The calf's presence and foraging and social behavior were also found to be associated with dolphin whistle variation. The prominent differences in the acoustic environments between the two areas, which contributed to the acoustic variability in the first principal component (PC1), were found. The study revealed that both geographic distance/isolation and local environment are associated with whistle variations between localities. We first applied a principal component analysis to reduce the number of collinear whistle frequency and temporal characteristics and then generalized linear mixed models on the first two principal components. We explored which factors, among (a) geographical isolation of populations, (b) different environments in terms of noise and boat presence, and (c) social factors (including group size, behavior, and presence of calves), were associated with whistle characteristics. In the present study, we investigated the factors associated with the acoustic variability in the whistles of common bottlenose dolphin ( Tursiops truncatus), inhabiting two Mediterranean areas (Sardinia and Croatia). Although it is known that they are influenced by different environmental and social variables, the factors influencing the variation between populations have received scant attention. The dolphin whistles are communication signals that can vary significantly among and within populations. The studies on the variation of acoustic communication in different species have provided insight that genetics, geographic isolation, and adaptation to ecological and social conditions play important roles in the variability of acoustic signals.

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