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1

Osugi, Mizuho. "Measuring Auditory Thresholds in Brushtail Possums (Trichosurus Vulpecula)." The University of Waikato, 2008. http://hdl.handle.net/10289/2422.

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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.
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2

Eymann, Jutta. "Management of urban common brushtail possums (Trichosurus vulpecula)." Doctoral thesis, Australia : Macquarie University, 2007. http://hdl.handle.net/1959.14/6.

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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
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3

Caley, Peter, and n/a. "Inference on the host status of feral ferrets (Mustela furo) in New Zealand for Mycobacterium bovis infection." University of Canberra. Resource, Environment & Heritage Studies, 2001. http://erl.canberra.edu.au./public/adt-AUC20050621.140940.

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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.
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4

Morgan, David R. "Maximising the effectiveness of aerial 1080 control of possums (Trichosurus vulpecula)." Lincoln University, 2004. http://hdl.handle.net/10182/20.

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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.
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Mella, Valentina S. A. "Physiological and behavioural responses of Australian and exotic prey to the scent of native and introduced predators." Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/350.

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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.
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McDowell, Arlene, and n/a. "Oral delivery of bioactive compounds to the common brushtail possum (Trichosurus vulpecula)." University of Otago. School of Pharmacy, 2005. http://adt.otago.ac.nz./public/adt-NZDU20070306.151503.

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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.
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Foulkes, Jeffery Neil, and N/A. "The ecology and management of the common brushtail possum Trichosurus vulpecula in Central Australia." University of Canberra. Applied Science, 2001. http://erl.canberra.edu.au./public/adt-AUC20050411.101222.

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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.
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Clarke, Judith Rebekah. "Translocation outcomes for the Western Ringtail Possum (Pseudocheirus occidentalis) in the presence of the Common Brushtail Possum (Trichosurus vulpecula): health, survivorship and habitat use." Thesis, Clarke, Judith Rebekah (2011) Translocation outcomes for the Western Ringtail Possum (Pseudocheirus occidentalis) in the presence of the Common Brushtail Possum (Trichosurus vulpecula): health, survivorship and habitat use. PhD thesis, Murdoch University, 2011. https://researchrepository.murdoch.edu.au/id/eprint/5119/.

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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.
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9

Owen, Hamish John. "Mistletoe and the brushtailed possum in silver beech forest, South Westland, New Zealand." Thesis, University of Canterbury. Forestry, 1993. http://hdl.handle.net/10092/7027.

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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.
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10

Veitch, Colleen Evelyn. "Aspects of female reproduction in the marsupials, the brushtail possum, Trichosurus vulpecula and the northern brown bandicoot, Isoodon macrourus /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19371.pdf.

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11

Harfoot, Natalie Ann, and n/a. "Molecular identification of membrane transporters associated with secretion in the ileum and colon of the common brushtail possum, Trichosurus vulpecula." University of Otago. Department of Physiology, 2009. http://adt.otago.ac.nz./public/adt-NZDU20090903.143108.

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Electrolyte transport in the intestine of the common brushtail possum (Trichosurus vulpecula) differs from that observed in eutherian mammals. This study has used molecular physiology to identify and characterise the expression and distribution of membrane transporters potentially responsible for these differences in electrolyte transport in the possum intestine. In the possum ileum, secretagogues stimulate an electrogenic Cl⁻-independent HCO₃⁻ secretory response but secretagogue-stimulated Cl⁻ secretion does not occur in this tissue. Based on the ion dependence and pharmacology of the stimulated secretory response, the expression of the cystic fibrosis transmembrane conductance regulator (CFTR), pancreatic Na⁺ HCO₃⁻ cotransporter (pNBC) and Na⁺ K⁺ 2Cl⁻ cotransporter (NKCC1) were investigated in the ileum. Reverse transcription PCR experiments showed that CFTR, pNBC and NKCC1 mRNA transcripts were expressed in the ileal epithelium. It was then demonstrated by in situ hybridisation that both CFTR and pNBC were localised predominantly in the crypts and the levels of expression decreased along the crypt-villous axis towards the lumen. Significantly, the in situ hybridisation results showed that there were low levels of NKCC1 transcript in the ileal epithelium. Western blot studies confirmed that mature CFTR and pNBC proteins were expressed in the ileum, while NKCC1 protein was not detected. The findings of the present study suggest that the absence of Cl⁻ secretion in the ileum is because NKCC1 expression is not elevated in the epithelium. The expression of mature CFTR and pNBC protein suggest that these membrane transporters are involved in the stimulated electrogenic HCO₃⁻ secretory response. The evidence also suggests that CFTR may mediate HCO₃⁻ efflux in the ileum. In contrast, secretagogues do not stimulate an electrogenic secretory response in the proximal and distal colon. This study has shown that CFTR, NKCC1 and pNBC proteins are expressed in the proximal and distal colon. Both NKCC1 and pNBC transcripts were localised to the crypt base in the proximal colon. However, it was shown that CFTR has a punctate distribution and the transcript was predominantly observed in the upper crypt and surface cell region. This study indicated that NKCC1 and pNBC were distributed in a different region of the epithelium compared to CFTR. It was concluded that the distribution of these membrane transporters in different regions of the epithelium accounts for the absence of a stimulated electrogenic secretory response in the possum colon. Given that no stimulated electrogenic secretory response is observed in the colon, it is suggested that HCO₃⁻ secretion by the ileum may have an important physiological role in maintaining an appropriate fluid and pH composition for fermentation in the colonic lumen.
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12

