Cayo Santiago

Cayo Santiago, also known as Monkey Island, is a small island located off the southeastern coast of Puerto Rico. The island is renowned for its free-ranging population of approximately 1,500 Rhesus macaques. These monkeys are the descendants of an initial group of 409 individuals that were relocated from India to Cayo Santiago in 1938. The island serves as a field site for primatological research, providing valuable insights into social behavior, cognition, and genetics of non-human primates.

The island spans an area of approximately 38 acres (15.5 hectares) and is managed by the Caribbean Primate Research Center (CPRC), which is part of the University of Puerto Rico. Access to Cayo Santiago is restricted to scientists, researchers, and staff to ensure the well-being of the monkey population and the integrity of the research. The monkeys are provisioned with food and water to supplement their natural foraging, but otherwise live in a state that is as wild as possible.

Research on Cayo Santiago has contributed significantly to our understanding of primate behavior, social structures, and the biological underpinnings of health and disease. Studies have included topics such as social hierarchy, communication, mating patterns, and the effects of environmental stressors on physical and mental health. The long-term nature of the research on Cayo Santiago has allowed for multi-generational studies, providing insights into the genetic and environmental factors influencing primate behavior and physiology.

The establishment of the Cayo Santiago research facility was spearheaded by Clarence Ray Carpenter, a pioneering figure in the field of primatology. The island's isolation and controlled environment have made it an ideal location for behavioral and biomedical research. Over the years, the data collected from the Cayo Santiago macaque population have contributed to over 1,000 scientific publications, making it one of the most extensively studied groups of non-human primates in the world.

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