Trichosurus Caninus Research Articles

The population density and trap-revealed home range of short-eared possums (

Investigating how the population density of a species changes over time is an integral step in determining whether that species is stable or needs assistance from conservation managers. The short-eared possum (Trichosurus caninus) is a species that has been poorly studied with only one previous population density estimate. Short-eared possums were live-trapped between August 2020 and January 2021 in the Northern Tablelands, New South Wales, to estimate their current density using a spatially explicit capture–recapture (SECR) model. The average density of short-eared possums was 0.46 possums/ha (95% CI: 0.32–0.66) in temperate rainforest and 0.13 possums/ha (95% CI: 0.06–0.28) in wet sclerophyll forest. No individuals were caught in dry sclerophyll forest. Trap-based home ranges were estimated to be 12.5 ha (95% CI: 8–19) for males and 5.5 ha (95% CI: 3–11) for females. This study provides a reference for determining trends in short-eared possum population density within the Northern Tablelands in the future. Adequate conservation of temperate rainforest and wet sclerophyll forest habitat is important to the conservation of the species.

Assessment of anti-bovine IL4 and IFN gamma antibodies to label IL4 and IFN gamma in lymphocytes of the koala and brushtail possum.

We assess anti-bovine IL4 and IFN gamma (IFNg) antibodies for their ability to label IL4 and IFNg in koala (Phascolarctos cinereus), common brushtail possum (Trichosurus vulpecula) and mountain brushtail possum (Trichosurus caninus) lymphocytes using flow cytometry and immunohistochemistry to determine their applicability to studies of host response to intracellular pathogens. Anti-IFNg labelled a product of PMA-ionomycin stimulated sheep, koala and possum lymphocytes. High intensity labelling was not reduced by blocking non-specific binding with 10% FCS; and non-permeabilised koala lymphocytes labelled less, demonstrating that the labelled product was intracellular. The anti-IL4 antibody labelled variably more cells than the irrelevant antibody in some stimulated and non-stimulated preparations in all species but intensity of this labelling was similar to that of cells labelled with the irrelevant antibody. In this study, the antibodies did not label frozen or formalin-fixed tissues in a range of immunohistochemical techniques. We expect the anti-IFNg antibody to be effective in evaluating Th1 responses of koalas and possums exposed to various host, pathogen and environmental factors and add to the limited tools available for investigating the pathogenesis of marsupial diseases, especially those caused by intracellular organisms, such as tuberculosis of brushtail possums and chlamydial disease of koalas.

Responses to threat by female bobucks, Trichosurus caninus, during different stages of offspring development

The costs of reproduction are widely recognised as a major selective force in the evolution of various behavioural and life-history characteristics. In particular, the behaviour of reproductively active animals is likely to change when breeding increases risk of predation. We investigated the effect of an experimentally derived threat on the vigilance and escape behaviour of female Trichosurus caninus with and without dependent offspring and at different stages of offspring development. Females with offspring showed a heightened response to the threat in comparison to females without offspring. In addition, females with offspring displayed a stronger response at earlier stages of their offspring's development.

Geographic dimorphism in the mountain brushtail possum (Trichosurus caninus): the case for a new species

The morphological and genetic characteristics of the mountain brushtail possum (Trichosurus caninus) are described for animals from a range of locations throughout its known geographic distribution in eastern Australia. Although there is considerable variation among populations, unequivocal morphological and genetic differences exist between northern and southern populations of the species. Specimens from southern populations (from Victoria) have a significantly (P < 0.001) larger ear conch, a significantly (P < 0.001) longer pes, and a significantly (P < 0.001) shorter tail than do specimens from northern populations (from New South Wales and Queensland). Animals can be clearly distinguished using a simple index based on these three morphological measures, which are gathered from live animals. North–south dimorphism is strongly supported by patterns in genetic data that show genetic distances of 2.7–3.0% between the southern and northern populations. The combined outcomes of morphological and genetic analyses suggest the existence of two distinct species. We recommend that the northern form, distributed from central New South Wales north to central Queensland, retain the name Trichosurus caninus; the southern form from Victoria is described here as Trichosurus cunninghami, sp. nov. The common names of these new species should be the 'short-eared possum' and the 'mountain brushtail possum', respectively.