Head, Nicholas. "The impacts of possum herbivory and possum control on threatened palatable species (Pittosporum patulum, Alepis flavida and Peraxilla tetrapetala) in the Lake Ohau Catchment, South Island, New Zealand." Lincoln University, 2005. http://hdl.handle.net/10182/1957.

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The impacts of possum herbivory were assessed on 713 individual plants of the nationally endangered Pittosporum patulum and 115 individual plants of the threatened ('Gradual Decline') mistletoes (Alepis flavida & Peraxilla tetrapetala) over three years in the Temple and Huxley river valleys in the Ohau catchment, South Island New Zealand. Statistical models were used to test the influence of several explanatory variables on the probability of survival and growth rates of these rare palatable plants. Increasing defoliation levels were the most significant predictors of mortality for both P. patulum and mistletoe, and reduced growth rates in P. patulum. Mortality of P. patulum increased with plant size although smaller plants were also affected by mortality. P. patulum mortality was greater for non-forest habitats, and growth rates were greatest on warm aspects. Mistletoe mortality increased with warm aspect, steeper slopes and at lower altitudes. Plant survival and growth increased in the Temple valley following possum control. Although indicative of a positive treatment effect, other factors may have also influenced this result. Possums are the major herbivore responsible for the widespread decline of P. patulum and beech forest mistletoes throughout New Zealand, although the autecology of P. patulum predisposes it toward extinction more so than mistletoe. Monitoring in conjunction with possum control operations provide good opportunities for understanding the impacts of possums on palatable plants and ecosystems. Assessing defoliation levels on indicator species like P. patulum and mistletoes can serve as a guide for managers to assess ecosystem stress from herbivory.
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13

Pickett, Karolyne. "Sublethal impacts of risk of predation by the introduced red fox on the common brushtail possum (Trichosurus vulpecula) in New South Wales, Australia." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ45504.pdf.

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14

van, Eyndoven Erik. "Resource selection by the brushtail possum (Trichosurus vulpecula Kerr) in a mixed red - silver beech (Nothofagus fusca - N. menziesii) forest, north Westland, New Zealand : a multi-scale, GIS-based approach." Thesis, University of Canterbury. Forestry, 2003. http://hdl.handle.net/10092/6059.

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Resource selection by the brushtail possum (Trichosurus vulpecula) was studied in a beech (Nothofagus) forest in order to elucidate possum ecology in an extensive forest type lacking extensive possum research. The study was conducted in the Upper Grey Valley, north Westland, on a post-glacial terrace dominated by Nothofagus fusca and Nothofagus menziesii and dissected by a gravel road. Five principal research questions were posed for the study of possums within the site. These were: 1. What are the movement parameters of the resident possum population? 2. What are the patterns of vegetation heterogeneity? 3. What constitutes possum diet? 4. What are the relationships between possum diet and vegetation heterogeneity? 5. What are the relationships between possum movements and vegetation heterogeneity? Twelve possums were radio-collared and radio-tracked over a year. Home ranges calculated with the kernel method averaged 8.1 ± 1.0 ha (mean ± s.e.), which is large when compared to possum home ranges observed in other continuously forested sites. Range lengths were similarly large (456 ± 42 m). Bi-monthly variation was only displayed with significantly smaller home ranges in winter when compared to autumn. Despite the fact that the study site was generally dominated by N fusca and N menziesii, considerable heterogeneity existed with respect to the possum palatable species within the site. Many palatable species such as Aristotelia serrata, Fuchsia excorticata, Muehlenbeckia australis and Trifolium repens occurred predominately along the roadside, whilst Weinmannia racemosa occurred predominately on steep areas within the forest. TWINSPAN classification of the forest identified three vegetation communities. These were open sites, including the road and swamp areas, steep areas, including the hill and escarpments, and terrace areas. Resource selection by possums within the site was investigated with diet preference analysis, habitat selection analysis and modelling of use of space versus resource variables. Diet preference was analysed by comparing the level of consumption of food types with their level of availability within the site at multiple scales. The top five ranked preferred food types, calculated overall, were, in decreasing rank, Fuchsia excorticata foliage, Carpodetus serratus fruit, Rubus cissoides foliage, Muehlenbeckia australis foliage and Pseudopanax colensoi fruit. Habitat selection analysis indicated that although overall selection was not occurring, possums exhibited a degree of preference towards the terrace community. Modelling of resource variables against use of space indicated that although there was latent variability between individual possums, there was a trend for greater use of areas with high abundance of preferred species. Modelling of pooled possum use of space on an annual scale indicated that use was positively correlated with species richness and negatively correlated with N fusca, Quintinia acutifolia, and Coprosma rotundifolia abundance, which are all unpreferred species. Annual home ranges of possums were found to be negatively correlated with forage quality as defined by preferred species. A model of possum resource selection within the site was postulated to the effect that possums choose their home range location randomly, with respect to vegetation heterogeneity, and then modify the size of their home range to suit nutritional needs rather than modifying range location. The ranging behaviour and resource selection of possums observed in this study have implications for the management of possums in similar forest types. Efficiency of control and monitoring operations may be increased by using a spacing regime derived from possum home ranges. Inferences obtained from habitat selection analysis indicate that stratification of control and monitoring operations is not warranted in similar forest types. The development of extensive models with predictive capabilities for the distribution of possums within the environment has the ability to become a useful tool for possum managers. Further research of potential benefit could include investigation into resource quality and availability, the effect of home range size on residual trap catch (RTC) indices, improving diet assessment techniques and assessing possum preference for non-foliar food types.
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15

