Thesis (Ph.D.)--Murdoch University, 2007. / Thesis submitted to the Division of Health Sciences. Includes bibliographical references (leaves 241-273)

Thesis (Ph. D.)--University of Western Sydney, 2002. / Includes bibliographical references.

Leukocytes play a central role in protecting the body against infectious organisms and their research is essential for understanding the mechanisms of immunity. By studying leukocytes across a range of species, insights are provided into differing strategies employed to ensure resistance to disease. Surprisingly, the structure and function of marsupial leukocytes has received very limited study. Marsupials represent a major evolutionary pathway with distinct differences in reproduction and development from placental mammals. These differences in the life history of marsupials place unique challenges on the immune system, and differences in leukocyte structure and function could be reasonably expected. In this thesis, studies were undertaken to examine the cytochemical, ultrastructural and functional features of leukocytes from species of marsupials, belonging to the family Macropodidae (kangaroos and wallabies). The aim of these studies was to elucidate the characteristics of macropodid leukocytes and to compare and contrast these features with the known characteristics of other mammalian leukocytes. Leukocytes from two species of macropodid, the tammar wallaby (Macropus eugenii) and the western grey kangaroo (Macropus fuliginosis), formed the basis of this study with additional material provided from quokka (Setonix brachyurus), woylie (Bettongia pencillata) and red kangaroo (Macropus rufus). Staining characteristics of cells were examined following reaction with Sudan black B, peroxidase, chloroacetate esterase, naphthyl butyrate esterase, alkaline phosphatase and periodic acid-Schiff. Peroxidase and Sudan Black B reactions were similar to domestic animal species but chloroacetate esterase and naphthyl butyrate esterase were unreliable as markers for macropodid neutrophils and monocytes, respectively. Significant variation in staining for alkaline phosphatase was seen between species of macropodid. Tammar wallabies and quokka demonstrated strong neutrophil alkaline phosphatase activity whereas western grey kangaroos, red kangaroos and woylies contained no activity within their leukocytes. Peroxidase and alkaline phosphatase cytochemistry were also assessed at the ultrastructural level with transmission electron microscopy. This allowed the identification of distinct granule populations within macropodid neutrophils. Two subcellular compartments containing alkaline phosphatase activity were identified within tammar wallaby neutrophils. These were considered equivalent to secretory vesicles and a subpopulation of specific granules. Tubular vesicles containing alkaline phosphatase were also identified within the eosinophils of tammar wallabies. These structures were a novel finding having not been reported previously in the eosinophils of other animal species. In addition to cytochemistry, the general ultrastructure of leukocytes from tammar wallabies and western grey kangaroos were reported. Results were similar to previous reports for other marsupial species. The current body of knowledge was extended by the first detailed description of the ultrastructure of basophils in a marsupial. To assess functional aspects of macropdid neutrophils, flow cytometric assays were performed examining oxidative burst responses and phagocytosis. Reactive oxygen species were generated by neutrophils from tammar wallabies and western grey kangaroos in response to phorbol 12-myristate 13-acetate but not N-formyl-Met-Leu-Phe or opsonised bacteria. Phagocytosis of opsonised bacteria was also measured in neutrophils from tammar wallabies, which was poor in contrast to ovine neutrophils. However, flow cytometric studies were limited by sample preparation. Further optimisation of isolation methods for tammar wallaby leukocytes should be undertaken before dogmatic conclusions are drawn. Overall, the results of this thesis demonstrate that, in the areas examined, the general characteristics of leukocyte structure and function of mammals are present in macropodids. However differences were identified both within and outside of the macropodid group. These differences have important ramifications for the use of ‘model’ species in the study of leukocyte biology in marsupials. The results also provide potentially useful tools for the clinical diagnosis of haematological disease in macropodids and may be of interest to those studying comparative and evolutionary aspects of leukocyte structure and function.

Thesis (Ph. D.)--University of Western Sydney, Nepean, 2000. / Includes bibliographical references (leaves 203-235).

