Observations on oetrus and the oestrous cycle in the marsupials Isoodon Macrourus and Perameles nasuta

Abstract

Observations have been made on oestrus and the oestrous cycle in the bandicoots I. macrourus and P. nasuta caged indoors. Oestrus was diagnosed from a number of criteria, particularly the sexual behaviour of the males. Attempted matings, non-fertile matings and matings leading to pregnancy were restricted to one day of the oestrous cycle, except on one occasion when a male I. macrourus attempted to mate on two consecutive days. The lips of the urogenital opening of the female were usually greatly swollen at oestrus but pouch changes at this time were not detected. Vaginal smears at oestrus usually showed an increase in the number of partly and fully cornified epithelial cells and few, if any, polymorphonuclear leucocytes. During the winter and spring of 1972 and spring of 1973, over 1000 vaginal smears were taken from 29 P. nasuta and about 700 smears were taken from 21 I. macrourus. Information on the length of the oestrous cycle in P. nasuta, using all criteria, was obtained from only nine cycles in eight animals. The cycle length averaged 21 days but the range was from 10 to 34 days. Considerably more information on the length of the cycle was obtained from the smaller number of I. macrourus; the average length of 39 cycles in 15 animals was 20 days, the range being 9-34 days.