Photoperiod and some other factors affecting reproduction in female Sminthopsis crassicaudata (Gould) (Marsupialia : Dasyuridae) in captivity

In central and southern Australia, S. crassicaudata is a widespread species which shows morphological and biochemical variation throughout its range. A laboratory colony was established from wild-caught animals from central, southern and south-eastern populations. The origin of wild-caught females or the parentage of laboratory-bred females did not affect their response to any of the investigated factors influencing reproduction. Very few females produced litters after they had reached 30 months of age. The colony was maintained for nearly 10 years in one artificially illuminated room. The lighting schedule was usually 16L : 8D, but at approximately 6-monthly intervals the animals were subjected to 3 weeks of 8L : 16D. Significantly more litters were born in pairings that had experienced short days than in those continuously exposed to long days. Oestrous cycles ceased in the 8L : 16D periods and resumed at about 20-30 days after the onset of 16L : 8D in many females, although some took longer to come into oestrus. Two of 27 females did not come into oestrus within 88 days, and, of the 25 females that came into oestrus, five did not ovulate. Pathological conditions in the reproductive system were rare. Most litters were born within the first 6 weeks of pairs being formed. Females which had produced one litter were more likely to produce a second litter when returned to the father of their first litter than when caged with a different male. When two females were caged with one male, one or occasionally both females produced a litter. Breeding in response to onset of long days is not consistent with the opportunistic breeding of many desert animals.