The quokka (Setonix brachyurus Quoy & Gaimard 1830) is a medium-sized, macropodid marsupial that is endemic to the mesic, south-western corner of Australia. While being a tourist icon on Rottnest Island, the species is threatened with extinction. It has been intensively studied on Rottnest Island in the 1960s and 1970s, however very little is known of its ecology on the mainland. Additionally the insular and mainland environments are extremely different suggesting that ecological differences between the two populations are likely. Consequently, this study sought to determine the basic autecology of the quokka and identify what factors have attributed to its threatened conservation status. The northern jarrah forest of Western Australia was selected as the study region due to it being at the northern limit of extant quokka distribution and because it was thought that the factors threatening the quokka would be exacerbated there. Fossil deposits suggest that the quokka originally occupied an area of approximately 49,000 km2 in the south-western corner of Australia. Historical literature show that they were widespread and abundant when Europeans colonised the region in 1829 but a noticeable and dramatic decline occurred a century later. The arrival of the red fox to the region coincided almost exactly with this decline and so it was probably ultimately responsible. Continued predation by both it and the feral cat are likely to have continued the decline, along with habitat destruction and modification through altered fire regimes. Specific surveys and literature searches show that since the 1950s, the area occupied by the quokka has declined by 45% and since 1990 by 29%. Based on the criteria of the IUCN (Hilton-Taylor 2000), the conservation status of the quokka should remain as vulnerable. An endangered status may be more applicable if the quokkas restriction to patches through its existence as a metapopulation is considered. Trapping of eight sites supporting quokka populations in the mid-1990s revealed three sites now locally extinct despite the ongoing, six year old, fox control programme. Another three are at serious risk of extinction. Extant population sizes ranged from one to 36 and population density ranged from 0.07 to 4.3 individuals per hectare. This is considered to be below the carrying capacity of each site. The overall quokka population size in the northern jarrah forest may be as low as 150 adult individuals, of which half are likely to be female. Even the largest extant populations are highly susceptible to stochastic extinction events. This small size was surprising considering the six year old, introduced predator control programme. Historically, the restriction to discrete habitat patches, the occasional inter-patch movement, the lack of correlation between the dynamics of each population and reports of frequent localised extinctions and colonisations suggest that the quokka population once existed as part of a classic metapopulation. The massive decline of the quokka in the 1930s pushed the metapopulation structure into a non-equilibrium state such that today, the extant populations are the terminal remnants of the original classic metapopulation. Wild mainland quokkas breed throughout the year. A significant reduction in the number of births occurs over summer and this coincides with a decline in female body weight. Despite this, the mainland quokka is relatively fecund and is able to wean two offspring per year. The level of recruitment from pouch young to independence was low and this may explain the apparent lack of population increase following the initiation of fox control. A total of 56 trapped quokkas were fitted with a radio collar. Mean home range size for quokkas was 6.39 ha with a core range of 1.21 ha and this was negatively related to population density. Male home ranges were larger than females but not significantly when the sexual size dimorphism was considered. Nocturnal ranges were larger than diurnal ranges reflecting nocturnal departures from the swamp refugia. Home range sizes varied seasonally, probably due to changes in the distance required to move to obtain sufficient nutrients and water over the dry summer compared to the wet winter and spring. Telemetry confirmed trapping results that showed no movement between swamps or populations. Home range centres shifted to the periphery of the swamp following the winter inundation and this may increase the species susceptibility to predation. The lack of dispersal is probably caused by quokka populations existing below carrying capacity and following selection for philopatry under the threat of predation for dispersing individuals. Without dispersal to recolonise or rescue unpopulated patches, the collapse of the original quokka metapopulation appears to have occurred. On a macrohabitat scale, the quokka in the northern jarrah forest is restricted to Agonis swamp shrubland habitats that form in the open, upper reaches of creek systems on the western side of the forest. This restriction was probably initially due to the high water requirements of the quokka but is likely to have been exacerbated by increased predation pressure since the arrival of the fox. On a microhabitat scale, the quokka is a habitat specialist, preferring early seral stage swamp habitats, probably for foraging, as part of a mosaic of old age swamp that provides refuge. Despite the six year old, introduced predator control programme, foxes and cats are still the major cause of mortality to quokkas. Road kills was the other identifiable cause. Individuals alive at the start of the study had an 81% chance of staying alive until the end. The likelihood of dying was minimised by grouping together with conspecifics, maximising home range size and maximising the time spent within the swampy refuge. Current rates of adult and juvenile survivorship should allow population recovery and so it seems pouch young mortality, reflected by low recruitment, has inhibited the anticipated population increase following predator control. The confounding effect of inadequate unbaited controls meant that little statistical evidence was available on the impact of introduced predators on the quokka, however the models provided support for earlier hypotheses of these. The presence of a quokka population at a site was related to the amount of poison baits delivered ??? reflecting predation pressure, the average age of the swamp and a mosaic of early and late seral stages within the swamp habitat. Recently burnt habitat is thought to provide food for quokkas and long unburnt habitat provides refuge from predation.

