Isoodon Obesulus Research Articles

Myosin isoforms and fibre types in limb muscles of Australian marsupials: adaptations to hopping and non-hopping locomotion

Using immunohistochemistry and SDS-PAGE, we studied the myosin heavy chain (MyHC) composition and fibre type distribution of hindlimb muscles of hopping and non-hopping Australian marsupials. We showed that hindlimb muscles of a bandicoot (Isoodon obesulus, order Peramelomorphia) and a small macropodoid, the brushtail bettong (Bettongia penicillata) expressed four MyHCs, slow, 2a, 2x and 2b, and had the corresponding fibre types as other macropods reported earlier. The fastest and most powerful 2b fibres predominated in most bettong hindlimb muscles, but were absent in the gastrocnemius and the flexor digitorum profundus, which are involved in elastic strain energy saving during hopping. The gastrocnemius of four large macropodids also showed little or no 2b MyHC, whereas this isoform was abundant in their tibialis anterior, which is not involved in elastic energy saving. In contrast, 2b MyHC predominated in the gastrocnemius of four non-hopping marsupials. These results suggest that absence of 2b fibres may be a general feature of macropodoid muscles involved in elastic energy saving. Large eutherians except llamas and pigs also have no 2b fibres. We hypothesize that 2x and 2a fibres perform better than 2b fibres in the storage and recovery of kinetic energy during locomotion in both marsupials and eutherians.

KLOSSIELLA QUIMRENSIS (APICOMPLEXA: KLOSSIELLIDAE) CAUSES RENAL COCCIDIOSIS IN WESTERN BARRED BANDICOOTS PERAMELES BOUGAINVILLE (MARSUPIALIA: PERAMELIDAE) IN WESTERN AUSTRALIA

Previous studies have described a range of Klossiella species parasitic in marsupial hosts. Klossiella quimrensis is the etiologic agent of renal coccidiosis in the peramelid marsupial hosts Isoodon obesulus and Perameles gunnii in Eastern Australia, but there is no previous report of klossiellosis in Western Australian peramelids. This study describes klossiellosis diagnosed by histology of renal tissue sections collected during necropsy of 20 Perameles bougainville between 2000 and 2005. Sporonts, sporoblasts, and macrogametes were identified within parasitophorous vacuoles of epithelial cells located near the renal corticomedullary junction. The prevalence of renal coccidiosis in P. bougainville diagnosed by renal histology is estimated at 30%. Only a single unsporulated sporocyst was detected by examination of cystocentesis-collected urine, indicating that microscopic evaluation of urine samples is an insensitive diagnostic test for detection of K. quimrensis in P. bougainville. This infection in P. bougainville is indirectly associated with mild multifocal interstitial lymphohistiocytic nephritis and is likely to be only minimally pathogenic in otherwise healthy individuals. Our study also extends the host and geographic range of K. quimrensis to include P. bougainville and Western Australia.

Increasing the target-specificity of ERADICAT® for feral cat (Felis catus) control by encapsulating a toxicant

ERADICAT®, a sausage-type meat bait, has been developed for use in managing feral cat (Felis catus) populations throughout Western Australia. However, concern about potential exposure of non-target species to bait-delivered toxicants has led to the development of a technique to more specifically target feral cats using a pellet. Research into the consumption, by cats and native animals, of toxic pellets implanted within the ERADICAT® bait has been simulated using ball bearings as a substitute pellet. Results from our work indicate that encapsulating the toxicant may pose less risk of poisoning to chuditch (Dasyurus geoffroii), woylies (Bettongia pencillata) and southern brown bandicoots (Isoodon obesulus) as they consumed significantly fewer ball bearings (P = 0.003, <0.001, <0.001) than semi-feral cats (P = 0.07). Theoretically, a toxic pellet will not reduce the effectiveness of the ERADICAT® bait as there was no significant difference between consumption of baits and the consumption of ball bearings in feral cats (P = 0.07). Therefore, baits containing a toxic pellet have the potential to be a more selective method to control feral cats.

