A new study published in the open-access journal PLoS Biology shows strong
genetic evidence of a catastrophic collapse in orangutan populations living
in the fragmented forests of the Kinabatangan Wildlife Sanctuary in Sabah,
Malaysia. Benoit Goossens, Loun*s Chikhi, Michael Bruford, and their
colleagues report that the collapse occurred within the past hundred years,
and most likely within the past decades-coinciding with massive
deforestation, which began in the region in the 1890s and accelerated in the
1950s and 1970s.
"This is the first time that a recent and alarming decline of a great ape
population-brought about by man-has been demonstrated, dated, and quantified
using genetic information," says Goossens, a wildlife geneticist at Cardiff
University who conducted the genetic study. "Developing effective
conservation and recovery programs depends on determining when the decline
of a population began, its trajectory, and the original population size."
For their study, the researchers collected hair from tree nests and feces
found under nests or near orangutans encountered along the Kinabatangan
River. Two hundred orangutans were identified using genetic markers called
microsatellites. "We used the DNA information to simulate population history
and detect evidence of a population decline," Goossens explains.
"The genetic study shows that there is a high risk of extinction of the
orangutan in Sabah in the near future if this decline goes on unabated,"
says Marc Ancrenaz, who also participated in the study. "The major threat to
the long-term survival of orangutans in Sabah is linked with oil palm
plantation development and forest destruction. Illegal killing also
contributes to this decline."
Sixty percent of orangutans found in Sabah are living outside the network of
protected areas. "The largest population of the East Bornean orangutan
subspecies existing on Earth occurs in the forests of the Sabah Foundation
concession, with a population of about 5,000 individuals," says Laurentius
Ambu, Sabah Wildlife Department's Deputy Director. Most of these forests are
exploited for timber under natural forest management, but orangutans cannot
survive in industrial tree plantations.
"This population will disappear forever if these forests are converted to
oil-palm agriculture," Ambu says. "The results of our genetic study
underscore the need to act now to protect the long-term survival of the
species. The animals still show enough genetic diversity to stabilize, if
immediate steps are taken to reconnect remnant forest patches and halt
further deforestation."
Citation: Goossens B, Chikhi L, AncrenazM, Lackman-Ancrenaz I, Andau P, et
al. (2006) Genetic signature of anthropogenic population collapse in
orang-utans. PLoS Biol 4(2): e25
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