SPATIAL-DISTRIBUTION, RESOURCE UTILIZATION AND INTRASPECIFIC COMPETITION IN THE DUNG BEETLE APHODIUS ATER

Competitive interactions in northern temperate dung beetles are poorly understood. This investigation therefore comprises a series of field and experimental work on a dung beetle species common in northern Euro pe, Aphodius ater, with special focus on intraspecific competitive int eractions. The between-pat distribution of adult A. ater in relation t o the age of sheep dung pats was studied in the field. The distributio n of both sexes was contagious in the fresh pats but became more regul ar with increasing pat age. The successional occurrence of males and f emales did not differ, but immature females tended to occur in fresh p ats while mature females were mainly found in older pats. With increas ing age of pats, the egg load of females also increased. Egg-laying be haviour of the beetles was studied in laboratory experiments. The mean number of eggs laid per female per dung pat decreased with increasing beetle density. Thus, density-dependent processes seem to regulate re source utilisation with regard to breeding behaviour, resulting in equ al exploitation of the available pars. Survival and weight of recently hatched beetles decreased with increasing initial density of eggs. He nce, in A. ater, competition between larvae for food within pats does occur.