The quokka (Setonix brachyurus Quoy & Gaimard 1830) is a medium-sized, macropodid marsupial that is endemic to the mesic, south-western corner of Australia. While being a tourist icon on Rottnest Island, the species is threatened with extinction. It has been intensively studied on Rottnest Island in the 1960s and 1970s, however very little is known of its ecology on the mainland. Additionally the insular and mainland environments are extremely different suggesting that ecological differences between the two populations are likely. Consequently, this study sought to determine the basic autecology of the quokka and identify what factors have attributed to its threatened conservation status. The northern jarrah forest of Western Australia was selected as the study region due to it being at the northern limit of extant quokka distribution and because it was thought that the factors threatening the quokka would be exacerbated there. Fossil deposits suggest that the quokka originally occupied an area of approximately 49,000 km2 in the south-western corner of Australia. Historical literature show that they were widespread and abundant when Europeans colonised the region in 1829 but a noticeable and dramatic decline occurred a century later. The arrival of the red fox to the region coincided almost exactly with this decline and so it was probably ultimately responsible. Continued predation by both it and the feral cat are likely to have continued the decline, along with habitat destruction and modification through altered fire regimes. Specific surveys and literature searches show that since the 1950s, the area occupied by the quokka has declined by 45% and since 1990 by 29%. Based on the criteria of the IUCN (Hilton-Taylor 2000), the conservation status of the quokka should remain as vulnerable. An endangered status may be more applicable if the quokkas restriction to patches through its existence as a metapopulation is considered. Trapping of eight sites supporting quokka populations in the mid-1990s revealed three sites now locally extinct despite the ongoing, six year old, fox control programme. Another three are at serious risk of extinction. Extant population sizes ranged from one to 36 and population density ranged from 0.07 to 4.3 individuals per hectare. This is considered to be below the carrying capacity of each site. The overall quokka population size in the northern jarrah forest may be as low as 150 adult individuals, of which half are likely to be female. Even the largest extant populations are highly susceptible to stochastic extinction events. This small size was surprising considering the six year old, introduced predator control programme. Historically, the restriction to discrete habitat patches, the occasional inter-patch movement, the lack of correlation between the dynamics of each population and reports of frequent localised extinctions and colonisations suggest that the quokka population once existed as part of a classic metapopulation. The massive decline of the quokka in the 1930s pushed the metapopulation structure into a non-equilibrium state such that today, the extant populations are the terminal remnants of the original classic metapopulation. Wild mainland quokkas breed throughout the year. A significant reduction in the number of births occurs over summer and this coincides with a decline in female body weight. Despite this, the mainland quokka is relatively fecund and is able to wean two offspring per year. The level of recruitment from pouch young to independence was low and this may explain the apparent lack of population increase following the initiation of fox control. A total of 56 trapped quokkas were fitted with a radio collar. Mean home range size for quokkas was 6.39 ha with a core range of 1.21 ha and this was negatively related to population density. Male home ranges were larger than females but not significantly when the sexual size dimorphism was considered. Nocturnal ranges were larger than diurnal ranges reflecting nocturnal departures from the swamp refugia. Home range sizes varied seasonally, probably due to changes in the distance required to move to obtain sufficient nutrients and water over the dry summer compared to the wet winter and spring. Telemetry confirmed trapping results that showed no movement between swamps or populations. Home range centres shifted to the periphery of the swamp following the winter inundation