Wild female orangutan and her offspring in the Lower Kinabatangan floodplain. (Photo credit: Rudi Delvaux)
KOTA KINABALU: Bornean orangutans experienced a major demographic decline and local extirpation during the Pleistocene (2,558,000 to 12,000 years ago) and Holocene (from 12,000 years to the present) due to climate change, the arrival of modern humans, of farmers and recent commercially-driven habitat loss and fragmentation.
This is the main conclusion of a recent paper published in the scientific journal PLOS ONE by a team of scientists from the Instituto Gulbenkian de Ciência (IGC, Portugal), the Anthropological Institute and Museum of the University of Zürich (Switzerland), the CNRS (France), Cardiff University (UK) and the Danau Girang Field Centre (DGFC, Sabah).
“The recent loss of habitat and its dramatic fragmentation has affected the patterns of genetic variability and differentiation among the remaining population of orangutans and increased the extinction risk of the most isolated ones,” said Dr Reeta Sharma from IGC, the lead author of the paper.
“We used orangutan samples collected in six different study sites in Sabah (Kinabatangan and Danum Valley) and Kalimantan and genetic markers to identify signals of population decline,” added Sharma.
Dr Benoit Goossens, director of DGFC and a co-author on the paper, said that the dating of the population decline varied across sites but was always within the 200-2,000 years period.
He said this suggests that in some sites at least, orangutan populations were affected by demographic events that started before the recent anthropogenic effects that occurred in Borneo.
“However, these results do not mean that the recent forest exploitation did not leave its genetic mark on orangutans but suggests that the genetic pool of orangutans is also impacted by more ancient events,” suggested Goossens.
According to him, the orangutan population in the Lower Kinabatangan Wildlife Sanctuary is an example of a recent collapse due to anthropogenic pressure which culminated 50 years ago.
“The recent findings complement those published in 2006 by our team on the Kinabatangan population and underscore the need to expand the conservation measures that we are suggesting in our recent Orangutan Action Plan, such as protection of private lands to connect the existing protected forest lots, corridor establishment, wildlife monitoring and law enforcement.
“This need was emphasised by Datuk Masidi Manjun, Minister of Tourism, Culture and Environment, when he recently asked for a moratorium on any new land development in the Kinabatangan floodplain during the closing remarks of the Sabah Orangutan Conservation Dialogue held in Kota Kinabalu at the end of October,” Goossens added.