Dasyurus Hallucatus Research Articles

Monitoring indicates rapid and severe decline of native small mammals in Kakadu National Park, northern Australia

Context. Australia has a lamentable history of mammal extinctions. Until recently, the mammal fauna of northern Australia was presumed to have been spared such loss, and to be relatively intact and stable. However, several recent studies have suggested that this mammal fauna may be undergoing some decline, so a targeted monitoring program was established in northern Australia’s largest and best-resourced conservation reserve. Aims. The present study aims to detect change in the native small-mammal fauna of Kakadu National Park, in the monsoonal tropics of northern Australia, over the period of 1996–2009, through an extensive monitoring program, and to consider factors that may have contributed to any observed change. Methods. The small-mammal fauna was sampled in a consistent manner across a set of plots established to represent the environmental variation and fire regimes of Kakadu. Fifteen plots were sampled three times, 121 plots sampled twice and 39 plots once. Resampling was typically at 5-yearly intervals. Analysis used regression (of abundance against date), and Wilcoxon matched-pairs tests to assess change. For resampled plots, change in abundance of mammals was related to fire frequency in the between-sampling period. Key results. A total of 25 small mammal species was recorded. Plot-level species richness and total abundance decreased significantly, by 54% and 71%, respectively, over the course of the study. The abundance of 10 species declined significantly, whereas no species increased in abundance significantly. The number of ‘empty’ plots increased from 13% in 1996 to 55% in 2009. For 136 plots sampled in 2001–04 and again in 2007–09, species richness declined by 65% and the total number of individuals declined by 75%. Across plots, the extent of decline increased with increasing frequency of fire. The most marked declines were for northern quoll, Dasyurus hallucatus, fawn antechinus, Antechinus bellus, northern brown bandicoot, Isoodon macrourus, common brushtail possum, Trichosurus vulpecula, and pale field-rat, Rattus tunneyi. Conclusions. The native mammal fauna of Kakadu National Park is in rapid and severe decline. The cause(s) of this decline are not entirely clear, and may vary among species. The most plausible causes are too frequent fire, predation by feral cats and invasion by cane toads (affecting particularly one native mammal species). Implications. The present study has demonstrated a major decline in a key conservation reserve, suggesting that the mammal fauna of northern Australia may now be undergoing a decline comparable to the losses previously occurring elsewhere in Australia. These results suggest that there is a major and urgent conservation imperative to more precisely identify, and more effectively manage, the threats to this mammal fauna.

The original mammal fauna of the Pilbara biogeographic region of north-western Australia

The hills and ranges of the Pilbara contain large numbers of caves, but only a miniscule proportion of these holds mammal remains that can be used to reconstruct the original (i.e. pre-European) fauna. During two field seasons in 1985 and 2004, only 12 sites with bones were discovered. Material from three other sites lodged in the collections of the Western Australian Museum was also used. Thirty-six native mammal species plus the introduced House Mouse were identified from cave surface remains. Compared with the fauna known from live-caught specimen records and the results of the Pilbara Biodiversity Survey, rodent species are comprehensively represented among the remains, dasyurid marsupials and bandicoots are moderately well represented, macropodoids are poorly represented, and bats (except two cave-roosting species) hardly represented at all. Results of this study indicate that the Central Rock-rat (Zyzomys pedunculatus), and probably the Golden-backed Tree-rat (Mesembriomys macrurus), originally occurred throughout the Pilbara ranges. Chuditch (Dasyurus geoffroii) is recorded from the Pilbara for the first time, suggesting that it may have occurred in the lowlands, while Northern Quoll (D. hallucatus) occupied the ranges. New records of Melomys burtoni and Pseudomys fieldi represent substantial extensions of geographic range. Overall, these results confirm the Pilbara as the western outpost of several northern mammal species, but show that the original fauna is less distinctive than previously thought, with a higher proportion of species widespread in the arid zone.

