Golden Bandicoot Research Articles

A review of the Acanthocephala of Australian bandicoots (Peramelidae), with a comment on New Guinean hosts, based on material held in the South Australian museum

ABSTRACT A total of 103 vials of acanthocephalans held in the Australian Helminth Collection of the South Australian Museum whose contents derive from 456 Australian bandicoots (Peramelidae) were examined. The number of individuals of each bandicoot species that had been examined for helminths was determined from the SAM AHC database. None of three individuals of Isoodon auratus were infected. One of 63 individuals of I. fusciventer, 23 of 127 I. macrourus, 35 of 92 I. obesulus, none of 15 Perameles bougainville, 34 of 83 P. gunnii, one of 54 P. nasuta and none of 19 P. pallescens were infected. Nine bandicoots identified only as Peramelinae were also infected. Australiformis semoni (Linstow, 1898) occurred in 78 bandicoots, Plagiorhynchus (Prosthorhynchus) cylindraceus (Goeze, 1782) in 15 bandicoots and one animal, P. gunnii, harboured both species of acanthocephalan. Australiformis semoni normally occurs in bandicoots with occasional infections reported from the brush tailed phascogale Phascogale tapoatafa (Dasyuridae) and the long nosed potoroo Potorous tridactylus (Potoroidae). Plagiorhynchus (P.) cylindraceus is usually found in passerine birds and is also an occasional parasite of bandicoots. Host diet and feeding behaviour are likely determinants of which bandicoot species harbour infection.

Population genomic diversity and structure in the golden bandicoot: a history of isolation, extirpation, and conservation

Using genetic information to develop and implement conservation programs is vital for maintaining biodiversity and ecosystem resilience. Evaluation of the genetic variability within and among remnant populations can inform management of both natural and translocated populations to maximise species’ adaptive potential, mitigate negative impacts of inbreeding, and subsequently minimise risk of extinction. Here we use reduced representation sequencing to undertake a genetic assessment of the golden bandicoot (Isoodon auratus), a threatened marsupial endemic to Australia. The currently recognised taxon consists of three subspecies distributed among multiple natural and translocated populations. After confirming the genetic distinctiveness of I. auratus from two closely related taxa, I. fusciventer and I. macrourus, we identified four genetic clusters within I. auratus. These clusters exhibited substantial genetic differentiation (pairwise FST values ranging from 0.18 to 0.65, pairwise DXY ranging from 0.1 to 0.168), reflecting long-term isolation of some populations on offshore islands and the influence of genetic drift. Mainland natural populations in the Kimberley region had the highest genetic diversity and the largest contribution to overall allelic and gene diversity compared to both natural and translocated island populations. A population translocated to Guluwuru Island in the Northern Territory had the lowest genetic diversity. Our data suggest that island populations can appear genetically unique due to genetic drift and this needs to be taken into account when considering genetic diversity in conservation efforts to maintain overall genetic diversity of the species. We effectively demonstrate how genomic information can guide practical conservation planning, especially when declining species are represented by multiple isolated populations.

Notes on a new method to identify Golden Bandicoot and Northern Brown Bandicoot in the Kimberley region

– The two species of bandicoots that occur in the Kimberley region are particularly difficult to tell apart as they have no distinctive features other than size. A new method is proposed here to identify the two species based on dental measurements, by taking an imprint of the teeth with dental impression paste.

Two species, one island: Retrospective analysis of threatened fauna translocations with divergent outcomes.

Translocations are globally a popular tool used with the intention of improving threatened species conservation and re-establishing ecosystem function. While practitioners strive for successful outcomes the failure rate of translocations continues to be high. We demonstrate how predictive modelling can contribute to more informed decision making and hence potentially improve the success rate of translocation programs. Two species, the Djoongari (Shark Bay mouse) Pseudomys fieldi and the golden bandicoot Isoodon auratus barrowensis, were introduced independently to Doole Island in the Exmouth Gulf of Western Australia. We used population viability analysis to critique the outcomes of these translocations and provide an example of how this tool can be incorporated with expert knowledge to predict likely outcomes of translocations. Djoongari did not establish on the island after seven translocations over nine years, while golden bandicoots established a population after just one release event. Retrospective population viability analysis (of data that was unavailable prior to the translocations) predicted and clarified the reasons behind the outcomes of both translocations. Golden bandicoots have considerably higher demographic plasticity than Djoongari, which were never likely to establish on the island. We conclude that the failure of the Djoongari translocation was due to interactions between sparse habitat, native predators and cyclonic storm surges, whereas golden bandicoots have demonstrated habitat flexibility and an ability to recover from multiple natural disasters. As a result we (1) remind conservation planners of the importance of quantifying likely refuges and habitat availability at release sites, (2) suggest practitioners consider how different threats (including natural disasters) may interact at potential release sites and (3) advocate for the incorporation of predictive modelling during the planning stages of translocations, particularly for conservation introductions where no precedent exists for the species’ survival at a particular location.

