Energy reallocation during and after periods of nutritional stress in Steller sea lions: low-quality diet reduces capacity for physiological adjustments.
Two groups of female Steller sea lions (groups H and P) were subjected to periods of energy restriction and subsequent refeeding during winter and summer to determine changes in energy partitioning among principal physiological functions and the potential consequences to their fitness. Both sea lion groups consumed high-quality fish (herring) before and after the energy restrictions. During restrictions, group H was fed a lower quantity of herring and group P a caloric equivalent of low-quality fish (pollock). Quantitative estimates of maintenance and production energies and qualitative estimates of thermoregulation, activity, and basal metabolic rate were measured. During summer, all animals compensated for the imposed energy deficit by releasing stored energy (production energy). Group H also optimized the energy allocation to seasonal conditions by increasing activity during summer, when fish are naturally abundant (foraging effort), and by decreasing thermoregulation capacity when waters are warmer. During winter, both groups decreased the energy allocated to overall maintenance functions (basal metabolic rate, thermoregulation, and activity together) in addition to releasing stored energy, but they preserved thermoregulatory capacity. Group H also decreased activity levels in winter, when foraging in the wild is less efficient, unlike group P. Overall, sea lions fed pollock did not change energy allocation to suit environmental conditions as readily as those fed herring. This implies that a low energy-density diet may further reduce fitness of animals in the wild during periods of nutritional stress.
Jeanniard du Dot
Tiphaine
T
Department of Zoology and Marine Mammal Research Unit, Fisheries Center, University of British Columbia, 2202 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada. dudot@zoology.ubc.ca
Rosen
David A S
DA
Trites
Andrew W
AW
D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001481:Basal Metabolism; D001823:Body Composition; D001833:Body Temperature Regulation; D001835:Body Weight; D031204:Caloric Restriction; D004032:Diet; D002149:Energy Intake; D004734:Energy Metabolism; D005260:Female; D005399:Fishes; D005082:Physical Exertion; D046070:Sea Lions / Q000033:anatomy & histology / Q000502:physiology*; D012621:Seasons; D013312:Stress, Physiological