Andy Rouse / Mountain gorilla (Gorilla beringei) silverback in Susa group, Parc National des Volcans, Rwanda

Andy Rouse / Mountain gorilla (Gorilla beringei beringei) silverback male portrait, Volcanoes NP, Virunga Mountains, Rwanda

John Sparks / David Attenborough with mountain gorillas, on location during filming for BBC 'Life on Earth' series in Rwanda 1978

Jeff Foott / Gorilla (Gorilla beringei beringei) sub adult male feeding on vegetation, close up. Volcanoes National Park, Rwanda, Africa.

Oriol Alamany / Mountain gorilla (Gorilla berengei) female holding newborn baby, from Titus Group in the Visoke rainforest, Volcanoes National Park, Rwanda, August

Fabio Pupin / Ruwenzori side-striped chameleon, (Trioceros rudis), hanging from fern, Nyungwe Forest NP, Rwanda, December . Non-ex.

Mary McDonald / Adult Mountain gorilla (Gorilla beringei beringei) holding baby, Hirwa group, Volcanoes National Park, Rwanda

Pedro Narra / Mountain Gorilla (Goriila beringei) resting, Volcanoes National Park, Virunga Mountains, Rwanda.

Christophe Courteau / Mountain gorilla (Gorilla beringei beringei), silverback and juvenile son. Volcanoes National Park. Rwanda.

Christophe Courteau / Mountain gorilla (Gorilla beringei beringei), dominant silverback in forest clearing. Volcanoes National Park, Rwanda.

Christophe Courteau / Mountain gorilla (Gorilla beringei beringei) blackback, juvenile male demonstrating power. Volcanoes National Park, Rwanda.

Christophe Courteau / Mountain gorilla (Gorilla beringei beringei) blackback, juvenile male demonstrating power. Volcanoes National Park, Rwanda.

Christophe Courteau / Mountain gorilla (Gorilla beringei beringei) silverback sitting on boundary wall between Volcanoes National Park and a Potato crop, looking into valley. Area to be restored to forest. Rwanda.

Christophe Courteau / Mountain gorilla (Gorilla beringei beringei) female with baby, portrait. Volcanoes National Park, Rwanda.

Mary McDonald / Mountain gorilla (Gorilla beringei beringei) female with baby age, 4 months, Volcanoes National Park, Rwanda

Ole Jorgen Liodden / Red-chested Sunbird (Cinnyris erythrocercus) backlit on flower, Rwanda.

Ole Jorgen Liodden / Golden monkey (Cercopithecus kandti) foraging, portrait, Virunga, Rwanda.

Ole Jorgen Liodden / Mountain gorilla (Gorilla beringei beringei) baby chewing on stick, Virunga, Rwanda.

Ole Jorgen Liodden / Grey-cheeked mangabey (Lophocebus albigena) in Nyungwe NP, Rwanda

Ole Jorgen Liodden / L'Hoest's monkey (Cercopithecus lhoesti) feeding on leaves, Rwanda.

Andy Rouse / Mountain gorilla (Gorilla beringei) silverback yawning with mouth wide open. Rwanda.

Andy Rouse / Mountain gorilla (Gorilla beringei) female portrait, Rwanda.

Andy Rouse / Mountain gorilla (Gorilla beringei) baby held by mother, Rwanda

Andy Rouse / Mountain gorilla (Gorilla beringei beringei) mother with young, and silverback in background. Virunga Mountains, Rwanda. Non-ex.

Andy Rouse / Mountain gorilla (Gorilla beringei beringei) portrait of blackback male, Virunga Mountains, Rwanda

Andy Rouse / Mountain Gorilla (Gorilla beringei beringei) mother and baby Rwanda, Africa.

Suzi Eszterhas / Mountain Gorilla (Gorilla gorilla beringei) mother lying on back and holding baby age one year. Parc National des Volcans, Rwanda. Endangered species

Andy Rouse / Mountain gorilla (Gorilla beringei) silverback walking in front of watching tourists, Virunga Volcanoes, Rwanda 2012. No release available.

Christophe Courteau / Mountain gorillas (Gorilla beringei) Hirwa group led by the silverback dominant male Munyinya, Volcanoes National Park, Rwanda, elevation 2610 m

Christophe Courteau / Close up of man's hand harvesting Pyrethrum, which refers to several Old World plants of the Chrysanthemum genus which are cultivated as ornamentals for their showy flower heads. Pyrethrum is also the...

Christophe Courteau / Silverback Mountain gorilla (Gorilla beringei) in the bamboo forest, this is Munyinya the leader of Hirwa group, Sabyinyo volcano, Volcano National Park, Rwanda

Christophe Courteau / Mountain gorilla silverback, male called Munyinya, (Gorilla beringei) with tourist taking photo, part of Hirwa Group, Volcanoes National Park, Rwanda

Ole Jorgen Liodden / Young Mountain Gorilla (Gorilla beringei beringei) portrait, looking thoughtful. Parc des Volcans National Park, Rwanda, December.

Andy Rouse / Mountain Gorilla (Gorilla beringei) infant peering through vegetation. Rwanda, Africa

Andy Rouse / Mountain Gorilla (Gorilla beringei) infant riding on its mother's back. Rwanda, Africa

Andy Rouse / View from the undergrowth looking up into the canopy of rainforest; prime Gorilla (Gorilla beringei) habitat of the Susa group on the upper slopes of Karisimbi Volcano. Virunga Volcanoes National Park...

Andy Rouse / Virunga Volcanoes National Park at dawn. Rwanda, Africa, April 2010.

Andy Rouse / Harvested potatoes in Virunga Volcanoes National Park with agricultural land behind and forest beyond where the mountain gorillas live, Rwanda, April 2010. Encroachment of the human population on habi...

Andy Rouse / Mountain Gorilla (Gorilla beringei) in habitat seen through leaves. Rwanda, Africa

Andy Rouse / Mountain Gorilla (Gorilla beringei) adult holding infant close to her. Rwanda, Africa

Andy Rouse / Mountain Gorilla (Gorilla beringei) family sitting in groupm male looking to camera. Rwanda, Africa

Andy Rouse / Mountain Gorilla (Gorilla beringei) male and female after mating. Rwanda, Africa

Andy Rouse / Portrait of a Mountain Gorilla (Gorilla beringei) with a view over forest canopy. Rwanda, Africa, March.

Andy Rouse / Mountain Gorilla (Gorilla beringei) adult playing with an infant. Rwanda, Africa