Scientists have reported that putty-nosed monkeys string two warning sounds ("pyows" and "hacks") together to create a third call with an entirely different meaning. No animals other than humans have previously been known to do this. From News@Nature:
..Two calls seem to be the only sounds in the putty-nosed monkey's repertoire. Researchers had observed that the monkeys sometimes use these calls in an apparently non-meaningful way: to yell at a fellow monkey, for example, without communicating a specific message.
But now zoologists have realized that at least one combination of these sounds has its own distinct meaning: up to three pyows followed by up to four hacks seems to mean 'let's move on'. This call sequence is given both in response to the presence of predators or simply as a sign to head for new terrain.
"Whenever a male gave these sequences the group would move on and leave," says Klaus Zuberbühler of the University of St Andrews, UK, who carried out the research in Nigeria's Gashaka Gumti National Park with his colleague Kate Arnold.
