We recently had a manuscript accepted by the Journal of Mammalogy reporting the potential use of whistles as indicators of stress in bottlenose dolphins. In particular, we examined the possibility that parameters of bottlenose dolphin signature whistles may serve as indicators of some level of stress. Bottlenose dolphins in Sarasota Bay, Florida, have been recorded during brief capture-release events, which are potentially a source of short-term stress to these dolphins, although no effects of chronic or long-term stress have been observed over the 38 year duration of the research. Whistles recorded during both brief capture-release and undisturbed, free-ranging conditions were examined to determine whether whistle parameters differ: (1) during capture-release versus undisturbed conditions; (2) at the beginning of a capture-release session versus at the end of a session; (3) during an individual’s first capture-release session versus later capture-release sessions; and (4) when a mother is caught and released with a dependent calf versus when she is between calves (i.e., she has no dependent calf at the time of capture-release). We examined a variety of acoustic parameters, including whistle rate, number of loops (repetitive elements), maximum and minimum frequency, and loop, inter-loop, and whistle duration. In addition, we developed a generalized linear model to determine the effects of age, capture-release number, and sex on whistle rate. We found that: 1) whistle rate and number of loops were greater during brief capture-release events than during undisturbed conditions; 2) number of loops decreased and loop duration increased over the duration of a capture-release session; 3) whistle rates decreased with increased number of capture-release sessions; and 4) females caught and released with dependent calves produced whistles with higher maximum frequencies and shorter inter-loop intervals than when they did not have dependent calves. Decreases in whistle rate with capture-release experience remained robust when the influence of age and sex were considered.
        Thus, whistles appear to have potential as non-invasive indicators of stress in bottlenose dolphins. Further research is warranted in this area, for example, by correlating physiological indices to whistle rates under varying levels of stress. Reliable, non-invasive correlates of stress could be used to monitor dolphins in a variety of circumstances, such as during exposure to anthropogenic noise.