Floral nectar sugar composition and flowering phenology of the food plants used by the western pygmy possum, <Emphasis Type="Italic">Cercartetus concinnus</Emphasis>, at Innes National Park,South Australia

The western pygmy possum (Cercartetus concinnus) is a small nocturnal marsupial that relies primarily on the nectar and pollen of myrtaceous species at Innes National Park and may occasionally also ingest invertebrates. This study confirmed plant utilization by C. concinnus using scat samples and pollen swabs, and investigated the flowering phenology of dietary plants to determine resource availability. We compared nectar composition between day and night and analyzed nectar sugar production for dietary species. Pollen swabs and scats suggested that C. concinnus relied primarily on the nectar and pollen of Kingscote mallee, Eucalyptus rugosa (76.8% of grains counted in combined scat samples) at Innes National Park, when available; only one of 30 scat samples contained numerous moth scales. The nectars of the species investigated showed marked differences in their composition, but only Melaleuca gibbosa and M. halmaturorum sugar composition changed between day and night. The nectar sugar ratio of E. rugosa differed from those of most other species investigated. C. concinnus may select this plant’s flowers because its nectar is relatively high in hexose sugars. Although E. diversifolia was abundant, its flowers were mostly ignored by possums, perhaps because the nectar in these flowers was proportionately much richer in sucrose than other species’. E. rugosa’s flowering index (calculated from flower load and canopy size) was greatest in December. Six of the seven eucalypt species flowered between November and April; for half of the year pygmy possums must find other resources.