In vivo digestibility trials of a captive polar bear (Ursus maritimus) feeding on harp seal (Pagophilus groenlandicus) and Arctic charr (Salvelinus alpinus)

Energetic requirements of free-ranging polar bears are still poorly understood due to the limited information available. the need for such data is emphasized through imminent climatic changes impacting wild populations,and the recent development of energy-based population forecast models that are data-limited. we therefore conducted four feeding trials with a captive polar bear to investigate how 2 novel untested diets such as arctic charr (salvelinus alpinus) and harp seal meat/fat (pagophilus groenlandicus) are digested and energetically utilized. energy content,proximate nutrient values,digestive efficiency,metabolizable energy (me) requirements,and body mass change associated with these 2 diets were quantified. the seal meat/fat diet (1:1 ratio) had a 1.5 times greater digestible energy content (kg dm basis) than the charr diet. digestibility coefficients for nutrients (organic matter,crude protein,fat) of both diets were high (> 0.960),which corresponds well with other carnivores,and other fatty polar bear diets. body mass increased significantly over the course of the feeding trials,consuming an average of 403 and 1149 kj/kg bm075 of me per day of charr and seal meat/fat,respectively. it was discovered that daily energy requirements of our adult,non-reproducing polar bear was lower than previously estimated (∼ 1.4 instead of 2 times basic metabolic rate). despite our limitations,we provide baseline data that should be evaluated during further feeding trials. copyright 2011 zoological society of pakistan.