Oecologia (Berlin) (1987) 72:21-27 Oecologia 9 Springer-Verlag 1987 Dung exploitation by the dung beetle Typhaeus typhoeus (Col., Geotrupidae)* L. Brussaard* and W.J.F. Visser Department of Soil Science and Geology, Agricultural University, P.O. Box 37, 6700 AA Wageningen, The Netherlands Summary. This paper deals with the functional aspects of the exploitation of dung by the dung beetle Typhaeus ty- phoeus. 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 effi- ciently 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. Key words: Typhaeus typhoeus - Dung beetle - Foraging efficiency The reproductive behaviour of the dung beetle Typhaeus typhoeus (Linnaeus, 1758) consists of burrowing a branch- ing shaft, laying an egg in an egg chamber at the distal end of each branch, provisioning the branches with dung for the larvae and partly sealing the remaining burrow with sand (Fig. 1) (Brussaard 1983). Up to 450 kg of sand per hectare may thus the transported to the surface annually (Brussaard and Runia 1984). In addition to the back-filled * Communication no. 290 of the Biological Station, Wijster, The Netherlands * Present address and address for offprint requests." Institute for Soil Fertility, P.O. Box 30003, 9750 RA Haren, The Netherlands parts of the burrows that seal the "dung sausages", back- filled burrows come about when the newly emerged adults make their way to the surface (Fig. 1). The activities of T. typhoeus and of related scarab bee- tles with similar behaviour contribute appreciably to the mixing of soil constituents and to the disturbance of strati- fied structures in sandy soils (Brussaard 1985; Brussaard and Runia 1984; Kalisz and Stone 1984). To predict the extent of these activities, the effects of soil temperature on reproductive behaviour and larval development were stud- ied (Brussaard 1983). To predict the places where these activities will occur, the effects of soil density and moisture on the habitat selection by T. typhoeus were investigated (Brussaard and Slager 1986). This paper will deal with the exploitation of the main food resource, rabbit droppings, by T. typhoeus, because dung is a prerequisite for the pres- ence of the beetles. Knowledge of the exploitation of dung will eventually help to predict the effect of the beetles' activ- ities on certain soil characteristics. General biology of T. typhoeus T. typhoeus is distributed from Morocco to southern Swe- den, westwards to Ireland and eastwards to Poland and Yugoslavia. In The Netherlands the beetles are active from the second half of September onwards and throughout the winter whenever the temperature is above zero and there is no snow. Intense activity occurs in October and No- vember, which is the main period of maturation feeding and from February to April, which is the main period of reproduction (Brussaard 1983). Their habitat is semi-open heathland where they are mainly associated with rabbit dung (Brussaard 1983). The beetles thrive in sandy soils in which the bulk den- sity of the profile below the 0.40 m depth (where the larvae develop) exceeds 1.30x 103 kg-m -3, provided the water table is permanently below 0.80 m (Brussaard and Slager 1986). In The Netherlands the generation time is two years when the overwintering larvae are exposed to temperatures approximating 5~ C. When such a low temperature is not reached, the generation time is usually longer (Brussaard 1983). Male and female co-operate during excavation of the nest and when provisioning the brood chambers with dung. The male gathers the dung pellets on the surface, the female stays below-ground to transform them into dung sausages (Brussaard 1983).