Milk composition and growth in the southern brown bandicoot, Isoodon obesulus (Marsupialia:Peramelidae)

Milk and growth data from six litters of southern brown bandicoots (Isoodon obesulus) from south-eastern Tasmania were analysed. Five of these were born in the wild and one was born in captivity. The quantitative changes in milk composition were examined for total protein, carbohydrates (hexose and lactose), lipid, dissolved solids, and estimated energy content. During ‘early-phase’ lactation (before Day 30) protein levels were 10.5 g (100 mL)–1, hexose 0.34 g (100 mL)–1, lipids 10.4 g (100 mL)–1, and solids 27.3 g (100 mL)–1. ‘Mid-phase’ milk (Days 31–45) showed an increase in all constituents: protein 13.8 g (100 mL)–1, hexose 1.66 g (100 mL)–1, lipid 12.2 g (100 mL)–1, and solids 41.4 g (100 mL)–1. Protein and hexose levels decreased in ‘late-phase’ milk (Day 46–60) to 11.3 g (100 mL)–1, and 1.58 g (100 mL)–1, respectively, and the amount of lipids and dissolved solids increased to 26.4 g (100 mL)–1, and 52.3 g (100 mL)–1, respectively. There was no evidence of lactose in milk from the latter half (final 28 days) of lactation. Total milk energy increased from 6.0kJmL–1 in early-phase milk, to 8.9 kJ mL–1 in mid-phase, and 12.0 kJ ml–1 in late-phase. Changes in body mass, head, tail, and pes lengths were examined for 16 pouch young. Instantaneous relative growth rates were calculated for the final 42 days of lactation, revealing a decrease in overall growth rates from 14.0% increase in bodyweight per day in early-phase, to 7.8% daily during mid-phase, and 3.5% daily increase during late-phase lactation. Analysis of the relationship between milk and growth in I. obesulus demonstrates that morphological and developmental changes, especially the development of endothermy and time of first pouch exit, directly correlate with changes in growth rates, milk energy, and milk composition.

Body temperature variation of free-ranging and captive southern brown bandicoots Isoodon obesulus (Marsupialia: Peramelidae)

To investigate patterns of thermoregulation in free-ranging and captive southern brown bandicoots Isoodon obesulus, we measured abdominal body temperature ( T b) of five free-ranging bandicoots over 42 days using implanted data loggers and T b of three captive bandicoots over 3 months using implanted temperature-sensitive radio transmitters. Bandicoots in the wild had a mean T b of 36.5±1.0 °C (range 33.4–39.8 °C) and showed a pronounced nychthemeral pattern with two distinct temperature phases. T b increased at 13:30±2.6 h each day and remained high for 10.65±2.07 h, suggesting a crepuscular and early evening activity pattern. Daily T b variation of I. obesulus would save considerable energy by reducing daytime thermoregulatory costs in the wild. Captive bandicoots had a similar mean body temperature (36.9±0.2°C) and range (33.0–39.9°C) as free-ranging bandicoots. However, the nychthemeral T b pattern of captive bandicoots was different from free-ranging bandicoots, with a less pronounced daily cycle and the nocturnal rise in T b occurring mainly at sunset and the daily decline occurring mainly at dawn.

Effects of long-term captivity on thermoregulation, metabolism and ventilation of the southern brown bandicoot (Marsupialia: Peramelidae)

Thermoneutral metabolic and ventilatory parameters were measured every 3 months over 2 years for southern brown bandicoots held in captivity, and from a nearby reserve. Captive bandicoots were 130 g (9.9%) heavier than wild bandicoots. Long-term captivity had no effect on body temperature, basal metabolic rate (oxygen consumption), thermal conductance or respiratory ventilation, but there was an effect on carbon dioxide production, respiratory exchange ratio and total evaporative water loss (values were between 15 and 25% higher for captive than for wild bandicoots). Diet may be influencing these aspects of captive bandicoot physiology; the diet of captive bandicoots would be considerably different to that of wild bandicoots. Water availability seems to have a minimal effect. This study has important implications regarding physiological measurement for captive and wild mammals. For bandicoots at least, captive animals are equivalent to wild animals for some physiological parameters at thermoneutrality (body temperature, resting metabolic rate and thermal conductance), but not others.

