Quantitative analysis of bottlenose dolphin movement patterns and their relationship with foraging
Helen Bailey, University of Aberdeen, School of Biological Sciences, Lighthouse Field Station, Cromarty, Ross-shire IV11 8YJ, Scotland, UK. Tel./fax: 44 1381600548; E-mail: email@example.com
- 1Broad-scale telemetry studies have greatly improved our understanding of the ranging patterns and habitat-use of many large vertebrates. However, there often remains considerable uncertainty over the function of different areas or the factors influencing habitat selection. Further insights into these processes can be obtained through analyses of finer scale movement patterns. For example, search behaviour may be modified in response to prey distribution and abundance.
- 2In this study, quantitative analysis techniques are applied to the movements of bottlenose dolphins, recorded from land using a theodolite, to increase our understanding of their foraging strategies. Movements were modelled as a correlated random walk (CRW) and a biased random walk (BRW) to identify movement types and using a first-passage time (FPT) approach, which quantifies the time allocated to different areas and identifies the location and spatial scale of intensive search effort.
- 3Only a quarter of the tracks were classed as CRW movement. Turning angle and directionality appeared to be key factors in determining the type of movement adopted. A high degree of overlap in search effort between separate movement paths indicated that there were small key sites (0·3 km radius) within the study area (4 km2). Foraging behaviour occurred mainly within these intensive search areas, indicating that they were feeding sites.
- 4This approach provides a quantitative method of identifying important foraging areas and their spatial scale. Such techniques could be applied to movement paths for a variety of species derived from telemetry studies and increase our understanding of their foraging strategies.