Molloy, Shaun. "Applying the principles of spatial modelling to the management of biodiversity in the fragmented landscapes of south-western Australia." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2013. https://ro.ecu.edu.au/theses/870.

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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.
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16

Nugent, Graham. "The role of wild deer in the epidemiology and management of bovine tuberculosis in New Zealand." Phd thesis, Lincoln University. Bio-Protection and Ecology Division, 2005. http://theses.lincoln.ac.nz/public/adt-NZLIU20070212.130927/.

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The eco-epidemiology of bovine tuberculosis (Tb) in wild deer (mainly red deer Cervus elaphus) in New Zealand was investigated. Bovine Tb is caused by Mycobacterium bovis. Specific aims were to clarify the likely routes of infection in deer, and to determine the status of deer as hosts of Tb, the likely rates and routes of inter- and intra-species transmission between deer and other wildlife hosts, the role of deer in spreading Tb, and the likely utility of deer as sentinels of Tb presence in wildlife. As the possum (Trichosurus vulpecula) is the main wildlife host of Tb, the research also included some investigation of transmission routes in possums. Patterns of infection were measured in 994 deer killed between 1993 and 2003. Tb prevalence varied between areas (range 8–36%). Few deer had generalised infection, with 21–68% of infected deer having no visible lesions, depending on the area. The retropharyngeal lymph nodes and oropharyngeal tonsils were commonly infected. No dependent fawns less than 0.75 years old were infected, indicating intra-species transmission is rare in wild deer. Where possums were not controlled, the net (cumulative) force of infection in young (1–4 y) deer was 0.10–0.24 per year in males and 0.09–0.12 per year in females, but much lower in older deer (less than 0.05 per year). Possum control reduced the net force of infection quickly, and eventually to zero. However, Tb persisted in possum-controlled areas through immigration of infected deer and, for almost a decade, through the survival of resident deer infected before possum control. Tb was lost from infected deer at an exponential rate of 0.13 per year, mostly as a result of deer recovering from infection rather than dying from it. Wild deer do die of Tb, but there was no discernible effect on age structure. The occurrence of infection in deer was not linked to the local deer or possum density at their kill sites (i.e. in their home range), but the area-wide prevalence of Tb in deer was closely correlated with Tb levels in possums, which were in turn correlated with area-wide measures of possum density. For wild deer in New Zealand, Tb is a persistent but usually inconsequential disease of the lymphatic system. It is acquired mainly by young independent deer, usually orally via the tonsils, and probably as a result of licking infected possums. Many species fed on deer carrion, including possums. Most possums encountering carrion did not feed on it, but a few fed for long periods. Other scavengers such ferrets (Mustela furo), hawks (Circus approximans), and weka (a hen-sized flightless native bird; Gallirallus australis) fed in a way that probably increased the infectivity of carrion to possums. Commercial deer hunting may have facilitated the historical establishment of Tb in possums. Scavenging (including cannibalism) and interactions with dead and dying possums are identified for the first time as potentially important routes for transmission of Tb to possums, and I develop new hypotheses involving peri- and post-mortem transmission in possums that explain many of the epidemiological patterns that are characteristic of the disease in possum. In continuous native forest, deer home range size averaged 250 hectares for six young females, and over twice that for two males. Over 90% of infected deer are likely to die within 2 km (females) or 6 km (males) of where they acquired Tb, but deer could occasionally carry Tb up to 30 km. Deer will be useful as sentinels, but only where other sentinels are rare, because the force of infection for a deer with a single infected possum in its home range is only 0.004 per year, compared to greater than 0.2 per year for deliberately released pigs. Deer are occasionally capable of initiating new cycles of infection in wildlife, but deer control is not essential to eradicate Tb from wildlife.
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17

Viggers, Karen. "Assessment of health, condition and the effects of parasites in the mountain brushtail possum." Phd thesis, 1996. http://hdl.handle.net/1885/145879.

