Seasonality, dung specificity and competition in dung beetle assemblages in the Australian Wet Tropics, north-eastern Australia

A trapping study of five mammal species in wet sclerophyll forest adjacent to rain forest in the Australian Wet Tropics was used to examine the seasonal diversity, abundance and dung-specificity of dung beetles associated with mammal dung. A total of 542 dung beetles from 11 species within three genera was recovered from beneath the traps of 1104 mammal captures. The diversity of beetles associated with the dung of the northern bettong (Bettongia tropica), a mycophagous marsupial, differed significantly from the diversity predicted by a null model. Numbers of beetles varied significantly with type of dung, indicating preference by beetles. Beetle numbers were related positively to a 1-mo lag in monthly mean minimum temperature and less strongly to maximum temperature and rainfall. Significantly more beetles per mammal capture were detected in the wet season than in the dry season. Dung beetles showed a strong preference for either the Eucalyptus woodland (six species) or the adjacent Allocasuarina forest (four species), with only one species occurring in both habitat types. Beetle species from the Eucalyptus woodland were typically only detected in the late wet and early dry seasons, while species in the wetter Allocasuarina forest were generally collected during the late dry and early wet seasons. A significant ‘checkerboard’ species effect was detected in both time and space in both habitat types, suggesting that competition for dung was strong.