Academic literature on the topic 'Brushtail possums'

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.

The common brushtail possum (Trichosurus vulpecula) is an arboreal marsupial that has adapted well to urban landscapes. Fifteen adult possums (12 female, 3 male) caught in small patches of indigenous vegetation (remnants) in the south-east of metropolitan Melbourne were radio-tracked over a three-month period to investigate nocturnal behaviour and den use. Minimum convex polygon (100%) home-range estimates of both female (1.02 ± 0.28 ha) and male (1.19 ± 0.33 ha) urban brushtail possums trapped in urban forest remnants appear to be smaller than those previously reported for urban brushtail possums. All the brushtail possums foraged extensively in remnants but made repeated forays into adjacent residential areas. The use of few dens, by both female (2.21 ± 0.35 ha) and male (2.51 ± 1.45 ha) brushtail possums, in close proximity to their nocturnal ranges is similar to the behaviour of non-urban brushtail possums

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.

Brushtail possums (Trichosurus vulpecula) have been variously described as endangered, pests, prized native wildlife and, recently, as a potential meat export. This article reports information on the increasing decline of the brushtail possum and on attitudes towards these animals. The ‘fit’ between values and attitudes and prevailing governance arrangements is assessed. While the range of this animal is certainly shrinking, areas do exist where the brushtail possum is present at high or very high densities. It is in these areas of high possum density (some urban areas and certain agricultural regions) that conflicts arise, both over the ‘identity’ of the brushtail possum and as to what would be appropriate management. It is argued that although brushtail possums enjoy significant legal protection, these provisions are treated as a nuisance to be circumvented by many residents in areas where possums are in high abundance. Existing policies on possum management somewhat unhelpfully focus attention on situations where possums are overabundant, thus overshadowing situations where active management of declining possum populations would be appropriate.

DESPITE their almost ubiquitous presence across Australia, contemporary research on the biology, ecology and conservation status of the so-called 'common' possums is scant and inadequate. The majority of possum studies have been a result of the huge research effort in New Zealand to control and eradicate the common brushtail possum, a notorious introduced pest, and have concentrated primarily upon reproductive physiology. The conspicuous lack of ecological data on the larger possums across their native Australian range is particularly disturbing since evidence suggests that a number of these species are disappearing from large tracts of Australia. However, Possums: the brushtails, ringtails and greater glider, part of the Australian Natural History Series, provides a long overdue summary of up-to-date research on these familiar and intriguing marsupials.

AbstractBrushtail possums, Trichosurus vulpecula, are New Zealand's most serious vertebrate pest, facilitating the spread of bovine tuberculosis to livestock, and causing severe damage to native flora and fauna. Possum control has become a national research priority, involving the use of large numbers of captive possums. Successful adaptation of these animals to captivity is important for the welfare of the possums and for the validity of experimental results. The objective of this study was to determine, by behavioural means, the time individually caged possums required for adaptation to captivity. We used a simple behavioural measure - a possum's daily response to a caregiver at feeding (a feeding test) - to assess changes in the behaviour of possums after arrival in captivity. We also recorded changes in possum body weight throughout this period. Initially most possums ‘avoided’ the caregiver, but within 7 days more than 80 per cent of animals no longer avoided. ‘In den’ and ‘approach’ behaviour rapidly increased for the first 14 days in captivity, after which den use became less common as more possums ‘approached’ the caregiver. By day 29 of captivity, more than 80 per cent of the possums ‘approached’ the caregiver. The possums’ body weight did not change significantly during the first 14 days in captivity, but had increased significantly by day 28, and continued to increase for at least 6 weeks after capture. These data suggest that most possums adapt to captivity within 4 weeks. For the welfare of possums and the reliability of experimental results, we recommend that possums are not used in experiments until at least 4 weeks after capture.