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18

Vlahos, Lisa Marie. "Possum magic : exploring colour vision in the common brushtail possum (Trichosurus vulpecula)." Phd thesis, 2012. http://hdl.handle.net/1885/150889.

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Research into the diversity and evolution of mammalian colour vision has become even more exciting with the recent discovery of both trichromatic and dichromatic colour vision in the Australian marsupials. Our knowledge about these colour vision systems is limited, with a number of discrepancies in the research. Methodology issues with some of the anatomical and behavioural studies may have falsely indicated trichromacy. It is also uncertain whether only the tammar wallaby (Macropus eugenii) has dichromatic colour vision, or if dichromacy is represented in a number of marsupials. It is believed that most marsupials can perceive ultraviolet light, yet the transmission properties of ocular media have not yet been measured. In this thesis, I use anatomical and behavioural methods to examine colour vision in the Common Brushtail Possum (Trichosurus vulpecula). I firstly present a detailed analysis of the spectral transmission of light through the ocular media. Here, I demonstrated the variability of ocular media for three marsupial species: the ultraviolet light sensitive fat-tailed dunnart (Sminthopsis crassicaudata), non-ultraviolet light sensitive tammar wallaby, and common brushtail possum. I then examine the topographical arrangement and spectral sensitivities of photoreceptors in the common brushtail possum. Using opsin antibodies known to label photoreceptors, I show that brushtail possums have an anatomical basis for at least dichromatic colour vision, with both M/LWS ({u03BB}max = 545nm) and SWS cones present in the retina. There is also a small population of unlabelled cones, which may form a third cone population. Their extremely low densities,however, would hardly contribute to visual processing. By tracking cone densities across the retina, I provide the first evidence for regionalisation in both opsin and cell morphology types in an Australian mammal. Finally, I showed functioning dichromatic colour vision with behavioural operant conditioning techniques. Brushtail possums have an innate preference to using brightness rather than colour vision. By introducing spatial information which faded over time, I was able to encourage subjects to choose between colours irrespective of brightness. Both increment-threshold spectral sensitivity and wavelength discrimination experiments indicate their perception of colours is based on dichromatic colour vision. By comparing behavioural and microspectrophotometry results, I conclude that SWS cones peak in sensitivity around 435 nm. This is the first non-macropod known to have a violet, rather than an ultraviolet visual pigment. This thesis confirms a diversity of both trichromatic and dichromatic colour vision in marsupials, with the tammar wallaby not the only marsupial with dichromatic colour vision. I propose that brushtail possums have selectively reduced spectral sensitivity to dichromacy, evidenced by the presence of three cone types, yet perception of colours based on two cone types. The study of marsupial colour vision provides a rich resource for examining the diversity and use of dichromatic and trichromatic colour vision in mammals other than primates.
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19

Blyton, Michaela. "Connecting social system dynamics, population genetics and symbiotic interactions : insights from the mountain brushtail possum." Phd thesis, 2014. http://hdl.handle.net/1885/156092.

