First proof of rhinoceroses’ ability to compensate for gender imbalance

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First proof of rhinoceroses’ ability to compensate for gender imbalance

Associate Professor Wanye Linklater using a radio antennae to locate a black rhino in iMfolozi Park in South Africa. Photo credit: Ian Hutcheson

New Zealand – Rhinoceroses have the ability to modify the sex of their offspring, according to new research led by Victoria University of Wellington. The study, spearheaded by Associate Professor Wayne Linklater, provides the first experimental evidence in the wild that shows a sex imbalance in rhinoceroses can result in a compensatory response by the parents to “correct” the imbalance.

Associate Professor Linklater says this is known as a homeostatic sex allocation response (HSA) – a biological theory first proposed in 1930.

“Almost all population models assume birth sex ratio is fixed. Our evidence indicates that this may not be the case. This sex bias is especially important in rhinoceros populations because of their critically low numbers. But this evidence of HSA means we don’t need to be so concerned about a sex imbalance threatening population growth. They’ll be more resilient as a species because they’ll be able to populate habitats faster and will be less susceptible to random demographic processes and genetic drift.”

The research team comprised Dr Peter Law from Nelson Mandela Metropolitan University in South Africa, Pierre du Preez from Namibia’s Ministry of Environment and Tourism and former Victoria University postdoctoral researcher Dr Jay Gedir.

Together, they examined 24 years of rhinoceros data gathered during the course of 45 reintroductions of the animals across southern Africa. Associate Professor Linklater is now turning his attention to the HSA response in Australian brushtail possums.

“We will not just be testing for the ability to correct a gender imbalance, but trying to find out how it happens. We’ll do this by manipulating the adult sex ratio to be extremely male-or female-biased in different wild populations in discrete bush fragments in New Zealand and measuring what happens to correct the imbalance.”

Possums are invasive mammals in New Zealand devastating native forests and bird populations. Associate Professor Linklater says understanding their reproductive processes can provide new ways of managing population numbers.