Habitat selection by vulnerable golden bandicoots in the arid zone.

In 2010, vulnerable golden bandicoots (Isoodon auratus) were translocated from Barrow Island, Western Australia, to a mainland predator‐free enclosure on the Matuwa Indigenous Protected Area. Golden bandicoots were once widespread throughout a variety of arid and semiarid habitats of central and northern Australia. Like many small‐to‐medium‐sized marsupials, the species has severely declined since colonization and has been reduced to only four remnant natural populations. Between 2010 and 2020, the reintroduced population of golden bandicoots on Matuwa was monitored via capture–mark–recapture data collection, which was used in spatially explicit capture–recapture analysis to monitor their abundance over time. In 2014, we used VHF transmitters to examine the home range and habitat selection of 20 golden bandicoots in the enclosure over a six‐week period. We used compositional analysis to compare the use of four habitat types. Golden bandicoot abundance in the enclosure slowly increased between 2010 and 2014 and has since plateaued at approximately one quarter of the density observed in the founding population on Barrow Island. The population may have plateaued because some bandicoots escape through the fence. Golden bandicoots used habitats dominated by scattered shrubland with spinifex grass more than expected given the habitat's availability. Nocturnal foraging range was influenced by sex and trapping location, whereas diurnal refuge habitat, which was typically under a spinifex hummock with minimal overstory vegetation, was consistent across sex and trapping location. Our work suggests that diurnal refuge habitat may be an important factor for the success of proposed translocations of golden bandicoots.

New evidence of seed dispersal identified in Australian mammals

Context Mammal–seed interactions are important for structuring vegetation communities across a diverse range of ecosystems worldwide. In Australia, mammals are typically considered to be seed predators and to play insignificant roles in seed dispersal. However, very few studies have investigated endozoochorous seed dispersal in Australian species. The translocation of Australian mammals for the purposes of ecosystem restoration is increasing. Digging mammals (i.e. species that dig to obtain food or create shelter) are commonly the focus of these translocations because they are considered to be ecosystem engineers, but an understanding of their role in seed dispersal is lacking. Aims The aim of the present study was to expand the understanding of endozoochory in Australian digging mammals by determining whether seeds consumed by select species remain viable and able to germinate. Methods Scat samples were collected from five digging mammal species, known to consume seeds or fruit, across nine sites in Western and South Australia. The samples were searched for seeds, with the recovered seeds identified and tested for viability and germination capacity. Key results The abundance of intact seeds in scats was generally low, but 70% of the retrieved seeds appeared viable. Five species of seed germinated under laboratory conditions. These seeds were retrieved from bilby (Macrotis lagotis), boodie (Bettongia lesueur), golden bandicoot (Isoodon auratus) and quenda (I. fusciventer) scats. Conclusions Seeds consumed by Australian digging mammals can remain viable and germinate, indicating that digging mammals play a more important role in seed dispersal than previously considered. Implications Digging mammals have the potential to contribute to ecosystem restoration efforts through the dispersal of viable seeds, but there is also a risk that non-native species could be dispersed. These costs and benefits should be considered by practitioners when planning reintroductions of digging mammals.