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The mating system and dispersal patterns of a species can profoundly affect fine-scale spatial genetic structure. Conversely, fine-scale spatial genetic patterns can have important ramifications for kin cooperation and mate choice. In my PhD, I explored these connections between social system dynamics and spatial genetic patterns using a combination of empirical research and modelling techniques. My empirical research centred on a field study of the mountain brushtail possum in the central highlands of Victoria, Australia. This semi-social, arboreal marsupial shelters in tree hollows, alone or shared, during the day and interacts at night. I used proximity logger collars to document the social interactions of this elusive species. By combining these data with microsatellite markers and mitochondrial sequences, I found that maternal lineages are a better predictor of interactions between individuals than bi-parental relatedness. This is likely to represent, in part, mother-offspring associations and suggests that kin recognition may occur through familial cues. Furthermore, the duration of nocturnal interactions were longer between females than males, which may be attributed to an interaction between kin selection and male-biased dispersal. Sex-biased natal dispersal can facilitate inbreeding avoidance by spatially separating kin. However, I showed through spatially explicit simulation modelling that the spatial clustering of kin cannot be prevented by sex-biased dispersal when dispersal distances are limited or a species has overlapping generations. Consistent with these simulations, spatial genetic autocorrelation analysis revealed that in mountain brushtail possums opposite-sexed kin remain in proximity, despite short range male-biased dispersal. To investigate how mountain brushtail possums respond to this inbreeding risk, I explored two inbreeding avoidance mechanisms; mate choice and mate-fidelity. Genetic parentage assignment analyses suggested that this species actively avoids kin during mate choice. Additionally, using probability modelling, I determined that individuals are more genetically monogamous than expected by chance. This high level of genetic monogamy may be due to social pair-bonding, which can be characterised by frequent interactions and overlapping home ranges. In addition to species-level processes, community-level interactions can influence social system dynamics. For instance, pathogen transmission can potentially constrain social interactions. To understand transmission dynamics associated with mountain brushtail possum behaviour, I used commensal Escherichia coli strains as a model system. I found high levels of temporal variability in E. coli community structure within host individuals, suggesting that strain sharing between individuals likely represents contemporary transmission. Additionally, within and among host E. coli strain abundance were correlated and predicted by the same aspects of the strains' functional genotype. Finally, I showed that strain sharing was better explained by social interactions than spatial proximity, suggesting that host-to-host contact maybe an important transmission route in this study system. Furthermore, I revealed that nocturnal interactions were more strongly associated with strain sharing than den sharing. Together, my results highlight how a multidisciplinary approach can provide detailed insights into the factors shaping a species social system dynamics. Further, they show how recent advances in animal tracking and surveillance technology combined with new genetic techniques can allow us to understand the socio-biology of elusive species.
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20

Isaac, Joanne Louise. "Life history variation and reproductive success of the common brushtail possum Trichosurus vulpecula /." 2004. http://eprints.jcu.edu.au/74.

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21

Isaac, Joanne. "Life history variation and reproductive success in the common brushtail possum, Trichosurus vulpecula." Thesis, 2004. https://researchonline.jcu.edu.au/74/1/01front.pdf.

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Life history theory aims to describe and explain patterns in the life cycles of organisms and relate these patterns to intrinsic and extrinsic influences. The life history of an organism is commonly defined as a set of co-evolved strategies that relate directly to an individuals genetic fitness, lifetime reproductive success (LRS) and survival. The great majority of research on life history variation in mammals has concentrated on placental mammals, while marsupials have been largely overlooked. This thesis investigates life history variation, and the influence of this variation on reproductive strategy and success, among individuals in an arboreal marsupial, the common brushtail possum (Trichosurus vulpecula). A population of T. vulpecula was studied from 2001-2004 on Magnetic Island, north Queensland; the population was censused each month by live-trapping. Demographic changes in the population were modelled using capture-mark-recapture data. The population size remained stable over the study period and there was little temporal variation in recruitment or survival. T. vulpecula on Magnetic Island displayed life history traits similar to those reported for other populations of the species. The majority (>80%) of females began to reproduce at the age of two and the main birth period occurred in the autumn months of April and May. Some females went on to produce a second young in the spring, after successfully raising a first. Males became sexually mature at the age of three. Survival, body mass and body condition declined in both males and females after the age of six, although the declines were more pronounced in males. Variation in life history was strongly related to differences in female reproductive strategy and success. In terms of somatic investment, older females invested significantly more into individual offspring than younger females; older females also gave birth earlier in the season and were more likely to produce a second offspring in the spring birth cohort. Maternal age also influenced the birth sex ratio; young, primiparous females gave birth to significantly more male offspring than older females, regardless of their condition while older, multiparous females were more likely to give birth to a male offspring when in good condition. The extent of male biased sexual dimorphism in T. vulpecula was extremely variable among 11 populations in northern Australia. Dimorphism was related to seasonality of breeding, being greatest in populations where births occurred all year round. Mean body mass of male possums also decreased with increasing population density, while there was no effect of density on female mass. There was also some evidence that population density influenced the degree of breeding synchrony within populations, particularly in locations with a more seasonal climate. In the Magnetic Island population, mating effort also varied considerably among male possums and young males lost more mass during the mating period than did older males. There was also some indication that males demonstrated age-specific variation in mating behaviour, which may be related to their size and experience. The results of my study show that life history traits in both male and female T. vulpecula are phenotypically plastic. Age-specific variation in reproductive strategy was found in both male and female possums and is likely associated with the trade-off between current and future reproduction. Increased reproductive effort in older females also appears to entail significant costs in terms of an associated decline in survival, condition and body mass. Variation in body condition also influenced offspring sex allocation in females and is most probably an adaptation to maximise LRS. Male possums displayed a more pronounced decline in survival and condition after the age of five compared to females and this may be a direct cost of increasing mating effort as a young adult.
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22

Isaac, Joanne. "Life history variation and reproductive success in the common brushtail possum, Trichosurus vulpecula." 2004. http://eprints.jcu.edu.au/74/1/01front.pdf.

