Onthophagus taurus, sometimes referred to as the bullhorned dung beetle, is a small black beetle active throughout the summer months in southern Australia. Although small in size (8-10 mm long), this day-active species can be an important player in the disposal of livestock dung in the warmer months by virtue of its high reproductive potential. It has a relatively short life cycle, going from egg to adult in a couple of months, and does not require a chilling period to complete its life cycle as some species do, which means it can go through at least two generations during an average year in southern Australia, with peaks in October and March.
As with many of the introduced dung beetles in Australia, O. taurus has a preference for cattle dung. It seems to favour sandier soils, so is generally more abundant where these soils predominate. It’s thought that the sandier soils make it easier for the beetles to tunnel under dung piles and construct chambers for their offspring, which feed on parcels of dung brought underground by the females. The species is found throughout much of southern Australia, with notable absences in central to northwestern Victoria and much of South Australia.
As the common name suggests, males of O. taurus have prominent horns, sometimes reaching several mm in length. Curiously, a large percentage of the males in a population have very short horns. Although the longer horns enable males to more ably fight off other males that might want to mate with their partners, the shorter-horned males have evolved to sneak around the major males or even dig side tunnels to reach the females, allowing them to reproduce as well.
Although O. taurus is now on the decline for this growing season, they’ll be back again in the spring to continue their important work of ridding pasture of dung and improving pasture soil quality.