Industry environmental offset funding facilitates a large multi-species fauna translocation program

Worldwide deterioration in natural communities has led to an increased use of fauna translocations to improve conservation status and restore ecological function. However, few translocation programs have sufficient resources to involve multiple species and destination locations with appropriate threat management and monitoring before and after release. As part of conservation actions to mitigate impacts of the Chevron Australia Gorgon liquefied natural gas project on Barrow Island Nature Reserve, biodiversity offset funding was provided to benefit species impacted by the development. Animals were translocated from three islands to two mainland locations in Western Australia. We aimed to: (1) improve conservation status and security of several threatened species; and (2) contribute to reconstruction of pre-European fauna assemblages. Nine hundred and seventy five individuals of six mammal and two bird species were translocated. These included 421 golden bandicoots (Isoodon auratus barrowensis), 111 spectacled hare-wallabies (Lagorchestes conspicillatus conspicillatus), 105 Barrow Island boodies (Bettongia lesueur ssp. Barrow Island), 104 brushtail possums (Trichosurus vulpecula hypoleucus), 62 mala (Lagorchestes hirsutus ssp. Tanami), 88 djoongari (Pseudomys fieldi), 37 black and white fairy-wrens (Malurus leucopterus edouardi) and 47 spinifexbirds (Eremiornis carteri). Of 11 new populations, only two failed to establish; attributed to native and feral predators. Additional populations of four species of threatened mammal (one of which has now been reduced in conservation listing) and one species of threatened bird were established. To our knowledge, this is the largest translocation effort ever undertaken in Australia and is a rare example of an offset that has provided tangible threatened species benefit.

Environmental determination of body size in mammals: Rethinking ‘island dwarfism’ in the golden bandicoot

AbstractThere are several cases of insular animal species exhibiting dramatic differences in body size when compared with mainland counterparts. Such pronounced morphological changes can arise from divergent selection via differing resource availability, competition or predation pressure. Past studies have not been able to demonstrate a reversal of these morphological changes when populations are removed from their island situation. This study examines the body size response of populations of the Barrow Island ‘dwarf’ subspecies of golden bandicoot (Isoodon auratus barrowensis: Ramsay, 1887) following translocation to an island and mainland site within their former range. Skeletal and mass measurements, body condition and fecundity of released animals and their offspring were compared to data from the source population. When comparing bandicoots born at translocation sites to source populations, males were significantly larger in skeletal size and mass, females were also significantly larger and exhibited higher reproductive output (number, frequency and average mass of pouch young). These effects occurred in a gradient according to environmental conditions, where animals were smallest and least productive at the densely populated source site, larger and more productive on a nearby island, and largest and most productive at a mainland site with some nutritional supplementation. These changes in skeletal size, mass and fecundity took place in the first 1–4 generations (18 months post‐release), suggesting that the response is not explained by natural selection. We posit that the small size of golden bandicoots on Barrow Island (315.8 ± 4.2 g, this study, cf 569.4 ± 19.3 g, mainland) is not a genotypic response to selective pressures, but rather a reversible phenotypic response to more favourable environmental conditions. A reduction in competitive pressures appeared to allow bandicoots to grow to a larger size and mass, and allow greater reproductive output. Ecological processes relating to resource limitation appear to drive ‘island dwarfism’ in I. auratus, and may apply to other insular species with morphological differentiation.

Phylogeography of southern brown and golden bandicoots: implications for the taxonomy and distribution of endangered subspecies and species

Southern brown (Isoodon obesulus) and golden (Isoodon auratus) bandicoots are iconic Australian marsupials that have experienced dramatic declines since European settlement. Conservation management programs seek to protect the remaining populations; however, these programs are impeded by major taxonomic uncertainties. We investigated the history of population connectivity to inform subspecies and species boundaries through a broad-scale phylogeographic and population genetic analysis of Isoodon taxa. Our analyses reveal a major east–west phylogeographic split within I. obesulus/I. auratus, supported by both mtDNA and nuclear gene analyses, which is not coincident with the current species or subspecies taxonomy. In the eastern lineage, all Tasmanian samples formed a distinct monophyletic haplotype group to the exclusion of all mainland samples, indicative of long-term isolation of this population from mainland Australia and providing support for retention of the subspecific status of the Tasmanian population (I. o. affinis). Analyses further suggest that I. o. obesulus is limited to south-eastern mainland Australia, representing a significant reduction in known range. However, the analyses provide no clear consensus on the taxonomic status of bandicoot populations within the western lineage, with further analyses required, ideally incorporating data from historical museum specimens to fill distributional gaps.

