Hello Bioacoustics-l,
Here is a bioacoustics article from the current issue of Journal of
Mammalogy. As usual, the articles can be downloaded from my web site at
http://www.uvm.edu/~bmitchel/Bioacoustics.html.
Esch, H. C., L. S. Sayigh, J. E. Blum, and R. S. Wells. Whistles as
potential indicators of stress in bottlenose dolphins (Tursiops
truncatus). Journal of Mammalogy 90(3):638-650.
Abstract: We examined the possibility that parameters of bottlenose
dolphin signature whistles may serve as indicators of stress. Bottlenose
dolphins (Tursiops truncatus) in Sarasota Bay, Florida, were 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 37+-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 during capture–release versus undisturbed
conditions; at the beginning of a capture–release session versus at the
end of a session; during an individual’s 1st capture–release session
versus later capture–release sessions; and when a mother is caught and
released with a dependent calf versus without a dependent calf (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,
interloop, and whistle duration. We found that whistle rate and number
of loops were greater during brief capture–release events than during
undisturbed conditions; number of loops decreased and loop duration
increased over the duration of a capture–release session; whistle rates
decreased with number of capture–release sessions; and females caught
and released with dependent calves produced whistles with higher maximum
frequencies and shorter interloop intervals than when they did not have
dependent calves. Thus, whistles appear to have potential as noninvasive
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, noninvasive
correlates of stress could be used to monitor dolphins in a variety of
circumstances, such as during exposure to anthropogenic noise.
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