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Spatiotemporal distribution of foraging in a marine predator: behavioural drivers of hotspot formation

Tom Brough*, William Rayment, Elisabeth Slooten, Stephen Dawson

*Corresponding author:

ABSTRACT: Many species of marine predators display defined hotspots in their distribution, although the reasons why this happens are not well understood in some species. Understanding whether hotspots are used for certain behaviours provides insights into the importance of these areas for the predators’ ecology and population viability. In this study, we investigated the spatiotemporal distribution of foraging behaviour in Hector’s dolphin (Cephalorhynchus hectori), a small, endangered species from New Zealand. Passive acoustic monitoring of foraging ‘buzzes’ was carried out at four hotspots and six lower-use, ‘reference areas’, chosen randomly based on a previous density analysis of visual sightings. The distribution of buzzes was modelled among spatial locations and on three temporal scales (season, time of day, tidal-state) with generalised additive mixed models using 82,000 hours of monitoring data. Foraging rates were significantly influenced by all three temporal effects, with substantial variation in the importance and nature of each effect among locations. The complexity of the temporal effects on foraging is likely due to the patchy nature of prey distributions and shows how foraging is highly variable at fine-scales. Foraging rates were highest at the hotspots, suggesting that feeding opportunities shape fine-scale distribution in Hector’s dolphin. Foraging can be disrupted by anthropogenic influences. Thus, information from this study can be used to manage threats to this vital behaviour in the locations and at the times where it is most prevalent.