The population ecology of Trichosurus vulpecula has been studied extensively in temperate Australia and in New Zealand. This paper provides the results of a trapping study of a population of the northern brushtail possum (T. vulpecula arnhemensis Collett 1897) in the wet–dry tropics of Australia’s Northern Territory. Possums were readily trapped and the population had a comparatively high density for Australian brushtails of around 3 per hectare. The core home-range size and range length for males was 1.12 ha and 165 m; this was a little larger than for females (0.89 ha and 155 m). The possums were not very agressive when handled and were apparently quite socially tolerant. The ready availability of nutritious food sources throughout the year enables them to breed continuously, producing 1.7 young per year per adult female. If environmental conditions become unfavourable with a series of poor wet seasons or frequent fires, the habitat will resemble the less-productive eucalypt forest not occupied by possums. Mortality of pouch young and immatures will increase under these conditions but with a potential reproductive rate of nearly two per year, populations of the northern brushtail can readily recover from short periods of unfavourable conditions.

The paucity of evidence on eucalypt browsing by common brushtail and common ringtail possums suggests that ringtails preferentially eat foliage from trees within the subgenus Monocalyptus. In contrast, brushtails eat less eucalypt foliage than do ringtails and prefer trees from the subgenus Symphyomyrtus. Trees from these subgenera differ in their defensive chemicals. Both contain tannins but it appears that only the symphyomyrts synthesise formylated phloroglucinol compounds (FPCs). We fed possums foliage from several individual Eucalyptus rossii and E. consideniana, both monocalypts, to avoid the confounding factor of FPCs, and examined the effects of blocking tannins by dipping foliage in polyethylene glycol (PEG). Ringtails and brushtails differed in their abilities to eat foliage from these eucalypts. The ringtails ate much more than did the brushtails and showed a small (about 10%) but significant increase in feeding in response to PEG. The brushtails were reluctant to eat foliage from either eucalypt species but doubled their intake when leaves were coated with PEG. Even so, they still did not eat enough to meet maintenance requirements for energy and nitrogen. Neither ringtails nor brushtails preferred foliage from any individual E. rossii tree, suggesting that all trees were equally defended. However, brushtails preferred foliage from some E. consideniana to others. Monocalypt tannins are clearly important barriers to feeding in brushtail possums, but further research with higher doses of PEG will confirm whether they are the only deterrent chemicals in monocalypt foliage.

We studied the influence of a group of plant secondary compounds, the sideroxylonals, on feeding by the common brushtail possum (Trichosurus vulpecula), a generalist herbivore. Possums were offered synthetic diets either with or without sideroxylonals or, in separate experiments, foliage from 28 individual Eucalyptus melliodora trees. Possums ate less of the synthetic diet at sideroxylonal concentrations of 4 and 7 mg g–1 when offered a choice or no choice, respectively. Possums fed foliage in no-choice protocols ate 12–61 g of dry matter per day. Sideroxylonal concentration was an essential determinant of feeding on foliage but the wide variation, particularly at intermediate sideroxylonal concentrations, suggests that other secondary plant chemicals, e.g. tannins, are important also. The normal distribution of sideroxylonal concentrations (mean = 27.7, s.d. = 7.85 mg sideroxylonals per g dry leaf) in a natural population of 150 E. melliodora trees shows that brushtail possums will rarely encounter highly palatable trees (<10 mg sideroxylonals per g dry leaf) nor highly unpalatable foliage (>40 mg sideroxylonals per g dry leaf). When foraging on E. melliodora, brushtail possums must contend with intermediate sideroxylonal concentrations (20–30 mg per g dry leaf), where variability in food intake is most noticeable.

The comparative plasma pharmacokinetics of iophenoxic acid was studied in the cat and brushtail possum (Trichosurus vulpecula) to evaluate the suitability of this compound as a bait marker in these species. In cats, a mean peak plasma concentration of 946 micro g per 100 ml was obtained after administration of 1.5 mg/kg of iophenoxic acid. However, at the same dose level in possums, mean peak plasma concentration was only 157 micro g per 100 ml. Even after administration of 10 mg/kg of iophenoxic acid, the maximum peak plasma concentration in possums was only 459 micro g per 100 m/litre. The plasma elimination half-life for iophenoxic acid was 107 days in cats and close to one day in possums. Iophenoxic acid is therefore a suitable marker for cats but is unsuitable for use as a long-term or quantitative bait marker for possums. Differences between the possum and other mammals in gastrointestinal physiology and plasma protein configuration by account for the poor absorption and rapid elimination of iophenoxic acid in the possum.