and this may increase the species susceptibility to predation. The lack of dispersal is probably caused by quokka populations existing below carrying capacity and following selection for philopatry under the threat of predation for dispersing individuals. Without dispersal to recolonise or rescue unpopulated patches, the collapse of the original quokka metapopulation appears to have occurred. On a macrohabitat scale, the quokka in the northern jarrah forest is restricted to Agonis swamp shrubland habitats that form in the open, upper reaches of creek systems on the western side of the forest. This restriction was probably initially due to the high water requirements of the quokka but is likely to have been exacerbated by increased predation pressure since the arrival of the fox. On a microhabitat scale, the quokka is a habitat specialist, preferring early seral stage swamp habitats, probably for foraging, as part of a mosaic of old age swamp that provides refuge. Despite the six year old, introduced predator control programme, foxes and cats are still the major cause of mortality to quokkas. Road kills was the other identifiable cause. Individuals alive at the start of the study had an 81% chance of staying alive until the end. The likelihood of dying was minimised by grouping together with conspecifics, maximising home range size and maximising the time spent within the swampy refuge. Current rates of adult and juvenile survivorship should allow population recovery and so it seems pouch young mortality, reflected by low recruitment, has inhibited the anticipated population increase following predator control. The confounding effect of inadequate unbaited controls meant that little statistical evidence was available on the impact of introduced predators on the quokka, however the models provided support for earlier hypotheses of these. The presence of a quokka population at a site was related to the amount of poison baits delivered ??? reflecting predation pressure, the average age of the swamp and a mosaic of early and late seral stages within the swamp habitat. Recently burnt habitat is thought to provide food for quokkas and long unburnt habitat provides refuge from predation.

The quokka (Setonix brachyurus Quoy & Gaimard 1830) is a medium-sized, macropodid marsupial that is endemic to the mesic, south-western corner of Australia. While being a tourist icon on Rottnest Island, the species is threatened with extinction. It has been intensively studied on Rottnest Island in the 1960s and 1970s, however very little is known of its ecology on the mainland. Additionally the insular and mainland environments are extremely different suggesting that ecological differences between the two populations are likely. Consequently, this study sought to determine the basic autecology of the quokka and identify what factors have attributed to its threatened conservation status. The northern jarrah forest of Western Australia was selected as the study region due to it being at the northern limit of extant quokka distribution and because it was thought that the factors threatening the quokka would be exacerbated there. Fossil deposits suggest that the quokka originally occupied an area of approximately 49,000 km2 in the south-western corner of Australia. Historical literature show that they were widespread and abundant when Europeans colonised the region in 1829 but a noticeable and dramatic decline occurred a century later. The arrival of the red fox to the region coincided almost exactly with this decline and so it was probably ultimately responsible. Continued predation by both it and the feral cat are likely to have continued the decline, along with habitat destruction and modification through altered fire regimes. Specific surveys and literature searches show that since the 1950s, the area occupied by the quokka has declined by 45% and since 1990 by 29%. Based on the criteria of the IUCN (Hilton-Taylor 2000), the conservation status of the quokka should remain as vulnerable. An endangered status may be more applicable if the quokkas restriction to patches through its existence as a metapopulation is considered. Trapping of eight sites supporting quokka populations in the mid-1990s revealed three sites now locally extinct despite the ongoing, six year old, fox control programme. Another three are at serious risk of extinction. Extant population sizes ranged from one to 