Andrew Walmsley / Sumatran orangutan (Pongo abelii) mother and baby Bukit Lawang, North Sumatra.

Robin Chittenden / Tufted grey langur (Semnopithecus priam priam) baby, Sri Lanka.

Jabruson Motion / Conservation workers carrying a sedated Sumatran orangutan (Pongo abelii) towards vehicles and a transport box, part of a relocation programme, Sei Serdang, Prima, Batang Serangan, Langkat, North Suma...

Claudio Contreras / Central American spider monkey (Ateles geoffroyi) juveniles hanging by tails and playing, Calakmul Biosphere Reserve, Yucatan Peninsula, Mexico, August

Tim Laman / Tapanuli orangutan (Pongo tapanuliensis) Togus, adult flanged male, Batang Toru Forest. Sumatran Orangutan Conservation Project, North Sumatran Province, Indonesia.

Tim Laman / Tapanuli Orangutan (Pongo tapanuliensis). Togus, adult flanged male Batang Toru Forest Sumatran Orangutan Conservation Project North Sumatran Province Indonesia

Tim Laman / Tapanuli Orangutan (Pongo tapanuliensis). Togus, adult flanged male. Batang Toru Forest, Sumatran Orangutan Conservation Project, North Sumatran Province, Indonesia.

Tim Laman / Tapanuli Orangutan (Pongo tapanuliensis) Beti, juvenile female, daughter of Beta, in the trees, Batang Toru Forest, Sumatran Orangutan Conservation Project, North Sumatran Province, Indonesia

Anup Shah / Olive baboon (Papio anubis) male approaching with curiosity - remote camera. Masai Mara National Reserve, Kenya.

Anup Shah / Vervet monkey (Cercopithecus aethiops) male scratching itself - remote camera . Masai Mara National Reserve, Kenya..

Alex Hyde / Brown / Tufted Capuchin (Cebus apella) family group in cloud forest, Manu Biosphere Reserve, Peru.

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.

Magnus Lundgren / Wild Wonders of China / Tibetan macaque (Macaca thibetana) juvenile climbing in a tree in Tangjiahe Nature Reserve, Sichuan Province, China

Magnus Lundgren / Wild Wonders of China / Central Yunnan black crested gibbon (Nomascus concolor jingdongensis), mother and baby hanging in canopy. Wuliangshan Nature Reserve, Jingdong, Yunnan Province, China.

Klein & Hubert / Red ruffed lemur (Varecia rubra) hanging in banana tree, holding a flower, Masola, Madagascar.

Klein & Hubert / Red ruffed lemur (Varecia rubra) in banana tree, holding stalk of flower, Masaola, Madagascar.

Klein & Hubert / Red-ruffed lemur (Varecia rubra) lying on branch in tropical forest, Madagascar.

Cyril Ruoso / Long-tailed macaque (Macaca fascicularis) head portrait, Koram island, Khao Sam Roi Yot National Park, Thailand.

Cyril Ruoso / Long-tailed macaque (Macaca fascicularis) grooming, Koram island Khao Sam Roi Yot National Park, Thailand.

Cyril Ruoso / Long-tailed macaques (Macaca fascicularis) two juveniles sitting close together. Koram island, Khao Sam Roi Yot National Park, Thailand.

Cyril Ruoso / Long-tailed macaque (Macaca fascicularis) approaching camera, Koram island, Khao Sam Roi Yot National Park, Thailand.

Staffan Widstrand / Wild Wonders of China / Portrait of a Golden snub-nosed monkey (Rhinopithecus roxellana) full frame of the face, Foping Nature Reserve, Shaanxi, China. Endangered species

Staffan Widstrand / Wild Wonders of China / Golden snub-nosed monkey (Rhinopithecus roxellana) jumping from branch to branch, Foping Nature Reserve, Shaanxi, China. Endangered species

Fiona Rogers / Eastern chimpanzee (Pan troglodytes schweinfurtheii) juvenile female 'Fadhila' aged 5 years and her brother 'Fifty' aged 3 years playing together.Gombe National Park, Tanzania.

Fiona Rogers / Eastern chimpanzee (Pan troglodytes schweinfurtheii) infant male 'Fifty' aged 3 years portrait.Gombe National Park, Tanzania.

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

Eric Baccega / Mountain gorilla (Gorilla beringei beringei) juvenile female stretching hand out towards camera, member of the Kabirizi group, Virunga National Park, North Kivu, Democratic Republic of Congo, Africa,...

Jabruson Motion / Silverback Mountain gorilla (Gorilla beringei beringei) and family resting in vegetation, with a juvenile peering into the camera lens Bukima, Virunga National Park, Democratic Republic of Congo, 1996...

Jabruson Motion / Close-up of a male Mountain gorilla (Gorilla beringei beringei) and juvenile resting, captivated by reflection in camera lens, knocks juvenile over, Bukima, Virunga National Park, Democratic Republic...

Jabruson Motion / Wide angle shot of a juvenile Mountain gorilla (Gorilla beringei beringei) swinging from a branch and looking at camera, with a silverback nearby, Bukima, Virunga National Park, Democratic Republic of...

Jabruson Motion / Close-up of a tracker, shot pans to a silverback Mountain gorilla (Gorilla beringei beringei) looking at camera, Bukima, Virunga National Park, Democratic Republic of Congo, 1996.

Cyril Ruoso / Ring-tailed Lemur (Lemur catta) basking, Anja Park, Madagascar

Cyril Ruoso / Ring-tailed Lemur (Lemur catta) basking, Anja Park, Madagascar

Cyril Ruoso / Ring-tailed Lemur (Lemur catta) trio basking, Anja Park, Madagascar

Cyril Ruoso / Ring-tailed Lemur (Lemur catta), Anja Park, Madagascar

Cyril Ruoso / Ring-tailed Lemur (Lemur catta) mother with young drinking, Anja Park, Madagascar

Cyril Ruoso / Ring-tailed Lemur (Lemur catta) in tree, Anja Park, Madagascar

Anup Shah / Olive Baboon (Papio anubis) curious male investigating camera, Masai Mara, Kenya

Shane P. White / Japanese Macaque (Macaca fuscata) in hot spring, Jigokudani, Nagano, Japan

Fiona Rogers / Hanuman Langur (Semnopithecus entellus) group on temple, Virupaksha Temple, Hampi, Karnataka, India

Anup Shah / Eastern Chimpanzee (Pan troglodytes schweinfurthii) sixteen month old baby female, named Gossamer, in tree, Gombe National Park, Tanzania

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) five year old juvenile female, named Fadhila, playing with her three year old brother, named Fifty, Gombe National Park, Tanzania

Chien Lee / White-footed Sportive Lemur (Lepilemur leucopus) in cavity, Madagascar

Jami Tarris / Japanese Macaque (Macaca fuscata) in hot spring, Jigokudani, Nagano, Japan