Apparent digestive efficiency in walruses (Odobenus rosmarus) fed herring (Clupea harengus) and clams (Spisula sp.)

Abstract

The digestive efficiency in 4 captive walruses (2 males, 2 females) was determined. All 4 walruses were fed a diet of herring (Clupea harengus), and the adults (1 male, 1 female) were fed clams (Spisula sp.), for a total of 6 animal–diet combinations. The digestive coefficient for energy was the same for both diets ([Formula: see text] SD: 92.7 ± 2.1%; n = 6) but significantly (P = 0.02) higher in females (94.4 ± 1.2%, n = 3) than in males (91.0 ± 0.8%, n = 3). No age effects were found. The mean digestive coefficient of protein was 93.8% ± 1.8% (n = 6) and did not vary among diets or animals. The digestive coefficient for lipid was lower for the clam diet (73.2 ± 0.1%, n = 2) than for the herring diet (94.4 ± 2.3%, n = 4), but this is likely an artifact due to the low lipid content of the clams (5.8 ± 0.7%) and the influence of endogenous lipid loss. The approximate maintenance gross energy requirements for the 1200-kg nonpregnant, nonlactating adult walrus in captivity were 31 350 kcal∙day−1 (1 kcal = 4.18 kJ) or 155 kcal∙kg−0.75∙day−1.