Seasonal changes in energy requirements of harp seals

Abstract

Seasonal changes in energy intake of northwest Atlantic harp seals were modelled and implemented as a Microsoft Excel™ spreadsheet. Energy intake of adults during the fourth quarter is almost double estimated intake during the second quarter, with intermediate values during the fi rst and third quarters. Reproduction increases female annual energy requirements by 18%, and adds 4% to the estimated population energy intake. The model was sensitive to changes in metabolizable energy, body mass, and the activity factors selected to estimate cost of activity. Changes in blubber conductivity and body composition had intermediate effects, while changes in water and air temperature and activity had little effect on model output. Comparing annual energy intake between a seasonally varying model and a simplifi ed model (Growth•Activity•Mass0.75) intake estimates were similar if an annual maximum body mass was used. Using minimum estimates of body mass underestimated annual energy intake, but provides more reasonable estimates of energy consumption when seasonal requirements are at a minimum. A simple model adequately describes pinniped gross energy intake. More realistic estimates of gross energy intake would be obtained without increasing model complexity by incorporating seasonal changes in body mass. © Crown, 2010.