Conservation challenges and benefits of multispecies reintroductions to a national park – a case study from New South Wales, Australia

Species reintroductions into predator-controlled areas are an increasingly used conservation tool. Typically, ecological outcomes of such projects (e.g. recruitment, predation) are the focus but seldom necessary legislative, policy, social and institutional processes required for establishing large projects. This particularly applies to protected areas, managed by governments for conservation. Reintroductions are recommended for a third of threatened Australian vertebrates, with the New South Wales Government boldly embarking on a 2013 initiative to return locally extinct mammals to three protected areas. We detail the legislative, policy, social and institutional processes required for one of these sites, Wild Deserts, in Sturt National Park. Seven locally extinct species, including the greater bilby (Macrotis lagotis), western barred bandicoot (Perameles bougainville), golden bandicoot (Isoodon auratus), greater stick-nest rat (Leporillus conditor), crest-tailed mulgara (Dasycercus cristicauda), western quoll (Dasyurus geoffroii) and burrowing bettong (Bettongia lesueur) will be reintroduced into two exclosures. The scale of the project required identification of an appropriate location, satisfaction of statutory requirements for major infrastructure in a national park, assessments of potential ecological costs and benefits, engagement of the national park agency and other stakeholders (Traditional Owners, other government agencies, neighbours), and staff training to meet government agency requirements. We outline the resourcing, costs and benefits of such a project on government-managed land along with lessons learnt for similar large-scale restoration and reintroduction projects. Future projects would benefit from understanding legislative and policy frameworks and the need for transparency, while maximising efficiencies.

Cardiac autonomic innervation of the western pygmy possum (Cercatetus concinnus) and golden bandicoot (Isoodon auratus)

Evidence for a functional ventricular parasympathetic innervation of the mammalian heart between and within taxa remains controversial. We have previously proposed that the presence of a functional parasympathetic innervation of the ventricle was indicative of heterothermy, and is essential for maintaining ventricular stability at low body temperature. However, it is possible that the presence of such an innervation is also representative of the primitive mammalian state. In this study, we aimed to determine whether a functional parasympathetic innervation of the ventricle, that is capable of actively reducing the force of contraction, is present across metatherian mammals. Using in vitro isolated cardiac preparations, we examined evidence for a functional ventricular parasympathetic innervation of the ventricle in two species of metatherian mammal, one heterotherm (Western pygmy possum; Cercatetus concinnus) and one homeotherm (Golden bandicoot; Isoodon auratus), from different families to complement existing data from a heterothermic dasyurid. Both C. concinnus and I. auratus had a potent biphasic response to transmural electrical stimulation in both atrial and ventricular preparations. Both the decrease and increase in the force of contraction in response to stimulation were almost entirely blocked by the cholinergic and adrenergic antagonists, atropine and propranolol, respectively. These observations provide clear evidence for a parasympathetic innervation of the ventricle that is capable of directly influencing the force of contraction across metatherian mammals with different thermoregulatory strategies. While this innervation may facilitate heterothermy, this suggests that the presence of such an innervation pattern is indicative of the primitive mammalian state.

Evaluating success of translocations in maintaining genetic diversity in a threatened mammal

The effectiveness of fauna reintroduction programs has been limited by the availability of source animals and the lack of follow up monitoring to assess whether viable populations have been successfully established, particularly in terms of conserving genetic diversity. Here we present genetic assessment of the translocation of golden bandicoots (Isoodon auratus) from a large source population on Barrow Island off the north-west coast of Western Australia to two other island sites and a mainland fenced enclosure. We assessed the genetic diversity of animals translocated to each site and their wild-born progeny, and whether wild-born animals showed evidence of genetic bottlenecks or genetic drift from the source population. Encouragingly, we found no significant loss of genetic diversity in any of the wild-born populations compared to the source population and no significant increase in inbreeding or relatedness amongst wild-born individuals compared to founder populations two years post-translocation. However, we detected an approximately 10-fold reduction in effective population size between founding and wild-born populations. We found no apparent differentiation between wild-born populations and the original source population, or between wild-born animals and their respective founders. Population viability modeling predicts that each of the translocated populations is susceptible to loss of genetic diversity over time. Taken together these results suggest that the golden bandicoot reintroduction program has been initially successful as a result of large founding sizes and high reproductive rates; however, ongoing augmentation will be required to prevent genetic erosion and maintain evolutionary potential in the long-term.