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Life history theory aims to describe and explain patterns in the life cycles of organisms and relate these patterns to intrinsic and extrinsic influences. The life history of an organism is commonly defined as a set of co-evolved strategies that relate directly to an individuals genetic fitness, lifetime reproductive success (LRS) and survival. The great majority of research on life history variation in mammals has concentrated on placental mammals, while marsupials have been largely overlooked. This thesis investigates life history variation, and the influence of this variation on reproductive strategy and success, among individuals in an arboreal marsupial, the common brushtail possum (Trichosurus vulpecula). A population of T. vulpecula was studied from 2001-2004 on Magnetic Island, north Queensland; the population was censused each month by live-trapping. Demographic changes in the population were modelled using capture-mark-recapture data. The population size remained stable over the study period and there was little temporal variation in recruitment or survival. T. vulpecula on Magnetic Island displayed life history traits similar to those reported for other populations of the species. The majority (>80%) of females began to reproduce at the age of two and the main birth period occurred in the autumn months of April and May. Some females went on to produce a second young in the spring, after successfully raising a first. Males became sexually mature at the age of three. Survival, body mass and body condition declined in both males and females after the age of six, although the declines were more pronounced in males. Variation in life history was strongly related to differences in female reproductive strategy and success. In terms of somatic investment, older females invested significantly more into individual offspring than younger females; older females also gave birth earlier in the season and were more likely to produce a second offspring in the spring birth cohort. Maternal age also influenced the birth sex ratio; young, primiparous females gave birth to significantly more male offspring than older females, regardless of their condition while older, multiparous females were more likely to give birth to a male offspring when in good condition. The extent of male biased sexual dimorphism in T. vulpecula was extremely variable among 11 populations in northern Australia. Dimorphism was related to seasonality of breeding, being greatest in populations where births occurred all year round. Mean body mass of male possums also decreased with increasing population density, while there was no effect of density on female mass. There was also some evidence that population density influenced the degree of breeding synchrony within populations, particularly in locations with a more seasonal climate. In the Magnetic Island population, mating effort also varied considerably among male possums and young males lost more mass during the mating period than did older males. There was also some indication that males demonstrated age-specific variation in mating behaviour, which may be related to their size and experience. The results of my study show that life history traits in both male and female T. vulpecula are phenotypically plastic. Age-specific variation in reproductive strategy was found in both male and female possums and is likely associated with the trade-off between current and future reproduction. Increased reproductive effort in older females also appears to entail significant costs in terms of an associated decline in survival, condition and body mass. Variation in body condition also influenced offspring sex allocation in females and is most probably an adaptation to maximise LRS. Male possums displayed a more pronounced decline in survival and condition after the age of five compared to females and this may be a direct cost of increasing mating effort as a young adult.
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23

Chan, Judy. "Characterisation of delayed release granules for diphacinone: formulation for the control of brushtail possum in New Zealand." 2009. http://hdl.handle.net/2292/5483.

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Background and Aim: The common brushtail possum (Trichosurus velpecula) causes more damage to the environment than any other vertebrate species in New Zealand. The use of poison remains the main method for possum population control. Diphacinone is an anticoagulant that produces toxic effects by inhibiting the production of vitamin K–dependent coagulation factors which lead to profuse haemorrhage and eventually, death. The objective of this thesis was to investigate the potential of diphacinone as a toxin for the control of possum population in New Zealand. Methods: The preformulation of diphacinone included the development and validation of an analytical method, spectral identification, investigation of melting behaviour, solubility, and the determination of ionisation constant. The permeability of diphacinone across the ileal tissue of possum was assessed using a modified Ussing chamber model. Diphacinone granules were developed to prolong drug release and retention by in vitro dissolution and tensile testing. A factorial study was employed to optimise the granulation process by identifying significant process variables that influenced the yield percentage, size distribution and water uptake of granules.
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24

DeGabriel, Jane Louise. "Demographic constraints imposed by plant nutrients and secondary chemistry on the common brushtail possum (Trichosurus vulpecula Kerr)." Phd thesis, 2008. http://hdl.handle.net/1885/150327.

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Kerr, Sarah Emily. "Divergence of a mammal along a habitat gradient: a study of the coppery brushtail possum, Trichosurus vulpecula johnsonii." Thesis, 2011. https://researchonline.jcu.edu.au/23451/1/01front.pdf.

