The Colombian Black-faced Spider Monkey (Ateles fusciceps robustus) lives in the mature rainforests of Colombia. The group size of the monkeys varies from 4 to 5 to over 100 depending on the time of year and the amount of food available. 'Ateles' means 'not complete' - spider monkeys have no thumbs. This is an adaptation to swinging through the trees, thumbs being unnecessary for this kind of movement. World Wildlife Zoo, Phoeniz, Arizona.