The influence of time since fire and distance from fire boundary on the distribution and abundance of arboreal marsupials in Eucalyptus regnans-dominated forest in the Central Highlands of Victoria

The impact of time since fire after two consecutive wildfires 44 years apart (1939 and 1983) within the same area, and the distance from the fire boundary (<100 m or 500-2000 m), were investigated in relation to the distribution and abundance of arboreal marsupials in 1994. Arboreal marsupials were censused by stagwatching and spotlighting in two relatively young age classes of mountain ash (Eucalyptus regnans) dominated forest in the Central Highlands of Victoria. Five species of arboreal marsupial were detected, but only three were detected in sufficient numbers to determine habitat preferences. Petauroides volans (greater glider) was statistically more abundant in 1939 regrowth forests, while Trichosurus caninus (mountain brushtail possum) showed no significant preference for either age class of forest. All but one record of Gymnobelideus leadbeateri (Leadbeater's possum) came from young forest, though the effect of age-class was not statistically significant. Distance from fire boundary explained little or no variation in mammal distribution or abundance. While the actual number of hollow-bearing trees was similar in both age classes of forest, the long-term lifespan of hollow-bearing trees in more recently burnt forest is predicted to be lower than in unburnt or not recently burnt forest. Post-fire salvage logging following the 1983 wildfires appears to have reduced the number of hollow-bearing trees at sites burnt in 1983.

Climate and animal distribution: a climatic analysis of the Australian marsupial Trichosurus caninus

AimA detailed bioclimatic analysis was completed for an Australian arboreal marsupial, the mountain brushtail possum Trichosurus caninus. This was done to explore climatic factors underpinning the distribution of the species.LocationLocation data used for bioclimatic modelling comprised of 879 records, covering the entire known range of T. caninus throughout eastern Australia.MethodsThe computer package BIOCLIM was used to generate a bioclimatic profile of T. caninus. Frequency distributions of climatic attributes in the profile were examined using histograms and a pattern analysis (using the computer package PATN) to determine if there were bioclimatically distinct groups of possums.ResultsInitial analyses of bioclimatic attributes of all records split the location data into two discrete groups based on the frequency distribution of ‘mean temperature of the wettest quarter’ of an average year, as this had a discontinuous, bimodal frequency distribution. Pattern analysis produced groupings congruent with this. When analysed separately, the bioclimatic domains of the two groups were geographically discrete. Although many key bioclimatic attributes were similar (particularly those defining light and moisture regimes that relate to vegetation structure), temperature regimes and seasonality of rainfall regime were very different for each group.Main conclusionsThe two groups identified in this study were congruent with two groups established by an earlier multivariate morphometric analysis of T. caninus. Further targeted field research together with genetic analyses, are needed to further investigate the taxonomic significance of findings on (1) the bioclimatic domain(s) and (2) the morphology of T. caninus.

Assessing spatial PVA models of arboreal marsupials using significance tests and Bayesian statistics

The predictions of stochastic metapopulation models of four species of arboreal marsupial were compared to field data on patch occupancy. The species examined were the greater glider Petauroides volans, the mountain brushtail possum Trichosurus caninus, the ringtail possum Pseudocheirus peregrinus and the yellow-bellied glider Petaurus australis. The models were developed for a system of 39 eucalypt patches in southeastern Australia, embedded within an exotic plantation of radiata pine Pinus radiata. Additionally, two alternative (null) models were developed for each species: one in which it was assumed that there was no impact of fragmentation; and a second that only modeled local population dynamics with no dispersal between patches. Congruence between the probability of occupancy of patches predicted by the metapopulation model and the actual occupancy observed in the field was assessed using tests of significance based on logistic regression. The relative performance of the three competing models was assessed for each species using Bayesian statistics. The results demonstrated that the metapopulation model made reasonable predictions for the greater glider and the yellow-bellied glider. However, none of the models predicted the observed increase in population density of mountain brushtail possums and ringtail possums in patches relative to continuous forests. Incorporating edge effects and inter-specific interactions would improve the predictions for these two species.

