Will Burrard-Lucas / Tufted gray langur (Semnopithecus priam) Close up portrait of head and shoulders. Minneriya National Park, Sri Lanka. September

Anup Shah / Olive Baboon (Papio anubis) male with three month old young, Gombe National Park, Tanzania

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

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

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

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...

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

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

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

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