Suzi Eszterhas / Sumatran Orangutan (Pongo abelii) two and a half year old baby calling, Gunung Leuser National Park, north Sumatra, Indonesia

Paul Bertner / Spiderlings, Gunung Leuser National Park, Sumatra, Indonesia

Suzi Eszterhas / Orangutan (Pongo pygmaeus) orphan baby bottle fed by photographer Suzi Eszterhas, Indonesia

Suzi Eszterhas / Orangutan (Pongo pygmaeus) orphan baby held by photographer Suzi Eszterhas, Indonesia

Pete Oxford / Southern Cassowary (Casuarius casuarius) chick, Biak Island, West Papua, Indonesia

Gerry Ellis / Orangutan (Pongo pygmaeus) orphan resting on caretaker during air pollution incident caused by burning forests, Yayasan IAR, Ketapang, West Kalimantan, Borneo, Indonesia. October, 2015

Fiona Rogers / Long-tailed Macaque (Macaca fascicularis) baby nursing, Gunung Leuser National Park, Sumatra, Indonesia

Fiona Rogers / Sumatran Orangutan (Pongo abelii) female baby, named Sandri, playing in tree, Gunung Leuser National Park, Sumatra, Indonesia

Fiona Rogers / Sumatran Orangutan (Pongo abelii) female baby, named Sandri, Gunung Leuser National Park, Sumatra, Indonesia

Fiona Rogers / Sumatran Orangutan (Pongo abelii) female baby, named Sandri, Gunung Leuser National Park, Sumatra, Indonesia

Cyril Ruoso / Orangutan (Pongo pygmaeus) close-up of an infant's hand holding tightly to its mother, Kalimantan, Indonesia

Suzi Eszterhas / Orangutan (Pongo pygmaeus) two year old infant playing with towel, Orangutan Care Center, Borneo, Indonesia