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

Jerry Monkman / Boy playing on rope swing over the Androscoggin River, Mollidgewock State Park in Errol, New Hampshire, USA, August 2008. Model released.

Carol Walker / Silhouette of cowboy trotting, swinging a loop at sunset, Flitner Ranch, Shell, Wyoming, USA Model released

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

Bruno D'Amicis / Young Barbary Macaque (Macaca sylvanus) playing among Cedar (Cedrus atlantica) trees, backlit, Endangered species. Atlas mountains, Morocco, NW Africa

Tim Laman / Proboscis monkey (Nasalis larvatus) juvenile playing by swinging from a vine. Kinabatangan Wildlife Sanctuary, Sabah, Malaysia, Borneo, Endangered

Carol Walker / Cowboy galloping while swinging a rope lassoo at sunset, Flitner Ranch, Shell, Wyoming, USA, model released

Anup Shah / Juvenile orang utan (Pongo abelii) swinging on liana over water Gunung Leuser NP Sumatra Indonesia

Anup Shah / Juvenile orang utan (Pongo abelii) swinging on liana Gunung Leuser NP Sumatra Indonesia

Anup Shah / Juvenile orang utan (Pongo abelii) swinging on liana Gunung Leuser NP Sumatra Indonesia

Anup Shah / Juvenile orang utan (Pongo abelii) swinging on liana Gunung Leuser NP Sumatra Indonesia

Anup Shah / Sumatran Orang utan baby hanging upsidedown in tree {Pongo pygmaeus abelii} Gunung Leuser NP, Sumatra, Indonesia