Academic literature on the topic 'Common ringtail possums'

The common ringtail possum (Pseudocheirus peregrinus) is considered abundant throughout its distribution in eastern Australia but appears to be declining at a regional level in inland New South Wales. Previous studies of the common ringtail possum in south-eastern Australia have focussed on coastal populations and little is known about the ecology of inland populations. In south-western Australia studies of the closely related western ringtail possum (Pseudocherius occidentalis) have found that coastal populations differ from inland populations, particularly in their nesting behaviour. In this preliminary study of an inland population of the common ringtail possum at Black Rock Ridge in central west New South Wales population density has been estimated and the habitat and nesting preference assessed. Up to one ringtail per hectare and 4.5 ringtails per spotlight hour were recorded. Tree hollows appeared to be the preferred nest site, with possums seen entering hollows during spotlighting and no dreys being located. Threats to common ringtail possums at Black Rock Ridge include the isolation of the remnant ridge vegetation within an extensively cleared landscape and the associated change in fire regimes. Within this landscape there has been an extensive reduction in available habitat, and an overall lack of habitat connectivity has placed ringtail possums at an increased risk of predation.

Road-associated mortality has been identified as having major ecological effects on small, fragmented and declining populations. Both the common brushtail possum (Trichosurus vulpecula) and common ringtail possum (Pseudocheirus peregrinus) appear to be in decline in some regions across their natural ranges. Urban populations may be an exception; however, little is known of their population ecology. This study investigates age trends in a subset of road-killed brushtail and ringtail possums collected along eight northern Sydney roads between March 2004 and March 2006. From a total of 591 recorded road-killed possums, 86 were collected for use in this study (36 brushtails, 50 ringtails). Age was estimated using tooth wear patterns on cleaned skulls. Both species showed trends associated with age, and younger possums of both species were more likely to be killed on roads than older animals. Male-biased dispersal of subadult possums is considered a major contributing factor to the over-representation of young brushtail possums in this road-kill sample.

Animal–vehicle collisions impact wildlife populations and in the northern suburbs of Sydney, both the common brushtail possum (Trichosurus vulpecula) and the common ringtail possum (Pseudocheirus peregrinus) are killed in large numbers. Over a two-year period almost 600 road-killed possums were observed from 217 road surveys covering over 7800 km, equating to 5.45 possums per week over the 36-km study area. Surveys were conducted along roads where the environment ranged from low-rise suburban to continuous sclerophyll forest. Significantly more ringtail possums were observed as road-kill, outnumbering brushtail possums by almost three to one. No sex bias was found amongst road-killed ringtail possums; however, seasonal trends and weight fluctuations were significant, with both males and females being at their lowest weights during the autumn breeding season. For brushtail possums a bias towards young males was observed. Sex and weight of road-killed brushtail possums were comparable to live-trap data from a previous study in the same location. In areas of such high possum mortality, wildlife managers may need to take action to mitigate possum road-kill.

Populations of the common ringtail possum (Pseudocheirus peregrinus) in inland New South Wales have declined or disappeared. Habitat requirements and diet of these populations are poorly understood. Determining the diet of inland ringtail possums is crucial to understanding the factors limiting their survival, and was the focus of this study. Spotlighting surveys were conducted to locate ringtail possums, and scat and vegetation samples were collected for microhistological analysis. Ringtail possums were most frequently observed in red stringybark followed by bundy box and black cypress pine trees, and this correlated with the most common dietary items consumed.