TESTING A SIMULATION MODEL FOR POPULATION VIABILITY ANALYSIS

We conducted a field-based test of the widely available generic computer simulation model VORTEX for population viability analysis (PVA). The model was used to predict the abundance of three species of arboreal marsupials in a system of 39 remnant patches of Eucalyptus forest embedded within a 5050-ha area of exotic radiata pine (Pinus radiata) forest in southeastern Australia. The marsupial species were: greater glider (Petauroides volans), mountain brushtail possum (Trichosurus caninus), and common ringtail possum (Pseudocheirus peregrinus). Predictions were generated for scenarios in which: (1) the rate of exchange of animals between patches was varied, (2) different models for the migration of animals between habitat patches were invoked, (3) different levels of immigration (or dispersal) from a large, neighboring source area were simulated, (4) variations in habitat quality between remnant patches were incorporated in the model, and (5) the influence of the pine matrix surrounding the remnant patches...

A population study of the mountain brushtail possum (Trichosurus caninus) in the central highlands of Victoria

Life-history attributes are described for the mountain brushtail possum (Trichosurus caninus) in mountain ash (Eucalyptus regnans) forest at Cambarville in the central highlands of Victoria, south-eastern Australia. The population was trapped on a regular basis between 1992 and 1995. Population density of T. caninus at Cambarville was high (2.3 animals ha–1). The adult sex ratio was female-biased (1.4 : 1) and the age class structure differed between sexes. There were more adult females than males in very old age classes (those animals assigned to Age Classes 7–9 and exceeding an estimated 10 years of age), whereas there were more males in the young adult cohorts (Age Classes 3 and 4). The breeding season was restricted to March–April, when a single young was produced. A second young was not produced if the first was lost. The survival of young from birth to emergence from the pouch showed strong between-year variation (30–80%). Sex ratios at birth were strongly male-biased (average = 2.6 : 1) but female young were far more likely to survive to advanced back-young stage. Breeding success of females at Cambarville was not influenced by the presence of semi-independent young from a previous year remaining in the natal territory. There was some evidence of senescence in breeding success among females in older age cohorts (Age Classes 7–9) and these animals did not successfully rear young. Many animals were trapped repeatedly at the same place, whereas others ranged over a much wider area (up to 3 ha). There was also considerable overlap between individuals in the spatial location of the areas where they were trapped.

The conservation of arboreal marsupials in the montane ash forests of the central highlands of Victoria, south-eastern Australia. VIII. Landscape analysis of the occurrence of arboreal marsupials

We describe the results of landscape analysis of the occurrence of a suite of species of arboreal marsupials in the montane ash forests of the central highlands of Victoria, south-eastern Australia. The species targeted for study were: Yellow-bellied Glider ( Petaurus australis), Mountain Brushtail Possum ( Trichosurus caninus), Greater Glider ( Petauroides volans) and Leadbeater's Possum ( Gymnobelideus leadbeateri). Our analyses involved exploring statistical relationships between the presence/absence of these four species and compositional variables used to characterise the landscape within 20 and 80 ha circles surrounding each of 166, 3 ha, sites surveyed for arboreal marsupials. Many potential statistical models were examined for each of the four species targeted for analysis. With the exception of P. australis, the final model chosen was the null model; i.e. none of the landscape variables were statistically significant as predictors of the presence of animals at a site. In the case of P. australis, three measures of the landscape within the 80 ha circles surrounding our survey sites were found to be statistically significant: (1) the presence of old forest, (2) the steepness of the forest terrain, and, (3) the area of forest on different aspects. There was a significantly higher probability of detecting the species on northerly and westerly aspects, on either steep or flat terrain, and within circles supporting old growth montane ash forest. P. australis has a home range of 40–60 ha which is at least an order of magnitude larger than the other species of arboreal marsupials examined. Thus, the size of the 80 ha circle used to capture data on landscape composition matched the home range size of P. australis more closely than other species of arboreal marsupials examined in this study. This may, in part, explain why it was the only species for which landscape composition variables were found to be significant predictors of occurrence. Our findings tentatively suggest that changes in the spatial coverage of old growth forest that have resulted from past wildfires, post-fire salvage logging and more recent intensive and extensive clearfell logging operations, have created landscape patterns unsuitable for P. australis. The implications of our results for the conservation of the species are discussed. In addition, some difficulties were experienced in the use of landscape-scale data in our statistical analyses, such as identifying attributes of landscape composition that are biologically relevant to the taxa targeted for analysis. We briefly discuss the nature of these problems.

