A bioenergetic model for estimating the food requirements of

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Steller sea lions Eumetopias jubatus in Alaska, USA

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6606

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University of British Columbia

2002

rok

ABSTRACT: A generalized bioenergetic model was used to estimate the food requirements of Steller

sea lions Eumetopias jubatus in Alaska, USA. Inputs included age- and sex-specific energy

requirements by date, population size and composition, and diet composition and energy content.

Error in model predictions was calculated using uncertainty in parameter values and Monte Carlo

simulation methods. Our model suggests that energy requirements of individuals were generally

lowest in the summer breeding season (June to August) and highest in the winter (December to

February) and spring (March to May) mainly due to changes in activity budgets. Predicted relative

daily food requirements were highest for young animals (12 ± 3% SD and 13 ± 3% of body mass

for 1 yr old males and females respectively) and decreased with age (5 ± 1% and 6 ± 1% of body

mass for 14 yr old males and 22 yr old females respectively). The mean daily food requirement of

pregnant females predicted by the model was only marginally greater than the predicted mean

daily food requirement of non-pregnant females of the same age. However, the model suggested

that the mean daily food requirement of females nursing pups was about 70% greater than females

of the same age without pups. Of the 3 sets of model parameters (diet, population, and

bioenergetic), uncertainty in diet and bioenergetic parameters resulted in the largest variation in

model predictions. The model provides a quantitative estimate of the Steller sea lion population’s

food requirements and also suggests directions for future research.