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I investigated the role of habitat in shaping mammalian evolution by studying the divergence of two parapatric subspecies, the common brushtail possum, Trichosurus vulpecula vulpecula, and the coppery brushtail possum, T.v.johnsonii, which are found in close proximity on the Atherton Tablelands in North Queensland, Australia. Their reputed distribution and colour differences, then unquantified, suggested that these subspecies may be candidates for evolution through parapatric speciation. This has never before been demonstrated in a mammal. I discovered that along a habitat gradient from dry sclerophyll forest and mosaic ecotone to rainforest, brushtail possums differed significantly in fur colour. The two morphs were characterised by their fur colour saturation: its colour intensity. Possums with low colour saturation were grey and did not inhabit rainforest. Those with high fur colour saturation were a red-copper colour and did not occur in dry sclerophyll forest. There was a dichotomy in the shade of red expressed among coppery brushtails, which was either a red-orange or redpurple hue, with the different rainforest localities of brushtails significantly associated with this variation. Brushtails in ecotone were either coppery or grey. Fur colour did not vary with distance from the ecotone, nor did fur colour appear to change once established in early development. Ecotone habitats supported very few possums, which may suggest some potential for the ecotone to restrict gene flow along the habitat gradient. The population density in rainforest was 18.6 times that in ecotone, and dry sclerophyll forest supported 8.7 times more brushtails than ecotone habitat. Coppery and grey brushtail possums were also morphologically distinct in body size. On average, coppery brushtails had ears that were 8mm shorter and 3.4mm thinner, legs that were 3.6mm shorter from knee to heel, and tails 34mm longer than grey brushtail possums of the Atherton Tablelands. There was no sexual dimorphism among brushtail possums along a habitat gradient for body size or colour, suggesting that sexual selection is unlikely to be acting upon these traits to promote divergence. Comparing mitochondrial DNA control region sequences I found that the morphological distribution was not the result of secondary contact between reciprocally monophyletic populations: coppery and grey possums have evolved together in multiple, distantly related clades. Analyses of the morphology of these clades demonstrated that variation in body-shape morphology was not associated with genetic similarity but with fur colour. As such, possums with the same fur colour also shared body size morphology, whether they were from genetically distant clades or if they were genetically similar. These differences, together with the bimodal distribution of morphs along habitat gradients, indirectly suggested that selection is acting upon these morphological traits to produce the phenotypes and distribution observed. Examination of the population structure of Atherton Tablelands brushtail possums using mitochondrial DNA control region sequences demonstrated that grouping populations by colour morphology did not explain genetic variation. Genetic differences between populations were not explained by the latitudinal, longitudinal, straight-line or elevation distances between them. However 30.1% of variation could be explained through the identification and separate grouping of the four populations that were closest to rainforest habitat. Along a habitat gradient, grey and coppery populations were distinct. Investigation of population structure with microsatellite loci showed significant gene flow throughout the Tablelands. Along the habitat gradient, adjacent coppery and grey populations were genetically distinct despite this widespread gene flow. Indeed several geographically more distant populations were not distinct with these markers. This suggested that gene flow is restricted along the habitat gradient. However reproductive isolation was not complete: calculations revealed that gene are exchanged in both directions along the gradient. Both grey and coppery brushtail possums reproduced synchronously, suggesting that there was no temporal discontinuity to gene flow. However this reproductive synchronicity may limit the potential for polygyny. With selection acting on morphology and gene flow restricted along a habitat gradient, two possums separated by the same geographic distance should be less related if they are different morphs than if they are the same colour. However, while the pairwise relatedness between different brushtail colour morphs was significantly different to those among coppery brushtails, there was no difference to comparisons among greys. This may be a consequence of the higher population densities of coppery brushtails; relatives may possess smaller home ranges and be closer. However these genetic results did not match our theoretical expectations: possums of different colour morphs and habitats were not less related than possums of the same morph at the same distance of separation. My underlying assumption was that fur colour in the coppery brushtail possum, like so many other species, is a genetically determined trait. If true, then brushtail colour is inherited and determined via an unprecedented mechanism. While this can not be discounted, I questioned my underlying assumption. Fur colour can also be phenotypically plastic. Climate and diet can determine fur colour, though usually only temporarily. Fur colour did not appear to change once established in early development. The presence and fine-scale distribution of coppery and grey brushtails in rainforest fragments suggested that climatic effects are highly unlikely to be determining fur colour. There has been one previous demonstration of diet permanently determining fur colour via maternal diet acting in utero in laboratory mice. I found that determination of brushtail fur colour by maternal diet and selection upon this trait better explains the observed morphological distribution and genetic structure. Further experimental research is needed to conclusively demonstrate this effect, to explore how widespread this capacity for coppery brushtail colour is, and to discover which foods are involved in fur colour expression. Such an congenital change would be highly significant in evolutionary research as it allows, without mutation, the widespread single generation adaptation of offspring to the environmental conditions experienced by the parent.
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26

Stasiuk, Susan Josephine. "Functional analysis of the insulin/IGF signalling pathway and the infective larva developmental switch in Parastrongyloides trichosuri : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Molecular Genetics at Massey University, Palmerston North, New Zealand." 2010. http://hdl.handle.net/10179/1485.