36 and population density ranged from 0.07 to 4.3 individuals per hectare. This is considered to be below the carrying capacity of each site. The overall quokka population size in the northern jarrah forest may be as low as 150 adult individuals, of which half are likely to be female. Even the largest extant populations are highly susceptible to stochastic extinction events. This small size was surprising considering the six year old, introduced predator control programme. Historically, the restriction to discrete habitat patches, the occasional inter-patch movement, the lack of correlation between the dynamics of each population and reports of frequent localised extinctions and colonisations suggest that the quokka population once existed as part of a classic metapopulation. The massive decline of the quokka in the 1930s pushed the metapopulation structure into a non-equilibrium state such that today, the extant populations are the terminal remnants of the original classic metapopulation. Wild mainland quokkas breed throughout the year. A significant reduction in the number of births occurs over summer and this coincides with a decline in female body weight. Despite this, the mainland quokka is relatively fecund and is able to wean two offspring per year. The level of recruitment from pouch young to independence was low and this may explain the apparent lack of population increase following the initiation of fox control. A total of 56 trapped quokkas were fitted with a radio collar. Mean home range size for quokkas was 6.39 ha with a core range of 1.21 ha and this was negatively related to population density. Male home ranges were larger than females but not significantly when the sexual size dimorphism was considered. Nocturnal ranges were larger than diurnal ranges reflecting nocturnal departures from the swamp refugia. Home range sizes varied seasonally, probably due to changes in the distance required to move to obtain sufficient nutrients and water over the dry summer compared to the wet winter and spring. Telemetry confirmed trapping results that showed no movement between swamps or populations. Home range centres shifted to the periphery of the swamp following the winter inundation and this may increase the species susceptibility to predation. The lack of dispersal is probably caused by quokka populations existing below carrying capacity and following selection for philopatry under the threat of predation for dispersing individuals. Without dispersal to recolonise or rescue unpopulated patches, the collapse of the original quokka metapopulation appears to have occurred. On a macrohabitat scale, the quokka in the northern jarrah forest is restricted to Agonis swamp shrubland habitats that form in the open, upper reaches of creek systems on the western side of the forest. This restriction was probably initially due to the high water requirements of the quokka but is likely to have been exacerbated by increased predation pressure since the arrival of the fox. On a microhabitat scale, the quokka is a habitat specialist, preferring early seral stage swamp habitats, probably for foraging, as part of a mosaic of old age swamp that provides refuge. Despite the six year old, introduced predator control programme, foxes and cats are still the major cause of mortality to quokkas. Road kills was the other identifiable cause. Individuals alive at the start of the study had an 81% chance of staying alive until the end. The likelihood of dying was minimised by grouping together with conspecifics, maximising home range size and maximising the time spent within the swampy refuge. Current rates of adult and juvenile survivorship should allow population recovery and so it seems pouch young mortality, reflected by low recruitment, has inhibited the anticipated population increase following predator control. The confounding effect of inadequate unbaited controls meant that little statistical evidence was available on the impact of introduced predators on the quokka, however the models provided support for earlier hypotheses of these. The presence of a quokka population at a site was related to the amount of poison baits delivered ??? reflecting predation pressure, the average age of the swamp and a mosaic of early and late seral stages within the swamp habitat. Recently burnt habitat is thought to provide food for quokkas and long unburnt habitat provides refuge from predation.

