Milk consumption and growth in a marsupial arboreal folivore, the common ringtail possum, Pseudocheirus peregrinus

This study examines the milk consumption and growth energetics of the smallest arboreal folivore in Australia, Pseudocheirus peregrinus. Mass increase was sigmoidal, and young ceased sucking milk between 27 and 50 wk (mean = 29.3 ± 1 wk). This length of lactation was 129% of that predicted allometrically from data for other marsupials. The mean Gompertz constant (0.01) calculated for seven young suggests that P. peregrinus has a slow rate of growth compared with other marsupial species. Milk intake was measured with isotopic turnover techniques. The estimated total milk energy yield (11.9 MJ kg-1) for a ringtail possum suckling two young was similar to that of the only other marsupial herbivore for which data are available (Macropus eugenii). However, peak milk energy output (154.4 kJ kg-0.75 d-1) was lower than that in other herbivores. The body mass accrued from milk consumption by young ringtail possums at various stages of lactation was similar to that of other marsupials, suggesting that the slow rate of growth in this species is a result of a limited rate of supply of milk energy from the mother and not an inefficient conversion of milk energy in the young.