For females, the oestrus period lasts for several weeks, during which time females will mate with multiple partners, storing the sperm from these matings until ovulation occurs.  This project aims to determine markers that can be used to determine when females are receptive and when ovulation has occurred, such as changes in weight, pouch condition and faecal hormone levels, and to also investigate how females store sperm.  Variation in the timing of births between colonies, and under different environmental conditions, is also being examined to determine the cues that initiate breeding in this species.

Red-tailed phascogales can raise a maximum of eight young in a breeding attempt due to teat availability, but females are known to give birth to more young than they can raise.  With only ~30% of females surviving to a second breeding season, and a small proportion reaching a third breeding season, this over production of embryos is thought to ensure females carry a full complement of young in what could be their only breeding attempt.  This project is investigating the fecundity of females and whether the number of eggs ovulated and the number of embryos produced declines with age.  No age related differences in fecundity have been observed, with females producing on average twice as many eggs as they have teats for.  Knowledge of age related variation in fecundity can be used to plan captive breeding attempts to maximise the number of young produced.

This growth data is now being examined to determine the relationship between parental body weight and the body weight of offspring at weaning and at sexual maturity.  The degree of sexual dimorphism is also being assessed, with males being on average 1.5x as heavy as females, and 1.1x longer in skeletal measures compared to females.  Sexual dimorphism in body weight first appears during lactation, and as such may be associated with biased lactational investment by the mother, or differential usage of resources by male and female offspring.

Offspring from the 2004 breeding season were genotyped and paternity was determined.  Multiple paternity, more than one father within a litter, was confirmed to occur in 5/11 litters, with heavier males having greater than expected siring success.  The effective population size was calculated to be 15% of the census population size, and this was three times larger than that observed in the group managed studbook, and three times as large as would be obtained if a single male was placed with the group of females.  These results indicate that knowledge of multiple paternity, obtained through the genotyping of offspring, can provide a means for improving the retention of genetic diversity when practical considerations, such as the need to group house females restrict the optimum genetic management of a population.

Carotenoids are molecules that play a key role in binding free radicals, reducing oxidative stress, conferring protection from ultra violet radiation. Since animals cannot produce carotenoids, they must be acquired through the diet. A growing amount of research has focussed on the role of carotenoids for immune function, as well as the signalling function of carotenoids in integument (such as bill or feather colouration). We used an experimental approach to examine the effect of carotenoids on immunocompetence and bill colouration in the diamond firetail, Stagonopleura guttata. We show that experimental birds on a carotenoid diet will have higher immunocompetence (PHA response) and increased bill hue than birds in the control group, and the carotenoid concentration of the wild birds is comparable to the initial carotenoid concentration of the experimental birds. Our results show that dietary carotenoids may influence disease resistance and reproductive success (through their influence on bill colour, a sexual signal) in diamond firetails, one of a suite of declining woodland birds in Australia.

Frogs and toads (anurans) have taught us a great deal about the evolution of communication signals by sexual selection. Generally, male frogs and toads call at night to attract females, and females select their mates on the basis of their calls. One would not normally expect organisms that rely on acoustic signals to communicate in darkness to show sexually selected differences in morphology. However, the hylid frog (Litoria havina) has a sexually dimorphic proboscis. We observed these frogs over ten nights in the Star Mountains of New Guinea to test the hypothesis that the proboscis is subject to sexual selection. The potential for sexual selection varied from 1.7-2.3 on different nights. A comparison of mated and nearby unmated males, showed that both overall body size and proboscis length were independent targets of directional sexual selection by mate choice. Males with longer proboscis, but smaller body size were more likely to be mated. The mechanism by which females discriminate males with these characteristics in the dark is unknown.

Reintroductions and translocations have been used to re-establish species in areas where they have become locally extinct. The relative merits of these conservation techniques have been controversial and rarely tested. Reintroduced captive bred animals may have lost survival skills required for foraging and predator avoidance. Whereas translocated wild-born animals may have survival skills relevant for their home site, but must adapt to a new environment.

Bilbies are one of a number of mammal species that have been decimated in arid Australia since European settlement. After declining to occur in less than 20% of their former range, bilbies have been re-established at several sites where they had become locally extinct. We compared dispersal, movement patterns following establishment and survival of captive-bred bilbies (reintroduced), wild-born bilbies moved from another site (translocated) and wild-born bilbies within an established population (control) at the arid recovery project in South Australia.

All newly released bilbies exhibited an initial dispersal and exploration period. Translocated bilbies quickly established themselves within a few days, and thereafter displayed similar movement patterns and survival to resident bilbies. Reintroduced bilbies dispersed further than translocated animals, and were still roaming widely two weeks post-release.

Adult males suffered significantly greater weight loss than residents in both release groups. Mortality in the reintroduced group was considerably higher than the translocated and control groups. Captive bred bilbies benefit from training to provide them with survival skills, and translocation between established wild populations is the preferred approach to future management of these small, isolated, re-established populations.

Over a period of 12 months we trapped eight sites in areas fragmented by mineral exploration tracks and a further eight control sites where there has been no disturbance. Traps were placed in a grid design, straddling the exploration tracks at the explored sites. Nine field trips have been conducted to date, giving rise to a total of 14,524 trap nights and 3319 captures of 3007 individuals.  A total of 29 species were trapped. The overall fauna is similar for disturbed and undisturbed sites. However responses differ between species; some increased in abundance in response to track construction, and others decreased in abundance. Results indicate that exploration tracks may indeed affect fauna communities, and that the effects are likely to be species- and site-specific.

Reintroductions have been used (with varying success) to re-establish species into parts of their natural range where they no longer occur.  Improvements to the success of reintroductions require close monitoring of experimental releases to test specific hypotheses about factors that may improve the likelihood of establishing self-sustaining populations. 

The South Australian mainland tammar wallaby has been extinct in the wild since the 1930’s.  Habitat clearance and predation by introduced foxes were thought to be the major causes of extinction.  Fortunately, a wild population of this species were found living in New Zealand, and eighty two were captured and brought back to Australia to establish a captive breeding population.  Subsequently, forty six wallabies were used in an experimental reintroduction into their former range following a fox control program.  The release tested whether wallabies in established social groups (versus groups of animals unfamiliar with each other) would have an advantage against predation by foxes that evaded the fox-control or dispersed into the release site.

The wallabies were radio-tracked intensively for twelve months following release.  Foxes were one of two major causes of mortality, but survivorship did not differ between the experimental treatment groups.  We will describe the movement patterns and dynamics among the treatment groups, leading to the establishment of a small, breeding population of M. e. eugenii in its former range.