MATERNAL STRATEGIES OF PHASCOGALE-TAPOATAFA (MARSUPIALIA, DASYURIDAE).1. BREEDING SEASONALITY AND MATERNAL INVESTMENT

Phascogale tapoatafa, an arboreal carnivorous marsupial, is the larges t mammal in which an obligate yearly die-off of all males occurs. The species is one of the most widespread of Australian marsupials, being found in tropical, subtropical and temperate forests and woodlands of Australia. Its breeding season varies little throughout this range, wi th most births occurring in July. In three Victorian populations, 2-ye ar-old females typically gave birth earlier than first-year females, b irths were spread on average over 15 days, and, in some years, occurre d two weeks earlier than average. Modal litter size equalled the numbe r of teats (8), but litters of 1-6 young comprised 29% of the sample ( n = 45), and litter size averaged 6.6 young. The sex ratio of litters produced by second-year females was significantly male-biased (0.62); that of first-year females was 0.48. When juveniles first released the teats (c. 48 days of age), they weighed about 4 g. Weight gain by cap tive juveniles was more rapid than that of wild conspecifics prior to weaning, but skeletal growth rate and morphological development were s imilar. Total lactational investment by P. tapoatafa is much greater t han expected for a dasyurid of its size (wild litters at weaning avera ge 313% of maternal weight; captive litters average 370%). The high mo rtality of wild adult females during lactation may reflect this energe tic drain.