Gestational length in the koala, Phascolarctos cinereus
A. Gifforda, G. Frya, B.A. Houldena,b, T.P. Fletcherc, E.M. Deaned,∗
a Zoological Parks Board of New South Wales, P.O. Box 20, Mosman, NSW 2088, Australia
b School of Biological Sciences, University of New South Wales, New South Wales, NSW 2052, Australia
c Perth Zoo, 20 Labourchere Road, South Perth, WA 6151, Australia
d Division of Environmental and Life Sciences, Macquarie University, North Ryde, NSW 2109, Australia
We report a possible case of extended gestation in the koala, Phascolarctos cinereus. Birth of a pouch young was ﬁrst observed 127 days after the removal of the male from a multi-female colony at Taronga Zoo. No other males were present at that time or had access to the facility. Head measurements and other growth data collected at the time of detection and over the period of pouch life indicates the time from removal of the male and the date of birth to be between 50 and 77 days. DNA ﬁngerprinting using microsatellite loci unambiguously assigned paternity of the pouch young to this male. These observations suggest either an extended period of gestation of at least 50 days,or activation of a dormant blastocyst from the previous breeding season, as the female entered the period of seasonal oestrus.