Burial of bovine dung by coprophagous beetles (Coleoptera: Scarabaeidae) from horse and cow grazing sites in El Salvador

Dung beetles that colonise horse and cow dung were collected using baited pitfall traps at three contrasting Salvadoran sites subject to varying degrees of livestock grazing. The sites included a lowland coastal farm, a mid-altitude farm and a high altitude pine-grass site. The quantities of cow dung buried by each of ten tunnelling species from the sites (five Coprini and five Onthophagini) were evaluated through laboratory experiments. The quantities of dung buried in the absence of competition and the amount of dung provided for each egg were related to female beetle body size across species. The quantities of dung buried by pairs of each species and the low number of beetles colonising dung at the mid-altitude site suggest that much of the dung is not buried at the site. However, sufficient colonisation occurred at the coastal farm and at the pine-grass site for dung pads at these sites to be completely buried, indicating that competition is normally intense. In the face of such competition, the opportunistic Onthophagini quickly provision and lay eggs as long as favourable conditions persist while the Coprini, which are rapid dung pre-emptors, can rarely bury sufficient dung to attain full brood production. The importance and conservation of the small number of native dung beetles adapted to Central American pastures is discussed.