Auswahl der wissenschaftlichen Literatur zum Thema „Rufous Hare-wallaby“

Standard haematological parameters measured in the bilby (Macrotis lagotis) and the rufous hare-wallaby (Lagorchestes hirsutus) were not markedly different. Both species had very high levels of red blood cell 2,3-diphosphoglycerate, whilst the levels of adenosine triphosphate were within the range of most marsupials and mammals. The activities of red-cell enzymes were measured in these two species as well as in the brown antechinus (Antechinus stuartii). Some significant findings were (i) very high levels of hexokinase, glyceraldehyde phosphate dehydrogenase and lactate dehydrogenase in the antechinus and (ii) very high levels of glucose-6-phosphate dehydrogenase and glutathione peroxidase in the rufous hare-wallaby. The glycolytic rate, measured as the amount of lactate produced by the red cells incubated with eight different substrates, was found to be generally higher in the antechinus than in the other two species. The maximum rate of glycolysis was observed with mannose whilst galactose was a poor substrate in all three species.

The rufous hare-wallaby (Lagorchestes hirsutus) is now extinct in the wild on mainland Australia, but survives in captivity. However, endemic populations persist on Bernier and Dorre Islands, Western Australia. This study aimed to compare the genetic diversity and differentiation amongst three remaining rufous hare-wallaby populations using mitochondrial DNA (mtDNA) (cytochrome b, control region) sequence data and nuclear (microsatellite) markers. Levels of microsatellite diversity were low in both island populations but high in the captive mainland population. Levels of mtDNA diversity were low in all three populations. The mainland and island populations of L. hirsutus were found to be significantly differentiated for both microsatellite and mtDNA data, but the two island populations were significantly differentiated only for the microsatellite data. This pattern of differentiation is not consistent with the recognition of two separate island subspecies, but we recommend that the mainland and island populations be regarded as separate subspecies. The low diversity of the island populations and differentiation between island and mainland populations presents both challenges and opportunities for future management.

The diet preferences and selectivity of the rufous hare-wallaby in the Tanami Desert were examined at a number of sites and over a number of seasons by microscopic analysis of faecal pellets and direct observations. Perennial grasses were the most consistent plant items in the diet. Grass seeds were seasonally important as were the seeds and bulbs of sedges. Species of dicots were also used but most represented only minor components in the diet. Several species of plant common to the area were noticeably absent from the diet. Differences in the diets between four sites of varying floristic composition and fire history were consistent with differences in vegetation cover at each site. Overall, the absolute proportions and ratios of monocots and dicots and of leaf and seed portions were strongly similar for all sites, as were seasonal changes in the proportions of the four main plant categories (monocots, dicots, seeds and fruits). These changes correlated with local rainfall. Comparisons of plants eaten and plants available indicate the hare-wallabies' preference for monocots, particularly seed and fruit components. In contrast consumption of dicots was influericed by the declining quality of other preferred plants. Insects were seasonally important in the diet and appear to be a potentially important nitrogen supplement during drier times. The feeding strategy of the rufous hare-wallaby is flexible and enables it to exploit fully food resources whose availability is often limited in both time and space. During droughts it seems likely that the species is food stressed and this could lead to localised declines.

A metal detector was used to recover passive integrated transponder (PIT) tags from below wedge-tailed eagle and barn owl nests and roost trees. The effectiveness of four different metal detectors to locate PIT tags and Australian Bird and Bat Banding Scheme (ABBBS) bands were compared. Twenty PIT tags from 14 golden bandicoots, five burrowing bettongs and one rufous hare-wallaby were recovered from wedge-tailed eagle sites. One unreadable PIT tag was recovered from a barn owl site. This technique has potential for use in determining the survivorship of translocated threatened species.

This paper reports a study of the interactions between a remnant population of the rufous hare-wallaby, Lagorchestes hirsutus, and populations of several introduced mammal species in a region of the Tanami Desert. Transect counts of faecal pellets and tracks were used to determine the local distributions of all species and analysis of faeces from both predators and competitors of hare-wallabies was undertaken. Six species of introduced mammals were recorded within the study area: dingoes, rabbits, camels, foxes, feral cats and cattle. The local distributions for a number of these species were found to be significantly correlated with that of L. hirsutus during some seasons. Analysis of dingo scats collected from fire trails within the study area identified a total of 12 different food classes including harewallabies which occurred in 6.9% of the scats. Foxes and feral cats appear to be more important predators as demonstrated by their impacts on natural and reintroduced populations of hare-wallabies. Comparison of the diets of the rabbit and L. hirsutus identified significant overlap in utilised plant species, particularly during drier times. Competition between rabbits and L. hirsutus seems probable, given the overlap of their diets and their similar body sizes and metabolic requirements. Cattle and camels are potentially as important at densities above present levels. The complex web of interactions between L. hirsutus and these introduced species have important implications for management of remnant and reintroduced hare-wallaby populations.

