Spores of nine species of coprophilous fungi germinated more rapidly and produced longer germ-tubes on 1 % rabbit dung extract agar than on media of lower water activity (Aw). With decreasing Aw the latent period of germination increased and shorter, broader and vacuolated germ tubes were produced. At 090 Aw and below there was no germination after 144 h. In almost all cases, radial growth occurred at all Aw which permitted germination. Sporormiella intermedia was the most tolerant of the ascomycetes, being able to germinate and grow at 0.92 Aw. In the absence of competition from other coprophiles, Pilobolus crystallinus produced fewer sporangia with decreasing relative humidity (r.h.) with no fruiting occurring at 86% r.h. At lower r.h. sporangia were small and discharged 2–3 d earlier than in the presence of free water. The fungus survived at 81 % r.h. for at least 20 d. Onychophora coprophila produced more synnemata at 86%-100% r.h. than in the presence of free water. When growing in combination with P. crystallinus, fewer ascocarps were produced by 5. intermedia, Saccobolus versicolor and Podospora tetraspora than when these species grew on their own. On previously air-dried pellets, fruiting of all fungi except O. coprophila was observed only when free water was subsequently provided. Onychophora coprophila continued to produce numerous synnemata even at 86% r.h. on previously air-dried pellets. When eleven fungi were fed simultaneously to laboratory rabbits, the number of fruit bodies produced by each was considerably smaller than when each fungus was fed on its own. The sequential appearance of the fruit bodies and the response of these fungi to water availability were similar to those occurring on pellets from free ranging rabbits.