Abstract
Methods of determining rates of feeding in marine endotherms are needed to assess impacts on marine resources. Thus, we investigated the use of temperature telemetry to measure food and water intake in captive harp seals (Phoca groenlandica) for possible application to free-ranging marine endotherms. We obtained profiles of changes in stomach temperature while the seals ingested ice, snow, seawater, and meals of fish. Ingestion of any of the substances caused a precipitous drop in stomach temperature in every instance. The rate of recovery to stable temperature was related (r2 = 0.71, P = 0.001) to the mass of the meal ingested. The stomach temperature technique provides conclusive evidence of fresh and seawater intake in harp seals and should enable detection and measurement of food and water intake in a variety of species. J. WILDL. MANAGE. 57(3):514-519 Rates of food intake in seals need to be de- termined to assess their impact on marine re- sources and commercial fisheries. Four methods have been used to estimate quantities of food consumed by wild seals: fecal and stomach con- tents, labelled water, serial changes in mass, and extrapolation from food intake and energy ex- penditure in captive seals. Each method has lim- itations making its application inappropriate to relatively inaccessible species like harp seals. To date, foraging habits and feeding behavior of seals are interpreted from diving patterns where foraging is inferred from examination of dive profiles. Until recently there was no direct meth- od to detect and measure food intake in wild marine animals. Wilson et al. (1992) described data from both jackass penguins (Spheniscus demersus) and wandering albatrosses (Diome- dea exulans) derived from an archival device they developed that records and stores stomach temperature. They found that ingestion of water by penguins caused large drops in stomach tem- perature and provided estimates of the amount
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