(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
“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
“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.”