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Mouth gaping in sharks has been considered to be either a threat display or a response to sharksucker irritation, but has never been examined in greater detail. Another form of gaping was observed frequently around feeding scenarios, primarily when sharks swam away from the food source. This form of a yawn-like behavior of Caribbean reef sharks, Carcharhinus perezi, was videotaped during both standard feeding and non-feeding scenarios, and examined for both proximate causation and function. This type of gaping reflects a simulated bite process, including all bite phases, but differs from actual bites in that the duration is as great as 10 times longer, with the expansion phase disproportionally prolonged and a pause at the gape's peak. Of all the possible functions discussed, a maintenance behavior to reposition the jaw elements after feeding fits all of the measured parameters. [ABSTRACT FROM AUTHOR]