Lack of law enforcement against illegal trade in Indonesia threatens the survival of orang-utans and gibbons on Sumatra, a new study by the wildlife trade monitoring network TRAFFIC shows.

Despite considerable investment in wildlife conservation, numbers of the critically endangered orang-utans captured mainly for the pet trade exceeded the levels of the 1970s.

A lack of adequate law enforcement is to blame, TRAFFIC says. Records of orang-utans and gibbons put into rehabilitation centers serve as an indicator of how many of these animals were illegally held. Meanwhile numbers continue to decline in the wild, with the most recent estimate of just 7,300 Sumatran Orangutans surviving.

Orang-utans, which can weigh up to around 90 kilograms and reach 1.5 metres in length, end up in such centers after they become too old and big to be held as pets. But owners of the reddish-brown coloured apes do not face any legal consequences.

"Confiscating these animals without prosecuting the owners is futile," said Chris R Shepherd, Acting Director of TRAFFIC Southeast Asia. "There is no deterrent for those committing these crimes, if they go unpunished. Indonesia has adequate laws, but without serious penalties, this illegal trade will continue, and these species will continue to spiral towards extinction."

An estimated 2,000 orang-utans have been confiscated or turned in by private owners in Indonesia in the last three decades but no more than a handful of people have ever been successfully prosecuted.

Between 2002 and 2008, for example, the newly opened Sibolangit rehabilitation centre in Sumatra took in 142 Sumatran orang-utans, while its predecessor, Bohorok rehabilitation centre accepted just 30 animals between 1995�2001 (when it closed), and 105 orang-utans between 1973�1979.

"When the first rehabilitation centres were established for orang-utans and later for gibbons it was hoped that with more apes being confiscated, levels of illegal trade would fall," said Vincent Nijman, a TRAFFIC consultant and author of the report, based at Oxford Brookes University. "But with hundreds of orangutans and gibbons present in such centres, and dozens added every year, it is hard to view these numbers as anything other than an indictment against Indonesia's law enforcement efforts," he said.

The report also documents the 148 Sumatran gibbons and siamangs and 26 Sumatran orang-utans kept in Indonesian zoos. "Proper enforcement of laws protecting orang-utans is critical in Indonesia" said Wendy Elliott, species manager at WWF International.

"If the situation continues, the Sumatra orang-utan could well face extinction." The report recommends that the root causes of trade be examined and that laws be better implemented for the protection of orang-utans, gibbons and the island's other wildlife. Sumatra's wildlife is also threatened by habitat loss due to deforestation, logging, land conversion, encroachment, and forest fires.

WWF is working to reduce the destruction of wildlife habitat in Sumatra by working with industry to ensure High Conservation Value Forests are not converted for agriculture, empowering local communities to manage natural resources in a sustainable way, and providing alternatives.