Watch Online Free on Watchseries. Rhesus Monkeys of Santiago Island, Puerto Rico" (1966) is an in-depth documentary that explores the establishment and subsequent study of a rhesus monkey colony on Cayo Santiago, a small island located off the southeastern coast of Puerto Rico. This colony, established by the National Institutes of Health (NIH), serves as a significant site for research into the social behavior and population ecology of rhesus monkeys (Macaca mulatta).