Threatened mammals become more predatory after small-scale prescribed fires in a high-rainfall rocky savanna

Understanding mechanisms underlying fire regime effects on savanna fauna is difficult because of a wide range of possible trophic interactions and feedbacks. Yet, understanding mechanisms underlying fauna dynamics is crucial for conservation management of threatened species. Small savanna mammals in northern Australia are currently undergoing widespread declines and regional extinctions partly attributable to fire regimes. This study investigates mammal trophic and ecosystem responses to fire in order to identify possible mechanisms underlying these declines. Mammal trophic responses to fire were investigated by surveying mammal abundance, mammal diet, vegetation structure and non-mammal fauna dynamics in savannas six times at eight sites over a period of 3 years. Known site-specific fire history was used to test for trophic responses to post-fire interval and fire frequency. Mammal and non-mammal fauna showed only minor responses of post-fire interval and no effect of fire frequency. Lack of fauna responses differed from large post-fire vegetation responses. Dietary analysis showed that two mammal species, Dasyurus hallucatus and Isoodon auratus, increased their intake of large prey groups in recently burnt, compared to longer unburnt vegetation. This suggests a fire-related change in trophic interactions among predators and their prey, after removal of ground-layer veg- etation. No evidence was found for other changes in food resource uptake by mammals after fire. These data provide support for a fire-related top-down ecosystem response among savanna mammals, rather than a bottom-up resource limitation response. Future studies need to investigate fire responses among other predators, including introduced cats and dingoes, to determine their roles in fire-related mammal declines in savannas of northern Australia.

Metabolic and ventilatory physiology of the Barrow Island golden bandicoot ( Isoodon auratus barrowensis) and the northern brown bandicoot ( Isoodon macrourus)

Metabolic and ventilatory parameters were measured for the smallest and largest Isoodon bandicoots; the arid-adapted Barrow Island golden bandicoot ( Isoodon auratus barrowensis) and the tropical northern brown bandicoot ( Isoodon macrourus). I. a. barrowensis has a number of physiological characteristics that aid its tolerance of high T a and survival in a hot and dry climate, including a low and labile body temperature, a very low basal metabolic rate, low total evaporative water loss, and an effective panting mechanism. I. macrourus generally has an “average” physiology for a bandicoot despite its size, although a number of its physiological characteristics aid survival in (sub)tropical conditions. These include a low body temperature, low total evaporative water loss and minute ventilation at high ambient temperatures, and an average thermal conductance. These data support the theory that phylogeny is a more important predictor of bandicoot physiology than habitat/distribution.

Distributional patterning of mammals on the Wessel and English Company Islands, Arnhem Land, Northern Territory, Australia

Eighteen non-marine mammal species (including seven species of bats) were recorded from a total of 49 islands in the Wessel and English Company island chains off north-eastern Arnhem Land, Northern Territory. Most individual species were restricted to, or had higher incidence on, larger islands, and species richness as a whole increased as island size increased. The most notable exception was the semi-aquatic Hydromys chrysogaster, which occurred relatively equitably across island sizes; this species, two bat species and the macropod Petrogale brachyotis were recorded from islands smaller than 10 ha. However, the variation between islands in the number of native terrestrial mammal species was not best predicted by island size, but rather by a combination of sampling effort and altitude (which explained 64% of the deviance in species richness), or altitude and distance to larger land mass (explaining 63% of deviance). Richness–area patterns for individual islands in these chains were reasonably consistent with those of other islands sampled in northern Australia. However, the fauna of the Wessel and English Company groups as a whole was less rich than that of the Pellew and Kimberley islands, and individual islands appeared to have lower species richness than comparable mainland areas. Species that were notably absent or that were recorded from relatively few islands include large macropods, Tachyglossus aculeatus, Antechinus bellus, Phascogale tapoatafa, Sminthopsis spp., Mesembriomys gouldii, Rattus colletti, Leggadina lakedownensis and Pseudomys calabyi. Some of these species may be absent through lack of suitable habitat; others have presumably disappeared since isolation, possibly due to Aboriginal hunting. Richness at the quadrat (50 × 50 m) scale was generally very low. Habitat relationships are described for the 7 species recorded from more than 5 quadrats. At a quadrat-scale, the richness of native mammals was greater on islands larger than 1000 ha than on islands smaller than 1000 ha. Quadrat-scale species richness varied significantly among the islands sampled by the most quadrats (even when the comparison was restricted to either of the two most extensive vegetation types), but this variation was not closely related to either area or altitude. The two most frequently recorded species, the rodents Melomys burtoni and Zyzomys argurus, showed distinct habitat segregation on islands where both were present, but tended to expand their habitat range on islands where only one of the species occurred. The most notable conservation feature of the mammal fauna of the Wessel and English Company Islands is the occurrence of the golden bandicoot, Isoodon auratus, a vulnerable species apparently now extinct on the Northern Territory mainland. Four feral animal species (Rattus rattus, Canis familiaris, Bubalus bubalis and Capra hircus) were recorded from a total of 6 islands.

