There has been wide empirical and theoretical interest in how diving animals allocate time between obtain-ing oxygen at the surface and foraging at depth. Assuming diminishing returns in oxygen gain at the sur-face, classic diving models predict that time on the surface should increase, while time s...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.542.9844 http://www.sfu.ca/~jpheath/Research/pdf/Animal-Behaviour07.pdf |
| Summary: | There has been wide empirical and theoretical interest in how diving animals allocate time between obtain-ing oxygen at the surface and foraging at depth. Assuming diminishing returns in oxygen gain at the sur-face, classic diving models predict that time on the surface should increase, while time spent foraging at depth should first increase and then decrease as travel time increases. Controlled laboratory experiments have indicated partial support for predictions of diving models; however, their usefulness in understanding patterns of diving behaviour in the wild is still in question.We assessed the applicability of divingmodels to foraging patterns of common eiders, Somateria mollissima sedentaria, wintering in the Canadian Arctic. Un-derwater footage was used to quantify time foraging at depth and duration of surface pauses in relation to changes in travel time induced by strong tidal currents. Consistent with predictions of diving models, bot-tom foraging time decreased with increasing travel time, while total dive duration was relatively constant at 58.47 5.32 s, close to the estimated aerobic dive limit for this species. However, durations of surface pauses were not associated with diving parameters, as anticipated from diving models. Durations of surface pauses were highly variable (183.05 158.06 s) and often considerably longer than necessary to replenish oxygen stores. While the duration of surface pauses predicted by diving models in relation to travel time may be an optimal strategy when obtaining oxygen at the surface is the predominant constraint to foraging |
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