A total of 9 brushtail possums (Trichosurus vulpecula) were trained to perform a two-manipulanda, conditional discrimination task. The possums learned to press a right lever in the presence of a tone (80 dB(A)) during tone-on trials, and a left lever in the absence of the tone on tone-off trials. Overall sessions of 11 conditions contained tone frequency between 100 Hz and 35 kHz were tested. Each condition contained training and then probe sessions. In training sessions, the possums were presented with tone-on and tone-off trials, pseudo-randomly. Once the possums responded with over 90% accuracy for five consecutive sessions, then probe sessions were introduced. Probe sessions were similar to the training sessions, except that the tone intensity for tone-on trials was reduced by 8 dB(A) across blocks of 20 trials until their response accuracy in a block fall below 60% or reached 24 dB(A). Data were analysed using overall percentages correct and log d analysis. Both measures indicated that overall response accuracy decreased for all possum as tone intensity reduced. Based on these data analyses, threshold values were calculated using the criterions at 75% correct and a log d of 0.48. The threshold values for each possum and across all possums were plotted as a function of the tone frequency to produce an audiogram. A curvilinear regression was fitted for each threshold values. The functions of both measures were very similar. Both audiograms showed that the possums could hear the tones between 100 Hz and 35 kHz, and were most sensitive to tones between 15 and 20 kHz. This experiment involved many difficulties with producing and measuring tones especially outside of human hearing range. Due to these difficulties, several problems and concerns were raised during the experiment, these were discussed in this study and also recommendations for future research were then presented.

Thesis by publication -- 8 co-authored articles.
Thesis (PhD)--Macquarie University, Division of Environmental and Life Sciences, Department of Biological Sciences.
Includes bibliographical references.
Preface -- Management issues of urban common brushtail possums (Trichosurus vulpecula): a loved or hated neighbour -- Effects of deslorelin implants on reproduction in the common brushtail possum (Trichosurus vulpecula) -- Brushtail possums (Trichosurus vulpecula) in metropolotan Sydney: population biology and response to contraceptive implants -- Strategic survey for Toxoplasma gondii and Neospora caninum in the common brushtail possum (Trichosurus vulpecula) from urban Sydney, Australia -- Leptospirosis serology in the common brushtail possum (Trichosurus vulpecula) from urban Sydney, Australia -- Conclusions.
The common brushtail possum (Trichosurus vulpecula) is indeed a common inhabitant of many Australian citites, and one of the few marsupials that has adapted well to the urban environment. Their close proximity to people provides a great opportunity to experience native wildlife in the backyard, however, their utilization of house roofs, bold behaviour and appetite for garden plants often leads to conflict with householders. Population numbers are sufficiently high to require ongoing management to minimise negative impacts for humans and brushtail possums alike in a socially acceptable manner. The aim of this thesis was to identify current management issues and address the need for improved and novel management strategies. The potential of slow-release implants, containing the GnRH agonist deslorelin, as a contraceptive agent for brushtail possums was tested on a captive population. Males appeared resistant to treatment, but deslorelin was found to inhibit reproduction in female brushtail possums for at least one breeding season, making it a promising tool to control fertility in some wild populations. A further aim was to trial deslorelin implants on a wild urban population, to collect more information about the urban biology of this species and to point out issues which have previously not been addressed. Close proximity and interaction of urban brushtail possums with humans and their domestic animals can increase the risk of disease exposure and transmission and influence the health of wild populations. Serosurveys showed that animals were readily exposed to Leptospira spp. and Toxoplasma gondii. This thesis also provides the first data on brushtail possum dispersal in urban areas, knowledge which is highly relevant to the development of management strategies such as fertility control. The findings from this research broaden our knowledge about urban brushtail possums and should assist wildlife authorities in developing alternative or improved management procedures.
Mode of access: World Wide Web.
xxv, 287 p. ill., maps

