jamie writes "The Campbell's monkey has a vocabulary with at least six types of basic call, but new research published in the PNAS claims that they combine them and string them together to communicate new meanings. (Login may be required on the NY Times site.) For example, the word for 'leopard' gets an '-oo' suffix to mean 'unseen predator.' But when that word is repeated after 'come over here,' the combination means 'Timber!' — a warning of falling trees. Scientists have known for some time that vervet monkeys have different warning calls for different predators — eagle, leopard, and snake — but unlike the Campbell's monkeys, vervets don't combine those calls to create new meanings, a key component of syntax. The researchers plan to play back recordings to the monkeys to test their theories for syntax errors."