Morphological and molecular characteristics of a species of Hepatozoon Miller, 1908 (Apicomplexa: Adeleorina) from the blood of Isoodon obesulus (Marsupialia: Peramelidae) in Western Australia

Examination of blood films as part of a study to assess the health status of the southern brown bandicoot Isoodon obesulus (Shaw) in Western Australia revealed the gamonts of a haemogregarine parasite in some samples, the first to be recognised in a bandicoot in this state. Light microscope morphological characteristics and partial sequence of the 18S rRNA gene were used to describe these organisms. Morphological characters did not differentiate the organism in the current study from previously reported Hepatozoon peramelis (Welsh & Dalyell, 1909). Phylogenetic analysis has not previously been reported for any species of Hepatozoon from Australian marsupials and consequently could not be used to confirm the identity of the organism in the current study as that described in the 1900s. If this organism is H. peramelis, then it has a wide distribution, being found in three species of bandicoot, in western and eastern Australia and the in island state of Tasmania.

Machine learning of poorly predictable ecological data

This paper reports on research using a variety of machine learning techniques to a difficult modelling problem, the spatial distribution of an endangered Australian marsupial, the southern brown bandicoot ( Isoodon obesulus). Four learning techniques – decision trees/rules, neural networks, support vector machines and genetic programming – were applied to the problem. Support vector and neural network approaches gave marginally better predictivity, but in the context of low overall accuracy, decision trees and genetic programming gave more useful results because of the human comprehensibility of their models.

Habitat utilisation by small mammals in a coastal heathland exhibiting symptoms of Phytophthora cinnamomi infestation

Phytophthora cinnamomi is a soil-inhabiting ‘water mould’ that is pathogenic to many native plant species in Australia, and has been shown to alter plant species abundance and richness, as well as the structure of vegetation in sclerophyllous vegetation. This study investigated the effects of P. cinnamomi-induced vegetation disturbance and habitat degradation on microhabitat associations of small mammals in a coastal heathland in southern Australia. Seven small mammal species were trapped in a P. cinnamomi-infested heathland community over four years. Trap stations were classified into three disease classes (non-diseased, active disease and post-disease) and structural and floristic aspects of the vegetation were recorded at each station. The mean number of species captured was greatest in non-diseased areas and least in post-disease areas. The total capture frequency of small mammals was lower in post-disease areas except where they were covered by thick stands of tall tea-tree (Leptospermum sp.). Combined small mammal captures were associated with thick vegetation and floristic factors. Captures of Antechinus agilis, Rattus fuscipes, Rattus lutreolus and Sminthopsis leucopus were greatest in non-diseased vegetation and were less frequent in areas of diseased vegetation. A. agilis and R. fuscipes captures were correlated with a floristic factor associated with non-diseased vegetation, while R. lutreolus was associated with structural factors, preferring thick vegetation. The impact on Cercartetus nanus and Isoodon obesulus could not be assessed owing to low captures of these species. Modification of vegetation structure and floristics associated with P. cinnamomi infestation is having a significant impact on the habitat utilised by the small mammal communities in the area. This impact highlights the need to identify and protect those areas that remain free of P. cinnamomi infestation. Continued spread of the pathogen will reduce the area of suitable small-mammal habitat able to support the diverse communities of the eastern Otway Ranges, Victoria, Australia.

2006 Southern brown bandicoots Isoodon obesulus obesulus in Belair National Park.

A population of southern brown bandicoots (Isoodon obesulus obesulus) in Belair National Park (NP) and neighbouring areas was studied from 1995 to 2002. From 1997 to 2002, 181 bandicoots (91 females, 89 males, one unknown) were microchipped. Many animals were captured only once or twice, but data from a few animals showed that bandicoots may live up to four years. Breeding occurred year round, with a mean litter size from 33 litters of 1.8. Bandicoots were trapped close to water courses in areas with thick ground cover. Black rats (Rattus rattus) were active nocturnally in all areas of Belair NP which were trapped, and may be in competition with bandicoots for food and shelter resources. Bandicoots have recently been seen in north-western areas of Belair NP where they have not been seen in years. This expansion of their distribution in the park may be related to a translocation to this area in 1998 and a fox control program which has been carried out since 1988.

