Trichosurus Vulpecula Research Articles

Quantifying short-term foraging movements in a marsupial pest to improve targeted lethal control and disease surveillance.

In New Zealand, the introduced marsupial brushtail possum (Trichosurus vulpecula) is a pest species subject to control measures, primarily to limit its ability to transmit bovine tuberculosis (TB) to livestock and for conservation protection. To better define parameters for targeted possum control and TB surveillance, we here applied a novel approach to analyzing GPS data obtained from 44 possums fitted with radio-tracking collars, producing estimates of the animals’ short-term nocturnal foraging patterns based on 1-, 3- or 5-nights’ contiguous data. Studies were conducted within two semi-arid montane regions of New Zealand’s South Island High Country: these regions support low-density possum populations (<2 possums/ha) in which the animals’ home ranges are on average larger than in high-density populations in forested habitat. Possum foraging range width (FRW) estimates increased with increasing monitoring periods, from 150-200m based on a single night’s movement data to 300-400m based on 5 nights’ data. The largest average FRW estimates were recorded in winter and spring, and the smallest in summer. The results suggest that traps or poison-bait stations (for lethal control) or monitoring devices (for TB surveillance), set for > 3 consecutive nights at 150m interval spacings, would likely place >95% of the possums in this type of habitat at risk of encountering these devices, year-round. Modelling control efficacy against operational expenditure, based on these estimations, identified the relative cost-effectiveness of various strategies that could be applied to a typical aerial poisoning operation, to reduce the ongoing TB vectorial risk that possums pose in the High Country regions. These habitat-specific findings are likely to be more relevant than the conventional pest control and monitoring methodologies developed for possums in their more typical forested habitat.

The epidemiology of Mycobacterium bovis in wild deer and feral pigs and their roles in the establishment and spread of bovine tuberculosis in New Zealand wildlife

In New Zealand, wild deer and feral pigs are assumed to be spillover hosts for Mycobacterium bovis, and so are not targeted in efforts aimed at locally eradicating bovine tuberculosis (TB) from possums (Trichosurus vulpecula), the main wildlife host. Here we review the epidemiology of TB in deer and pigs, and assess whether New Zealand's TB management programme could be undermined if these species sometimes achieve maintenance host status.In New Zealand, TB prevalences of up to 47% have been recorded in wild deer sympatric with tuberculous possums. Patterns of lesion distribution, age-specific prevalences and behavioural observations suggest that deer become infected mainly through exposure to dead or moribund possums. TB can progress rapidly in some deer (<10%), but generalised disease is uncommon in wild deer; conversely some infected animals can survive for many years. Deer-to-deer transmission of M. bovis is rare, but transmission from tuberculous deer carcasses to scavengers, including possums, is likely. That creates a small spillback risk that could persist for a decade after transmission of new infection to wild deer has been halted.Tuberculosis prevalence in New Zealand feral pigs can reach 100%. Infections in lymph nodes of the head and alimentary tract predominate, indicating that TB is mostly acquired through scavenging tuberculous carrion, particularly possums. Infection is usually well contained, and transmission between pigs is rare.Large reductions in local possum density result in gradual declines (over 10 years) in TB prevalence among sympatric wild deer, and faster declines in feral pigs. Elimination of TB from possums (and livestock) therefore results in eventual disappearance of TB from feral pigs and wild deer. However, the risk of spillback infection from deer to possums substantially extends the time needed to locally eradicate TB from all wildlife (compared to that which would be required to eradicate disease from possums alone), while dispersal or translocation of pigs (e.g. by hunters) creates a risk of long-distance spread of disease. The high rate at which pigs acquire M. bovis infection from dead possums makes them useful as sentinels for detecting TB in wildlife.It is unlikely that wild deer and feral pigs act as maintenance hosts anywhere in New Zealand, because unrestricted year-round hunting keeps densities low, with far less aggregation than on New Zealand farms. We conclude that active management of wild deer or feral pigs is not required for local TB eradication in New Zealand.

Optimising the application of multiple-capture traps for invasive species management using spatial simulation.