Acrosomal integrity, viability, and DNA damage of sperm from dasyurid marsupials after freezing or freeze drying

Dasyurids are a diverse group of Australian native carnivores and insectivores that contains several threatened species. Despite successful cryopreservation of sperm from several marsupials, only 3% postthaw motility is reported for dasyurid marsupials. This study examined sperm preservation in the fat-tailed dunnart ( Sminthopsis crassicaudata), an experimental model, with supplementary observations on the eastern quoll ( Dasyurus viverrinus) and northern quoll ( Dasyurus hallucatus). In S. crassicaudata, a toxicity trial demonstrated that incubation with up to 40% glycerol did not reduce sperm viability, suggesting that glycerol is not toxic to dasyurids. On the basis of this finding, S. crassicaudata, D. viverrinus, and D. hallucatus sperm were extended to a final concentration of 20% or 40% glycerol in Tris-citrate fructose and frozen in liquid nitrogen vapor. Postthaw sperm from all three species were nonmotile, and vital staining (SYBR14 and propidium iodide) indicated that sperm were nonviable. However, there was no evidence suggesting disruption of normal gross morphology or loss of acrosomal integrity when assessed by Bryan's staining. After freeze drying, Bryan's staining indicated that approximately 80% of S. crassicaudata sperm had normal acrosomes and no head loss. Despite being nonviable, terminal deoxynucleotidyl transferase–mediated dUTP nick-end labeling showed that S. crassicaudata sperm frozen in 40% glycerol or freeze-dried had no DNA damage compared with fresh controls. This study has described a method for preservation of the dasyurid sperm nuclei, but continued studies are required to achieve viable motile sperm and establish tools for the long-term storage of dasyurid sperm.

Island populations have high conservation value for northern Australia's top marsupial predator ahead of a threatening process

AbstractThe rarity of top predators has been identified as a contributing factor in the collapse of entire ecological systems. Elucidating the ecology, evolutionary potential and population response of species before a threatening process requires a combination of measures of phenotypic variation, demography and genetic diversity using an array of markers. Here we use such information to determine the population structure and its conservation implications for a keystone marsupial carnivore in Western Australia, the northern quoll Dasyurus hallucatus, ahead of the spread of the exotic and poisonous cane toad Chaunus marinus from the east. The western populations occur in two discrete geographic regions on the mainland, the Kimberley and Pilbara, separated by the arid Great Sandy Desert, and on several continental islands. Both mitochondrial DNA sequences and 11 nuclear microsatellite loci reveal clear differentiation of the Kimberley and Pilbara regions. Offshore islands with permanent sea‐channels from the mainland show reduced diversity and were genetically distinct indicating genetic isolation, whereas those separated from the mainland by very shallow channels were more similar to the adjacent mainland populations, suggesting on‐going gene flow. There was little indication that any population within the distribution of the species had experienced recent declines but there was marked variation in sexual dimorphism suggesting diversity in demographic performance. These populations in Western Australia differ from those remaining to the east in Queensland and the Northern Territory, in both genetic structure and demographic parameters and represent the last intact populations in Australia that have not experienced major declines concomitant with the spread of the cane toad. Consequently, the genetic and demographic flexibility recorded by this study provides guidance for the conservation and management of a major marsupial predator before and during its potential decline associated with an invasive, threatening prey species.

143. THE FIRST EVIDENCE OF HIGH SUSCEPTIBILITY TO COLD SHOCK BY THE SPERMATOZOA OF A MARSUPIAL, THE FAT TAILED DUNNART (SMINTHOPSIS CRASSICAUDATA)

