Dung Exploitation of the Dung Beetle Typhaeus-Typhoeus Coleoptera Geotrupidae

This paper deals with the functional aspects of the exploitation of dung by the dung beetle Typhaeus typhoeus. In horizontal brood chambers of a nest in the soil these beetles make "dung sausages" chiefly from rabbit droppings, as a food source for the larvae. Their foraging behaviour was shown to be positively correlated with the occurrence of rainy periods. The beetles foraged more efficiently on clustered dung pellets than on dispersed ones. Body sizes of beetles were positively correlated with the lengths of the dung sausages from which they emerged. In laboratory experiments the lengths of the dung sausages made by a pair of beetles did not significantly differ within a wide range of frequencies of supply of various amounts of rabbit dung pellets, despite the longer time spent per dung sausage when less dung was supplied per unit of time. It is suggested that dung provisioning does not stop before the dung sausages have reached lengths (approximately 8.5-9.5 cm) anticipated by the lengths of the brood chambers. However, there appeared to be a critically low value between 1-2 and 4-5 dung pellets supplied per day, below which the finished dung sausages were significantly shorter (approximately 3.5 cm). When, at the places of settlement, dung was scarce near the nest entrances, the number of nests excavated by the beetles and, thus, the beetles' physical effect on the soil, was shown to be higher than when dung was plentiful near the nest. The ecological and evolutionary consequences of the foraging behaviour by the beetles are discussed.