Abstract:
Indo-Pacific Humpback Dolphins (IPHD) occur in the coastal waters of the Indo-Pacific region from the Eastern coast of Africa through Southeast Asia to the Northern coast of Australia. Throughout their range, the habitat and vocalization patterns of IPHD remains poorly known, with the exception of populations off South Africa and Hong Kong, where the animals have been relatively well studied. In January 2012, passive acoustic recording of IPHD at Puttalam Lagoon, located Western shores of Sri Lanka were taken and their vocalizations were classified as broadband click trains, burst pulses, whistles and grunts generally similar to those of some other delphinid cetaceans. The frequency of highest intensity (energy), frequency range, the maximum frequency and the interval were compared. A comparison of our results to previous vocalization of humpback dolphins of Eastern Australia and Western Hong Kong waters showed similar patterns except the absence of quacks in the present study. The spectra of broad band click pulses ranged from 8 to >48 kHz showing the highest intensity around 38 kHz. Narrow banded, frequency modulated whistles ranging between 5.5 and 17 kHz. Low frequency narrow band grunt vocalizations were identified in the range of 0.4-2.5 kHz having highest intensity around 1 kHz. IPHD in Puttalam Lagoon often are found at fishing vessel routes, where their feeding grounds are crossed.