- [Narrator] Deep in the protected river lands of Guizhou, China,

a forest ranger has forged a special relationship with some of the rarest monkeys in the world.

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Xiao is tasked with monitoring the monkeys.

It has taken decades of patience

to build a mutually trusting relationship with them.

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Over the past 20 years, Xiao has become an expert

in the group's rituals and behavior

and has given scientists unique insight into the species.

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Under his care, Xiao has seen the number of his group

increase, but the species remains endangered.

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