The first evidence monkeys can string "words" together to communicate in a similar way to humans has been found.
The monkeys used two main call types to warn of predators
Putty-nosed monkeys in West Africa share the human ability to combine different sounds to mean different things, according to researchers.
St Andrews University, UK, scientists found the creatures, in Nigeria's Gashaka Gumti National Park, used two main call types to warn of predators.
But a particular sequence of calls also appeared to mean something else.
The scientists identified two call types - "pyows" and "hacks" - which the monkeys use to alert each other to danger; but found a string of pyows warned of a loitering leopard, while a burst of hacks indicated a hovering eagle.
A sentence made up of several pyows, followed by a few hacks, told the group to move to safer ground.
Dr Kate Arnold, a primate psychologist, discovered the phenomena by playing variations of the calls back to the monkeys to see how they behaved.
This showed they could encode fresh information by combining two existing calls, rather than creating a new sound, she said.
"These calls were not produced randomly and a number of distinct patterns emerged," she said.
"The pyow-hack sequence means something like 'let's go', whereas the pyows by themselves have multiple functions and the hacks are generally used as alarm calls.
"This is the first good example of animal calls being combined in meaningful ways.
"The implications of this research are that primates, at least, may be able to ignore the usual relationship between an individual call and any meaning that it might convey under certain circumstances."
The research has been carried out over the past three years, and has been published in the scientific journal Nature.