Adjustments of gastric pH, motility and temperature during long-term preservation of stomach contents in free-ranging incubating king penguins

Male king penguins are able to store undigested food in their stomach for up to 3 weeks during their incubation fast, which evidently implies some modification of their digestive process. Using small electronic recorders, we studied the change in gastric pH, motility and temperature during the first week of food storage. The pH could be maintained at values as high as 6 throughout the incubation fast, a pH that is unfavourable for avian gastric proteinase activity. Gastric motility was never completely inhibited but could be markedly reduced. Stomach temperature was maintained at around 38degreesC. The fact that stomach temperature of incubating birds did not show a daily rhythmic fluctuation as seen in non-breeding birds could be due to temperature constraints on embryo development. Thus the present study demonstrates substantial adjustments of pH and gastric motility in incubating king penguins, which may contribute to the inhibition of digestive gastric processes.