Vocal mimicry requires a Bio-Mask to be utilized, and should not be confused with a Yautja's natural ability to copy human speech — while Predators can naturally "speak" human words to some extent, vocal mimicry refers specifically to the perfect imitation of a particular human voice.
Mimicry usually involves the repetition of phrases used by other prey previously encountered by the Predator, although it appears the Yautja also have some kind of "database" of pre-recorded statements from which hunters can draw. In fact, some individuals have been heard to repeat phrases used by victims that they had never before encountered themselves, but who were hunted by other Yautja at an earlier time. Typically, mimicry consists of the use of distress calls, beckons or insults to lure a target to a specific location, often with the intent of separating them form their comrades and thereby making them an easier target. Predators have also been known to use mimicry to circumvent electronic security systems that require the use of a specific spoken password to deactivate. Occasionally (and somewhat less commonly), vocal mimicry is used for no purpose other than to taunt or scare prey, or as a form of celebration following a particularly significant victory.
Due to the often appropriate use of mimicry, it appears Yautja have at least some understanding of the phrases they repeat.