Internationally, invasive vertebrate species pose a significant threat to biodiversity, agricultural production and human health. To manage these species a wide range of tools, including traps, are used. In New Zealand, brushtail possums (Trichosurus vulpecula), stoats (Mustela ermine), and ship rats (Rattus rattus) are invasive and there is an ongoing demand for cost-effective non-toxic methods for controlling these pests. Recently, traps with multiple-capture capability have been developed which, because they do not require regular operator-checking, are purported to be more cost-effective than traditional single-capture traps. However, when pest populations are being maintained at low densities (as is typical of orchestrated pest management programmes) it remains uncertain if it is more cost-effective to use fewer multiple-capture traps or more single-capture traps. To address this uncertainty, we used an individual-based spatially explicit modelling approach to determine the likely maximum animal-captures per trap, given stated pest densities and defined times traps are left between checks. In the simulation, single- or multiple-capture traps were spaced according to best practice pest-control guidelines. For possums with maintenance densities set at the lowest level (i.e. 0.5/ha), 98% of all simulated possums were captured with only a single capacity trap set at each site. When possum density was increased to moderate levels of 3/ha, having a capacity of three captures per trap caught 97% of all simulated possums. Results were similar for stoats, although only two potential captures per site were sufficient to capture 99% of simulated stoats. For rats, which were simulated at their typically higher densities, even a six-capture capacity per trap site only resulted in 80% kill. Depending on target species, prevailing density and extent of immigration, the most cost-effective strategy for pest control in New Zealand might be to deploy several single-capture traps rather than investing in fewer, but more expense, multiple-capture traps.

Using multiple‐source occurrence data to identify patterns and drivers of decline in arid‐dwelling Australian marsupials

Many of the world's terrestrial mammal species are imperilled, but recent extinctions and declines have been most severe in Australia. In particular, arid‐dwelling marsupials in a critical weight range (35–5500 g) have declined dramatically following European settlement. In the absence of long‐term monitoring, documenting these declines or distribution shifts and their causes often relies on occurrence data from multiple sources. Using atlas records, we compared the distributions of all currently extant marsupials in the critical weight range in Australia's arid Northern Territory pre‐ and post‐1975. For taxa with evidence of range contraction, we evaluated alternative hypotheses to explain this contraction (i.e. competition, predation, productivity, climate) using several techniques to improve our confidence in the results. Despite a substantial increase in the number of mammal records across the study region post‐1975, the bilby Macrotis lagotis and desert form of the common brushtail possum Trichosurus vulpecula appear to have contracted in distribution by 25 and 40%, respectively. These changes in distribution were best explained by hypotheses of competition and climate‐change, respectively. Macrotis lagotis was more likely to occur on land without a history of cattle grazing and with low rabbit densities, while T. vulpecula has contracted to parts of its distribution that experience cooler maximum temperatures over the hottest months of the year. For five other taxa (including the vulnerable black‐footed rock‐wallaby Petrogale lateralis) we recorded increases in distribution post‐1975, probably reflecting increased survey effort rather than actual range expansion. We conclude that models using multiple‐source occurrence data can provide key insights into the patterns and drivers of contemporary species’ declines, and represent useful tools for conservation.

Epidemiology and control of Mycobacterium bovis infection in brushtail possums (Trichosurus vulpecula), the primary wildlife host of bovine tuberculosis in New Zealand

The introduced Australian brushtail possum (Trichosurus vulpecula) is a maintenance host for bovine tuberculosis (TB) in New Zealand and plays a central role in the TB problem in this country. The TB-possum problem emerged in the late 1960s, and intensive lethal control of possums is now used to reduce densities to low levels over 8 million ha of the country. This review summarises what is currently known about the pathogenesis and epidemiology of TB in possums, and how the disease responds to possum control. TB in possums is a highly lethal disease, with most possums likely to die within 6 months of becoming infected. The mechanisms of transmission between possums remain unclear, but appear to require some form of close contact or proximity. At large geographic scales, TB prevalence in possum populations is usually low (1–5%), but local prevalence can sometimes reach 60%. Intensive, systematic and uniform population control has been highly effective in breaking the TB cycle in possum populations, and where that control has been sustained for many years the prevalence of TB is now zero or near zero. Although some uncertainties remain, local eradication of TB from possums appears to be straightforward, given that TB managers now have the ability to reduce possum numbers to near zero levels and to maintain them at those levels for extended periods where required. We conclude that, although far from complete, the current understanding of TB-possum epidemiology, and the current management strategies and tactics, are sufficient to achieve local, regional, and even national disease eradication from possums in New Zealand.