This thesis is about making inference on the host status of feral ferrets in New Zealand for Mycobacterium bovis, the aetiological agent of bovine tuberculosis. The central question addressed is whether the rate of intra-specific transmission of M. bovis among ferrets is sufficient for the disease to persist in ferret populations in the absence of external, non-ferret sources of infection (inter-specific transmission). The question is tackled in three parts�firstly using model selection to identify suitable models for estimating the force of M. bovis infection in ferret populations; secondly applying statistical hypothesis testing to the results of planned manipulative field experiments to test the relationship between M. bovis infection in brushtail possums and that in ferrets; and thirdly using modelling to estimate intra-specific disease transmission rates and the basic reproductive rate (Ro) of M. bovis infection in ferrets. The model selection approach clearly identified the hypothesis of oral infection related to diet was, as modelled by a constant force of infection from the age of weaning, the best approximation of how M. bovis infection was transmitted to ferrets. No other form of transmission (e.g., during fighting, mating, or routine social interaction) was supported in comparison. The force of infection (λ) ranged from 0.14 yr-1 to 5.77 yr-1, and was significantly higher (2.2 times) in male than female ferrets. Statistical hypothesis testing revealed transmission of M. bovis to ferrets occurred from both brushtail possums and ferrets. The force of M. bovis infection in ferrets was reduced by 88% (λ=0.3 yr-1 vs. λ=2.5 yr-1) at sites with reductions in the population density of sympatric brushtail possum populations. A smaller decline in the force of infection resulting from the lethal cross-sectional sampling of the ferret populations was also demonstrated. The modelling approach estimated the basic reproductive rate (Ro) of M. bovis infection in ferrets in New Zealand to vary from 0.17 at the lowest population density (0.5 km-2) recorded to 1.6 at the highest population density (3.4 km-2) recorded. The estimates of Ro were moderately imprecise, with a coefficient of variation of 76%. Despite this imprecision, the Ro for M. bovis infection in ferrets was significantly less than unity for all North Island sites surveyed. Hence it is inferred ferrets are spillover hosts (0Kt), the rate of intra-specific transmission of M. bovis among ferrets is sufficient for the disease to establish in ferrets in the absence of interspecific transmission. In these areas, ferrets would be considered maintenance hosts for the disease. Active management (e.g., density reduction or vaccination) of ferrets would be required to eradicate M. bovis from ferret populations in these areas, in addition to the elimination of sources of inter-specific transmission, particularly brushtail possums.

