An ecological study of a population of Pseudantechinus macdonnellensis (Marsupialia : Dasyuridae) in central Australia. I. Invertebrate food supply, diet and reproductive strategy

Abstract

The invertebrate food supply, diet and reproductive strategy of a population of the dasyurid marsupial, Pseudantechinus macdonnellensis, living in an arid rocky habitat was investigated at a site in the West MacDonnell National Park, Northern Territory, over two and a half years. Invertebrate food supply displayed high month to month predictability and no marked seasonal cycle correlated with temperature. Analysis of faeces indicated that P. macdonnellensis is a generalist insectivore. There was some discrepancy between the pattern revealed by invertebrate sampling and the prey types taken but it was concluded that the invertebrates sampled broadly reflected those available to P. macdonnellensis. Individual females reproduced only once per year; the estimated time of mating was in July–August, and births occurred in September–October. The maximum litter size was six and nearly all females in each season produced a full complement of young. Some males survived and showed spermatorrhea in two breeding seasons and some females survived and produced young in up to three. The seasonal pattern of invertebrate food supply at the study site appeared to be more dependable than that found in studies carried out in arid plains habitats. The difference may result from a microtopographical amelioration in the rocky habitat of the effects of extreme weather conditions that in open, arid habitats are believed to produce increased short-term unpredictability and pronounced, temperature-driven seasonality in food supply. The ameliorating effect may also increase longevity in P. macdonnellensis by reducing density-independent mortality. The monoestrous highly seasonal reproductive strategy in P. macdonnellensis differs from that displayed by most species that inhabit arid plains habitats (the latter are polyoestrous with an extended breeding season). The shortterm predictability in food supply together with a high longevity in P. macdonnellensis may account for its reproductive strategy. The results of this study provide support for the notion that habitat-specific selective pressures in arid environments may favour divergent ecological strategies in functionally similar species.