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Diet, feeding behaviour and habitat-use patterns of bowhead whales in the Eastern Canadian Arctic Fortune, Sarah Marie Elizabeth


Climate induced changes in prey quality and quantity may affect the foraging success of bowhead whales (Balaena mysticetus) in coming years. However, little is known about the diet and feeding behaviour of bowhead whales under present environmental conditions. I studied the eastern Canada-West Greenland population (ECWG) of bowhead whales to determine 1) where their important feeding areas occurred, 2) what their primary prey was, and 3) how they foraged. Through analysing long-term movement and dive data to assess behaviour (satellite-telemetry time-depth recorders), I concluded that ECWG bowhead whales feed year-round, with peak feeding occurring between July and September. Of all their feeding habitats, Cumberland Sound, Nunavut, appears to be the most important because of the dominance of large-bodied, energy rich Arctic copepods (e.g., Calanus glacialis). I found that the depth where the whales fed varied temporally over seasonal and diel time-scales, and matched the ontogenetic vertical movement of zooplankton (assessed using an optical plankton counter and mesh nets). Collecting fine-scale information about dive behaviour and prey distribution, I found that bowheads in Cumberland Sound used two alternate feeding strategies. They either 1) exploited shallowly aggregated prey that occasionally occurred in high concentrations, or 2) dove to a deeper layer of lower but more consistent abundance comprising larger and more energy rich organisms. Using drones to record whale behaviour, I observed bowhead whales moulting during summer and actively rubbing against large rocks. Thus, Cumberland Sound is a multi-use habitat that supports skin exfoliation and year-round feeding—and is of greatest importance during summer and fall. Overall, my findings provide new insight into the diet, seasonal movements, habitat-use and year-round foraging behaviour of bowhead whales in the eastern Canadian Arctic.

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