Cayo Santiago, Research islet off Humacao, Puerto Rico
Cayo Santiago is a small island off the coast of Humacao, lying east of Punta Santiago and home to around 1,800 rhesus macaques. The islet serves as a research site where scientists study primate behavior and social structures.
The island was established in 1938 by the Caribbean Primate Research Center, when rhesus macaques from India were first brought there. Since then, the animals and their descendants have served as subjects for behavioral and evolutionary research.
The islet is known for its monkey colony, which researchers have observed and studied for many decades. Visitors can watch from boat tours as the animals live and interact with one another in their natural habitat.
The island is reserved for researchers, but visitors can observe the monkeys through guided boat tours departing from the mainland. It is best to go early in the day and bring binoculars to see the animals more clearly from a distance.
After Hurricane Maria in 2017, the monkeys showed increased cooperation and shared resources with one another. This unexpected shift in their social behavior helped researchers gain new insights into adaptation and resilience.
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