Aerial control using 1080 (sodium monofluoroacetate) baits is widely used in New Zealand for the control of introduced brushtail possums (Trichosurus vulpecula), with the aim of protecting national conservation and agricultural values from these damaging pests. This thesis integrates research, completed over 25 years, that was motivated by growing recognition in the 1970s of the extent of possum impacts and the need to improve the effectiveness and efficiency of the control operation. Field research assessed the palatability of three types of cereal-based pellet baits and carrot baits in different regions, habitat types and seasons. Palatability was assessed by the consumption of the different bait types presented independently of each other on 15-30 plots, with rotation of bait types at plots on successive nights to provide equal exposure to each bait type. There was regional variation in possums' bait preferences, possibly reflecting genotypic differences, whereas seasonal variation was less evident. Carrot bait was preferred or equally preferred to cereal bait in 14 out of 20 field trials. The proportion of possums eating baits was then investigated by, firstly, developing a technique for tracing bait acceptance using rhodamine B, a UV-fluorescent dye. In four field trials, more than 95% of possums accepted three types of dye-marked bait, eliminating bait refusal as a major reason for low kills in winter control operations. In a fifth trial, conducted in summer, only 68% of possums accepted bait suggesting that seasonal availability of favoured foods may influence bait acceptance. Since possums must encounter baits before deciding whether to eat them, field studies were undertaken to assess the coverage achieved in normal aerial baiting operations. Large gaps, up to 400 m in width, were often found between baiting swaths; these could allow some possums to survive. A controlled field experiment, using acceptance of rhodamine-dyed bait as a measure of effectiveness, showed that bait distribution was least accurate where flight paths were not marked. Where gaps of 100 m between flight paths were deliberately created, bait acceptance was slower and less than where coverage was complete. Sowing baits at 3 kg/ha was as effective as at 10 kg/ha, indicating the potential for substantially reducing operational costs by using machinery capable of faultlessly distributing baits at low rates. Navigational guidance systems were evaluated and found to improve the accuracy of bait distribution. During 1993-1997, when a lower sowing rate of 5 kg/ha was adopted operationally by regional managers, control effectiveness was unchanged but annual savings of around $9 million accrued. Because of the lack of suitable sowing machinery, a bucket was developed to permit faultless distribution of baits at lower rates, demonstrating the possibility of yet further cost-savings. The possibility of seasonal food availability affecting bait acceptance was investigated in three different forest habitats. Dyed baits were aerially distributed on 100 ha at each site in each season over two years. In each trial, fat-based condition indices of possums were calculated and the abundance of possum-preferred plant foods described. Bait acceptance was consistently high (85-100%) in the 24 trials, and was not influenced by either condition or availability of preferred foods. It seems likely that seasonal variation in operational effectiveness is caused by either the availability of sharply seasonal, scarce foods that possums may feed on intensively for brief periods, or by warmer temperatures that render 1080 less effective. The influence of 1080 on acceptance of (rhodamine-dyed) baits was investigated in a field trial. Examination of possums for dye-marking showed that 25% of possums refused to eat either a lethal quantity of bait or any bait at all, compared with 98% of possums eating non-toxic bait. This indicated that 1080 is aversive to possums, which is a potential major reason for their surviving control operations. Pen trials were therefore conducted to further examine the problem and to seek solutions. Toxic carrot baits were rejected by 27.5% of possums, equally by smell and taste aversion, whereas toxic cereal pellets were rejected by 34%, mainly by taste aversion. Orange and cinnamon were shown to be among the most preferred of 42 flavours tested and, when applied to toxic baits, 1080 was effectively masked. Bait refusal was reduced to ≤7%, the same as that recorded for possums presented with flavoured non-toxic baits. For long-term control of possum populations, aerial 1080 baiting can be used sequentially with other poisoning methods. However, the compatibility of these methods is dependent on the likelihood of possums developing bait shyness if sublethally dosed. Studies were therefore conducted to characterise and compare the four main toxicants used (1080, cyanide, cholecalciferol and brodifacoum) for induction and mitigation of bait shyness. Shyness was induced in approximately 80% of possums sublethally dosed with cyanide, 60% with 1080, 20% with cholecalciferol, and 0% with brodifacoum. Cyanide and 1080 shyness were found to persist in many possums for at least 12 and 24 months, respectively. Use of alternative bait types, and of baits containing an alternative slow-acting toxin (brodifacoum) were shown to be effective ways of overcoming shyness. This, and other related research, is reviewed to provide operational specifications that maximise the likelihood that all targeted possums will (i) encounter bait, (ii) eat it, and (iii) die. The likely future use of aerial 1080 baiting is described and the technological, economic, environmental and social constraints on its sustainability are discussed. Finally, the uptake of the research by possum managers is considered, and areas identified in the thesis where information is incomplete are summarised as prioritised topics for further research.

