A male orangutan in the forest of the Lower Kinabatangan Wildlife Sanctuary. Photo courtesy of Rudi Delvaux.
KOTA KINABALU: Scientists have recently shown that orangutan males disperse over much longer distances than females.
The study, carried out by researchers from the Institute of Anthropology in Zurich, Switzerland, Danau Girang Field Centre (DGFC) in Sabah and Cardiff University in in the United Kingdom, was recently published in the scientific journal Molecular Ecology.
“Faecal samples were collected non-evasively from wild, mature orangutan males at seven study sites on Borneo (including Kinabatangan South and North and Danum Valley in Sabah) and two on Sumatra,” explained Benoit Goossens, Director of the DGFC and a co-author on the paper.
“Genetic material (DNA) was then extracted from the faeces and sex-biased dispersal was assessed by comparing paternally and maternally transmitted genetic markers.
“Our results showed male-biased long-distance dispersal in orangutans.
“In a previous study published in 2006, we showed a recent drastic decline in orangutan population size which was mostly due to habitat loss.
“In addition, a loss of male dispersal due to habitat fragmentation will significantly increase the effects of genetic drift (loss of genetic variation) due to small local population sizes and extreme female philopatry.
“In order to conserve the natural genetic structure and the genetic health of orangutan populations, it is therefore crucial to ensure that males are able to move between suitable habitat patches, even if they are far apart.
“An effective immigration rate of one to two animals per generation (every 15-20 years) is considered to be the minimum to reduce the negative fitness effects of inbreeding depression (reduced fitness in a given population as a result of breeding of related individuals),” said Goossens.
“It is therefore highly desirable that all orangutan populations are connected through gene flow. If orangutans are to be efficiently protected, a sufficient network of high-quality natural forest and dispersal corridors has to be restored across Borneo (and Sumatra) to allow orangutans to disperse naturally,” said Sabah Wildlife Department director Dr Laurentius Ambu.
“It is a big challenge in front of us, where governments, industries and NGOs (non-governmental organisations) should work hand-in-hand in order to achieve it,” concluded Ambu.