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

Maxime Aliaga / Keepers holding hands of infant Sumatran orangutan (Pongo abelii) as they walk to 'forest school' ,Quarantine centre of SOCP (Sumatran Orangutan Conservation Program) near Medan, North Sumatra

Ben Hall / Langur monkey (Semnopithecus) climbing tree in misty forest at dawn, India, November.

Eric Baccega / Portrait of male silverback Mountain gorilla (Gorilla beringei beringei) feeding. Bwindi Impenetrable Forest National Park, Uganda, Africa

Eric Baccega / Mountain gorilla (Gorilla beringei beringei) silverback male, portrait, member of the Nyakagezi group, Mgahinga National Park, Uganda.

Suzi Eszterhas / Northern muriqui monkey (Brachyteles hypoxanthus) juvenile aged one year, in tree playing with its mother's tail, RPPN Feliciano Miguel Abdala, Atlantic Forest, Brazil. June.

Nick Hawkins / Central American spider monkey (Ateles geoffroyi) juvenile, Corcovado National Park, Costa Rica. January.

Nick Hawkins / White-faced capuchin monkey (Cebus capucinus) in Tenorio Volcano National Park, Costa Rica

Nick Garbutt / RF - Ring-tailed lemurs (Lemur catta) back lit and sun bathing at first light. Berenty Private Reserve, southern Madagascar. (This image may be licensed either as rights managed or royalty free.)

Nick Garbutt / Female ring-tailed lemurs (Lemur catta) carrying infants (3-4 weeks) on their backs across open ground. Berenty Private Reserve, southern Madagascar.

Sylvain Cordier / Golden snub-nosed monkey (Rhinopithecus roxellana), two females embracing with baby, Qinling Mountains, Shaanxi province, China

Sylvain Cordier / Phayre's leaf monkey (Trachypithecus phayrei) group on branch, Tripura state, India

Sylvain Cordier / Golden snub-nosed monkey (Rhinopithecus roxellana),standing up on river boulders, Qinling Mountains, Shaanxi province, China

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

Sylvain Cordier / RF-Gelada baboon (Theropithecus gelada) dominant male running. Debre Libanos, Rift Valley, Ethiopia. 2017. (This image may be licensed either as rights managed or royalty free)

Sylvain Cordier / Gelada baboon (Theropithecus gelada) female carrying baby on back, dominant male in background. Debre Libanos, Rift Valley, Ethiopia.

Anup Shah / Olive baboons standing on the lake shore. Gombe National Park, Tanzania.

Oriol Alamany / Gelada Baboon (Theropithecus gelada) male lying in a forest glade at around 3,000 metres of altitude, Simien Mountains National Park, Amhara, Ethiopia.

Ernie Janes / Ring-tailed lemur (Lemur catta) two huddled together for warmth. Captive.

Bernard Castelein / Coquerel's sifaka (Propithecus coquereli) in tree, relaxing, Ankarafantsika National Park, Madagascar

Bernard Castelein / Silky sifaka (Propithecus candidus) in tree, Marojejy National Park, Madagascar. Critically endagered species.

Heather Angel / Northern white cheeked gibbon (Nomascus leucogenys) female standing in tree with baby aged two weeks. Parents captive bred and released. Wild Elephant Valley / Xishuangbanna, Yunnan Province, China, 2...

Lucas Bustamante / Toque Macaques (Macaca sinica) Polonnaruwa, Central Province, Sri Lanka

Cyril Ruoso / Ringed-tailed lemur (Lemur catta) amongst granite rocks in cave. Lemurs lick minerals from the rocks. Anja Community Reserve, Madagascar.

John Shaw / Snow monkey or Japanese macaque (Macaca fuscata) female with baby clinging to her back. Jigokudani, Japan, February.

Bernard Castelein / Rhesus macaque (Macaca mulatta), mixed group of female and juveniles, walking along a track, Keoladeo National Park, Bharatpur, India

Bernard Castelein / Rhesus macaque (Macaca mulatta), juveniles playing in tree, Keoladeo NP, Bharatpur, India

Bernard Castelein / Guianan brown capuchin (Sapajus apella) chewing on branch, Pampas del Yacuma Protected Area, Bolivia

Bernard Castelein / Bolivian red howler (Alouatta sara), Pampas del Yacuma Protected Area, Bolivia

Suzi Eszterhas / Bornean Orangutan (Pongo pygmaeus) next to signs which say 'Silence please. Respect the orangutans' and 'No Smoking' Tanjung Puting National Park, Borneo, Indonesia.

Suzi Eszterhas / Red-shanked douc langur (Pygathrix nemaeus) infant sucking thumb while caretaker holds it. Animal was rescued from illegal wildlife trade, Endangered Primate Rescue Center, Cuc Phuong National Park, V...

Lorraine Bennery / White-fronted brown lemur (Eulemur albifrons) in tree, Rainforests of the Atsinanana, Marojejy National Park, Madagascar. Endangered species, endemic.

Lorraine Bennery / Red-bellied lemur (Eulemur rubriventer) huddling together in tree branches. Anjozorobe Special Reserve, Madagascar. Vulnerable species, endemic.

Lorraine Bennery / White-fronted brown lemur female (Eulemur albifrons), sitting in tree, Rainforests of Atsinanana, Marojejy National Park. Madagascar, Endangered, endemic.

Matthew Maran / Delacour's langurs (Trachypithecus delacouri) resting, Van Long Nature Reserve,Ninh Binh, Vietnam. Critically endangered

Matthew Maran / Red shanked douc langur (Pygathrix nemaeus) Son Tra Nature Reserve, Vietnam

Eric Baccega / Chimpanzee female (Pan troglodytes schweinfurthii) sleeping in a nest built in a tree, Kibale National Park, Uganda, January.

Eric Baccega / Chimpanzee juvenile (Pan troglodytes schweinfurthii) in a tree. Kibale National Park, Uganda. January.

Eric Baccega / Chimpanzee male (Pan troglodytes schweinfurthii) sleeping on the forest floor with feet up, Kibale National Park, Uganda. January.

Eric Baccega / Mountain gorilla (Gorilla beringei) juvenile aged 2 years, hanging from branch, member of the Nyakagezi group, Mgahinga National Park, Uganda. January.

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

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

Ernie Janes / Celebes crested macaque (Macaca nigra) infant, captive.

Ernie Janes / Black howler (Alouatta caraya) male and female, captive, occurs in Brazil and Paraguay. With digitally added leaf pattern.

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...

Jed Weingarten / Wild Wonders of China / Tibetan macaque (Macaca thibetana) carrying young baby, Tangjiahe Nature Reserve, Sichuan Province, China

Lorraine Bennery / White-fronted brown lemur (Eulemur albifrons) climbing tree, looking at camera. Rainforests of the Atsinanana, Marojejy National Park, Madagascar.

Lorraine Bennery / Blue-eyed lemur (Eulemur flavifrons) male looking down from branch. Sahamalaza, Madagascar.