Hormonal changes associated with reproductive activity in the unique pollen and nectar-feeding marsupial Honey possum, Tarsipes rostratus, have been monitored by the measurement of sex steroids excreted via the faeces. From a radio-metabolism study, 63% of administered [C-14] oestradiol was excreted in the faeces and 37% via the urine. Peak levels in the faeces were reached 6 h after injection and by a mean 12 h, 95% of steroid was eliminated. The principal metabolic products of progesterone that were identified by chromatographic analysis were the isomers 5alpha- and 5beta-pregnan-3beta-ol-20-one with only trace amounts of progesterone and the isomers 5beta-pregnan-3beta,20beta- and 20alpha-diols. Extended excretory profiles for faecal progestagens (PM) and oestradiol-17beta (E-2) are reported for the first time in a marsupial. The profiles from 4 females held in indoor cages with an artificial photoperiod suggest that long days inhibit reproductive activity in this species, as is the case in a number of other marsupials. One female appeared to resume cycling after a 5-month period and the time between peak levels of both E-2 and PM suggest that the length of the oestrous cycle in the Honey possum is approximately 25 days. The PM profile suggests that the corpora lutea secrete low levels of progesterone for approximately the first 19 days after ovulation, followed by increased rates of excretion during the final 6 days. (C) 2004 Elsevier Inc. All rights reserved.