Male-induced oestrus and ovulation in female brush-tailed bettongs (Bettongia penicillata) suckling a young in the pouch

Abstract

Female brush-tailed bettongs isolated from males usually do not come into oestrus or ovulate. Individuals isolated during pregnancy and at parturition do not ovulate post partum and are in the unusual condition for a macropodoid of suckling a pouch young but lacking a quiescent corpus luteum or a diapause embryo. Females in this condition were tested for their ability to come into oestrus and to ovulate after re-introduction to the male. When returned to the male on Day 1 of lactation, females generally mated before Day 2 and ovulated; at all later stages of lactation, six or seven days after being returned to the male > or = 50% of females came into oestrus, mated and ovulated. The vaginal smears of most females in isolation were typical of post oestrus on Day 2; after being returned to the male on Day 11, these females came into oestrus in seven days, mated and ovulated. The results show that suckling a young in the pouch does not suppress ovulation in this species provided that an adult male is present. Moreover, the results indicate that the mechanism of male-induced ovulation 24 h post partum differs from that of the remainder of the pouch suckling period.