Red Alert for Red Apes: DNA shows big losses for Borneo orangutans

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http://www.sciencenews.org/articles/20060128/fob1.asp

 

Week of Jan. 28, 2006; Vol. 169, No. 4 , p. 51

 

Red Alert for Red Apes: DNA shows big losses for

Borneo orangutans

Bruce Bower

 

Because they hang out in nests high up in trees and

lead relatively solitary lives, orangutans have

challenged scientists trying to study them. Now,

orangutans face their own challenge, and it's urgent.

 

Increasingly steep population declines over the past

century or two have imperiled orangutans' survival in

northeastern Borneo, according to a new DNA analysis.

In just the past few decades, the population has

dropped from more than 20,000 to about 5,000

orangutans, report geneticist Benoit Goossens of

Cardiff University in England and his colleagues. This

trend coincides with extensive forest clearance that

began in the 1890s and accelerated during the past 50

years, the scientists note.

 

" This is the first time that a recent and alarming

decline of a great ape population, brought about by

[people], has been demonstrated, dated, and quantified

using genetic information, " Goossens says.

 

DNA evidence of dwindling orangutan numbers emphasizes

the need for intensive conservation efforts, the

scientists conclude in the February PLoS Biology.

 

During a 2001 survey of the still-forested parts of a

Borneo wildlife sanctuary, Goossens and his coworkers

collected orangutan feces found under nests or near

orangutans that they encountered. The team also

collected hair from tree nests. A total of 200

individuals were identified by chemically tagging DNA

segments known as microsatellites. Studies in people

indicate that individual genetic differences evolve

relatively quickly in microsatellites.

 

The researchers used computer programs to analyze the

distribution of genetic variants that had evolved

within the sample and to estimate changes in

population size that would have produced that

distribution.

 

The results indicate that orangutan populations in

northeastern Borneo decreased by more than 95 percent

over the past 100 to 200 years. The decline was most

rapid in the past few decades, the researchers report.

Their new findings are consistent with a controversial

1987 report in which another investigator estimated a

population of more than 20,000 after counting

orangutan nests observed from a helicopter.

 

East Borneo orangutans, including the groups that

Goossens' team studied, face a high risk of extinction

within the next few decades, the researchers conclude.

Major survival threats come from forest destruction to

develop oil palm–tree plantations and from illegal

hunting.

 

The arrival of the first farmers in Borneo about 5,000

years ago apparently had little impact on the numbers

of resident orangutans, Goossens' team says.

 

The new investigation supports the findings of the

2004 Orangutan Population and Habitat Viability

Assessment. After surveying orangutans on Borneo and

Sumatra, researchers concluded that habitat loss and

other factors would wipe out the animals on both

islands within about 50 years.

 

Neither the new genetic study nor the 2004 project

appears likely to spark conservation efforts, remarks

anthropologist Roberto A. Delgado Jr. of Hunter

College, City University of New York. " There are

larger socioeconomic and political forces at play in

Southeast Asia, " he says.

 

A proposal to expand timber harvesting is now being

considered by the government of Borneo, Delgado notes.

Orangutans also suffer from the illegal trade in

exotic animals.

 

References:

 

Goossens, B., et al. 2006. Genetic signature of

anthropogenic population collapse in orang-utans. PLoS

Biology 4(February):e25. Available at

http://dx.doi.org/10.1371/journal.pbio.0040025.

 

Orangutan PHVA Final Report. August 2004. Available at

http://www.cbsg.org/reports/reports/exec_sum/

OrangutanPHVA04_LowRes.pdf.

 

Further Readings:

 

A version of this article written for younger readers

is available at Science News for Kids.

 

Sources:

 

Roberto A. Delgado Jr.

Department of Anthropology

Hunter College CUNY

695 Park Avenue

New York, NY 10021

 

Benoit Goossens

Cardiff University

P.O. Box 915

Cathays Park

Cardiff CF10 3TL

United Kingdom

 

From Science News, Vol. 169, No. 4, Jan. 28, 2006, p.

51.