The manner in which dolphin calves acquire their whistle repertoire is largely unknown. This paper focuses on whistle development in four bottlenose dolphin calves during the first thirty days of life in order to increase our understanding of the early emergence of whistle-like vocalizations. The acoustic parameters of whistle-type vocalizations (i.e., whistles and whistlesquawks) that coincide with a bubblestream emission from the focal calf and/or its mother are investigated. Mother and calf whistle rates are inversely related, with the mother whistling significantly more often in the first ten days of the calf’s life, and the calf whistling significantly more often in the third ten days. A calf is able to produce a predominantly stereotyped whistle contour in the first thirty days, a whistle that still retains the “tremulous and quavery” quality commonly characteristic of young calf whistles [Caldwell & Caldwell, 1979; Gnone et al., 2001]. Whistle-squawks are significantly more common than adult-like, clear narrowband whistles throughout this developmental period. The maximum frequency, frequency range, and duration of calf whistle-type vocalizations increase with age, suggesting that the acoustic prowess of dolphin calves develops over the first month of life.