Carnivorous marsupials are native Australian predators including the highly threatened northern quoll (Dasyurus hallucatus) and Tasmanian devil (Sarcophilus harrisii). These species are currently actively managed in captive populations but assisted reproductive techniques such as gamete banking may also contribute to their conservation. Previous studies on a model dasyurid, the fat tailed dunnart (Sminthopsis crassicaudata), have found that spermatozoa do not survive freezing and thawing using a variety of freezing protocols and cryoprotectants. We have re-examined cold shock to investigate problems with sperm cryopreservation in S. crassicaudata. Epididymal spermatozoa were rapidly cooled to 0.5ºC in a pre-cooled tube held in an iced water slurry and upon re-warming the spermatozoa were non-motile (n=6). The addition of up to 20% egg yolk, which is considered protective to the spermatozoa of cold shock sensitive eutherians, did not improve the outcome (n=6). Similarly when S. crassicaudata spermatozoa were rapidly cooled to 4ºC, just 2% remained motile upon re-warming (n=10). However when spermatozoa were combined with at least 10% egg yolk and rapidly cooled to 4ºC only small reductions in motility were observed upon rewarming (n≥8). In order to achieve motile spermatozoa at 0ºC, controlled rate cooling at 0.5ºC/minute was examined. In the absence of egg yolk there was a decline in the percentage of motile spermatozoa below 4ºC (n=6). However if spermatozoa were combined with at least 10% egg yolk there was no significant loss of motility at temperatures as low as 0ºC (n=6). This study has revealed that at least one species of marsupial is highly susceptible to cold shock. These paradigm shifting findings give direction to future experiments aiming to develop a robust technique for sperm preservation in endangered dasyurids.

156 ENZYMATIC DISSOCIATION AND VITRIFICATION OF PREANTRAL FOLLICLES FROM THREATENED CARNIVOROUS MARSUPIALS

The mammalian ovary contains a rich resource of immature preantral follicles present regardless of cycle stage or seasonality. These follicles can be harvested enzymatically and are preserved more successfully than larger, more mature follicles. Thus, the collection and storage of preantral follicles is an applicable technique for the opportunistic harvesting of ovarian tissue from wildlife for the purpose of genebanking. This study examined the potential of such tools for the conservation of two endangered Australian carnivorous marsupials (dasyurids): the northern quoll, Dasyurus hallucatus, and the Tasmanian devil, Sarcophilus harrisii. The fat-tailed dunnart, Sminthopsis crassicaudata, is a representative model dasyurid with the typical attributes of large gametes (220 μm oocytes) and short polyovular reproductive cycles. Ovarian tissue was dissociated with 0.05–0.1% collagenase and 0.01–0.02% DNase in DMEM (all Sigma-Aldrich, St. Louis, USA) for up to 30 min before being neutralized with DMEM +10% fetal calf serum (FCS, Trace Biosciences, Castle Hill, Australia). Survival was determined using membrane permeability stains targeted to the nucleus (SYBR14 and propidium iodide, Molecular Probes, Carlsbad, CA, USA) or cytoplasm (trypan blue, Sigma) and assessed with a four-level survival score (1 = 100% live, 2 = 50–99% live, 3 = 1–49% live, 4 = 0% live) for each stage of follicular maturation: primordial (PF), early (EF), and late (LF) primary and secondary (SF) follicles (n = 100 each). Dissociated EF and LF (n = 45) from S. crassicaudata were vitrified with a three-step medium composed of up to 18% DMSO and ethylene glycol in 1 m sucrose (all Sigma; Vajta G et al. 1998 Mol. Reprod. Dev. 51, 53–58), and post-thaw viability was confirmed with trypan blue. All experiments were carried out on at least three individuals; values are presented as mean ± SEM and differences were determined with ANOVA and post hoc Tukey tests. In all species, 100% of PF were highly viable (score 1) and there was a significant decrease (P < 0.05) in the percentage of highly viable PF, EF, and LF when compared with SF, which were most commonly observed with minor damage (score 2). An incomplete layer of granulosa cells was observed in 11.92 ± 1.08% of freshly dissociated S. crassicaudata follicles. This increased to 30.34 ± 12.22% after preservation. Of the surrounded follicles, 48.40 ± 14.09% were classified as score 1 or 2 after vitrification. Nonviable staining of the oocyte was observed only in naked oocytes. Although these protocols demonstrate a reliable method for follicle collection and preliminary evidence for tools allowing the preservation of female gametes, further optimization is recommended. The demonstrated techniques are highly applicable to genebanking because they utilize material from unstimulated ovaries, as is regularly seen with tissues collected opportunistically from anestrus, ill, or old wildlife. This study was made possible by the cooperation and collection of tissues by the staff from Territory Wildlife Park, Northern Territory, and Tamara Keeley from Western Plains Zoo, New South Wales.