The quokka (Setonix brachyurus Quoy & Gaimard 1830) is a medium-sized, macropodid marsupial that is endemic to the mesic, south-western corner of Australia. While being a tourist icon on Rottnest Island, the species is threatened with extinction. It has been intensively studied on Rottnest Island in the 1960s and 1970s, however very little is known of its ecology on the mainland. Additionally the insular and mainland environments are extremely different suggesting that ecological differences between the two populations are likely. Consequently, this study sought to determine the basic autecology of the quokka and identify what factors have attributed to its threatened conservation status. The northern jarrah forest of Western Australia was selected as the study region due to it being at the northern limit of extant quokka distribution and because it was thought that the factors threatening the quokka would be exacerbated there. Fossil deposits suggest that the quokka originally occupied an area of approximately 49,000 km2 in the south-western corner of Australia. Historical literature show that they were widespread and abundant when Europeans colonised the region in 1829 but a noticeable and dramatic decline occurred a century later. The arrival of the red fox to the region coincided almost exactly with this decline and so it was probably ultimately responsible. Continued predation by both it and the feral cat are likely to have continued the decline, along with habitat destruction and modification through altered fire regimes. Specific surveys and literature searches show that since the 1950s, the area occupied by the quokka has declined by 45% and since 1990 by 29%. Based on the criteria of the IUCN (Hilton-Taylor 2000), the conservation status of the quokka should remain as vulnerable. An endangered status may be more applicable if the quokkas restriction to patches through its existence as a metapopulation is considered. Trapping of eight sites supporting quokka populations in the mid-1990s revealed three sites now locally extinct despite the ongoing, six year old, fox control programme. Another three are at serious risk of extinction. Extant population sizes ranged from one to 36 and population density ranged from 0.07 to 4.3 individuals per hectare. This is considered to be below the carrying capacity of each site. The overall quokka population size in the northern jarrah forest may be as low as 150 adult individuals, of which half are likely to be female. Even the largest extant populations are highly susceptible to stochastic extinction events. This small size was surprising considering the six year old, introduced predator control programme. Historically, the restriction to discrete habitat patches, the occasional inter-patch movement, the lack of correlation between the dynamics of each population and reports of frequent localised extinctions and colonisations suggest that the quokka population once existed as part of a classic metapopulation. The massive decline of the quokka in the 1930s pushed the metapopulation structure into a non-equilibrium state such that today, the extant populations are the terminal remnants of the original classic metapopulation. Wild mainland quokkas breed throughout the year. A significant reduction in the number of births occurs over summer and this coincides with a decline in female body weight. Despite this, the mainland quokka is relatively fecund and is able to wean two offspring per year. The level of recruitment from pouch young to independence was low and this may explain the apparent lack of population increase following the initiation of fox control. A total of 56 trapped quokkas were fitted with a radio collar. Mean home range size for quokkas was 6.39 ha with a core range of 1.21 ha and this was negatively related to population density. Male home ranges were larger than females but not significantly when the sexual size dimorphism was considered. Nocturnal ranges were larger than diurnal ranges reflecting nocturnal departures from the swamp refugia. Home range sizes varied seasonally, probably due to changes in the distance required to move to obtain sufficient nutrients and water over the dry summer compared to the wet winter and spring. Telemetry confirmed trapping results that showed no movement between swamps or populations. Home range centres shifted to the periphery of the swamp following the winter inundation and this may increase the species susceptibility to predation. The lack of dispersal is probably caused by quokka populations existing below carrying capacity and following selection for philopatry under the threat of predation for dispersing individuals. Without dispersal to recolonise or rescue unpopulated patches, the collapse of the original quokka metapopulation appears to have occurred. On a macrohabitat scale, the quokka in the northern jarrah forest is restricted to Agonis swamp shrubland habitats that form in the open, upper reaches of creek systems on the western side of the forest. This restriction was probably initially due to the high water requirements of the quokka but is likely to have been exacerbated by increased predation pressure since the arrival of the fox. On a microhabitat scale, the quokka is a habitat specialist, preferring early seral stage swamp habitats, probably for foraging, as part of a mosaic of old age swamp that provides refuge. Despite the six year old, introduced predator control programme, foxes and cats are still the major cause of mortality to quokkas. Road kills was the other identifiable cause. Individuals alive at the start of the study had an 81% chance of staying alive until the end. The likelihood of dying was minimised by grouping together with conspecifics, maximising home range size and maximising the time spent within the swampy refuge. Current rates of adult and juvenile survivorship should allow population recovery and so it seems pouch young mortality, reflected by low recruitment, has inhibited the anticipated population increase following predator control. The confounding effect of inadequate unbaited controls meant that little statistical evidence was available on the impact of introduced predators on the quokka, however the models provided support for earlier hypotheses of these. The presence of a quokka population at a site was related to the amount of poison baits delivered ??? reflecting predation pressure, the average age of the swamp and a mosaic of early and late seral stages within the swamp habitat. Recently burnt habitat is thought to provide food for quokkas and long unburnt habitat provides refuge from predation.