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Food Consumption and Body Mass of Captive Harbor Seals (Phoca vitulina)
Abstract: The food consumption (recorded as kg of individual fish species) of nine male and six female captive harbor seals is described. This longitudinal study is based on data originally archived for short-term husbandry purposes. The chemical composition and caloric value of the diet were not measured. Because caloric content of fish varies seasonally and annually, and depends on the geographical region where it was caught, the average food intake variations seen in this study may reflect the caloric content of the diet. However, because the effects of season, age, gender, and reproductive state are consistent in various seals, and all seals entered the study at different times, and food was caught in different seasons and stored for different lengths of time before being fed, the general patterns described are believed to be independent of variation in caloric content of the diet. There was a great deal of individual variation in the annual food consumption of male harbor seals, but generally it increased from around 950 kg at the age of one year to around 1,200 kg (estimated at 98 × 105 kJ/year) at the age of 13 years. The annual food consumption of the nonreproductive female harbor seals also varied much among individuals, but generally fluctuated around 1,000 kg (estimated at 82 × 105 kJ/year). Adult male and female harbor seals had slightly different seasonal cycles in food consumption. Reproduction (producing a pup and suckling it) increased the degree of seasonal fluctuation in consumption by females. Immature animals did not experience seasonal changes in food intake. During molting, the seals usually lost weight. In males, molt occurred in August; and in females, usually in July. Males and females grew rapidly between birth and the age of 4 to 5 years. Thereafter, the growth rate decreased. Males reached a maximum body mass of around 100 kg and females around 90 kg. A negative relationship occurred between body mass and food intake when expressed as a percentage of body mass.
Key Words: BODY MASS; ENERGETICS; FEEDING; NUTRITION; PHOCID; PINNIPED; REPRODUCTION; WEANING; HARBOR SEALS; PHOCA VITULINA
Document Type: Research article
Page Numbers: 34 – 42