Three-dimensional analysis of search behaviour by ringed seals

Author： Simpkins M.A. Kelly B.P. Wartzok D.

Publisher： Elsevier

ISSN： 0003-3472

Source： Animal Behaviour, Vol.62, Iss.1, 2001-07, pp. : 67-72

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Abstract

We analysed the use of three-dimensional space by 13 freely diving ringed seals, Phoca hispida, to distinguish between local search, presumably within prey patches, and travel or exploration between prey patches. We subdivided the three-dimensional home ranges of ringed seals into 3×3×3 m grid cells. For each dive, we determined the time spent swimming through each grid cell and the frequency of grid cell revisits. The seals generally spent 1–3 s in each cell and rarely revisited cells. During 34% of all dives, however, ringed seals focused their effort within a reduced volume, suggesting local search within patches of prey. The disproportionate effort within restricted volumes resulted from seals revisiting cells (18% of dives), reducing speed within cells (9% of dives), or both reducing speed and revisiting cells (7% of dives). Ringed seals searched locally in less than 10% of descents and ascents but did so in 41%of bottom phases (time spent at depth between the end of descent and the beginning of ascent).