Monkey Calls Have Different Meanings.

Putty-nosed monkey has code words to warn others of predators:

If you're a putty-nosed monkey and you hear a friend whoop out a loud "pyow" call, you know there's a leopard sneaking around and it's time to boogie.

Similarly, if you hear a "hack," it means you should watch out for a hungry eagle.

If the male let's out a "pyow," the monkeys scramble away from the lower levels of the trees. If they hear a "hack," they climb away from the canopy to avoid getting picked off by an eagle.

But, if the monkey mixes the call into "pyow-hack", it means something entirely different:

"They might make a 'pyow-hack' in response to a predator, but the strange thing is they also do it early in the morning while foraging," said study co-author Klaus Zuberbuhler. "If the male wants to move on, he produces that sequence, which is followed by the group moving."

http://www.livescience.com/animalworld/060517_monkey_codewords.html