Diving and ranging behaviour of odontocetes: a methodological review and critique

Movements can be analysed in terms of horizontal or vertical dimensions, bu t cetacean movement is ultimately three-dimensional, and it is the integrat ion of analyses of both horizontal and vertical movements that will provide the most insight about an animal's behaviour. Current field techniques can provide simultaneous information on both diving (vertical movements) acid ranging (horizontal movements). We discuss the considerations, techniques a nd analyses for diving and ranging studies, together with the advantages an d disadvantages of each technique. Ranging studies using VHF or satellite-l inked radio-transmitters have evolved alongside studies of diving behaviour using time-depth recorders, and problems associated with deployment and at tachment techniques apply to both. The diving (and concurrent ranging behav iour) of 13 species of odontocetes has been studied using time-depth record ers or acoustic transponders with VHF-or satellite-transmitters. However, d ifferences in sampling techniques used, and summary statistics presented, h ave made comparisons difficult. We review these issues and suggest paramete rs that should be presented in future studies of diving and ranging. In gen eral, studies should be consistent in their presentation of the basic param eters and statistics, and provide enough information for the reader to asse ss the limitations of the data.