Vocal behaviour and abundance of bottlenose dolphins (Tursiops truncatus) in St Andrews Bay

The aim of this thesis was twofold. Firstly I investigate the fine scale abundance of the population of wild bottlenose dolphins off north-east Scotland and secondly I provide further insights into the vocalisation capabilities of bottlenose dolphins with the use of acoustic localisation and behavioural observations. Photo-identification undertaken during focal follows allowed sighting histories of individuals to be established. These histories were run through three abundance estimation techniques to establish the abundance of bottlenose dolphins in St Andrews bay. Results showed differences in estimation techniques, but all concluded that a large proportion of the bottlenose dolphin population found off north-east Scotland are present in the St Andrews bay area during the summer. The development of a mobile two dimensional hydrophone array allowed accurate localisation of calls to positions around the research boat that could then be correlated with surface observations of dolphin groups. By localisation of stereotyped sequences of whistles, to identify caller position, I was able to show a context related use for these sequences as a precursor to subgroups joining. These sequences were unlikely to occur by chance and the whistles in these sequences were shown to have stereotypy matching that seen in signature whistles. Stereotypy of these whistles was further investigated through a computer based categorisation program where the percentage similarity of contours was investigated when assigning whistles to like categories. Finally, whistle rates were shown to significantly vary with activity type and increased whistle rates were observed during direction changing and socialising compared to surface travel. These increased rates suggest a communicative function related to behavioural activity, as group size was shown to not be a significant predictor of increased whistle rates.