A large-scale “experiment” to examine the effects of landscape context and habitat fragmentation on mammals

A large-scale “experiment” was undertaken in a 100 000 ha region of south-eastern Australia to examine the response of mammals to landscape context, habitat fragmentation and other factors. The investigation examined the presence and abundance of mammals in three broad categories of sites for which there were strong contrasts in the composition of the surrounding landscape: • Large contiguous areas of Eucalyptus forest, • Areas dominated by exotic plantation softwood Radiata Pine ( Pinus radiata) trees, and • Fragments of eucalypt forest surrounded by an extensive P. radiata plantation. These sites provided the basis for assessing the effects of what we term “landscape context”. Eighty-six fragments of remnant eucalypt forest of varying size, shape, isolation age and other attributes were selected by a stratified, randomization process. Forty sites were located in large contiguous areas of Eucalyptus forest and these were matched to the sites in the remnants on the basis of forest type, geology and climatic conditions. A further 40 sites were selected in areas dominated by P. radiata trees and these also were matched to sites in the remnants and those in large contiguous areas of native forest on the basis of geology and climatic conditions. Two major surveys sampled mammals in the study. Hairtubing (a technique for detecting animals from the analysis of fur collected in a small portable bait station) was utilized at all 166 sites selected in the study. Trapping and a combination of different types of hairtubing was then employed at a subset of 58 sites. Data from these surveys was used to investigate the response of mammals to landscape context, habitat fragmentation and other attributes. A sub-theme of the study was to assess the efficacy of different methods to count mammals. There were large differences in the effectiveness of the different field techniques. The best technique (best in the sense of counting most animals) varied between species, particularly in relation to body size. Trapping and smaller-sized hairtubes were superior for small mammals such as Brown Antechinus ( Antechinus stuartii) and Bush Rat ( Rattus fuscipes). Large hairtubes performed best in the detection of large mammals like the Common Wombat ( Vombatus ursinus), Common and Mountain Brushtail Possums ( Trichosurus vulpecula and Trichosurus caninus), and Swamp Wallaby ( Wallabia bicolor). W. bicolor and V. ursinus showed no response to landscape context and were detected at similar rates in the remnants, sites in large contiguous areas of native forest and sites dominated by stands of P. radiata. Trichosurus spp. were recorded significantly less often in sites dominated by P. radiata trees. Landscape context effects for R. fuscipes and A. stuartii varied depending on the field methods employed to sample mammals. However, in general, R. fuscipes and A. stuartii were recorded significantly less frequently in P. radiata sites than sites in large contiguous areas of Eucalyptus forest or fragments of remnant eucalypt forest surrounded by the softwood plantation. An important finding of our work was that although some species were extremely rare in P. radiata stands, no significant differences were identified in mammal presence and abundance between sites located in large contiguous areas of Eucalyptus forest and sites in fragments of remnant eucalypt forest surrounded by the softwood plantation. This finding suggests that either: animals from potential population sources in contiguous eucalypt forest can move through the softwood plantation and colonise the remnants, or populations residing in the fragments of remnant eucalypt forest are large enough to resist local extinction. Softwood plantations are presently being expanded in south-eastern Australia, particularly on semi-cleared farmland that supports remnant fragments of native Eucalyptus forest and woodland. Our findings indicate that remnant native forest within plantations of exotic P. radiata trees are occupied by several species of native mammals even when these fragments are surrounded by extensive, largely unsuitable plantation forests that have been established for many decades. These fragments should not be cleared during efforts to expand the softwood plantation estate. Large remnants and those with particular habitat features such as a dense cover of vegetation should have priority for exemption from clearing.