Responses of four Critical Weight Range (CWR) marsupials to the odours of native and introduced predators

In Australia many critical weight range (CWR) species are threatened by predation from the introduced Red Fox Vulpes vulpes. Understanding how these prey species respond to native predators such as the Tiger Quoll Dasyurus maculatus, and comparing their responses to foxes is important in understanding why fox predation is such a problem. Many northern hemisphere mammalian species have developed responses to the odours of the main species which prey upon them. The situation in Australia remains unclear. We looked at the effect of scenting traps with the faeces of the Tiger Quoll and the Red Fox on the capture rates of four species of CWR marsupials, the Long-nosed Bandicoot Perameles nasuta, the Southern Brown Bandicoot Isoodon obesulus, the Northern Brown Bandicoot I. macrourus and the Common Brushtail Possum Trichosurus vulpecula. None of these species responded to fox odour. However despite low capture rates, Northern Brown Bandicoots and Common Brushtail Possums were captured significantly more often i...

Haematological characteristics of morbid southern brown bandicoots (Isoodon obesulus)

Haematological assessment often forms an important part of the diagnosis of disease in wildlife, as animals may not exhibit clinical signs until late in the disease process to avoid appearing vulnerable to predators. This study investigated the haematological changes occurring in southern brown bandicoots suffering from injury and illness that were caught from the wild or presented to a Perth wildlife rehabilitation centre. The blood was assessed by microscopy, manual techniques (packed cell volume, total solids and fibrinogen) and using an automated haematology analyser. Most (6/8) animals had evidence of an inflammatory response, in the form of an increased concentration of leukocytes. However, a few (2/8) animals had an increased concentration of fibrinogen, indicating that this is an inconsistent marker of inflammation in bandicoots. Anaemia was present in 2/8 animals and these both had a regenerative response evident. This study establishes that southern brown bandicoots are capable of mounting a neutrophilia in response to inflammation and exhibit a regenerative response to anaemia that releases polychromatophilic cells into the peripheral blood.

Clinical haematology of the southern brown bandicoot (Isoodon obesulus)

Haematological assessment may contribute in monitoring the health of wild animals. However, species-specific reference intervals are required for maximal information to be gained from any haematological assessment. The purpose of this study was to assess the haematological characteristics for a population of southern brown bandicoots (Isoodon obesulus), a small marsupial common, across southern Australia. Animals from a wild population (n=65) were sampled between March 2004 and February 2005. Blood from these animals was assessed by microscopy, manual techniques (packed cell volume, total solids, and fibrinogen) and using an automated haematology analyser. Southern brown bandicoots were found to have similar leukocytes and erythrocytes to those previously described for other species of bandicoots, and the measured values for the haematological analytes were similar to those previously published for the species. For most analytes there were no statistically significant differences observed between males and females, and lactating and non-lactating animals. The observed values for each of the analytes in the current study may be used to aid in the detection of disease and monitoring of health in wild and captive populations of bandicoots.

Cone topography and spectral sensitivity in two potentially trichromatic marsupials, the quokka (Setonix brachyurus) and quenda (Isoodon obesulus)

