An assessment of pedoturbation by two species of mound-building ants, Camponotus intrepidus (Kirby) and Iridomyrmex purpureus (F. Smith)

Abstract

Details of the size, structure and occurrence of Carnponotus intrepidus nests and the size, composition and source of the mound cover on Iridomyrmex purpureus nests are reported from several areas of eastern New South Wales. Both species are common, and construct large mounds of mixed topsoil and subsoil with surface covers, which appear to protect the mound from rainsplash erosion. Camponotus thatches the mound with charcoal, leaves and twigs; Iridomyrmex covers the mound in granules of inorganic or organic material that are sufficiently large to absorb most raindrop impact energy. This material is collected from the surface and carried 10-15 m to the nest. Rainsplash erosion protection is probably a factor contributing to nest longevity, which may be as much as 100 years for Iridomyrmex. It is concluded that, despite the impressive size of the nests and the selective use of materials, neither species is very significant in terms of soil mixing when compared with the smaller, more common ant Aphaenogaster longiceps.