Population and Habitat Characteristics of the Golden Bandicoot (Isoodon Auratus) on Marchinbar Island, Northern Territory.

The presence of the golden bandicoot (Isoodon auratus) on Marchinbar Island off north-eastern Arhemland, Northern Territory, was confirmed by means of morphological features, hair characteristics and allozyme electrophoresis. Evidence of I. auratus was found at most points sampled along the 50-km length of Marchinbar Island. The species showed a strong habitat preference for low heath or shrubland on sand or sandstone, a combination that covers some 70% or 140 km2 of the island. No sign was found in the remaining forest/thicket or strand/Casuarina habitat. No major changes occurred in the distribution of the species between seasons, and individuals maintained overlapping home ranges of similar size, about 10-35 ha. Considerable variation occurred in the characteristics of sites used for daytime shelter, including rocky shelves, shrubs and Triodia hummocks. Different shelter sites were frequently occupied on consecutive days. Foraging sites were sparsely vegetated and diet consisted mainly of a broad range of invertebrates. It is likely that the rocky habitat of Marchinbar Island is sufficiently dissected to ensure the availability of suitable habitat without the necessity of a managed fire regime. The bandicoot population on Marchinbar Island has at least two terrestrial predators, wild dogs (Canis familiaris) and carpet pythons (Morelia spilota). The current predation pressure is not considered to threaten the existence of the bandicoots on the island; however, the addition of another predator species (e.g. the feral cat) may create unacceptable conditions.

A Test of the Vegetation Mosaic Hypothesis: A Hypothesis to Explain the Decline and Extinction of Australian Mammals

The vegetation mosaic hypothesis suggests that medium‐sized mammals occupying arid and semi‐arid areas of Australia require a habitat that is a fine‐grained mosaic of different vegetation types or seral stages. This mosaic is believed to have been created in the spinifex deserts of central Australia by Aboriginal burning practices. Its loss in the period 1940–1960 is postulated to be a primary reason for both major reductions in range and mainland extinctions of many species of medium‐sized mammals at this time. This study measured the responses of three species of medium‐sized mammals to vegetation patterns within spinifex grasslands that ranged from comparatively uniform to highly diverse. The abundance, condition, and reproductive status of golden bandicoots (Isoodon auratus), northern brush‐tailed possums (Trichosurus vulpecula arnhemensis), and burrowing bettongs (Bettongia lesueur) were assessed within vegetation mosaics of various scales on Barrow Island, off the northwest coast of Australia. Scale of mosaic proved to have no significant effect on the numbers, condition, or reproductive status of any of the three species. Similarly, the creation of fine‐grained mosaics of early seral‐stage vegetation mixed within climax vegetation by extensive oil‐field operations over nearly half the island had no significant effect on the number or condition of animals. Hence, scale of mosaic seems unlikely to be related to the mainland decline or extinction of these species. The pattern of decline and extinction on the mainland but continued survival on offshore islands is more consistent with the presence (mainland) or absence (islands) of introduced predators (foxes and cats) and herbivores (rabbits and stock).

Field Metabolism and Turnover in the Golden Bandicoot (Isoodon-Auratus) and Other Small Mammals From Barrow Island, Western-Australia

