Reproductive physiology of the Tasmanian devil (Sarcophilus harisii) and spotted-tailed quail (Dasyurus maculatus)
Creators: name: Hesterman, H
Publisher: name: University Of Tasmania
Year: 2023

description: The Tasmanian devil (Sarcophilis harrisii) and the spotted-tailed quoll (Dasyurus maculatus) are the world's largest extant carnivorous marsupials. These two closely related dasyurid species coexist only on the island of Tasmania, and both are listed as Threatened. The aim of this study was to develop a definitive understanding of the reproductive processes of these large, sympatric dasyurids to gain insight into how aspects of the physical and social environment shape evolutionary life history strategies. Although both species are solitary, the devil is gregarious and relatively abundant in comparison with the spott~d-tailed quoll. Furthermore, in Tasmania D. maculatus experiences a high degree of interspecific competition for food - the ultimate factor influencing breeding timing and synchrony. I hypothesised that these differences in population density, the level of sociality, and access to nutritional resources would be reflected in the species' reproductive biology, including the duration of breeding season, mechanism of ovulation, synchrony of oestrus, fecundity and lifetime reproductive effort. The ovarian and testicular cycles were characterised in captive and free-ranging devil and spotted-tailed quoll populations, and breeding seasonality was compared with patterns found in other dasyurids. In female devil and spotted-tailed quoll, longitudinal endocrine profiles revealed a biphasic pattern of plasma progesterone, with a characteristic pro-estrous pulse during the follicular phase (FP), occurring up to several weeks prior to onset of the luteal phase (LP). The patterns of faecal metabolites (20a-OH-pregnanes, 20-oxo-pregnanes) were positively correlated with fluctuations in plasma progesterone. Mean duration of the oestrous cycle (FP + LP) was ~32 days for devils and ~38 days for spotted-tailed quolls. Significant differences between the pattern of progestagens and estrogens concentrations during the pregnant and non-mated oestrous cycle, suggest maternal recognition of pregnancy in the devil. Changes in pouch appearance during oestrous have been documented as an indicator of breeding condition in a number of dasyurids. Pouch condition of female devils and quolls was assessed based on size, colour and secretions, and found to accurately reflect reproductive status. The stage of pouch development was also correlated with underlying changes in development of the reproductive tract. In male devils peak androgen concentrations occurred between December - March (austral spring/summer). There was no seasonal change in scrotal dimension or size/mass of the testes, epididymides or prostate. In devils, an extended period of spermatogenesis was apparent: sperm were produced from November until August. In spotted-tailed quolls, peak androgen concentrations were recorded between April - July , (austral autumn/winter). Spermatogenesis in the spotted-tailed quoll began by January, and sperm were produced from April until August. Differences in the annual timing of breeding in these two species is likely caused by differing responses to photoperiod - with the devil cued by increasing day length during spring, and the quoll stimulated by decreasing photoperiod in autumn. Although breeding was not tightly synchronised within either devil or spotted-tailed quoll populations, late lactation and weaning usually occurred during the optimal period of late spring/summer. Findings indicate that timing of reproductive events can be relaxed in species where ecological and reproductive attributes permit a level of flexibility. In devils and spotted-tailed quolls these are large body size, generalist flesheating diet, facultative polyoestry and variation in the length of lactation. This study confirms the devil is facultatively polyoestrous and can breed at 12 months of age, therefore can now be classified alongside the spotted-tailed quoll as having a strategy III life-history. The fundamental information gained on the reproductive biology of the largest dasyurids will be applied to improve and assist in situ and ex situ conservation and management of these threatened marsupial species.