Field ecology of a brood-caring dung beetleKheper nigroaeneus-habitat predictability and life history strategy

Abstract

The life history strategy of the dung beetleKheper nigroaeneus was studied in Mkuzi Game Reserve, South Africa.K. nigroaeneus, a large ball-rolling dung beetle, brood-cares a single offspring per nesting occasion. Adults emerged from the ground following the first spring rain (≥17 mm) in October or November, occasionally September, and trap catches were at a maximum 1-2 weeks later. Females outnumbered males by 3:1 at the time of maximum catches, but thereafter declined steadily, as the numbers of females involved in brood-care increased. Brood-care lasted 12 weeks, and parental females then (a) entered a second brood-care period, or (b) remained underground in diapause, or (c) emerged to feed. Reproductive activity stopped after February, ensuring that the entire population reached the adult stage by winter. Females active above ground after February, in reproductive diapause, had low fat levels and resorbed oocytes. Females buried underground, in reproductive diapause prior to and during winter, had high fat levels, resorbed oocytes, a reduced metabolic rate and empty guts. The Mkuzi habitat is predictable forK. nigroaeneus in spring, since only one good fall of rain is sufficient to drive population events for the next three months. In the latter half of the season the life history ofK. nigroaeneus is more flexible, and hence less constrained by climate.