Digestive performance and rate of passage of fluid and particulate markers through the gastrointestinal tract were measured in captive rufous hare-wallabies (Lagorchestes hirsutus) maintained on a commercial pelleted diet. This diminutive (0.8-2.1 kg) marcropodid marsupial was found to have a large, basically tubiform forestomach (tubiform forestomach 71-74% of total stomach capacity), similar to that of the large grazing kangaroos and markedly different from those of small browsing wallabies and similar-sized rat-kangaroos. This 'kangaroo-like' gastric morphology, together with a low maintenance energy requirement (326 kJ digestible energy kg-0.75 day-1) and thus low food intakes (33 g dry matter kg-0.75 day-1) and long mean retention times of digesta in the gut (23 h for a fluid marker, 38 h for a particle marker), were considered to be major factors in the ability of this small arid-zone herbivore to digest fibre (50% of the neutral-detergent fibre and 31% of the acid-detergent fibre of the pelleted diet) and thus to utilise plant material that is often of low quality in the Tanami Desert.

The summer diet of a population of the rufous hare-wallaby, Lagorchestes hirsutus, was studied by survey of grazed plants and microscopic analysis of faecal pellets following a season of above-average rainfall. The fibre and nitrogen contents of food plants were examined and the abundance of food plants in the habitat was determined to assess dietary selectivity. L. hirsutus had a diverse diet but selectively grazed the seeds and shoots of certain grasses and sedges as well as some dicotyledons. High- and low-fibre food items occurred in faecal samples, suggesting that L. hirsutus possesses considerable dietary adaptability. Individuals may travel appreciable distances into saline interdune and recently burnt areas to feed. The future survival of the only known mainland population appears to be largely dependent on continued mosaic-burning of its habitat to maintain mature spinifex for shelter adjacent to areas of regeneration that provide a range of preferred food items.

A 2-year study was conducted to investigate two aspects of the local distribution of the rufous harewallaby, Lagorchestes hirsutus, in a region of the Tanami Desert. These were: (a) patterns of habitat use in response to changing environmental conditions and (b) environmental parameters influencing 'local' choice of habitat. Counts of faecal pellets and tracks were used to obtain indices of hare-wallaby activity within occupied sites and to gain an insight into the movements by individuals. Local choice of habitat was analysed by assessment of numerous habitat features at occupied and unoccupied sites in the region. Previous surveys over the greater part of the study area provide evidence of a significant local decline and local contraction of range by L. hirsutus during recent times. Hare-wallabies showed seasonal trends in the relative use of different vegetation systems in response to the relative availability of food items within each habitat. The home ranges of hare-wallabies consisted of two distinct areas of activity: a large sparsely used area within the dense Triodia pungens vegetation and a small concentrated feeding area within the neighbouring caliche system. Hare-wallabies were dependent upon a specialised form of spinifex habitat. Patchiness, hummock size, food diversity and the degree of floral senescence affected suitability for hare-wallabies. Within the Tanami Desert site, suitable combinations of these characters were associated with tight mosaics of different regenerative stages after fire. Fire is therefore clearly implicated as an important force in creating a greater diversity of feeding and sheltering habitats for the hare-wallabies in the otherwise uniform spinifex sandplains. There is an obvious role for the application of controlled burns as a means of managing habitats to favour L. hirsutus in the Tanami Desert.

Observations on the behaviour of the Rufous Hare-wallaby Lagorchestes hirsutus were obtained from a captive colony maintained in Alice Springs. This information was used to interpret observations of animals made during field studies in the Tanami Desert. Aspects of the species' behavioural repertoire which were recorded included activity patterns, postures, gaits, interactions, nesting habits and vocalisations. Lagorchestes hirsutus is predominantly nocturnal and its activity patterns and body postures resemble those recorded for other species of small macropods. It appears to be a relatively solitary animal but there was some evidence of social organisation within animals maintained in captivity. Aspects of the sexual and aggressive behaviour of L. hirsutus appear to resemble more closely those of the potoroids than of larger macropodids.

The transfer of threatened animals from one location to another in order to benefit the species is a technique frequently used by animal conservation managers. However, very few of these relocations have experimentally assessed the relative merits and disadvantages of commonly used release techniques. Two species of hare-wallaby, mala (Lagorchestes hirsutus) and merrnine (Lagostrophus fasciatus), were reintroduced in August 2001 onto Peron Peninsula in Western Australia. These threatened species were reintroduced using two release strategies (soft versus hard release), and their subsequent movements and body condition were monitored using radio-telemetry and trapping.

