAIROBI - ANJUM H. ASODIA, Mobile: 0733 775446 Tel: (+254) (020) 3744459

    © Coastweek Newspapers Limited               Tel: (+254) (41) 2230130  |  Wireless: 020 3549187  |  E-mail: