Ingo Arndt / White-handed gibbon {Hylobates lar} feeding in {Ficus sp} tree Khao Yai NP Thailand

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...

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.

Sandesh Kadur / Western hoolock gibbon (Hoolock hoolock) male hanging from branch, Assam, India.

Tim Laman / Skywalker hoolock gibbon (Hoolock tianxing) formerly described as Eastern hoolock gibbon (Hoolock leuconedys) Gaoligong Mountains National Nature Reserve, Yunnan Province, China.

Tim Laman / Skywalker hoolock gibbon (Hoolock tianxing) formerly described as Eastern hoolock gibbon (Hoolock leuconedys) Gaoligong Mountains National Nature Reserve, Yunnan Province, China.

Roland Seitre / Pileated gibbon (Hylobates pileatus) female climbing through trees, Angkor Centre for Conservation of Biodiversity, Siem Reap, Cambodia. Endangered species.

Visuals Unlimited / Agile Gibbon (Hylobates agilis) face portrait, Tanjung Puting National Park, Kalimantan, Borneo, Indonesia

Staffan Widstrand / Wild Wonders of China / Eastern hoolock gibbon (Hoolock leuconedys) hanging from a branch in its arms, resting between forays through the rainforest, Gaoligongshan Nature reserve, Yunnan, China

Rod Williams / Young male Northern White-cheeked Crested Gibbon (Nomascus leucogenys) Northern Vietnam. Critically Endangered, Captive

Rod Williams / Northern / Chinese white-cheeked gibbon (Nomascus leucogenys) female head portrait, Laos, Vietnam, critically endangered species. Captive.

Shibai Xiao / Hainan black-crested gibbon (Nomascus hainanus) young male in tree, Bawangling National Nature Reserve, Hainan Island, China.

Sandesh Kadur / Northern Pig-tailed Macaque (Macaca leonina) on branch. Gibbon Wildlife Sanctuary, Assam, India.

Sandesh Kadur / Stump Tailed Macaque (Macaca arctoides) female yawning in canopy holding infant. Gibbon Wildlife Sanctuary, Assam, India.

Sandesh Kadur / Stump Tailed Macaque (Macaca arctoides) among branches. Gibbon Wildlife Sanctuary, Assam, India.

Bernard Castelein / Hoolock Gibbon (Hylobates hoolock) male hanging from a branch. Assam, India, February.

Kevin Schafer / Western hoolock gibbon (Hoolock hoolock) female with young swinging through tree, Gibbon Wildlife Sanctuary, Assam, India, Endangered species

Juan Carlos Munoz / Grey gibbon (Hylobates muelleri) swinging from branch in rainforest and using foot to grip plant vine, Mount Kinabalu NP, Sabah, Borneo, Malaysia

Eric Baccega / Siamang Gibbon (Hylobates syndactylus) vocalising, vocal pouch inflated, captive, native to forests of Malaysia, Sumatra and Thailand

Rod Williams / White-handed / Lar gibbon {Hylobates lar} male. Portrait showing teeth. Captive.

Justine Evans / White handed gibbon, alpha male hanging in tree {Hylobates lar} Khao Yai NP, Thailand 'Cassius'

Xu Jian / White browed gibbon hanging {Hylobates hoolock} Yunnan, Chin

Anup Shah / White handed gibbon hanging from branch {Hylobates lar} C

Ingo Arndt / White-handed gibbon portrait {Hylobates lar} Thailand

Rod Williams / Young male Black Concolor gibbon portrait {Hylobates concolor} occurs Vietnam, N Laos, Isle of Hainan

Ingo Arndt / White-handed gibbon portrait {Hylobates lar} Khao Yai NP, Thailand

Rod Williams / Face portrait of female Black gibbon, occurs SE Asia

Anup Shah / White-handed gibbon with baby. Native to South East Asia

Anup Shah / White-handed gibbon with young. Species native to South East Asia

Anup Shah / White-handed gibbon with young. Native to South-East Asia

Anup Shah / White-handed gibbon baby. Endangered species native to South East Asia.

Anup Shah / Grey gibbon portrait

Anup Shah / Siamang gibbon male calling, pouch inflated

Thomas Marent / Buff-cheeked Gibbon (Nomascus gabriellae) female, Phnom Tamao Wildlife Rescue Center, Cambodia

Roland Seitre / Muller's Bornean Gibbon (Hylobates muelleri) in tree, native to Borneo

Roland Seitre / Muller's Bornean Gibbon (Hylobates muelleri) in tree, native to Borneo

Roland Seitre / White-handed Gibbon (Hylobates lar) calling while hanging from branch, native to Asia

Roland Seitre / Dwarf Gibbon (Hylobates klossii) sub-adult in tree, native to Asia

Thomas Marent / Bornean White-bearded Gibbon (Hylobates albibarbis) walking on liana, Tanjung Puting National Park, Borneo, Indonesia

Thomas Marent / Bornean White-bearded Gibbon (Hylobates albibarbis), Tanjung Puting National Park, Borneo, Indonesia

Kevin Schafer / Asian Elephant (Elephas maximus) throwing sand onto its back, Gibbon Wildlife Sanctuary, Assam, India

Thomas Marent / Agile Gibbon (Hylobates agilis) pair, Camp Leaky, Tanjung Puting National Park, Indonesia

Staffan Widstrand / Wild Wonders of China / Northern white-cheeked gibbon (Nomascus leucogenys), adult male, Xishuangbanna National Park, Yunnan, China. Critically endangered.

Staffan Widstrand / Wild Wonders of China / Northern white-cheeked gibbon (Nomascus leucogenys), adult male, Xishuangbanna National Park, Yunnan, China. Critically endangered.

Magnus Lundgren / Wild Wonders of China / Skywalker hoolock gibbon / Gaoligong hoolock gibbon (Hoolock tianxing) Gaoligong Mountains National Nature Reserve, Yunnan Province, China

Magnus Lundgren / Wild Wonders of China / Skywalker hoolock gibbon / Gaoligong hoolock gibbon (Hoolock tianxing) hanging from tree, Gaoligong Mountains National Nature Reserve, Yunnan Province, China

Magnus Lundgren / Wild Wonders of China / Skywalker hoolock gibbon / Gaoligong hoolock gibbon (Hoolock tianxing) hanging from tree, Gaoligong Mountains National Nature Reserve, Yunnan Province, China

Magnus Lundgren / Wild Wonders of China / Skywalker hoolock gibbon / Gaoligong hoolock gibbon (Hoolock tianxing) Gaoligong Mountains National Nature Reserve, Yunnan Province, China