Identification of signature whistle types from the bottlenose dolphin (Tursiops truncatus) population of Cardigan Bay, Wales

Identification of signature whistle types from the bottlenose dolphin (Tursiops truncatus) population of Cardigan Bay, Wales by Helen Hiley (CBMWC 2011)

Helen volunteered with the Cardigan Bay Marine Wildlife Centre during the field season in 2011. Following discussions between CBMWC's Science Officer, Sarah Perry and researchers from the Sea Mammal Research Unit, St Andrews University we set up a hydrophone project, a collaboration which enabled Helen to collect data for her research project as part of her degree from St Andrews University.

Abstract

The bottlenose dolphin, Tursiops truncatus, produces individually distinctive signature whistles that hold identity information in the frequency modulation of the signal. These signature whistles aid in group cohesion and account for 50% of all whistles produced by free ranging dolphins. Britain is home to two large ‘resident’ dolphin populations, found on the east coast of Scotland and in Cardigan Bay, Wales, and one small population found on the west coast of Scotland. Acoustic work has been carried out on both Scottish populations but little or no work has been carried out on the Welsh. Focal group follows were used to record and identify signature whistle types of the free ranging bottlenose dolphin population found in Cardigan Bay. A total of 2,101 whistles were recorded over 35 encounters. This resulted in the identification of 11 signature whistles using a sequential analysis. The mean parameters of these signature whistles were then compared to 4 other free ranging populations and 1 captive population. The results showed significant variation in at least two parameters between the Welsh population and all other populations. Mean end frequency varied significantly from all other populations. The data show the first signature whistles identified from the Cardigan Bay dolphins and offer further insight into geographic signature whistle variation between populations.