The ability of Ascobolus crenulatus Karsten, Chaetomium bostrychodes Zopf and Sordaria macrospora Auersw. to produce biomass within, fruit upon, and degrade rabbit faeces was followed using semi-natural faecal resource units (copromes) (Wood & Cooke 1984, 1987). On these criteria the performance of the fungi was in the order C. bostrychodes > S. macrospora > A. crenulatus. Species mixtures produced only slightly higher degradation rates than those effected by single species. This implied competition for available nutrients which was also indicated by depressed fruiting of all species in species mixtures when compared with fruiting levels of each species grown individually. For single species the time of onset and subsequent fruiting level were determined by the time at which sufficient resources could be allocated to reproduction rather than simply to hyphal extension rates.