The acoustic repertoire of wild dusky dolphins (Lagenorhynchus obscurus) in Golfo Nuevo, Patagonia.

NASTASI, A., J.F. BORSANI, E.A. CRESPO & S.L. DANS.

St. Andrews, Scotland,

Congreso; INTERNATIONAL CONFERENCE ON VOCAL COMMUNICATION IN BIRDS AND MAMMALS.; 2008

During April 2003 and March 2005 sounds and behavioral data of dusky dolphins in Golfo Nuevo, Argentina, were collected. Sound production and acoustic behavior of this species are little known; very basic parameters need to be investigated. Recordings were made with sampling rates of  96 kHz and 48 kHz and a preamplified HTI94SSQ hydrophone. 194 minutes of recordings were obtained in the space of several days at variable times of the day and different locations during a total of 18 encounters with groups with fluid numerical composition (min= 3, max > 60). Digitalized sounds are described with objective parameters such as type of sound (click, whistle or pulse train), repetition rate, duration, frequency range and signal to noise ratio. Only poor quality sounds were not analysed. A subset of 223 samples of sounds were analysed. Preliminary data suggest that clicks (n= 1249), whistles and pulse trains are all part of dusky dolphin repertoire. 4 whistles were found, the frequency of these whistles ranges from 279,9 Hz up to 1934 Hz. All show inflections, duration is included between 0,06s and 0,116s. So far at least two types of pulse trains are common: type A (n= 21) are long series (Ät > 1s; mean= 1,5s, repetition rate mean= 450 clicks s-1 ) with increasing repetion rate throughout the pulse train; type B (n= 87%) pulse trains are short (Ät < 1s; mean= 0,2s) and are subdivided respectively in Type B1  (n=37, without gaps, mean repetition rate= 425 clicks s-1), Type B2 (n=26, which show further structure wih 3 subcomponents: an initial high repetition rate sequence, a section with lower repetition rate and a final sequence (pt3) with high repetition rate; mean=493) and Type B3 (n=6, with gaps and up to 5 subcomponents; pt3 mean repetition rate=493)