This study examined the physiological and behavioural effects of a stress-inducing stimulus (predator odour) on potential prey species (Australian native and exotic). The aim was to determine if differences in the response of prey were related to the scent of evolutionary known predators compared to unfamiliar or short-term introduced ones. In laboratory experiments, responses were always restricted to changes in respiratory variables, with brushtail possums (Trichosurus vulpecula), rabbits (Oryctolagus cuniculus) and tammar wallabies (Macropus eugenii) showing no variation in metabolic rate after exposure to predator odours.Brushtail possums showed strong changes in ventilatory rate only when faced with the scent of an historical predator, increasing respiratory frequency (ratio after/before exposure = 4.55 ± 1.007) and decreasing tidal volume (ratio after/before exposure = 0.38 ± 0.113 ) in response to stale dingo urine. The changes were short-lived, lasting for only one minute of exposure. For this reason, it is unclear if the response observed could be considered as a fear reaction. However, there was no habituation after three exposures and this may indicate that possums were initially displaying an investigative approach to a predator scent and then relaxing once assessment was completed.The effect of predator and novel odours on the ventilation of rabbits appeared to be in general mediated by anxiety, as shown by the responses elicited by both predator and control scents. However, stronger reactions were observed in response to feral cat and quoll odours for both respiratory frequency (ratio after/before exposure to feral cat = 4.39 ± 0.721 and to quoll = 3.75 ± 0.486) and tidal volume (ratio after/before exposure to feral cat = 0.47 ± 0.065 and to quoll = 0.64 ± 0.129). This could be due to different intensity of the olfactory stimuli. Nevertheless, the effects of noxious odours on rabbits clearly demonstrate that they become highly vigilant at any sudden change in their environment.Tammar wallabies appeared to possess a mechanism for the recognition of predator odours as ventilatory responses were restricted to particular predator scents. After investigation, fox and cat odour provoked a stronger and more prolonged change in respiratory frequency (ratio after/before exposure to fox = 3.58 ± 0.918 and to feral cat = 2.44 ± 0.272) and tidal volume (ratio after/before exposure to fox = 0.84 ± 0.110 and to feral cat = 0.98 ± 0.155) compared to the other scents, suggesting that wallabies may have perceived these species as more immediate threats.For wild, free-living brushtail possums and southern brown bandicoots (Isodoon obesulus), there was no pattern of avoidance of historical or introduced predator odours, with no difference in number of animals captured in predator and control scented traps. This may indicate that predator odour avoidance has not evolved in these species and that they have poor possibilities of escaping potential predators. However it may also be explained by the long-term predator-free environment in which the study was conducted, and suggests loss of anti-predator behaviour in populations without predation risk.Wild, free-ranging western grey kangaroos (Macropus fuliginosus) reacted to the odour of both historical (dingo) and novel (fox) predators by reducing number of feeding events (5.2±2.08 for fox and 5.9±1.33 for dingo) and time spent foraging (17.7±7.2 sec for fox and 22.2±4.6 sec for dingo) when predator scents were present and by escaping areas tainted with predator odours (41.4±17.5 sec for fox and 33.8±13 sec for dingo). Clearly these results suggest that kangaroos are scared of predator odours. However, a close investigation of predator scents was necessary before a response could be elicited and feeding areas were not completely abandoned.It is still unclear if small Australian prey, such as southern brown bandicoots and brushtail possums, respond to olfactory cue of predation in the wild, as different results were obtained in the studies conducted in the laboratory and in free populations. However, this research showed that medium and large-sized macropods respond to both native, long-term and introduced predator odours. This indicates that at least some Australian prey species can recognise the odour of potential predators, although responses usually occur after a period of investigation, and do not always result in avoidance behaviour. Differential responses appear to be based on the perceived risk. Use of predator odour is unlikely to be an effective mechanism of deterring herbivores from preferred feeding locations.