Effects of founder events on the genetic variation of translocated island populations: implications for conservation management of the northern quoll

Translocation is a strategy commonly used to maximize the persistence of threatened species, but it may sometimes lead to undesirable genetic consequences. The northern quoll (Dasyurus hallucatus) is a carnivorous marsupial that is critically endangered in Australia’s Northern Territory due to rapid population declines in areas recently colonized by the exotic cane toad Chaunus [Bufo] marinus. In 2003, 64 quolls were translocated to two offshore islands to establish insurance populations and reduce the species’ risk of extinction. In this study, we assessed genetic diversity at five microsatellite loci in the translocated populations, two endemic islands and three mainland populations. In the short-term (three generations), the translocated populations showed a slight but non-significant reduction in genetic diversity (A = 4.1–4.2; He = 0.56–0.59) compared to the mainland source populations (A = 5.0–8.4; He = 0.56–0.71). In comparison, high genetic erosion was observed in the endemic island populations (A = 1.5–2.9; He = 0.11–0.34). Genetic bottlenecks were detected on both endemic islands and in one mainland population, indicating recent reductions in population size. Our results are consistent with previous studies describing greater losses of genetic diversity on islands compared to mainland populations. Divergence from ancestral allele frequencies in the translocated populations also suggests effects due to founder events. This study, although short-term, highlights the importance of continued monitoring for detecting changes in genetic diversity over time and makes a significant contribution to our understanding of the effects of founder events on island populations.

Changes in mammal populations in relatively intact landscapes of Kakadu National Park, Northern Territory, Australia

A previous study (Braithwaite & Muller 1997) reported substantial declines in mammal abundance over the period 1986–1993 for a large study area (300 km2) within Kakadu National Park in the tropical savannas of northern Australia. This decline was reported as being a ‘natural’ response to fluctuating groundwater levels, driven by runs of poor wet seasons. We resampled mammals in this area in 1999, following a series of unusually good wet seasons, and examined the prediction that mammal numbers should have recovered. Increases in abundance were evident for four species: the smallest dasyurid (red-cheeked dunnart Sminthopsis virginiae) and the three smallest rodents (delicate mouse Pseudomys delicatulus, western chestnut mouse Pseudomys nanus and grassland melomys Melomys burtoni). In contrast, the abundance of all mammals combined and that for seven individual mammal species (northern quoll Dasyurus hallucatus, fawn antechinus Antechinus bellus, common brushtail possum Trichosurus vulpecula, northern brown bandicoot Isoodon macrourus, dusky rat Rattus colletti, black-footed tree-rat Mesembriomys gouldii and pale field rat Rattus tunneyi) continued to decline. The decline in abundance of these mammal species is consistent with limited observations elsewhere in northern Australia. Although far from conclusive, these observations suggest that the biota of the vast relatively undisturbed tropical savannas can no longer be assumed to be intact nor safe. Further research is needed to test this possible pattern of decline and, if confirmed, to identify and ameliorate the processes contributing to it.

