The Monkeys That Survived

October 20, 2026Admin

Half a mile off Humacao, Puerto Rico, lies a 38-acre limestone cay that tourists aren’t allowed to set foot on: Cayo Santiago. The island belongs to roughly 1,800 rhesus macaque monkeys and the scientists who have watched them since 1938.

The colony descends from about 400 monkeys that primatologist Clarence Ray Carpenter brought from India in 1938. Every animal here today traces its family tree back to them.

Many of the monkeys carry Herpes B, which is harmless to them but deadly to us. Conversely, we could hand them a cold that would tear through the colony. Therefore, no one sets foot on the island without a research badge or a rare visitor pass.

The shoreline of Cayo Santiago seen from a dinghy — Our boat at anchor, as we explore the island by dinghy.

The Scouts

A rhesus macaque watching from the shoreline — They notice us before we notice them.

On the left: One monkey slips into the water and circles our dinghy. On the right: another seems to call out to the others.

An Island in Motion

Macaques moving across the island — A monkey in a hurry.

A macaque climbing through tree branches — A view through the trees.

A baby scrambling to keep up with its mother. Daughters stay in their mother’s group for life, and mothers usually outrank them. Sons leave at puberty and start over at the bottom of a new group.

A macaque climbing a rock face toward the island's summit — Rock climbing to the summit.

Slow Hours

A macaque eating leaves from a tree — A monkey snacks on fresh leaves off the branch.

A macaque lounging on the rocks — Most of the colony spends the afternoon lounging.

A mother macaque holding her baby — A mother and her infant. Researchers have recorded every birth and death on this island for more than 85 years, so this little one’s pedigree is already on file.

Dozens of macaque silhouettes spread across the island's ridge — Every silhouette is a monkey.

The Ones I Keep Coming Back To

It is amazing watching them leap from tree to tree fearlessly.

When Hurricane Maria stripped this island bare in 2017, fewer than 3 percent of the monkeys died. What surprised researchers came after: a famously competitive colony began sharing scarce shade and widening their circle of friends.

As I watch them, it is hard not to see a little of that still in them.

Notes

Getting here: Cayo Santiago is closed to the public, but you can circle it by boat.

Anchoring: We anchored in the Cayo Santiago anchorage and explored by dinghy

For the full history and science, read Puerto Rico: Cayo Santiago, aka “Monkey Island.”

Admin

Cori is an independent journalist, adventurer, and photographer who is currently sailing around the world full-time with her husband, Roy. She earned her bachelor's degree in journalism from the University of Southern California and her master's degree in communications from California State University, Fullerton. When she's not exploring new places, she can be found diving, hiking, or playing with pothounds. You can follow their journey here.

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