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Parasitism, in nematodes, is a very successful life strategy which has evolved throughout the Nematoda phylum in several independent events. However, the genetic basis for parasitism remains unknown. Parastrongyloides trichosuri is a facultative parasitic nematode of the Australian brushtail possum. This parasite has retained the unusual ability to sample its environment at each generation, and make the developmental decision to develop either into a free-living nematode or, in response to environmental stress, develop into an infective larva, which must then seek out a host in order to complete its life cycle. The nematode model organism, Caenorhabditis elegans, also responds to environmental stresses by developing into a dauer larvae. The dauer hypothesis proposes that dauer larvae and infective larvae are homologous and that dauer larvae may be an evolutionary pre-adaptation that facilitated the evolution of parasitism in nematodes. One of the signalling pathways which control dauer larva development in C. elegans is the Insulin/IGF signalling pathway. Gene orthologues of the insulin/IGF signalling pathway were cloned from P. trichosuri: the daf-2 tyrosine kinase receptor, the age-1 phosphatidylinositol 3′ kinase and the daf-16 FOXO forkhead transcription factor. The expression profiles of these genes were characterized by q-PCR which determined that they were differentially expressed during the developmental switch to infective larva. Rescue by complementation showed that a P. trichosuri daf-16 transgene was able to recover both stress and developmental phenotypes in C. elegans daf mutants, suggesting it might perform an orthologous role in P. trichosuri. This research also demonstrated that the biology of P. trichosuri infective larvae and C. elegans dauer larvae are quite similar. Some of the environmental signals which control the free-living/infective larva developmental switch in P. trichosuri were characterized in this study and found to be similar to the environmental signals which trigger dauer larval development. These are: population density, food availability and temperature. There is a genetic component to the ability to respond to the environmental signals and inbred lines which display diverse developmental plasticity were isolated.
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27

Porphyre, Thibaud Francois Christophe. "Factors associated with the transmission dynamics of bovine tuberculosis in New Zealand : a dissertation presented in partial fullfilment [sic] of the requirements for the degree of Doctor of Philosophy at Massey University, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, Turitea, New Zealand." 2008. http://hdl.handle.net/10179/761.

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This thesis presents the results of a series of studies on the epidemiology of TB in brushtail possum and domestic cattle populations in New Zealand. The first set of studies provides an analysis of the results of routine TB testing carried out in the Featherston area from July 1980 to June 2004. The median annual incidence rate of TB reduced from 4.7 cases per 1000 cattle-years at risk for the period 1986 to 1991 to 1.8 cases per 1000 cattle-years at risk for the period 1992 to 2003, coincident with the use of poisoning to control possums in the surrounding forest park (a major possum habitat area). We identified clusters of cattle TB cases adjacent to the forest park and found no evidence of spatio-temporal interaction of TB risk among farms. Our findings support the hypothesis that possums living in the forest park are a source of bovine TB in this area and that farm-to-farm transmission was not an important mechanism of infection spread. A mixed-effects Poisson regression model was developed to investigate the influence of farm-level covariates on the number of cattle confirmed with TB. The model showed that, despite intensification of possum control activities, proximity to forest parks remained a significant predictor of the number of confirmed TB cases per farm per year. Our analyses identified a significant, 3-fold increase in TB risk in dairy cattle relative to beef conditional on the size of local possum habitat, and confirmed the positive influence of cattle population size and the presence of previous infection status as a determinant of the number of confirmed TB cases per farm per year. The second set of studies investigates details of capture events recorded during a longitudinal, capturemark- recapture study of possums in a 22-hectare study site near Castlepoint, from April 1989 to August 1994. Social network analyses were used to identify contact patterns and to estimate the influence of contact on R0 for bovine TB. The average number of contacts per possum ranged from 20 to 26 per year. We estimated that TB would spread if an average of between 1.94 and 1.97 infective contacts occured per year per infected possum. We evaluated the effect of sex, habitat and contact behaviour of 26 postmortem confirmed TB cases in possums with those of 104 matched controls. Unit increases in the number of infected contacts increased the odds of TB infection by 2.61 (95% CI 1.29 – 5.29, P <0.01). Our results show that individual contact behaviour is a determinant of the presence of TB foci within this population and challenge the hypothesis that contact with many individuals increases the probability of infection. A model to predict spatial variation in possum abundance was developed using a Geographic Information System. Details of possum capture events were obtained from 157 10-trap lines distributed within 42 randomly located transects at Molesworth Station. Two GIS-based models were developed to predict the number of possums caught per line using Poisson regression techniques. The first model used remotely sensed environmental data; the second used a combination of remotely sensed and fine-scale data. Both models provided adequate predictive ability with Pearson correlation coefficients greater than 60%. We conclude that the prediction maps produced from this model provide a useful decision support tool for possum control managers. These results have implications for the management of TB in this area of New Zealand, providing the information that will allow effective control activities to be applied at significantly lower cost.
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