Arboreal Marsupial Incidence in Eucalypt Patches in South-Eastern Australia: A Test of Hanski's Incidence Function Metapopulation Model for Patch Occupancy

The results of field tests are described of a simple model for the occupancy of habitat patches developed by Hanski. Patch occupancy was predicted for several species of arboreal marsupials in a system of fragmented patches of Eucalyptus forest in the Tumut region of southern New South Wales (NSW) in south-eastern Australia. The species of arboreal marsupials for which the model was tested were: common brushtail possum (Trichosurus vulpecula), mountain brushtail possum (Trichosurus caninus), common ringtail possum (Pseudocheirus peregrinus), and greater glider (Petauroides volans). Predictions of the model were compared against actual data on patch occupancy gathered from extensive field surveys. Four sub-models were tested for each of the four species of arboreal marsupials: with and without rescue effects and with and without mainland effects (i.e. dispersal from large population source areas). These sub-models were tested by deriving model parameters from a subset of 40 patches and then applying the model to make predictions of patch occupancy in an array of 86 other patches of remnant Eucalyptus forest habitat. Comparisons were then made between the actual values for patch occupancy found during field surveys and the probabilities of patch occupancy predicted by the model. Our analyses revealed large differences in the results for different species. In the case of P. peregrinu there were several models for which it was not possible to derive the parameter estimates required by the model (i.e. relationships for extinction and colonisation as a function of patch size and patch isolation). The ability of the species to persist at low density in the surrounding landscape matrix may have precluded the calculation of these estimates. There was reasonable congruence between predictions and actual field data for patch occupancy for P. volans and also for most sub-models for T. vulpecula. Conversely, none of the sub-models for T. caninus produced results that were consistent with the observed data on patch occupancy for this species. The reasons for the marked differences in results for T. caninus and T. vulpecula are not clear, but they indicate that knowledge of the response of one species to disturbance (e.g. habitat fragmentation) may not necessarily provide a useful guide to the possible response of other taxa, including those that are very closely related.

Modelling dispersal behaviour on a fractal landscape

We use a spatially explicit population model to explore the population consequences of different habitat selection mechanisms on landscapes with fractal variation in habitat quality. We consider dispersal strategies ranging from random walks to perfect habitat selectors for two species of arboreal marsupial, the greater glider ( Petauroides volans) and the mountain brushtail possum ( Trichosurus caninus). In this model increasing habitat selection means individuals obtain higher quality territories, but experience increased mortality during dispersal. The net effect is that population sizes are smaller when individuals actively select habitat. We find positive relationships between habitat quality and population size can occur when individuals do not use information about the entire landscape when habitat quality is spatially autocorrelated. We also find that individual behaviour can mitigate the negative effects of spatial variation on population average survival and fecundity.

Population density and movement data for predicting mating systems of arboreal marsupials

A model, based on the number of encounters between male and female arboreal marsupials, was used to predict the rate of polygyny (the proportion of males fathering offspring with more than one female). The model predicted that the rate of polygyny would increase to an asymptote as population density increased. This result formalises previous suggestions that mating systems of arboreal marsupials may change with population density. Data on movements derived from radio telemetry and trap-recapture methods were used to predict the rate of polygyny in a population of the mountain brushtail possum ( Trichosurus caninus) at Cambarville, Victoria, southeastern Australia. The model predicted that 26% of males that successfully raised offspring in 1995 would be polygynous. In 1995, blood samples were taken from 13 offspring to determine paternity by DNA profiling. The model predicted that it is unlikely ( P=0.006) that the 13 offspring would be fathered by 13 different males if T. caninus mated polygynously. Thus, the model may be used to construct hypotheses about the mating system of arboreal marsupials that may be tested with subsequent genetic analysis.

The effects of parasites on a wild population of the Mountain Brushtail Possum (Trichosurus caninus) in south-eastern Australia

The effects of a reduction of parasite burdens were determined in adult female Mountain Brushtail Possums, Trichosurus caninus, on the birth, mortality and growth rates of pouch-dependent young, as well as the haematological and serum biochemical values of the mothers. The efficacy of the anthelmintic drug ivermectin for reducing parasite burdens in this host was assessed using faecal and necropsy examinations of a small number of animals. Ivermectin began to reduce parasite burdens by 48 h after treatment. In the second stage of the experiment, animals were treated or sham injected (control individuals) with ivermectin and praziquantel at 8–10-week intervals throughout the breeding season to the time of emergence of young from the pouch. Treatment with ivermectin and praziquantel had no significant effect on the proportion of females giving birth, or on the survival of young to emergence. An effect of treatment was recorded for absolute eosinophil counts in adult females, which, in spring, were higher among control animals than those that were treated.