The digestive tracts of preserved specimens of six species of New Guinean pseudocheirid (ringtail) possums (body mass 148-1250 g) and four species of New Guinean phalangerids (cuscuses) (730-2400 g) were compared. A preliminary study on Australian common ringtail possums (Pseudocheirus peregrinus) suggested that, within certain limits, data from preserved material were applicable to fresh specimens. The New Guinean ringtails were primarily folivorous, but the diet of the two smallest species contained more non-leaf material and was of higher quality, on the basis of higher (P<0.05) nitrogen levels in their gastric contents. Like P. peregrinus, New Guinean ringtail possums selectively retain fine feed particles and bacteria in their caecum, and may also be caecotrophic. The New Guinean phalangerids are less specialised in their diets, taking a wide range of leaves, bark and fruits. There was no evidence for caecotrophy or selective retention of bacteria in their caecum, but there was evidence for selective retention of fine feed particles. In the latter characteristic they differ from the Australian phalangerid Trichosurus vulpecula (the common brushtail possum).

The diet of powerful owls (Ninox strenua) living at Christmas Hills, 35 km north-east of Melboume, was examined by analysis of 686 regurgitated pellets collected over two years. Mammalian prey was found in 89%, insects in 13%, vegetation in 11% and birds in 10% of the pellets. Of the mammals, common ringtail possums occurred most frequently in the pellets over the year. There was no seasonal difference in the frequency of occurrences of common ringtail possums and sugar gliders in pellets. However, common brushtail possums were more likely to be taken in spring than in the other seasons. More adult common ringtail possums were taken as prey than were other age classes over the year, except in summer when high numbers of young were consumed by the owls.

Following bushfires in Sydney in 1994 a population of 20–30 common ringtail possums (Pseudocheirus peregrinus) that had been studied for four years was reduced to only one or two animals. In the intervening years population numbers remained at this low level. Four years after the fire, 22 ringtail possums were introduced into the study site and radio-tracked for 30 weeks. Nest usage shifted from predominantly dreys before the fire to an equal amount of time spent in dreys and tree hollows. Proportionally, the mortality due to predation by lace monitors (Varanus varius) and diamond pythons (Morelia spilota spilota) increased. Within 12 months the population returned to only two animals. We conclude that increased predation by native predators, added to continued predation by foxes and cats, has maintained a level of predation beyond a threshold that would allow the ringtail population to re-establish to previous levels.

The present study reports novel aspects of the reproductive biology of the male common ringtail possum (Pseudocheirus peregrinus). Plasma testosterone was measured through a stimulation test using the gonadotrophin-releasing hormone agonist, buserelin. Following intra-muscular administration of buserelin, there was an increase (P < 0.05) in testosterone concentration in the peripheral circulation 4 h later. Quantitative testicular histology of this species was described for the first time. Eight stages of the seminiferous epithelium cycle were identified in 10 possums and their relative frequency determined. Spermatozoa were recovered from the cauda epididymides of hemi-castrated possums and cryopreservation conducted in straws (6°C min–1) using final glycerol concentrations ranging between 2 and 20% in Tris-citrate egg yolk extender (v/v). Frozen straws were thawed and post-thaw motility, rate of motility, the percentage of live–dead spermatozoa and the percentage of sperm with swollen decondensed nuclei recorded. Similar to other marsupial sperm, common ringtail possum cauda epididymidal spermatozoa required high levels of glycerol (10–16%) in order to maintain post-thaw viability.

Museum specimens of seven Australian Pseudocheiridae (ringtail possums and greater glider) and six Australian Phalangeridae (brushtail possums and cuscuses) were examined to assess the extent of possible differences in gastrointestinal tract morphology and function within and between these two families of Australian folivorous possums. Although there were no differences between the two families in gut segment lengths, the Pseudocheiridae had less relative tissue mass in the small intestine (P < 0·05) and greater relative tissue mass in the caecum (P < 0·05) than the Phalangeridae. Total nitrogen concentrations of stomach, caecum and proximal colon digesta were greater in the Pseudocheiridae than in the Phalangeridae (P < 0·05), but in the distal colon they were similar. These differences suggest that the colonic separation mechanism previously documented in two pseudocheirid species is probably characteristic of the family Pseudocheiridae, but not of the Phalangeridae. They also reflect the more folivorous nature of the Pseudocheiridae, as leaves are generally higher than fruit in total nitrogen concentration. Among members of the Phalangeridae, there were no significant differences in any of the parameters measured, and it is concluded that the digestive strategy of the common brushtail possum (Trichosurus vulpecula) is probably representative of the family. In contrast, there were several notable differences among members of the Pseudocheiridae, indicating that the common ringtail possum (Pseudocheirus peregrinus) is not representative of all pseudocheirids. In particular, the digestive strategy of the rock ringtail possum (Petropseudes dahli) should be examined in relation to its unusual habitat, to its relatively simple caecum, and to the unusually low nitrogen concentrations found throughout its gastrointestinal tract.

