Range Utilization and Movement Patterns of Coastal Hector’s Dolphins (Cephalorhynchus hectori)

Abstract: Home range sizes have been determined for few odontocete populations, although the understanding of comparative trends in range utilization is important for conservation. Most of the published knowledge of the Hector’s dolphins (Cephalorhynchus hectori) of New Zealand, originates from one well-studied population around Banks Peninsula. Its ranging behavior has been described previously by a decades-long photo-identification (ID) study and by a shorter radio-telemetry study. Little is known, however, about how the dolphins utilize their home range in other coastal areas around the South Island of New Zealand. We used an intensive three-year photo-ID study to define the movement patterns of Hector’s dolphins over diel and seasonal scales. Significant differences in the average movement behavior between the East Coast populations off Kaikoura and Moeraki and the West Coast populations off Westport-Greymouth and in Jackson Bay are identified. Movement patterns optimizing range utilization in relation to prey abundance and accessibility are discussed. At the Kaikoura study area, the mean distances between consecutive sightings and speeds of dolphins were considerably reduced compared to other coastal areas. Therefore, the photo-ID study was extended off Kaikoura to cover a total of 14 years. Those findings can be explained by the existence of an environmental barrier (i.e., the deep-water Kaikoura Canyon) that almost completely interrupts Hector’s dolphin movements over the short distance of 15 km and very likely has led to a reduced genetic exchange. In conjunction with two recent studies, we present evidence of the impact of an environmental barrier on the population structure and foraging behavior of this shallow-water dolphin.
Key Words: environmental barrier, home range, Kaikoura Canyon, South Island of New Zealand, migration, site fidelity
Document: Article
DOI: https://doi.org/10.1578/AM.44.6.2018.633
Page Numbers: 633-642

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