"Investigations continue, but it seems likely that the gorillas were killed for food," he added. "We do not suspect that body parts have been taken as trophies or for sale on the black market."
The dead gorilla was identified as an 18-year-old silverback known as Karema. The name means "handicapped"—the male had lost his left hand, most likely to a poacher's snare, Ngobobo noted.
Karema was used to the presence of humans, because he was part of a group visited regularly by tourists before civil war broke out in the DRC in 1996.
"He died at the hands of a species he trusted completely," Ngobobo said.
The gruesome dismemberment echoed human atrocities in neighboring Rwanda during ethnic massacres in 1994, Ngobobo added.
"This terrible act was done to humans during the Rwandan genocide," he wrote in his blog.
The rebel group blamed for the slaughter is the Rally for Congolese Democracy-Goma (RCD-Goma), about 2,000 men led by Laurent Nkunda. Nkunda is wanted by the Congolese government for war crimes and crimes against humanity.
Last year, another rebel militia—the Mai Mai—was responsible for butchering hundreds of hippos along the shores of Lake Edward, also in Virunga National Park.
Since then, the DRC has completed its first democratic elections in more than 40 years, raising hopes of lasting peace in the war-ravaged country.
"The elections went remarkably well, all things considered," said Ian Redmond, chief consultant for the United Nations-led Great Apes Survival Project. "But there is the odd rebel faction which still hasn't accepted this."
But there are now good prospects of a peace deal between RCD-Goma and the government, he added.
In the meanwhile, conservation groups are calling on the international community to take immediate action to prevent further gorilla deaths.
The groups have also asked the United Nations to give extra support to Virunga's overburdened park wardens, 97 of whom have been killed in the park since 1996.
The wardens weren't able to protect the two slain mountain gorillas because heavily armed rebels had overrun ranger posts, Redmond said.
"The rangers might be well equipped for tackling poachers—but not when the poachers are well-trained, well-armed military," he said.
He pointed out that completely wild gorillas aren't difficult to hunt in the first place, because they leave a clear trail in the forest.
"But [the two killed] gorillas grew up in groups that are habituated for tourism, which means that they are very easy to kill," he said.
Tourism has been crucial to the successful conservation of Virunga's population over the past 25 years, he added. Numbers are up to about 380 from 240 in the late 1970s, when Redmond first visited the region.
"But tourism carries a risk that if you can no longer protect the gorillas, then they are very vulnerable," he said. "These rebels could continue munching their way through all these habituated groups, which would be catastrophic. Every individual is nearly a quarter of a percent of the population."
Even if the rebels eventually move out of the gorilla forests, Redmond added, "then the international support would be for rebuilding, because all the ranger posts have been looted and a lot of damage has been done."
African conservationist Richard Leakey, credited with helping to end the slaughter of elephants in Kenya in 1980s, said in a statement: "The survival of these last remaining mountain gorillas should be one of humanity's greatest priorities.
"Their future lies with a small number of very brave rangers, risking their lives with very little support from the outside world."
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