And, Wired says, we’re just about able to understand their vocabulary… and their grammar:
Lemasson’s team previously described the monkeys’ use of calls with specific meanings in a paper published in November. It detailed the monkeys’ basic sound structures and their uses: “Hok” for eagle, “krak” for leopard, “krak-oo” for general disturbance, “hok-oo” and “wak-oo” for general disturbance in forest canopies. A sixth call, “boom,” was used in non-predatory contexts, such as when calling a group together for travel or arguing with neighboring groups.
Impressive as that was, however, it was still relatively one-dimensional, not much different from verbalizations heard in many animal species, from other non-human primates to songbirds. The team’s latest findings, published Monday in the Proceedings of the National Academy of Sciences, describe something far more complicated: syntax, or principles of word sequence and sentence structure.
Though some researchers have ascribed syntax to animals, it’s never been formally demonstrated — until now.