Barrow Island, which lies about 90 km north of Onslow off the arid Western Australian Pilbara coast, experienced its driest year on record in 1990 with a total of only 122.4 mm of rain. Golden bandicoots captured in November 1990 evidenced poor condition and mean body mass was a low 242.6 +/- 10.9 g with-a total body water content (TBW) of 76.3 +/- 1.4%. Despite this substantial loss of body water and solids, the animals maintained water and electrolyte balance during the period of turnover [water influx 79.5 +/- 6.9 v. efflux 83.3 +/- 5-7 mL (kg0.82 day)-1 and sodium influx 4.9 +/- 0.7 v. efflux 5.3 +/- 0.7 mmol (kg day)-1]. By April 1991, although only a further 37.4 mm of rain had been recorded on Barrow Island, the condition of the bandicoots had improved markedly, as a result of exploitation of insect resources, and their mean body mass had increased to 306.5 +/- 22.6 g and TBW decreased to 62.5 +/- 1.4% (both P < 0.001), the latter reflecting enhanced fat stores. This general improvement in condition of the bandicoots was in marked contrast to that of other herbivorous marsupials on the island. Rates of water and sodium turnover of the golden bandicoots were, however, not significantly different from those measured in the previous November, Field Metabolic Rates (FMRs), measured with doubly labelled water ((HHO))-H-3-O-18, were extremely low, averaging only 0.45 +/- 0.26 mL CO2 (g h)-1, which is very close to laboratory estimates of 0.35 +/- 0.09 mL O2(g h)-1 for the basal metabolic rate of this species. A major cyclone struck Barrow Island on 3 March 1992, with 162 mm of rain falling in 24 h, and turnover measurements in May of that year revealed a substantial increase in rates of water flux. Mean body mass further increased to 332.6 +/- 8.5 g and TBW averaged 61.8 +/- 1.1%. Water turnover rates were significantly elevated when compared with April of the previous year with an influx of 112.5 +/- 7.3 and an efflux of 119.0 +/- 7.6 mL (kg0.82 day)-1 respectively (both P = 0.001). Rates of sodium turnover, however, were only slightly lower at 3.6 +/- 0.5 and 4.1 +/- 0.5 mmol (kg day)-1 for influx and efflux respectively (P = 0.056 for influx only), suggesting a slight decrease in the average sodium content of the diet. The volume of water required to maintain hygric balance was estimated by regression analysis at 26.7 mL day-1 [=88.3 mL (kg0.82 day)-1] in November 1990, and 33-9 mL day-1 [=85.2 mL (kg0.82 day)-1] in May 1992, following rain. The FMR of eight bandicoots was very significantly elevated to 1.39 +/- 0.23 mL CO2 (g h)-1 after rain, which is substantially higher than even the FMR of 0.91 +/- 0.07 mL CO2(g h)-1, or 644 kJ day-1, reported for the closely related southern brown bandicoot (Isoodon obesulus) studied in the region of Perth by Nagy et al. (1991). Turnover rates of water and sodium for two rodent species, the Barrow Island mouse (Pseudomys nanus) and the rock rat (Zyzomys argurus), were very similar to those recorded for golden bandicoots in the dry period, but FMRs were a little higher at 0.80 +/- 0.26 and 0.59 +/- 0-36 mL CO2(g h)-l respectively. The FMR of Barrow Island mice increased very significantly to a mean of 2.73 +/- 0.50 mL CO2(g h)-l after rain, but rock rats were not caught at this time. The data document the impressive ability of these mammals to avail themselves of extremely limited resources and maintain physiological homoiostasis under conditions of extreme aridity.

Stick-Nest Rat Middens as Sources of Paleoecological Data in Australian Deserts

The existing paleoenvironmental data from the Australian arid zone lack sensitivity and come from only a few sites. Macrofossils and pollen from four dated middens of the stick-nest rat ( Leporillus spp.) were analyzed from two sites in Western Australia. Animal and plant macrofossil remains were well preserved and provided evidence of change in species distribution within the last 1150 yr. Brush-tail possum and golden bandicoot have contracted their ranges in the recent past, possibly since the introduction of cats into Australia. An undescribed lacewing was also a significant find. Pollen preserved in parts of the same midden and in middens from different sites indicates that records are sensitive to the composition of the local vegetation when the midden was built. Pollen spectra are quite different from playa lakes, which record largely regional vegetation. Pollen preserved in the fecal pellets, desiccated urine, and grass mat nesting material provided similar information but some differences were apparent, suggesting dietary preferences were reflected in the fecal component. The pollen record suggested a trend to less-wooded vegetation cover in central Australia between 900 and 300 yr B.P.

Metabolism, Water-Balance and Temperature Regulation in the Golden Bandicoot (Isoodon-Auratus)

The Barrow I. golden bandicoot (Isoodon auratus) is a small arid-adapted marsupial. It has a low and labile body temperature, a low basal metabolic rate, a low thermal conductance, and a low rate of evaporative water loss. Its metabolic, thermal and hygric physiology resembles that of another arid-adapted bandicoot, the bilby, and differs from temperate and tropical bandicoots.