Shady field boundaries and the colonisation of dung by coprophagous beetles in Central American pastures

This study examines how the shade from field boundaries may enhance dung decomposition in tropical pastures through its effects on coprophagous beetles. Between August 1995 and January 1998, beetles were collected using dung-baited pitfall traps at a cattle ranch in coastal El Salvador. Fifteen species were recorded throughout the study and, although some species were significantly associated with field boundaries, there were no species exclusive to the boundaries. Diurnal specialist open-field beetles arrived predominantly on the day of dung deposition whereas nocturnal generalist species colonised older dung (one species) or colonised dung for longer (three species) particularly, in the shade. The endocoprid Aphodiinae (two species) generally colonised dung that was 3–7 days old, at a time when activity of the larger paracoprid Coprini and Onthophagini had diminished. Deposition of dung in the shade of field boundaries extended the period during which it was suitable for colonisation, raising the average dung colonisation time by generalist species. The importance of shady field boundaries in dung beetle conservation and efficient dung decomposition in pasture ecosystems is discussed.