Australian marsupial populations, particularly macropods, have a high percentage of species that are threatened due to habitat destruction and competition and predation from introduced species. These already stressed populations are vulnerable to introduced and endemic pathogens, both immunologically and environmentally. Yet this vulnerability also places ethical limits on the extent of disease research that is able to be carried out. This thesis firstly investigates the applicability of using available genomes of model marsupial species, specifically the tammar wallaby (Macropus eugenii), in investigating immunological function in disease of a closely related vulnerable species, the rufous hare-wallaby (Lagorchestes hirsutus). Disease vulnerabilities in a range of marsupials highlight susceptibilities associated with T-cell function, and while other avenues have been investigated, the nature and expression of more diverse cytokines involved in T-cell mediated immune responses is a key focus for research. This thesis project began with the characterisation of expressed cytokines, IL-6, IL-10, and IFN-γ confirming their expression in the tammar wallaby and providing sequence and annotation information to further that found in published genome databases. Further to this, both IL6 and IL10 genes were found to express splicing variants in the tammar wallaby. To clarify the potential functional characteristics of both these cytokines and their isoforms, the structural nature of the predicted proteins was analysed and compared to known mammalian homologs. The information obtained for these cytokines in the tammar wallaby, was applied to the closely related but more vulnerable rufous hare-wallaby to obtain expressed sequence for these cytokines. The expression of key T-cell markers and cytokines was confirmed in the rufous-hare wallaby across a range of tissues. To further this, selected cytokines were compared semi-quantitatively to determine comparative base levels of expression to inform further quantitative assessment. The use of archival samples, particularly formalin-fixed paraffin embedded (FFPE) tissues, is an important resource in studying marsupial immunology, where threatened, or even extinct species, may be the subject of research. This project examined the use of both genomic bacterial identification and gene expression of cytokines within archival FFPE tissues as a mode to inform disease research. While the methodology has limitations, the identification of an infective agent, Mycobacterium avium, and the ability to assess the expression of cytokines associated with that agent, will inform further research in archival samples. The thesis concludes that while the sequence and structure of marsupial cytokines are comparable to their mammalian homologs, the identification of splice variants presents novel regulatory mechanisms which may affect disease outcomes. Basal expression of T-cell related cytokines and T-cell markers in rufous hare-wallaby tissues, and semi-quantitative assessment of cytokine expression is presented providing fundamental data for further comparative research. Taken together, identification of Mycobacteria in archival tissues and the associated expression of key cytokines in the rufous hare-wallaby provides a key methodological approach to assist in research for which archival FFPE tissues are available while also presenting novel disease-associated cytokine expression information.

This thesis describes a comprehensive study of the cellular responses of a number of endangered marsupial species with a principal focus on the tammar wallaby (Macropus eugenii) as a model macropod species. The development of in vitro experimental assays for the assessment of immune responses in this model species are described, which provided a set of benchmarks for comparisons with other members of the Macropodidae and with eutherian mammals. Once this data was collected and protocols were established, the study was extended to include investigations of the immune responses in opportunistic samples obtained from the Rufous Hare-wallaby (Lagorchestes hirsutus), the Long-footed potoroo ( Potorous longipes) and the more common, but nonetheless still vulnerable, Long-nosed potoroo (Potorous tridactylus) with a view to investigating their apparent susceptibility to infection with intracellular pathogens, particularly mycobacterial species. The findings from the application of these assays suggest that the cellular immune responses of these species are relatively complex and involve a level of sophistication that rivals their eutherian counterparts. Specifically peripheral blood and tissue leukocytes were morphologically similar to those of other mammals, with the exception of tammar wallaby monocytes that appeared to contain few lysosomal granules, and the basophils of the Rufous Hare-wallaby that contained very large atypical granules. The overall findings of this study suggest that the immune systems of macropod species possess most of the sophistication associated with that of eutherian mammals. Whilst some differences were apparent in cells and their products in the test species, no single factor common to all macropods was identified as a cause for immune dysfunction. It appears likely that as yet undefined factors related to their confinement rather than an inherent defect in their immunocapacity is responsible for the apparent disease susceptibility of these animals.
Doctor of Philosophy (PhD)

This thesis describes a comprehensive study of the cellular responses of a number of endangered marsupial species with a principal focus on the tammar wallaby (Macropus eugenii) as a model macropod species. The development of in vitro experimental assays for the assessment of immune responses in this model species are described, which provided a set of benchmarks for comparisons with other members of the Macropodidae and with eutherian mammals. Once this data was collected and protocols were established, the study was extended to include investigations of the immune responses in opportunistic samples obtained from the Rufous Hare-wallaby (Lagorchestes hirsutus), the Long-footed potoroo ( Potorous longipes) and the more common, but nonetheless still vulnerable, Long-nosed potoroo (Potorous tridactylus) with a view to investigating their apparent susceptibility to infection with intracellular pathogens, particularly mycobacterial species. The findings from the application of these assays suggest that the cellular immune responses of these species are relatively complex and involve a level of sophistication that rivals their eutherian counterparts. Specifically peripheral blood and tissue leukocytes were morphologically similar to those of other mammals, with the exception of tammar wallaby monocytes that appeared to contain few lysosomal granules, and the basophils of the Rufous Hare-wallaby that contained very large atypical granules. The overall findings of this study suggest that the immune systems of macropod species possess most of the sophistication associated with that of eutherian mammals. Whilst some differences were apparent in cells and their products in the test species, no single factor common to all macropods was identified as a cause for immune dysfunction. It appears likely that as yet undefined factors related to their confinement rather than an inherent defect in their immunocapacity is responsible for the apparent disease susceptibility of these animals.