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

Paul D Stewart / 1853 illustration of Gorilla, contemporary coloured copperplate engraving from 'Das Buch der Welt' John Weik, Stuttgart. The lowland Gorilla was first accurately described outside Africa by the missio...

Cheryl-Samantha Owen / Mountain gorilla portrait (Gorilla gorilla), Bwindi Impenetrable Forest, Uganda, East Africa

Cheryl-Samantha Owen / Mountain gorilla (Gorilla beringei) resting on back yawning, Bwindi Impenetrable Forest, Uganda, East Africa

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

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

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 / Two male Mountain Gorilla (Gorilla beringei) facing up and chest-beating in a dominance / hierarchy behaviour. Rwanda, Africa

Andy Rouse / Two Mountain Gorilla (Gorilla beringei) in habitat. Rwanda, Africa

Andy Rouse / Portrait of a Mountain Gorilla (Gorilla beringei) with mouth wide open. Rwanda, Africa