Spatial relationships between predators and prey have important implications for landscape processes and patterns. Highly mobile oceanic birds and their patchily distributed prey constitute an accessible model system for studying these relationships. High-frequency echosounders can be used together with simultaneous direct visual observations to quantitatively describe the distributions of seabird consumers and their resources over a wide range of spatial scales, yielding information which is rarely available in terrestrial systems. Recent fine-scale investigations which have used acoustics to study the distribution of foraging marine birds have reported weak or ephemeral spatial associations between the birds and their prey. These results are inconsistent with predictions of optimal foraging, but several considerations suggest that traditional foraging models do not adequately describe resource acquisition in marine environments. Relative to their terrestrial counterparts, oceanic 'landscapes' are structurally very simple, but they generally lack visual cues about resource availability. An emerging view assumes that perceptually constrained organisms searching for food in multiscale environments should respond to patterns of resource abundance over a continuum of scales. We explore fractal geometry as a possible tool for quantifying this view and for describing spatial dispersion patterns that result from foraging behavior. Data on an Alaskan seabird (least auklet [Aethia pusilla]) and its zooplanktonic food resources suggest that fractal approaches can yield new ecological insights into complex spatial patterns deriving from animal movements. © 1992 SPB Academic Publishing bv.

The authors studied the relationship between the foraging radius and energy economy of A. pusilla breeding in colonies on three islands in the Bering Sea (St Lawrence, St Matthew, and St George Islands). The distance to which auklets commuted on foraging trips varied by more than an order of magnitude c5-56 km), but mean field metabolic rate did not vary significantly among birds from the three islands. The authors modeled the partitioning of energy to various activities and hypothesized that the added cost of commuting incurred by auklets from St Lawrence Island (foraging radius, 56 km) was offset by reduced energy costs while foraging at sea. Data indicated that auklets from St Lawrence Island fed on larger, more energy-rich copepods than auklets from St Matthew Island (foraging radius, 5 km). -from Authors