Studies of the oestrous cycle, oestrus and pregnancy in the koala (Phascolarctos cinereus)

Abstract

As an integral part of the development of an artificial insemination programme in the captive koala, female reproductive physiology and behaviour were studied. The oestrous cycle in non-mated and mated koalas was characterized by means of behavioural oestrus, morphology of external genitalia and changes in the peripheral plasma concentrations of oestradiol and progestogen. The mean (+/- SEM) duration of the non-mated oestrous cycle and duration of oestrus in 12 koalas was 32.9 +/- 1.1 (n = 22) and 10.3 +/- 0.9 (n = 24) days, respectively. Although the commencement of oestrous behaviour was associated with increasing or high concentrations of oestradiol, there were no consistent changes in the morphology or appearance of the clitoris, pericloacal region, pouch or mammary teats that could be used to characterize the non-mated cycle. As progestogen concentrations remained at basal values throughout the interoestrous period, non-mated cycles were considered non-luteal and presumed anovulatory. After mating of the 12 koalas, six females gave birth with a mean (+/- SEM) gestation of 34.8 +/- 0.3 days, whereas the remaining six non-parturient females returned to oestrus 49.5 +/- 1. 0 days later. After mating, oestrous behaviour ceased and the progestogen profile showed a significant increase in both pregnant and non-parturient females, indicating that a luteal phase had been induced by the physical act of mating. Progestogen concentrations throughout the luteal phase of the pregnant females were significantly higher than those of non-parturient females. Parturition was associated with a decreasing concentration of progestogen, which was increased above that of basal concentrations until 7 days post partum.

Birth of Pouch Young after Artificial Insemination in the Tammar Wallaby (Macropus eugenii)1

“…This success rate is comparable with 4-10% IUAI birth rates per cycle in humans [27,28], but well below 40-70% AI pregnancy rates regularly achieved in dairy cattle [29,30]. The relatively high success rate reported in the koala may be due to a prolonged estrus and the synchronization achieved as a result of ovulation induced by seminal factors [31]. In most other marsupials, however, ovulation is spontaneous and fertilization occurs long after mating [7].…”

The Evolutionary Origin of Female Orgasm

“…). Additional findings have been particularly informative, including the copulation‐induced ovulation in marsupials (koala: Johnston et al., ; Johnston et al., ), Xenarthra (pichi: Superina and Jahn, ; Superina et al., ), and Afrotheria (e.g., Eisenberg and Gould, ). This evidence supports the notion that male‐induced ovulation is ancestral in eutherians and spontaneous ovulation is a derived mode of ovarian cyclicity, which likely evolved from some form of the copulation‐induced type of ovulation.…”

Seasonal oestrous cycle activity of captive female koalas in south-east Queensland

“…Oestrous detection in this study used the method previously described by Blanshard (1994) and Johnston et al (2000a). A 'teaser' male was introduced into the female enclosure and allowed to scent mark objects with his sternal gland, bellow and urinate.…”

“…Non-mated female koalas have an anovulatory oestrous cycle of 32.9 AE 1.1 days and remain in behavioural oestrus for 10.3 AE 0.9 days, essentially entering a period of oestrus once a month, whereas mated non-fertile females ovulate and enter a luteal phase with a cycle length of 49.5 AE 1.0 days (Johnston et al 2000a). Due to the extended length of the ovulatory cycle, only female koalas that did not copulate or which experienced an anovulatory cycle were included in this analysis, which allowed for the calculation of a monthly percentage of teased koalas displaying behavioural oestrus.…”

“…Behavioural oestrus has been shown to correspond with elevated oestradiol-17b secretion (Johnston et al 2000a) and is commonly used as an effective tool for the timing of natural or artificial insemination in most captive koala populations in south-east Queensland (Johnston 1999;Johnston et al 2000aJohnston et al , 2000bJohnston et al , 2004Allen et al 2008). Captive koala populations provide a unique opportunity to study the effect of season on oestrous expression, without the confounding influence of lactational anoestrus and food resource availability, and in this way it may be possible to elucidate, with more confidence, the effect of temperature, photoperiod and rainfall on oestrous cycle activity.…”