EFFECT OF POPULATION DENSITY ON REPRODUCTION AND DUNG DISPERSAL BY THE DUNG BEETLE ONTHOPHAGUS BINODIS IN THE LABORATORY

Equal numbers of newly emerged male and female Onthophagus binodis Thunberg were placed at densities from 2–100 beetles on one‐litre pads of cattle dung. After one week the number of brood balls produced was counted and the volume of dung dispersed (buried and shredded) visually assessed. The surviving beetles from each box were then placed on another pad, and the process repeated until all beetles were dead. Beetle survival was not influenced by initial beetle density and fell linearly with time (P < 0.001). Brood ball production/female/week did not appear to be influenced by beetle age and could be predicted from current beetle density Y = 15.03e−0.045X, R2 = 0.42. Dung dispersal increased with increasing density up to about 35 beetles/pad, above which the proportion dispersed plateaued at about 90%. Dung burial, estimated from the number of brood balls produced/week, was on average greatest (450 ml) with 20–30 beetles/pad. The effect of density on production of brood balls was inferred to reflect the frequency of contact between adults in the pad.