What do dung beetles eat?

1. 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 um, 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 u m. 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 um 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 um are modest, especially in dung with a low C/N ratio.