The common brushtail possum (Trichosurus vulpecula) is the most significant vertebrate pest in New Zealand as an ecological threat to the indigenous biodiversity and an economic threat as a vector for bovine tuberculosis. Biological control is considered to be the most accepted management strategy to reduce the population, specifically by impairing fertility. Successful development of a biocontrol agent (most likely a protein or peptide macromolecule) requires identification of a compound that is species-specific and potent. The challenge is also to deliver the bioactive to this free-ranging, widespread, feral animal and ensure sufficient bioavailability. Macromolecules have low oral bioavailability, thus new formulation strategies are required to enhance stability and absorption in the gastrointestinal tract (GIT) of T. vulpecula. Oral administration of the bioactive contained within a non-toxic bait is the most practical delivery strategy. Essential to designing an oral delivery system is to quantify the transit time of different sized delivery systems. The gastrointestinal transit in T. vulpecula was investigated (n = 72) by gamma scintigraphy. Technetium-labelled (99mTc) anion exchange resin particles (75 - 125 (mu)m or 500 - 700 (mu)m) or solution (99mTc-DTPA) was administered orally. After 3, 6, 12, 24 or 32 h, distribution of radioactivity in excised GITs was determined. Transit profiles were similar for each formulation. For delivery to the hindgut, bioactives need protection for 12 h though the upper GIT. Particulate formulations may be retained in the caecum for up to 32 h. Transit time was not different between animals dosed in the evening or the morning. Furthermore, GIT morphology is different between specimens in this study from southern New Zealand and Australian specimens. This may reflect improved diet quality in New Zealand. A model protein (insulin) was incorporated into poly(ethyl 2-cyanoacrylate) (PECA) nanoparticles prepared by interfacial polymerisation of water-in-oil microemulsions. The mean size of nanoparticles was 220 nm with a mean entrapment efficiency of 78%, determined using reverse phase HPLC. In vitro release of insulin from PECA nanoparticles in phosphate buffer (0.067 M, pH 7.4) at 37°C was triphasic and not all entrapped insulin was released. Following in vitro incubation of nanoparticles with enzyme solutions prepared from the GIT of T. vulpecula, lumen enzymes were more aggressive towards insulin compared to mucosal enzymes and the hindgut lumen was the GIT region with the lowest degradation. For the first time in a marsupial species, the in vivo pharmacokinetics of insulin-loaded, PECA nanoparticles were investigated following i.v. and intra-caecal administration and measured by radioimmunoassay. The low cross reactivity of human and endogenous brushtail possum insulin means that T. vulpecula is a suitable non-diabetic model to study pharmacokinetics of insulin. The i.v. pharmacokinetics of insulin solution and insulin-loaded nanoparticles were similar. On intracaecal dosing, co-administration of a permeation enhancer (EDTA) resulted in a small increase in plasma insulin concentration compared to insulin-loaded nanoparticles alone. In conclusion, transit time to the caecum of T. vulpecula following oral delivery was 12 h for fluid and particulate formulations < 1 mm diameter and was independent of the time of day the dose was given. T. vulpecula is a potential non-diabetic model for the study of insulin pharmacokinetics. This thesis demonstrates the potential application of oral peptide and protein delivery technology in the area of wildlife management.

