Heres the follow up:

by 2006 population reduces by another third.Apparently, nothing was done about it.

http://www.wwf.org.au/articles/feature40/

A new aerial survey shows that the hippo population in Virunga National Park (Democratic Republic of Congo) will soon be extinct due to rampant poaching for hippo teeth and meat. Once the world's largest hippo population, with some 29,000 individuals in 1974, it has now dropped to under 1,000 individuals.

Hippos are being killed by soldiers and local militia, as well as local poachers. Hippos can be bought for around US$50 dollars, and hippo canine teeth often end up as part of the illegal ivory trade.

This latest survey and exhaustive count of hippos in the Virunga National Park was carried out last month by the Congolese Institute for the Conservation of Nature (ICCN), the EU and WWF, and showed that only 887 individuals were left - down from 1,309 two years ago.

Soldiers and armed groups are still found in parts of the park, which is a UNESCO World Heritage Site. This makes it difficult for ICCN and WWF to maintain consistent conservation work in these areas.

"Soldiers are left in the park without being fed nor paid and that's a recipe for disaster," said Marc Languy of WWF's Eastern Africa Regional Programme. "The Congolese government must urgently remove the army from this protected area and ensure that ICCN staff can continue with their official mandate to control the park."

The decline of the Virunga hippo population has also adversely affected the situation of local people, especially the thousands of fishermen living around Lake Edward, within the park. The lake is one of the most productive in the world, as hippo dung provides vital nutrients for fish. The dramatic fall of the hippo population has also resulted in a rapid decline of the lake's fish stocks.

"It the government does not take the hippo situation in Virunga seriously, this will not only lead to an environmental disaster, but also to an economic crisis for local communities," added Marc Languy.