The common ringtail possum (Pseudocheirus peregrinus), a member of the family Pseudocheiridae, is an arboreal folivorous marsupial that feeds predominantly on Eucalyptus foliage. Contrary to the expectation that small body size would inhibit utilisation of a diet containing such high levels of lignified fibre because of relatively low gut volume to body mass ratios and relatively high mass-specific metabolic rates and nutrient requirements (Hume 1999), the ringtail possum is able to survive solely on a diet of Eucalyptus foliage. The rabbit (Oryctolagus cuniculus) is a terrestrial herbivore and is a member of the family Leporidae that feeds predominantly on grasses. The rabbit was proposed as a digesta flow model for the ringtail possum since both are caecotrophic (periodically re-ingest caecal contents) and both are proposed to exhibit a colonic separation mechanism (CSM) where fluids and small, easily digested particles are preferentially returned to the caecum. The rabbit is of value for the modelling process since it is more accessible for experimental manipulation than the ringtail possum. This study investigated a proposal to use digesta passage through the gastrointestinal tract (GIT) of the rabbit as a model of digesta passage for the ringtail possum on the basis that both are caecotrophic caecum fermenters. A number of potential problems were identified with this proposal and investigation of these problems formed the basis for the research described in this thesis. Two main areas were identified as being potentially problematic: 1) fundamental flaws with the particulate markers used in digesta rate of passage studies; and 2) differences in animal behaviour and natural diet between the two subject species which suggested different digestive strategies and hence different patterns of digesta flow through the GIT. The proposed digesta passage markers were lanthanide metals (Dy, Tm, Eu and Yb) attached to either fibrous particles (1200 - 600�m) or formalin-fixed rumen bacteria (20 � 0.2�m). These markers were shown to not be of the assumed size classes and the extent of lanthanide metal binding differed between the four metals used. An effect due to method of dosing was also observed. The findings of marker inconsistencies caused major limitation to model development and further research is necessary to clarify these markers. The proposal to use digesta flow in the rabbit GIT as a model for digesta flow in the ringtail possum was shown to be idealistic due to the differences in anatomy and behaviour observed between the two herbivores. Laboratory observations, time series analysis and compartmental modelling confirmed the differences between the animals. This study showed: 1) the GIT of the rabbit was more complex both anatomically and functionally than that of the ringtail possum; 2) behaviour affecting digesta passage of the rabbit and ringtail were different and; 3) compartmental models confirmed the anatomical and behavioural findings. Digesta passage in the rabbit could not be modelled mathematically using data on digesta passage due to complexities of the system. In contrast, a basic model was constructed for digesta passage in the ringtail possum. On the basis of these findings, the research hypothesis "that digesta passage in rabbits is similar to that in ringtail possums" was rejected.

