Food and feeding habits determine the position of animals within food webs, and hence largely define their ecological role. This is also true for marine mammals, whose food and feeding habits have been reported in numerous published accounts based on analyses of stomach contents, or scats, or from direct observations, or inferred by indirect methods such as isotope ratios (Orstrom et al. 1993).
The majority of the available quantitative studies pertain, however, to small numbers of individuals, andlor a small fraction of a species range, both of which usually cannot be used for direct inferences involving the entire (global or oceanwide) distribution areas ofthese species. Some authors have attempted, on the other hand, to summarize scattered data on the food and feeding habits of mammals species (notably Evans 1987, and Klinowska 1991 for cetaceans, and King 1983 and Bonner 1990 for pinnipeds), but they have done so on a broad qualitative basis, precluding the direct use oftheir summaries for trophic modelling, or comparative studies.
This study is our attempt to combine the scattered quantitative studies with the broad qualitative summaries mentioned above, thus yielding standardized diet compositions for use in trophic modelling and related studies. These potential uses are here illustrated by our presentation of trophic levels for 108 species ofmarine mammals, derived from the diet composition, and contrasted with trophic level estimates obtained using different approaches.
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