This study investigates the ecology of one of the best known Australian marsupials, the Common Brushtail Possum Trichosurus vulpecula, in central Australia. Trichosurus vulpecula is one of few medium-sized mammal species that persist in arid Australia today. Its distribution within the arid zone has declined markedly since European settlement. Two populations, one within the East MacDonnell Ranges along the Hale River and the other on Irving Creek, a River Red Gum creek in the Petermann Ranges, were studied in the southern Northern Territory. Others locations in the region were visited opportunistically. Trie central Australian Trichosurus is not distinct genetically from populations elsewhere in Australia. The diet of T. vulpecula consisted of a range of leaves, flowers and fruits of perennial dicotyledonous species as well as some ephemeral herbs. Grasses were absent from the diet. Variation in the diet reflected seasonal availability in flowers and fruits. The species preferentially consumed at each site had significantly higher moisture content and dry matter digestibility than species not consumed. Preferred species included Amyema maidenii leaves (a mistletoe), Acacia spp. flowers and fruits, Santalum lanceolatum leaves (a shrub), Marsdenia australis leaves (a vine), Solarium quadriloculatum fruit (shrub) and Euphorbia spp. leaves (herb). Small amounts of invertebrate material were consumed throughout the year. Other non-plant material consumed included honeycomb and unfledged birds eg. Budgerigars. There were no significant differences in the diet between the sexes. Trichosurus vulpecula were found in six main habitats: Acacia aneura/Callitris glaucophylla on rocky hills; E. camaldulensis sandy creek-lines; mixed Acacia rocky hills, Rocky Eucalyptus creek-lines; Degraded drainage lines; and Wet gullies. Logistic regression modelling revealed a significant correlation between mistletoe species richness, higher levels of soil nitrogen and the presence of T. vulpecula. In habitats occupied by T. vulpecula species richness of mistletoes was associated with the absence of fire and the presence of reliable ground water supplies. Trichosurus vulpecula were highly mobile with mean home ranges at Hale River of 44.21 � 22.76 ha and considerably higher than those recorded in previous studies in Australia. Mean home ranges at Irving Creek were much smaller, at 4.99 � 1.46 ha and VII similar to that recorded in other studies in Australia. At both sites, males had larger home ranges and there was a high degree of overlap with other males and females. At the Hale River study site, T. vulpecula predominantly denned in caves or cavities in rocks, whereas at Irving Creek all den sites were in large Eucalyptus camaldulensis on the drainage line. Adult and pouch young sex ratios were at parity. During this study, T. vulpecula was found to breed continuously, with births recorded in almost all months. Growth of the young were more rapid than previously recorded for Trichosurus in Australia. This is interpreted as an adaptation for living in an arid environment, enabling the young to achieve independence before quality food supplies diminish. No single exotic predator or competitor was solely responsible for the decline of T. vulpecula in arid Australia, implying an interactive impact. Prey switching by dingoes from rabbits to T. vulpecula, macropods and echidnas followed the crash of rabbit populations at Hale River. Predation by dingoes on T. vulpecula was only recorded once, at the Irving Creek study site, where numbers of rabbits remained stable throughout the study. The impact of exotic herbivores occurred through habitat degradation rather than competition. Evaluation of the ecological data collected during this study generally supports current models of decline and extinction in medium-sized mammals in arid Australia, integrating the effects of predators, competitors, drought and fire. However, the importance of each factor on populations of T. vulpecula was found to vary depending on their location in the landscape. This study suggests two separate models to explain the decline of T. vulpecula in arid Australia after the arrival of Europeans. The first operates in the riparian lowlands and the second on the rocky ranges. In both models, prior to European settlement, T. vulpecula occupied refuge habitats characterised by readily available moisture for plant growth (run on areas and/or shallow water tables) and soils with higher soil nutrient concentrations. The impact of fires on these refugia was minimal, as Aboriginal burning practices protected them with mosaic burning generally preventing large-scale fires from developing. Following European settlement, the forces impacting on populations were different in the riparian lowlands from those affecting rocky ranges. In the riparian lowlands, the effects of rabbits and livestock together with predation were found to have the major impact on T. vulpecula populations. Fire was not a significant factor in these areas. In the rocky ranges, fire was the most significant factor affecting T. vulpecula populations. Introduced herbivores did not degrade these habitats as they did in the riparian lowlands because the rugged and steep nature of the ranges acted as a physical barrier. Similarly, predator numbers were lower because of the relative difficulty in moving over rough ground and the generally lower relative abundance of preferred prey such as rabbits. An adaptive management strategy needs to be implemented to determine the effects of different management regimes on T. vulpecula population viability. The key elements of a management strategy in the riparian lowlands involves the manipulation and monitoring of predators, rabbits and livestock numbers. In the rocky ranges, the key management strategy involves the implementation of a patch burning to prevent fires entering habitats occupied by T. vulpecula. Importantly, any management strategies should involve Aboriginal people. Trichosurus vulpecula is an important part of Aboriginal culture. Its decline is of great concern to many people and several of the remaining populations and potential reintroduction locations are on Aboriginal land. Because of their relationship with the land and the animals, people have both the knowledge of the animal and the skills (such as patch burning) to provide information to managers which will assist with management. To achieve these management directions a coordinated national education programme is required to inform and convince the Australian community that conservation of T. vulpecula is deserving of attention in arid and semi-arid Australia. This is particularly important given the perception that T. vulpecula is a common species throughout Australia, despite its massive decline in arid Australia since European settlement.

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.

The distribution of mistletoe in South Westland silver beech forest was investigated. Stand structure and densities of Peraxilla colensoi (pirita) were assessed along six altitudinal transects. Host size and forest structure were both found to be important factors influencing density and distribution of mistletoe. Generally large beech trees were favoured as mistletoe hosts. There was also significant variation in mistletoe density between forest types. In a different study the leaf area removed by possums and insects from a population of mistletoe plants was quantified over a nine month period. Insects browsed all plants, and on average consumed around 4% of each mistletoe's leaf area. The overall consumption of mistletoe leaf area by possums was around 2%, but possum browse was not evenly spread over the population. Of the forty plants sampled, seven were attacked by possums with one plant being heavily browsed. By the end of the monitoring period the leaf area retained by possum browsed plants was significantly lower than that of unbrowsed plants. If individual mistletoes continue to be selectively browsed then defoliation and death of some mistletoe plants seems a likely outcome. Possum diet was assessed by means of gut sample analysis and compared to estimates of food availability within silver beech forest. Possums utilised a wide range of food types but two or three species were dominant at any particular time of the year. Seral species such as wineberry, pohuehue, fuchsia, and lawyer were generally the most important foods. Mistletoe was not an important food item, contributing less than 1% of annual possum diet.