The common ringtail possum (Pseudocheirus peregrinus), a member of the family Pseudocheiridae, is an arboreal folivorous marsupial that feeds predominantly on Eucalyptus foliage. Contrary to the expectation that small body size would inhibit utilisation of a diet containing such high levels of lignified fibre because of relatively low gut volume to body mass ratios and relatively high mass-specific metabolic rates and nutrient requirements (Hume 1999), the ringtail possum is able to survive solely on a diet of Eucalyptus foliage. The rabbit (Oryctolagus cuniculus) is a terrestrial herbivore and is a member of the family Leporidae that feeds predominantly on grasses. The rabbit was proposed as a digesta flow model for the ringtail possum since both are caecotrophic (periodically re-ingest caecal contents) and both are proposed to exhibit a colonic separation mechanism (CSM) where fluids and small, easily digested particles are preferentially returned to the caecum. The rabbit is of value for the modelling process since it is more accessible for experimental manipulation than the ringtail possum. This study investigated a proposal to use digesta passage through the gastrointestinal tract (GIT) of the rabbit as a model of digesta passage for the ringtail possum on the basis that both are caecotrophic caecum fermenters. A number of potential problems were identified with this proposal and investigation of these problems formed the basis for the research described in this thesis. Two main areas were identified as being potentially problematic: 1) fundamental flaws with the particulate markers used in digesta rate of passage studies; and 2) differences in animal behaviour and natural diet between the two subject species which suggested different digestive strategies and hence different patterns of digesta flow through the GIT. The proposed digesta passage markers were lanthanide metals (Dy, Tm, Eu and Yb) attached to either fibrous particles (1200 - 600�m) or formalin-fixed rumen bacteria (20 � 0.2�m). These markers were shown to not be of the assumed size classes and the extent of lanthanide metal binding differed between the four metals used. An effect due to method of dosing was also observed. The findings of marker inconsistencies caused major limitation to model development and further research is necessary to clarify these markers. The proposal to use digesta flow in the rabbit GIT as a model for digesta flow in the ringtail possum was shown to be idealistic due to the differences in anatomy and behaviour observed between the two herbivores. Laboratory observations, time series analysis and compartmental modelling confirmed the differences between the animals. This study showed: 1) the GIT of the rabbit was more complex both anatomically and functionally than that of the ringtail possum; 2) behaviour affecting digesta passage of the rabbit and ringtail were different and; 3) compartmental models confirmed the anatomical and behavioural findings. Digesta passage in the rabbit could not be modelled mathematically using data on digesta passage due to complexities of the system. In contrast, a basic model was constructed for digesta passage in the ringtail possum. On the basis of these findings, the research hypothesis "that digesta passage in rabbits is similar to that in ringtail possums" was rejected.