Acrosome stability in the spermatozoa of dasyurid marsupials

The spermatozoa of most marsupials lack nuclear stabilising disulfide-bonded protamines found in eutherian mammals. However, disulfide stabilisation has been observed in the acrosome of macropodid (Macropus eugenii) and phalangerid (Trichosurus vulpecula) marsupials. As a result this organelle, which is normally fragile in eutherian mammals, is robust and able to withstand physical and chemical challenge in these marsupials. The present study examined acrosomal characteristics of the spermatozoa of three dasyurid marsupials; the fat-tailed dunnart (Sminthopsis crassicaudata), eastern quoll (Dasyurus viverrinus) and northern quoll (Dasyurus hallucatus). In all species examined Bryan's staining demonstrated that significant acrosomal loss occurred following physical challenge with osmotic stress, cryopreservation without cryoprotectant and exposure to detergent (Triton-X). Bromobimane staining indicated that the acrosomes of dasyurids lacked stabilising disulfide bonds. As reported for the wallaby and possum, calcium ionophore (A23187) did not induce the acrosome reaction-like exocytosis in dasyurid spermatozoa but treatment with diacylglycerol (DiC8) caused significant acrosome loss at concentrations similar to those effective for other marsupials. The present study found that the spermatozoa of dasyurids are more sensitive to physical challenge than the previously-studied marsupials and we suggest that this is due to the absence of acrosomal stabilising disulfide bonds.

Digital cranial endocast of Pucadelphys andinus, a Paleocene metatherian

ABSTRACT A digital cranial endocast of Pucadelphys andinus, a Paleocene metatherian from Bolivia, is described. This is the first cranial endocast described for the taxon and the only one (to date) from a stem marsupial (i.e., non-marsupial metatherian). The Pucadelphys endocast is compared with others generated from skulls from six taxa of extant marsupials (Monodelphis domestica, Didelphis virginiana, Dasyurus hallucatus, Vombatus ursinus, Phascolarctos cinereus, and Dromiciops australis). The Pucadelphys endocast is generally similar to the didelphid marsupial Monodelphis. However, the olfactory bulb casts and the cerebellar space (approximated using vermis cast length) of Pucadelphys are relatively large in comparison to those of these extant marsupials. The cerebral hemisphere casts of Pucadelphys are dorsoventrally thin in comparison to those of the extant marsupials examined here. With other dimensions of the cerebral hemisphere casts being comparable between Pucadelphys and the extant marsupials, this suggests that the overall volume of the cerebral hemispheres was smaller in Pucadelphys. Thus, two possible synapomorphies for crown Marsupialia are a decrease in size of the cerebellar space and an increase in cerebral hemisphere volume.

Combined Mitochondrial and Nuclear DNA Sequences Resolve the Interrelations of the Major Australasian Marsupial Radiations

Australasian marsupials include three major radiations, the insectivorous/carnivorous Dasyuromorphia, the omnivorous bandicoots (Peramelemorphia), and the largely herbivorous diprotodontians. Morphologists have generally considered the bandicoots and diprotodontians to be closely related, most prominently because they are both syndactylous (with the 2nd and 3rd pedal digits being fused). Molecular studies have been unable to confirm or reject this Syndactyla hypothesis. Here we present new mitochondrial (mt) genomes from a spiny bandicoot (Echymipera rufescens) and two dasyurids, a fat-tailed dunnart (Sminthopsis crassicaudata) and a northern quoll (Dasyurus hallucatus). By comparing trees derived from pairwise base-frequency differences between taxa with standard (absolute, uncorrected) distance trees, we infer that composition bias among mt protein-coding and RNA sequences is sufficient to mislead tree reconstruction. This can explain incongruence between trees obtained from mt and nuclear data sets. However, after excluding major sources of compositional heterogeneity, both the "reduced-bias" mt and nuclear data sets clearly favor a bandicoot plus dasyuromorphian association, as well as a grouping of kangaroos and possums (Phalangeriformes) among diprotodontians. Notably, alternatives to these groupings could only be confidently rejected by combining the mt and nuclear data. Elsewhere on the tree, Dromiciops appears to be sister to the monophyletic Australasian marsupials, whereas the placement of the marsupial mole (Notoryctes) remains problematic. More generally, we contend that it is desirable to combine mt genome and nuclear sequences for inferring vertebrate phylogeny, but as separately modeled process partitions. This strategy depends on detecting and excluding (or accounting for) major sources of non-historical signal, such as from compositional non-stationarity. [Base composition; combined data; marsupial; mitochondrial genome; phylogeny.].

