Gut-retention time in mycophagous mammals: a review and a study of truffle-like fungal spore retention in the swamp wallaby

Variation in the gut-retention time of macrofungal spores influences the distance to which spores are dispersed by mycophagous (fungus-feeding) mammals and is of interest in examining mammal-fungal interactions. In reviewing published studies of fluid and particle (including macrofungal spore) digesta gut-retention times in ground-dwelling mycophagous mammals, weighted mean retention times (MRT) were found to range 6.6–55.5hr. Among macropodoid marsupials, fluid and small particle weighted MRT was longer in mycophagous species than non-mycophagous species but statistical support for this difference was weak (estimated mean difference 7.2hr; 95% CL [−0.8, 15.1]hr). Gut-retention of truffle-like (below-ground fruiting) fungal spores was examined in the swamp wallaby (Wallabia bicolor), a browsing macropodid marsupial that regularly eats macrofungal fruit-bodies. Two wallabies of different body weights were examined in a captive feeding trial. MRT of marker spores were 26.9hr and 35.1hr for the larger and smaller animal respectively. A small number of marker spores were found in faecal pellets up to 69hr after ingestion, suggesting that there is potential for long distance dispersal of fungal spores by swamp wallabies. The studied swamp wallabies probably carry fungal spores for similar times to smaller mycophagous marsupials, including the strongly mycophagous potoroids. Further studies of spore gut-passage, including MRT, in mycophagous mammals would help clarify differences among species and groups of species.