The western ringtail possum, Pseudocheirus occidentalis, is classified as threatened, both nationally and internationally. Land clearing for building development threatens the last major coastal population stronghold in and around the town of Busselton in the south-west of Western Australia (WA). Translocation of displaced P. occidentalis from this locality into nearby conservation estates commenced in 1991, in the presence of fox control, with the aim of re-establishing populations of the species within suitable habitat outside its current range. Initial successes (1991-1998) were followed by a major population decline at one site for unclear reasons. The aim of this project was to determine which factors presently limit translocation success for P. occidentalis and thereby provide direction for future management of the species. Displaced and rehabilitated P. occidentalis were translocated into three sites, two of which were baited for fox control. Survival was monitored weekly, causes of mortality were ascertained and attributes of habitat use were mapped and analysed. Each individual P. occidentalis underwent comprehensive health and disease screening under isoflurane anaesthesia prior to translocation and whenever recaptured for re-collaring. Health, survivorship and habitat use of resident common brushtail possums, Trichosurus vulpecula, were similarly studied at each site. Pilot spotlight surveys using line transect methods were performed at the end of the study to provide provisional data on population densities. Health screening revealed no evidence that infectious disease currently limits translocation success for P. occidentalis. Possums of both species were negative for toxoplasmosis, leptospirosis, salmonellosis and chlamydiosis. Cryptococcal antigen was detected in one individual T. vulpecula but was not of pathological significance. Endoparasite levels were negatively correlated with body condition. Differences between pre- and post-translocation haematological values were found, suggesting that habitat quality or nutrient intake were lower at the translocation sites than at the sites of origin. Mortality rates of translocated P. occidentalis were high. The majority of P. occidentalis deaths were attributed to predation, with foxes, cats, pythons and raptors all implicated. Some P. occidentalis died in poor body condition from apparent hypothermia/hypoglycaemia, with moderate to heavy parasite burdens present at necropsy. Most T. vulpecula mortality was attributable to fox predation. Survivorship analyses were carried out using information-theoretic techniques to investigate which, if any, of a suite of hypothesised factors most influenced post-translocation survival of P. occidentalis. The most highly ranked models were those that included pre-release white blood cell counts and/or numbers of T. vulpecula at the release site. Survivorship of P. occidentalis was negatively correlated with each of these factors, and the two together acted in a synergistic fashion. Effects of fox control on P. occidentalis survivorship were equivocal. The average annual survival rate of established P. occidentalis was less than half that of resident T. vulpecula. Post-translocation dispersal distances varied among individual P. occidentalis. Mean home range sizes of translocated P. occidentalis were larger than those reported for other coastal populations. Individual home ranges overlapped one another, both within and between possum species. Vegetation dominated by peppermint (Agonis flexuosa) was utilised by translocated P. occidentalis where available, and habitat partitioning between the two possum species was observed in some areas. A greater range of diurnal rest site types were utilised by P. occidentalis than T. vulpecula. Spotlight surveys revealed presence of low density P. occidentalis populations, including juveniles, at two sites but numbers remained negligible in the site at which the post-1998 decline had occurred. Complex interactions involving health, predation, habitat quality and inter-specific competition influence the success or otherwise of wildlife translocation programs. The results of this project suggest that all these factors, particularly predation, affected translocation outcomes for P. occidentalis during the period of study. Complete exclusion of exotic predators (foxes and cats) from the translocation sites may be necessary in future, especially given the numbers of native predators (pythons and raptors) present. In addition to heavy predation pressure, the small size and apparently low carrying capacity of the translocation sites for P. occidentalis, along with high numbers of resident T. vulpecula, currently appears to limit P. occidentalis survival and population growth. While, in the short term, the most efficient use of funds and the best option for the species in its current coastal strongholds might be to put greater effort into conserving P. occidentalis in its natural environment, there could also be value in carrying out further experiments to determine whether or not translocation success can be improved through use of particular management actions. The principles of adaptive management apply both to management of P. occidentalis in its natural environment and to conduction of translocation programs. Possible experimental approaches are outlined and recommendations for further research proposed.

Biodiversity conservation throughout the world is challenged by the impacts of a changing climate on fragmented landscapes. To mitigate these threats, conservation managers require models which can demonstrate the consequences of both negative impacts and management actions. This need can be addressed through spatial modelling applications. Unfortunately, throughout much of the world, spatial modelling is forgone, being seen as requiring skills and resources beyond the means of many conservation planners and managers. This thesis seeks to address this dilemma by delivering criteria for a successful modelling application and by providing case studies which demonstrate how appropriate modelling can be undertaken without highly specialised skills or prohibitively expensive software and equipment. In this way it facilitates the delivery of better targeted and, consequently more effective, management actions. For my case studies I have used the south-western corner of Australia as a demonstration landscape. This region is recognised internationally as a “biodiversity hotspot,” not only for the biological richness and uniqueness of species but also for the level of threat to which they are subject. Like many landscapes throughout the world, much or this region’s natural biota exists in fragmented, fragile and degraded patches and is therefore highly vulnerable to the anticipated impacts of anthropogenic global warming. In this thesis I have: 1) examined the principles of spatial modelling and reviewed how spatial modelling has been applied to conservation management in this region, 2) conducted examples of different forms of spatial modelling using actual regional conservation management issues, and 3) demonstrated how these examples can be incorporated into conservation management planning. My key findings are: Spatial modelling provides users with an opportunity to effectively test hypotheses, thereby informing the planning process and improving conservation outcomes. Where spatial modelling is omitted from the process, knowledge gaps are often addressed by the axiomatic and by assumption. This is contrary to the principles of effective adaptive management. Modelling tools are inherently more effective when selected for their capacity to meet a planning objective rather than where projects are tailored to meet a model’s capacity. The coordinated use of multiple tools can often provide a more robust understanding of the consequences impacts and mitigating actions. All tools and data sets used should be utilised with a clear and acknowledged understanding of their suitability, strengths and limitations. A wide range of spatial modelling tools (and data sets) are freely and readily available to conservation managers. Most of these come with excellent tutorials and support services. Data gaps can often be addressed through targeted field observations, obtained through complimentary planning processes, or synthesised from accessible data sets. There is a very large body of peer reviewed literature demonstrating means by which others have applied existing modelling tools, or developed tools themselves, to meet a wide range of applications. Accessing this literature is an excellent means of building spatial modelling capacity. New and improved tools, methodologies and data sets are constantly being developed. A failure to implement effective spatial modelling is becoming increasing difficult to justify.

