The Reproductive Biology and Behaviour of Captive Female Matschie's Tree Kangaroos Dendrolagus matschiei.
PhD Thesis, University of Washington, Seattle, Washington.
All species of tree kangaroos (Dendrolagus spp.) are considered vulnerable or threatened in the wild. Their numbers have been reported to be adversely affected by hunting and habitat destruction in Australia and New Guinea (Martin 1992, Hutchins & Smith 1990, Kennedy 1986, Pernetta & Hill 1986). In captivity, breeding has not sustained viable populations for most species and the reproductive rates of all species are below their potential (Steenberg & Smith 1990). One reason for problems in captive management is a lack of knowledge about Dendrolagus reproductive biology. This genus differs morphologically and behaviorally from the more well known terrestrial kangaroo species.The present study documented both the physiological and behavioral aspects of estrous cycles of captive Dendrolagus matschiei females. The estrous cycle-length data based on steroid hormones were obtained from radioimmunoassay measurements of estrogen and progestin concentrations from fecal samples. This was the first quantitative fecal steroid analysis study on a marsupial species. Behavioral correlates of estrus were measured through focal animal observations. From both of these data sets, hypotheses were tested addressing how this genus fits into the general pattern of marsupial reproduction.The mean ($\pm$ one standard deviation) length of the estrous cycles for captive D. matschiei was 56.83 $\pm$ 3.12 days (n = 6) based on fecal estrogen profiles and 54.17 $\pm$ 5.74 (n = 6) based on fecal progestin profiles. For two of the females, reproductive behaviors occurred at approximately the calculated time of estrus, giving further support to the duration of estrous cycles. Several behavioral indicators of estrus were documented. Two other general patterns emerged from the hormone profiles of the female D. matschiei: (1) A spike of estrogen around the time of ovulation and (2) a rise in progestin after the estrogen peak. D. matschiei seems to have a similar reproductive cycle with several notable differences to those of other known macropodids. The D. matschiei estrous cycle is longer than all other known macropod cycles by at least 10 days. The gestation length of 44.2 days for D. matschiei (Heath et al. 1990) is also longer than any other known macropodid species by at least 6 days. Life history data obtained from captive tree kangaroo historical records showed that D. matschiei has an extended age of female sexual maturity which is later than other macropodids, and that D. matschiei has a reduced fecundity rate. The reason for these differences could be based on D. matschiei's ecological niche. It is an arboreal folivore with a relatively low metabolic rate (McNab 1978) which could result in an overall slower reproductive output.