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Chimps sometimes hang out with sticks in their mouths in a way that looks like smoking, but they do this in the wild too. Sort of like the traditional caricature of a farmer or cowboy with a stalk of wheat or other grass in their teeth.

It’s by a fake termite mound. My guess was that it’s a stick used to prod the mound.

Humans aren't the only animals with oral fixations, although I don't know how widely it's present. Indulging in pop-psych, possibly it's a part of all mammalian psychology.