Time and frequency parameters of bottlenose dolphin whistles as predictors of surface behavior in the Mississippi Sound.

Acoustic characteristics related to contour of the whistle (such as highest and lowest frequency, beginning and ending frequency, whistle duration, and number of turns) of bottlenose dolphin (Tursiops truncatus) whistles were measured to test whether any of the measurements were related to the behavioral state of the dolphins when the whistle was recorded (coded as mill, travel, mill/travel, feed, or social). Objective measures of time and frequency were obtained using Raven, while number of turns in a whistle was determined by human raters. In all a series of discriminant function analyses using the acoustic characteristics to predict the behavioral state, the highest standardized canonical discriminant function coefficients were: lowest frequency, number of turns, and duration. The models that incorporated these variables performed significantly better than chance at correctly assigning the whistles into the surface behavior category in which they were recorded. The rate of whistling was related to group size, surface behavior and season via a series of two-way ANOVAs (analysis of variance).