The potential for trichromacy in mammals, thought to be unique to primates, was recently discovered in two Australian marsupials. Whether the presence of three cone types, sensitive to short- (SWS), medium- (MWS) and long- (LWS) wavelengths, occurs across all marsupials remains unknown. Here, we have investigated the presence, distribution and spectral sensitivity of cone types in two further species, the quokka (Setonix brachyurus) and quenda (Isoodon obesulus). Immunohistochemistry revealed that SWS cones in the quokka are concentrated in dorso-temporal retina, while in the quenda, two peaks were identified in naso-ventral and dorso-temporal retina. In both species, MWS/LWS cone spatial distributions matched those of retinal ganglion cells. Microspectrophotometry (MSP) confirmed that MWS and LWS cones are spectrally distinct, with mean wavelengths of maximum absorbance at 502 and 538 nm in the quokka, and at 509 and 551 nm, in the quenda. Although small SWS cone outer segments precluded MSP measurements, molecular analysis identified substitutions at key sites, accounting for a spectral shift from ultraviolet in the quenda to violet in the quokka. The presence of three cone types, along with previous findings in the fat-tailed dunnart and honey possum, suggests that three spectrally distinct cone types are a feature spanning the marsupials.

Phylogenetics, population structure and genetic diversity of the endangered southern brown bandicoot (Isoodon obesulus) in south-eastern Australia

The southern brown bandicoot (Isoodon obesulus) has undergone significant range contractions since European settlement, and it is now considered “Endangered” throughout south-eastern mainland Australia. This species currently has a highly fragmented distribution inhabiting a mosaic of habitats. This project uses mitochondrial DNA (mtDNA) and microsatellite data to determine levels of genetic diversity, population structure and evolutionary history, which can aid wildlife managers in setting priorities and determining management strategies. Analyses of genetic diversity revealed low levels of mtDNA variability (mean h=50.42%, π=0.76%) and divergence (mean dA=0.29%) across all regions investigated, and was among the lowest recorded for marsupials. These data indicate a relatively small female effective population size, which is most likely a consequence of a large-scale population contraction and subsequent expansion occurring in pre-history (mismatch distribution analysis, SSDP-value=0.12). Individuals from the Sydney region experienced significant reductions in microsatellite diversity (A=3.8, HE=0.565), with the Garigal National Park (NP) population exhibiting “genetic reduction signatures” indicating a recent population bottleneck. Population differentiation analysis revealed significant genetic division amongst I. obesulus individuals from Sydney, East Gippsland and Mt Gambier regions (θ=0.176–0.271), but could not separate the two Sydney populations (Ku-ring-gai NP and Garigal NP). Based on these data and habitat type, translocations could readily be made between the two Sydney populations, but not between the others. Phylogenetic comparisons between I. obesulus and I. auratus show little support for current Isoodon taxonomy, consistent with the findings of Pope et al. 2001. We therefore recommend the recognition of only three I. obesulus sub-species and suggest that these comprise a single morphologically diverse species that once was widespread across Australia.

Fossil bandicoots (marsupialia, peramelidae) and environmental change during the pleistocene on the darling downs, Southeastern Queensland, Australia

Synopsis Systematic collecting from fluviatile Pleistocene fossil deposits of the Darling Downs, southeastern Queensland, Australia, has led to an increase in the region's fossil record of bandicoots. Isoodon obesulus, Perameles bougainville and P. nasuta are reported for the first time in the Darling Downs fossil record. Accelerator mass spectrometry 14C dates based on charcoal from bandicoot fossil‐bearing stratigraphic horizons indicates deposition 45–40 ka. Additional material attributed to the recently described Darling Downs P. sobbei is also described. P. sobbei retains plesiomorphic characters in the upper dentition including reduction of the metaconule on M3 and the lack of posterior cingula on M2 and M3. Phylogenetic interpretation of dental characters suggests that P. sobbei has closer affinities to the Pliocene P. bowensis than to any modern species. The presence of extant species such as P. bougainville and I. obesulus as fossils provides evidence that scrublands and closed woodlands with dense understories existed on the Darling Downs during the Pleistocene. The Darling Downs bandicoot assemblage represents the only known fauna, fossil or modern, where I. obesulus, P. bougainville and P. nasuta occur sympatrically. The Pleistocene Darling Downs may have had a more equable climate than occurs today and a greater range of habitat niches to support such populations. The southern and western contraction of the geographical ranges of I. obesulus and P. bougainville between the Pleistocene and the present was probably the result of significant environmental change that may have involved the contraction of woodlands and expansion of grasslands. The persistence of P. nasuta populations on the Darling Downs from the Pleistocene to the present may reflect that species’ ability to adapt to a wide range of habitats.

