What do ruffed lemurs sound like?

Lemurs make many types of sounds, depending upon the species. The indri, for instance, sings duets like a gibbon. Mouse lemurs make little chriping sounds. Ruffed lemurs make really loud roar/shriek chorus in response to disturbances. Ring-tailed lemurs can purr like house cats when they are content and make other cat-like sounds to keep in contact with one another. The aye-aye can make a loud shriek, and also appears to use snorts as a sort of communication.

You can learn more (as well as listen to samples) at the website listed in the Related Links.