Prairie dogs have a language so complex that they have a different "word" they can shout to identify what kind of predator is approaching, and thus have a specific noise that means "humans are coming." But one expert found that prairie dogs had variations in their calls depending on which human they saw. In experiments, the dogs' calls would differentiate based on what color shirts researchers were wearing, how tall or short they were, how close they were and how fast they were moving.
That's right -- the prairie dogs were actually describing each person in remarkable detail with a single chittering bark. A professor named Con Slobodchikoff has been studying prairie dog calls for 30 years, and says that one vocalization can translate into "There's a tall skinny guy in green a few yards away and he's sprinting toward us," sort of like that scene in Wayne's World where Mike Myers speaks five English sentences with one word of Cantonese.
They're probably also judging you.
This means that prairie dogs possess a level of communication more sophisticated than that of dolphins or chimps, and yet for some reason we have yet to dress them up as butlers or make them dive through hoops in front of spoiled children.