APPARENT DIGESTIVE EFFICIENCY IN WALRUSES (ODOBENUS-ROSMARUS) FED HERRING (CLUPEA-HARENGUS) AND CLAMS (SPISULA SP)

The digestive efficiency in 4 captive walruses (2 males, 2 females) wa s determined. All 4 walruses were fed a diet of herring (Clupea hareng us), and the adults (1 male, 1 female) were fed clams (Spisula sp.), f or a total of 6 animal-diet combinations. The digestive coefficient fo r energy was the same for both diets (xBAR +/- 1 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 d ue to the low lipid content of the clams (5.8 +/- 0.7%) and the influe nce of endogenous lipid loss. The approximate maintenance gross energy requirements for the 1200-kg nonpregnant, nonlactating adult walrus i n captivity were 31 350 kcal . day-1 (1 kcal = 4.18 kJ) or 155 kcal . kg-0.75 . day-1.