This study examines the annual cycle of energy and time expenditure in a small folivorous marsupial, the common ringtail possum, Pseudocheirus peregrinus. Particular attention was given to the energy expended in lactation by the females. Field metabolic rate (FMR) and water flux were measured using an isotopic technique (doubly labeled water). Feeding rates were estimated from measurements of FMR in conjunction with information on the composition of the diet and a digestibility study. FMR's and subsequent feeding rates estimated by the doubly-labeled water technique do not include the proportion of food consumed which is diverted to milk solids and is not metabolised by the mother. The amount of energy transferred directly to the young ringtail possum via the milk was estimated from measurements of milk composition and production. Reproduction in the common ringtail possum in Tasmania was seasonal, with the majority of births (mean litter size 1.8) in late autumn and early winter. In general, the young leave the pouch during early spring and are fully weaned by the early summer months. There was no significant seasonal variation in the energy expenditure or water influx of males. The mean FMR of males and non-lactating females was approximately 2.5 times basal metabolic rate which is consistent with the hypothesis that a low total energy cost of free existence (or field metabolic rate) is a characteristic shared by arboreal folivores. Females showed significant changes in water influx and energy expenditure according to their lactational status. The greatest metabolisable energy expenditure was that of females during Phase 3 of lactation (30% above nonreproductive metabolism). Water influx was correspondingly high in these females (36% above non-lactating females). In general, ringtail possums in both the field and captivity lactated for approximately seven months. However, the length of lactation was shorter in females which bred twice in a year. The composition of the milk varied throughout lactation. A peak in milk solids and energy content coincided with emergence of the young from the pouch. Milk solids represented around 18% (w/w) with milk fat representing only 10% of milk solids. Milk production peaked during Phase 3 of lactation. The dilute milk with a relatively low fat content combined with a long period of lactation result in slow growth of the young. Peak milk energy output was 154.5 kJ.kg-0·75 .d-1 and peak metabolisable energy allocation during lactation was 763.2 kJ.kg-0.75 .d-1. These were lower than values available for other herbivores. However, the total output of milk energy by ringtail possums ( 11 MJ/kg) and total metabolisable energy allocation during reproduction (23.4 MJ/kg) were similar to estimates available for other herbivores. The lactational strategy of the ringtail possum has been selected, most likely, in order to spread the energy demands of reproduction over time due to constraints on the rate of energy intake imposed by a leaf diet. The total energy requirement for reproduction (34.4 Ml/year, or 14% of total annual energy budget) suggests that the ringtail also has a relatively low overall energy investment in reproduction. Estimates of total body water made from isotopic dilution and measurements of body mass suggest that females utilise body fat stored during the early stages of lactation to cope with the additional energy required for late lactation. However, reproduction is apparently timed such that late lactation coincides with the increased production of young foliage. Therefore females may also increase their food and water intake during late lactation by consuming young foliage. Differences were found in the composition of milk collected from wild and captive animals. Chemical analyses of the leaves eaten suggested that these differences were due to variations in diet composition. It was, therefore, proposed that the intraand inter-population variation in reproductive traits shown by the common ringtail possum may be related to variations in milk composition and/or production caused by variations in diet quality.