RATE OF PASSAGE OF DIGESTA THROUGH THE ALIMENTARY-TRACT OF SOUTHERN ELEPHANT SEALS (MIROUNGA-LEONINA) (CARNIVORA, PHOCIDAE)

The inert markers chromium-EDTA (liquid phase marker) and ytterbium ni trate (solid phase marker) were added to the food of three southern el ephant seals in Taronga Zoo, Sydney, in a series of nine trials. The e nclosures were checked at 15 to 30 minute intervals for up to 60 hours after dosing, and all faeces voided on land were collected (91 sample s). Marker concentrations in faecal dry matter were determined and mea n retention times calculated from the concentration time curves. The f aeces were soft to semiliquid, with mean water content of 58% (range 2 4-80%). The marker concentration curves indicated a rapid rate of food transit through the gastro-intestinal tract in elephant seals compare d with other carnivores. The mean time between dosing and first recove ry of marker (Initial Recovery Time) was nine hours. This was signific antly longer than the figure of 4.8 hours for northern elephant seals reported previously, and possible reasons for the differences are disc ussed. Mean Retention Time, a better index of rate of passage of inges ta, was 13 hours for the three southern elephant seals. This compares with times of 22 hours for the dog, 15 hours for the raccoon; and 13 h ours for the cat, all carnivores with much shorter gastrointestinal tr acts, both absolutely and relative to body size, than the southern ele phant seal. It is suggested that the very long small intestine may be an adaptation to foraging at depth, combined with long periods of subm ergence and the need to ingest large amounts of food when the animal i s at sea continuously for weeks or months.