Most adult coprophagous beetles feed on fresh dung of mammalian herbivores, confining ingestion to small particles with measured maximum diameters from 2-5 to 130 µm, according to body size and kind of beetle. This study explores benefits and costs of selective feeding in a ‘typical' dung beetle with a maximum diameter of ingested particles (MDIP) of 20 µm.

2. Examined dung types (from Danish domestic sheep, cattle and horse, and African wild buffalo, white rhino and elephant) contained 76-89% water. Costs of a 20 µm MDIP were often low, since 69-87% of the total nitrogen in bulk dung other than that of elephant and rhino (40-58%) was available to selective feeders.

3. Nitrogen concentrations were high - and C/N ratios low - in most types of bulk dung compared with the average food of terrestrial detritivores or herbivores. Exceptions were elephant and rhino dung with low nitrogen concentrations and high C/N ratios.

4. Estimated C/N ratios of 13-39 in bulk dung (sheep-elephant) were decreased by selective feeding to 7.3-12.6 in the ingested material. In assimilated food, ratios are probably only 5-7, as most assimilable nitrogen and carbon may be of microbial origin. If so, the assimilable food contains a surplus of nitrogen relative to carbon.

5. The primary advantage of selective feeding, particularly in dung with a high C/N ratio, may be to concentrate assimilable carbon in the ingested food. Effects of changing the MDIP within 20-106 µm are modest, especially in dung with a low C/N ratio.