Robust recognition of whistle-like frequency contours by a bottlenose dolphin (Tursiops truncatus)

Whistle use by bottlenose dolphins serves several functions including individual identification, maintaining group cohesion, long-range communication, recruitment during feeding, and advertising emotional state. Whistles can vary considerably in amplitude, duration, and frequency. Despite this variability, dolphins must learn to associate specific whistle features (e.g., frequency contour) with meaningful events or objects, requiring plasticity in the dolphin’s recognition abilities. To test robust recognition, a bottlenose dolphin learned to associate whistle-like frequency contours with arbitrary objects. For example, whistle-A would cue the dolphin to touch object-A, and whistle-B would cue her to touch object-B. The whistles were then altered by varying amplitude, duration, and transposing frequency. Changes in amplitude and duration had little effect on recognition, however frequency transposition as small as 1/3 octave resulted in poor performance. The results are discussed from a comparative cognit...