Newborn gorilla twins
Twin mountain gorillas have been born in Volcanoes National Park in Rwanda.
The babies born on 3 February 2011 are only the fifth set of twins ever recorded in the history of Rwanda's mountain gorillas.
The last reported birth of mountain gorilla twins was in 2004, according to conservation group The Gorilla Organization.
Fewer than 800 mountain gorillas are thought to remain in the wild, though numbers are thought to be increasing.
"It is very rare to hear of mountain gorilla twins, so we were all excited to hear the news from rangers yesterday," says Emmanuel Bugingo, Programme Manager in Rwanda for The Gorilla Organization, which has staff in London, UK and Africa.
The twins are both boys.
"Gorilla mothers usually have only one baby every four years or so - which is one reason why they are so vulnerable - so twins give a rare double gain in one birth," adds Says Ian Redmond, Chairman of the Ape Alliance, an international coalition of organisations and individuals that works for the conservation and welfare of apes.
The mother, known fondly to rangers as Kabatwa, belongs to the Hirwa group of gorillas.
The last mountain gorilla twins, born in 2004, were named Byishimo and Impano by the President of the Republic of Rwanda, Paul Kagame, at a gorilla naming ceremony in 2005.
Mountain gorillas (Gorilla beringei beringei) are a subspecies of the Eastern gorilla.
The Eastern Lowland Gorilla (G. b. graueri) is the other subspecies, and is the most populous, at about 5,000 individuals.
Last year a census revealed that the population of endangered mountain gorillas has increased significantly in the last 30 years.
A survey carried out in the Virunga Massif - where most of the world's mountain gorillas live - revealed 480 individuals living in 36 groups.
Conservationists say that, 30 years ago, only 250 gorillas survived in this same area.
Along with the 302 mountain gorillas from a census in Bwindi in 2006, the world population is now more than 780.
The Virunga Massif includes three contiguous national parks: Parc National des Virunga in the Democratic Republic of Congo, Volcanoes National Park in Rwanda and Mgahinga Gorilla National Park in Uganda.
The only other location where mountain gorillas exist is Bwindi Impenetrable National Park in Uganda, and scientists are considering elevating the few hundred remaining Bwindi gorillas to the rank of subspecies.