Cyst morphology and sequence analysis of the small subunit rDNA and ef1α identifies a novel Giardia genotype in a quenda ( Isoodon obesulus) from Western Australia

Sequence analysis of the small subunit ribosomal DNA (SSU-rDNA) and elongation factor 1 alpha ( ef1α) was performed on Giardia cysts isolated from faeces collected from a quenda ( Isoodon obesulus) in the southwest of Western Australia. The SSU-rDNA and ef1α were sequenced in their entirety and correspondingly aligned with the published sequence information of other known species and genotypes of Giardia. Phylogenetic analysis of the SSU-rDNA and ef1α sequences identified the quenda isolate as a novel genotype of Giardia not previously reported. We believe that this quenda Giardia isolate constitutes a distinct species, which may be endemic within the Australian native fauna.

Diet and habitat preference of the Cape York short-nosed bandicoot (Isoodon obesulus peninsulae) in north-east Queensland

Diet and habitat preferences of the Cape York bandicoot (Isoodon obesulus peninsulae) were studied along a rainfall gradient from dry open woodland to wet Allocasuarina–Eucalyptus forest in the Lamb Range, Queensland. I. o. peninsulae was an omnivore-insectivore with invertebrates contributing 35–56% of faecal contents. Roots represented the most important plant food. Grass, forbs, fruits and hypogeous fungi were also eaten but in small quantities. The species was most abundant at the drier end of the rainfall gradient. Preferred habitats in open woodland were characterised by a high grass tree (Xanthorrhoea johnsonii) abundance and high shrub cover in the understorey. In contrast, areas with a tall and dense grass layer in conjunction with a high litter cover were avoided. I. o. peninsulae did not seem to share its habitat with the sympatrically occurring I. macrourus even though the habitat appeared suitable for the latter. More studies are required to evaluate the causes of differing habitat preferences of sympatric bandicoot species.

Activity rhythms of southern brown bandicoots Isoodon obesulus (Marsupialia: Peramelidae) in captivity.

The temporal activity patterns of individually housed captive southern brown bandicoots (Isoodon obesulus) were recorded using time-lapse infra-red videorecording. Recordings were made over a period of four continuous days per animal under natural lighting and climatic conditions for Perth, Western Australia during March 2002. Analysis showed that all bandicoots were almost entirely nocturnal and spent ~71% (~17 hr day-1) of their time in their nests. The times of onset of activity were remarkably regular, and occurred both following feeding during the late afternoon and again after dusk (average 1841 hrs). Bandicoots were active for an average of ~7 hr night-1. Virtually all activity involved the bandicoots running around their enclosures (~6.5 hr day-1). This running was interspersed with shorter periods spent feeding (~25 min day-1), grooming (~8 min day-1) and drinking (~2 min day-1). No other behaviours were observed. There was a greater degree of variation in the time of cessation of activity between individuals. Time of cessation ranged from 0039 hrs ± 20 min to 0504 hrs ± 25 min. The average time of cessation of activity was 0315 hrs ± 61 min and was not related to either time of onset of activity or sunrise.

A rapid PCR-RFLP diagnostic test for distinguishing sympatric bandicoot species (Marsupialia: Peramelidae) in southeastern Australia

The southern brown bandicoot (Isoodon obesulus) has a fragmented coastal distribution in Australia. It is found on Cape York Peninsula in north Queensland (QLD), in southeastern New South Wales (NSW), Victoria (VIC), Tasmania, southeastern South Australia (SA) and in southwest Western Australia. Although I. obesulus was originally widespread along the southeast coast of NSW (Strahan 1995), the species has declined since the European settlement of Australia and is now restricted to two small populations, located on the northern outskirts of Sydney and the far southeast corner of the state. As a result, I. obesulus is listed as an endangered species (Schedule 1) of the Threatened Species Act 1995 (NSW).