Home range and spatial organization of the marsupial carnivore, Dasyurus maculatus maculatus (Marsupialia: Dasyuridae) in south‐eastern Australia

AbstractThe tiger quoll or spotted‐tailed quoll Dasyurus maculatus, a nationally threatened species, is the largest surviving carnivorous marsupial on mainland Australia and the sole surviving member of the genus in south‐eastern mainland Australia. Live‐trapping and radio‐tracking studies at three sites in south‐eastern Australia found that tiger quolls were solitary, except when mating, and that male and female tiger quolls occupied very large home ranges, both during and after the breeding season. The mean size of the home range of male tiger quolls (minimum convex polygon (MCP) 1755.4 ha, kernel 3761.7 ha) was significantly larger than the mean size of the home range of females (MCP 495.9 ha, kernel 1113.0 ha). Adult female tiger quolls displayed intrasexual territoriality throughout the year, but they seemed to tolerate the presence of female offspring. Male tiger quolls were not territorial and their home ranges overlapped both with other males and with females throughout the year. Males were recorded regularly moving back and forth between a number of female territories during the breeding season. The spatial organization of the tiger quoll recorded in this study differs markedly from that of the eastern quoll Dasyurus viverrinus and the Tasmanian devil Sarcophilus harrisii, but is similar to that of the western quoll D. geoffroii, northern quoll D. hallucatus and brush‐tailed phascogale Phascogale tapoatafa. The spatial organization and home‐range size of the tiger quoll dictate that conservation of the species requires management across all land tenures at the landscape level.

Spatial and social organization of a carnivorous marsupial Dasyurus hallucatus (Marsupialia: Dasyuridae)

AbstractThe northern quoll Dasyurus hallucatus is a sexually dimorphic carnivorous marsupial found in northern Australia. Despite males weighing up to 1120 g, in at least some populations all males die after mating. Radio‐tracking and live‐trapping at a lowland savanna site in Kakadu National Park indicated that females occupied home ranges averaging 35 ha with intra‐sexually exclusive denning areas. There was some overlap of foraging ranges when the density was 3–4 females/km2, but no overlap during periods of lower population density (1–2 females/km2). Male home‐range size may be similar to females before the mating season, but expands during the mating season to > 100 ha to overlap extensively with several female ranges and numerous other male ranges. Despite this range overlap, both sexes were solitary. Even during the mating period, males denned on average 0.27 km from females during the day. During the mating period, each female was visited by at least one to four males per night. During this period, the increase in scat deposition in prominent positions in the landscape and the simultaneous increase in sternal gland activity of the males suggest the importance of olfactory communication to advertise the presence and sexual status of individuals. Males adopted a roving strategy, regularly visiting several widely spaced females in rapid succession, presumably to monitor the onset of oestrus. This intense physical effort during the mating period is likely to be a major contributor to the physiological decline of the males and subsequent die‐off after the mating period. The marked sexual dimorphism of D. hallucatus may be the result of selection for larger, wider‐ranging males in a promiscuous mating system and for energetically efficient smaller females, as females rear the young alone.

Changes in mammal populations in relatively intact landscapes of Kakadu National Park, Northern Territory, Australia

AbstractA previous study (Braithwaite & Muller 1997) reported substantial declines in mammal abundance over the period 1986–1993 for a large study area (300 km2) within Kakadu National Park in the tropical savannas of northern Australia. This decline was reported as being a ‘natural’ response to fluctuating groundwater levels, driven by runs of poor wet seasons. We resampled mammals in this area in 1999, following a series of unusually good wet seasons, and examined the prediction that mammal numbers should have recovered. Increases in abundance were evident for four species: the smallest dasyurid (red‐cheeked dunnart Sminthopsis virginiae) and the three smallest rodents (delicate mouse Pseudomys delicatulus, western chestnut mouse Pseudomys nanus and grassland melomys Melomys burtoni). In contrast, the abundance of all mammals combined and that for seven individual mammal species (northern quoll Dasyurus hallucatus, fawn antechinus Antechinus bellus, common brushtail possum Trichosurus vulpecula, northern brown bandicoot Isoodon macrourus, dusky rat Rattus colletti, black‐footed tree‐rat Mesembriomys gouldii and pale field rat Rattus tunneyi) continued to decline. The decline in abundance of these mammal species is consistent with limited observations elsewhere in northern Australia. Although far from conclusive, these observations suggest that the biota of the vast relatively undisturbed tropical savannas can no longer be assumed to be intact nor safe. Further research is needed to test this possible pattern of decline and, if confirmed, to identify and ameliorate the processes contributing to it.

