It's 7 a.m. and there's a strong wind blowing in Pute Santiago, off the eastern coast of Puerto Rico.

A group of 15 researchers meet at a dock and squeeze onto a boat.

The sun rises as the boats captain starts the engine and sails off to Kaya Santiago,

an island just around a mile offshore.

It's a place only researchers are allowed to go.

And it's beautiful.

The water is crystal clear, the breeze passing by is a perfect wake-up call,

and later in the day, the temperature will rise to 80 degrees.

But even so, everyone on the boat is covered up,

wearing long sleeves, pants, bucket hats, and face masks.

As the boat approaches the island,

drawing closer to the palm trees that line its coast,

the researchers start to hear something.

It sounds like a flock of birds, maybe the squeaks of dolphins,

but it's actually the sound of primates, recessed macaque monkeys.

And these monkeys aren't native to this island.

Just like the researchers, they arrive by boat.

For over 80 years, over nine generations,

nearly every birth, death, setback, and triumph of these monkeys

has been observed and recorded.

I think the Truman Show, but with monkeys.

I'm Dylan Thuras, and this is Atlas Obscura,

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