Modelling survival and capture probabilities of the mountain brushtail possum (Trichosurus caninus) in the forests of south-eastern Australia using trap-recapture data

Modelling survival and capture probabilities of the mountain brushtail possum (Trichosurus caninus) in the forests of south-eastern Australia using trap-recapture data

Modelling survival and capture probabilities of the mountain brushtail possum (Trichosurus caninus) in the forests of south‐eastern Australia using trap‐recapture data

AbstractThe results are described of a capture–recapture study of the Australian arboreal marsupial, the mountain brushtail possum (Trichosurus caninus Ogilby). Adult, subadult and juvenile T. caninus were captured during 11 trapping periods and at 70 different trap placement sites between June 1992 and November 1995 in a 40 ha area of mountain ash (Eucalyptus regnans F. Muell.) forest in the central highlands of Victoria, south‐eastern Australia. A total of 80 (37 male and 43 female) T. caninus were captured, comprising 45 adults, 14 subadults and 21 juveniles when first trapped. This gave a total of 333 captures of T. caninus from approximately 4600 trap nights.The Jolly–Seber–Cormack approach was employed to model the frequency of recapture as simple product functions of the survival and capture probabilities for each inter‐trapping interval. Using this method, we explored the relationships between survival and capture probabilities of T. caninus and a range of potential explanatory variables including sex, age class, time, and trap location.The results of our analyses indicated that there was a high probability of recapture of T. caninus–P= 0.80 (0.03 SE – with females significantly (P < 0.05) more likely to be caught than males. There was spatial heterogeneity across our study site in the probability of recapture of T. caninus, and animals inhabiting areas of old growth were more likely to be retrapped than animals in younger forest where potential nest sites within large standing dead trees with hollows are decaying rapidly and are at high risk of collapse. There were no significant differences between the survival rates of different sexes or age classes, and the monthly value for the probability of persistence calculated for T. caninus was 97.7% (0.48%).Our study demonstrated that T. caninus is long‐lived with high levels of survival among individuals of all age classes once young animals have emerged from the pouch. Animals have relatively high site affinity and are readily recaptured, often at exactly the same place, or very close to, where they were first caught. Some juveniles have taken up permanent residence in the natal territory, which may result in opportunities to mate with close relatives.

Consumption of hypogeous fungi by the mountain brushtail possum (Trichosurus caninus) in eastern Australia

Faecal samples collected from the Mountain brushtail possum ( Trichosurus caninus ) at several sites in eastern Australia showed the presence of spores from at least 21 hypogeous fungi, and several epigeous species. Most were found in faeces of animals at one site, where samples were collected in different seasons. Further collections are needed from the other sites at different times of the.year to clarify how widespread the mycophagous habits of T. caninus are. Many of the hypogeous fungi identified are either known or presumed to form mycorrhizal relationships with the roots of forest trees and shrubs and T. caninus may disperse their spores in its faeces.

Estimating body condition in the mountain brushtail possum, Trichosurus caninus

Two methods of assessing body condition were examined for the mountain brushtail possum, Trichosurus caninus (Ogilby) at a single study site in central Victoria, south-eastern Australia. Condition indices were derived from measures of skeletal size and body mass, and body water composition was determined using isotopic dilution of tritiated water to give an estimate of total body water space. There were significant negative relationships between body water composition and the condition indices for body length, total length and pes length. Body water composition of T. caninus was significantly higher in spring than in winter, and those animals with higher body water composition had lower absolute neutrophil counts and higher urea values. The relative usefulness of the two methods used for estimating body condition in T. caninus is discussed.

The use of nest trees by the mountain brushtail possum (Trichosurus caninus) (Phalangeridae : Marsupialia). V. Synthesis of studies

A general synthesis is presented of the key results of a series of studies of den tree use by the mountain brushtail possum (Trichosurus caninus) at Cambarville in the mountain ash (Eucalyptus regnans) forests of the central highlands of Victoria, south-eastern Australia. The project produced a range of unexpected results including (1) the number of den trees used, (2) the extent of den sharing, especially among adult males, (3) the overlap in denning ranges of animals, and (4) the predictability of transitions between den trees. Possible reasons for these findings are outlined. We also discuss the limitations of our study, how it could be improved if it were to be repeated, and some of the important implications of the findings for the management of forests where T. caninus occurs.