Semelparity in a large marsupial.

Complete mortality of males after mating is known in several small dasyurid and didelphid species (up to 300g) and has previously been suggested to be a consequence of their small size and their inability to sequester sufficient fat reserves for an intense rut in the winter. Males of these species use increased corticosteroid levels to allow protein catabolism, enabling them to support their mating effort with other body reserves. However, increased corticosteroid levels have negative consequences such as anaemia, gastrointestinal ulceration, immune suppression and disease. The Australian dasyurid Dasyurus hallucatus shows complete male die off after mating in tropical savannah, yet males of this species may weigh as much as 1120 g and continue to eat during the rut. Die off in D. hallucatus shows many similarities to that in the smaller species including weight loss, fur loss, parasite infestation, increased testosterone levels and anaemia. However, in contrast to smaller species, there is no evidence of elevated corticosteroid levels or gastrointestinal ulceration. Consequently, the phenomenon of male die off after mating lacks a universal explanation.

Reproduction and demography of the northern quoll, Dasyurus hallucatus, in the lowland savanna of northern Australia

Reproduction and demography of the northern quoll, Dasyurus hallucatus, was assessed using live-trapping and radio-tracking at a lowland savanna site in Kakadu National Park between 1992 and 1995. Northern quolls were found to exhibit a highly synchronous breeding cycle with mating occurring late May/early June. The greatest peak in apparent male abundance was during the mating season, but this was probably due to their increased mobility at this time. Males demonstrated complete post-mating mortality, with most males dying within two weeks of mating. Young were born in mid to late June with the mean initial litter size for 8-teated females being 7.3. First-year mothers were more likely to have predominantly male litters, whereas second-year mothers had more females. The survival rate of pouch young was high but, once young were left in the den, survival was poor. Peaks in abundance for both sexes occurred when the juveniles first entered the trappable population in November each year. Mortality of females was high, with only 27% of females surviving to wean a second litter, and none bore a third. The most common proximate cause of adult mortality was predation. Increased predation pressure on adults, in particular due to a reduction in shelter and ground cover from too-frequent fire may make northern quolls vulnerable to local extinction in lowland savanna.

Parasites of the northern quoll, Dasyurus hallucatus (Marsupialia:Dasyuridae) in tropical savanna, Northern Territory

The ectoparasites of northern quolls, Dasyurus hallucatus, are reported from 79 animals live-trapped at Kapalga Research Station, Kakadu National Park, during 1992–95. The ecto- and endoparasites are reported from 62 dead D. hallucatus during the same period; these were mostly road-kills collected from an 88-km section of the Arnhem Highway between Jabiru and the Northern Entry Station of Kakadu National Park. Tissues from 28 of the road-kills were examined histologically. Additionally, 214 scat samples were examined for ecto- and endoparasites. Seven species of ectoparasite, including two species of tick, a larval trombiculid mite, a louse and two (possibly three) species of flea, and 17 species of endoparasite including a trematode, a larval cestode, 13 species of nematode, a larval pentastome and a protozoan were recorded from D. hallucatus. Sarcocystis sp. was found in tissues but neither Toxoplasma gondii nor Trichinella pseudospiralis were detected in histological sections or tissue digests. Ticks, mites and nematodes were found in scats. The tick Haemaphysalis bancrofti, the flea Echidnophaga aranka and possibly E. ambulans, and the nematodes Mackerrastrongylus peramelis and Cylicospirura heydoni represent new host records for D. hallucatus. Although parasitism was common in D. hallucatus, few individuals harboured large burdens. Consequently, it appears unlikely that parasitism is a major factor contributing to the decline of northern quolls in this region.

