EFFECT OF CHANGING FROM A SHORT-DAY TO LONG-DAY PHOTOPERIOD ON THE BREEDING-SEASON OF THE BRUSHTAIL POSSUM (TRICHOSURUS-VULPECULA)

In Queensland, possums (Trichosurus vulpecula) in the wild and in capt ivity first give birth during March and April and continue to give bir th throughout the year until November. The possum has a gestation leng th of 17.5 days, gives birth to one young, and lactation continues for approximately 180 days. If the newborn possum is removed during the b reeding season, the possum will ovulate approximately 9 days later and give birth approximately 26 days after removal of the pouch young (RP Y). Repeated RPY may be used to determine the duration of the breeding season. In this study, the effect on the breeding season of a marked change in photoperiod from a short-day to a long-day was examined by c omparing three groups of possums in different photoperiods for 13 mont hs. One group of five female and two male possums (group A) was housed in a natural photoperiod and a second group (B) was housed in a short -day photoperiod (10 h Light: 14 h dark) throughout the study. The thi rd group (C) was housed in a short-day photoperiod until each possum g ave birth, the pouch young was removed, and the possum transferred to a long-day photoperiod room (14 h Light: 10 h dark) for the remainder of the study. The possums held in a natural photoperiod, group A, gave birth to a total of 27 births in the one breeding season from March t o October. The 5 possums of group B, held in a short-day photoperiod, gave birth to a total of 28 births, from January through August, no bi rths in September and October, and 3 births again in November and Dece mber. With group C, a total of 15 births was observed, 10 of them afte r transfer to a long-day photoperiod. All possums gave birth in Januar y and mere transferred to the long-day photoperiod following RPY. Ther e followed four births in February and March and a further six births from July to November. In conclusion, short-day photoperiods can haste n the onset of breeding activity in possums and are required for the m aintenance of the breeding season. (C) 1995 Wiley-Liss, Inc.