Cayo Santiago is a 38-rope islet of land that has been inhabited by rhesus macaques since 1938. That year, the first 403 monkeys from India were taken there by Dr. C. R. Carpenter, who was concerned that the outbreak of World War II would not allow scientists to travel to the Old World to study primates. Currently, the cay is inhabited by about 1,300 rhesus that are protagonists of scientific research.
From the highest point of the islet, also called “Monkey Island”, you can see the humacao coast, the municipality island of Vieques and another quite close piece of
land. “That is Cayo Pequeño and is connected to Cayo Santiago by a sandy path that serves as a bridge between the two islands and in turn forms a bay, in which the water is so crystal clear that you can see the sea herbs in the background. You can also observe the pelicans giving their spectacular nails to feed and sometimes the manatees that arrive at the place.