The island was hit by Hurricane Maria on September 20, 2017. It pounded the island with winds gusting at 170 miles per hour and torrential rains. This would be the island's first Category 4 hurricane in almost 85 years. Many residents were left without electricity, running water, or shelter. One community survived the storm's aftermath: 1,500 rhesus Macaques, who live a mile from the eastern shores of Puerto Rico, on Cayo Santiago.

Monkey Island was first home to these strange inhabitants in 1930s when Clarence Carpenter, a primatologist, brought about 450 monkeys from India by ship to the island's 38-acre area to study their sexual and social behaviors. The tree-studded island became the home of the Caribbean Primate Research Center. This educational and research facility is part of the University of Puerto Rico. Over the years, many generations of monkeys descended from the original colony. Today, those descendants can freely roam the island, exploring the endless canopy of trees and playing on the sandy beaches. Rhesus macaques, which weigh around 20 pounds each and are known for their fluffy tails and straw-colored hair, live largely without human intervention (minus feedings).

Researchers from the center worried about the monkeys after the hurricane devastated Puerto Rico. They were unsure if the animals would survive. Initial reports indicated that 65 people were killed in the hurricane. The scientists were amazed to discover that the furry inhabitants survived after it became safe to return to the island.

Alyssa arre, the center’s scientific director, says that two days after the storm, staff members took a boat to the island and fed the monkeys. "Everyone was worried that the monkeys would die, but it wasn't."

Arre states that it is impossible to know for certain if any monkeys died in the storm. However, the daily population census workers didn't detect any irregularities.

Arre believes that the macaques sought refuge by climbing on to one of two hills on the island and remaining low to the ground. However, there are no cameras available to record the entire event. Staff use the only buildings on the island for research and storage.

Arre states that the hurricane decimated all the vegetation the monkeys used to supplement their diets. "The wind was so strong [it knocked down twigs, branches], so we don’t believe that they climbed into trees."

Only the monkeys get daily human interaction. This is because they destroyed much of the vegetation when they arrived on the island.

Arre explains that Carpenter and his team initially believed the monkeys would live on the island unaffected by human intervention. However, the monkeys destroyed the island's vegetation and ate it all. "So they realized that they had to provide food for the population. This has been the case since the beginning.

Their current diet includes coconuts and corn, seeds, fruits, vegetables, papaya, Purina Monkey Chow, and apples. These are dry biscuits with a yellow egg-shaped shape. Arre confirmed that monkeys don't like bananas, despite what media and movies may portray.

She says that monkeys love to put their monkey chow in a puddle, roll it around and eat it before eating it.

It was only natural that a research institute has been studying these mammals for many decades. They wanted to see how trauma, in this instance a natural disaster, affects their behavior and relationships. The researchers were surprised at their results.

Arre explains that after Hurricane Maria, monkeys experienced more affiliative interactions and their social network expanded. This allowed them to interact with more people. "Researchers also looked at how trauma, particularly early-life adversity such as a hurricane, could affect monkey behavior and health.

This research was eventually published in Current Biology early last year. It concluded that macaques became more social and that monkeys who were more isolated before the hurricane "increased their social connections most immediately."

Another study showed that hurricanes caused females to reproduce less often.

The center was established in 1970 and has been a leader in primate research. It has also made important contributions to the understanding of human and primate behavior. William Windle, the late director of the National Institute of Neurological Diseases and Blindness in San Juan's perinatal biology lab, was closely involved with the island, which provided resources for naturalistic behavioral and reproductive research. Windle researched the effects of oxygen deprivation (asphyxia) on the brains of monkeys during birth and the permanent brain damage that these effects can cause. His research not only improved the delivery of human infants but also earned him the Lasker Prize for 1968. The institute is now focusing on Covid-19 and its effects upon monkeys.

Monkey Island was also featured in a 1939 Life magazine article, photographed by Hansel Mieth, a German photojournalist. Mieth's image of a rhesus monkey sitting in the water, soaking wet, is one of the most famous animal photos of all time.

Mieth later explained the process in a subsequent interview. She said that "One afternoon, all the doctors were gone and a little child came running to me and stated, 'A monkey is in the water I don’t think [the monkey] likes me, but he sat down on that coral reef and I took about twelve shots."

The island is closed to the public today to avoid unnecessary human contact. Visitors still visit the island every year to study the monkeys. They also have access to the extensive database, which contains over 60 years of data. This includes basic demographic information (age and social groupings, maternity rates, and gender) as well as genetic information and a collection with more than 3,300 monkey skulls. Their research continues to advance our understanding of primate behavior, and how it relates to our behavior as humans.

Arre states that the rhesus macaques are a good example for humans because we share many of our biology characteristics and live very social lives. The projects conducted at Caya Santiago with the rhesus Macaques help us to better understand the social nature of humans and how trauma and adversity might impact the lives of individuals.