The diet composition and feeding habits of the Eurasian otter (Lutra lutra) were studied by post mortem examination of individuals (n = 236) found dead in Hungary in order to test the dietary differences between sample types (stomach and rectum), calculation methods and different factors. A relationship was found between the summarized wet weight (W) and occurrence number (O) of food remains detected in the stomach. Otters preyed primarily on small-sized (< 100 g) cyprinids, mainly on non-commercial fish. The composition of stomach contents differed according to different factors: season — in autumn and winter fish were eaten in higher proportions but in spring and summer there were more amphibians; sex — males prey on fish in higher proportions; age group — juveniles consumed invertebrates in higher proportions; and cause of mortality — otters found dead on roads had consumed fish in higher ratios. The composition of rectum content showed a relationship according to the three calculation methods considered (W, O and B — estimated biomass composition). In the otters examined the composition of food items in the stomach (which is the nearest to the actual food ingested) and the rectum content (which relates to the composition in non-invasive collecting spraints) were basically similar.

To examine the effects of food intake on the gastrointestinal passage time of seeds in the Japanese marten (Martes melampus), we conducted four feeding experiments using captive animals (n = 4). We estimated passage time variables (transit time and mean retention time) of plant seeds (two types) using two different numbers of chicks (single and three) representing two seasons when the animal prey is abundant/scarce. There was no significant relationship between food intake and passage time, and seed type did not affect the passage time variables. Our results were different to those for herbaceous/omnivorous mammals, in which a shorter passage time was observed when food intake increased. The stability in the passage time of the martens could be attributed to the higher level of digestibility of the animal prey. Our data also suggests that martens possess an elastic gut that can expand in volume, which leads to a consistent passage time despite the increase in food intake and enables them to efficiently assimilate nutrients from the consumed food. The results of the present study suggest that the dispersal distance of seeds and defecation site density of martens is influenced by their ranging/activity pattern and not by their digestive physiology.