Variability and differentiation of microsatellites in the genus Dasyurus and conservation implications for the large Australian carnivorous marsupials

All four species of Australian quolls (Dasyurusspecies) have declined since European settlement in terms of bothrange and population numbers. Six highly polymorphic simplesequence repeats (CAn microsatellites) were used to estimate thegenetic variability and population differentiation within andamong twenty populations (including museum specimens from sixpopulations), as a preliminary means of assessing populationconservation status and relative levels of variability withinmembers of the genus. Overall mean expected heterozygosity (HE)and corrected allelic diversity (A′) were highest among westernquolls. Northern quolls, eastern quolls, and tiger quolls werenot significantly different from each other in either measure. There were also significant differences in diversity amongpopulations within species. Genetic differentiation wasestimated by a number of methods and showed that themicrosatellites used here were useful for defining differencesboth among species and populations. Allele frequency data weresummarised by two-dimensional MDS, which was able to partitionpopulations into distinct species clusters. Similarly, theassignment test was able to assign most individuals to both thecorrect species and population levels. Results of MDS and theassignment test may prove useful in forensic applications. Genetic distance and subdivision between pairs of populationswere assessed by two means based on different mutation models formicrosatellites: infinite alleles model (Nei's D, FST) andstepwise mutation model (Goldstein's δ mu;2, RST). Pairwisemeasures of population subdivision indicate that most populationsshould be conserved as separate management units. We discussresults of these analyses in terms of applications toconservation for each of the four Australian species of quoll andprovide a genetic basis for future population monitoring in thesespecies.

Notes on status, distribution and diet of Northern QuollDasyurus hallucatusin the Mackay-Bowen area, mideastern Queensland

A survey of the declining Northern Quoll Dasyurus hallucatus was conducted in coastal and near-coastal areas between Mackay and Bowen, mideastern Queensland. The survey used incidental records from the public and trapping and sightings from resource management agencies. The species was recorded at a total of 40 separate localities, which were associated mainly with rocky habitats close to permanent water. Preliminary scat analysis indicated that the species is primarily insectivorous, with small mammals consumed only where abundant. Populations of this species on flatland and coastal habitats in the study area appear threatened by continuing broadscale loss of habitat.

Linstowinema, Smales, 1997 (Nematoda : Seuratidae) from dasyurids (Marsupialia : Dasyuridae) from Australia.

Linstowinema edmondsi (Echinonematinae) from Dasyurus hallucatus (Dasyuridae) is redescribed. It can be differentiated from all species of Linstowinema occurring in bandicoots (Peramelidae) in having the first row of cephalic hooks as long as or longer than the second row. L. gracile n. sp. is described from Phascogale tapoatafa and Dasycercus cristicauda, and can be distinguished from all previously described species of Linstowinema in not having a cuticular dilation of the oesophageal region of the body. L. rosamondae n. sp. from Dasykaluta rosamondae, described from females, also lacks the cuticular dilation of the oesophageal region and can be distinguished from L. gracile in having 18-19 rows of body hooks compared with 15. Other Linstowinema spp. for which there is presently insufficient material available for a full description include a single female occurring in Dasyurus viverrinus from Sydney, New South Wales, a single male occurring in Parantechinus bilarni from Kakadu National Park, Northern Territory and three damaged immature males occurring in Sminthopsis leucopus from Timbillica State Forest, New South Wales. Fourth stage larvae of Linstowinema have three rows of cephalic hooks but no body hooks, only spines. Fourth-stage larvae moulting to fifth-stage have body hooks however. This suggests that the genus Linstowinema, with body hooks, may have been derived from the echinomatine genus Inglechina which does not have body hooks.