Epidemiology, diagnostics, and management of tuberculosis in domestic cattle and deer in New Zealand in the face of a wildlife reservoir

The control of tuberculosis (TB) in cattle and farmed deer in New Zealand has been greatly influenced by the existence of a wildlife reservoir of Mycobacterium bovis infection, principally the Australian brushtail possum (Trichosurus vulpecula). The reduction in possum numbers in areas with endemic M. bovis infection through vigorous vector control operations has been a major contributor to the marked reduction in the number of infected cattle and farmed deer herds in the past two decades. Management of TB in cattle and farmed deer in New Zealand has involved a combination of vector control, regionalisation of diagnostic testing of cattle and deer herds, abattoir surveillance and movement control from vector risk areas. Accurate diagnosis of infected cattle and deer has been a crucial component in the control programme. As the control programme has evolved, test requirements have changed and new tests have been introduced or test interpretations modified. Subspecific strain typing of M. bovis isolates has proved to be a valuable component in the epidemiological investigation of herd breakdowns to identify whether the source of infection was domestic livestock or wildlife. New initiatives will include the use of improved models for analysing diagnostic test data and characterising disease outbreaks leading to faster elimination of infection from herds. The introduction of the National Animal Identification Tracing programme will allow better risk profiling of individual herds and more reliable tracing of animal movements. TB in cattle and farmed deer in New Zealand can only be controlled by eliminating the disease in both domestic livestock and the wildlife reservoir.

Assessment of Demand for Food using Concurrent PR and FR Schedules in the Brushtail Possum (Trichosurus vulpecula)

The aim of this study was to compare the demand by possums for foods under different arrangements of concurrent progressive-ratio and fixed-ratio schedules of reinforcement. In Experiment 1, every possible food pair made up of berries, chicken, egg, foliage, insects and mushroom was presented (30 pairs in total). The requirement on the progressive-ratio schedule increased within a session and the fixed-ratio was kept constant at 30. In Experiment 2, a subset of the foods from Experiment 1 were used (chicken, mushroom, egg and berries) and in separate conditions the fixed-ratio was either 30 or 10 responses. In Experiment 3, the foods were the same as used in Experiment 2 and the progressive-ratio schedule increased every five sessions and the fixed-ratio schedule was 30 responses. Exponential models of demand were applied to consumption rates to compare the parameters of initial demand, essential value and P max, and break point and cross point across foods. The models described the data well and consumption rates were similar when the incrementing schedules increased within- and across sessions. Demand was highest for berries, egg and locust in Experiment 1 and egg and chicken in Experiments 2 and 3. This finding has practical implications for understanding possum food preferences in the wild as a function of other available food sources.

Monitoring the use of road-crossing structures by arboreal marsupials: insights gained from motion-triggered cameras and passive integrated transponder (PIT) tags

Context Wildlife crossing structures are installed to mitigate the impacts of roads on animal populations, yet little is known about some aspects of their success. Many studies have monitored the use of structures by wildlife, but studies that also incorporate individual identification methods can offer additional insights into their effectiveness. Aims We monitored the use of wildlife crossing structures by arboreal marsupials along the Hume Freeway in south-eastern Australia to (1) determine the species using these structures and their frequency of crossing, (2) determine the number and demographic characteristics of individuals crossing, and (3) use the rate of crossing by individuals to infer the types of movement that occurred. Methods We used motion-triggered cameras to monitor five canopy bridges and 15 glider pole arrays installed at 13 sites along the Hume Freeway. The five canopy bridges were also monitored with passive integrated transponder (PIT)-tag readers to identify the rate of use by individuals. Key results Five species of arboreal marsupial were detected using canopy bridges and glider poles at 11 sites. Our analysis suggested that increasing the number and the distance between poles in a glider pole array reduced the rate of use by squirrel gliders. The PIT tag and camera footage revealed that the structures were used by adult males, adult females and juveniles, suggesting that all demographic groups are capable of using canopy bridges and glider poles. At two canopy bridges, multiple squirrel gliders and common brushtail possums crossed more than once per night. Conclusions Given that previous studies have shown that the freeway is a barrier to movement, and that many of the species detected crossing are subject to road mortality, we conclude that canopy bridges and glider poles benefit arboreal marsupials by providing safe access to resources that would otherwise be inaccessible. Implications Although the factors influencing crossing rate require further study, our analysis suggests that glider pole arrays with fewer poles placed closer together are likely to be more successful for squirrel gliders. The individual identification methods applied here offer insights that are not possible from measuring the rate of use alone and should be adopted in future monitoring studies.

Novel interactions between non‐native mammals and fungi facilitate establishment of invasive pines

Summary The role of novel ecological interactions between mammals, fungi and plants in invaded ecosystems remains unresolved, but may play a key role in the widespread successful invasion of pines and their ectomycorrhizal fungal associates, even where mammal faunas originate from different continents to trees and fungi as in New Zealand. We examine the role of novel mammal associations in dispersal of ectomycorrhizal fungal inoculum of North American pines (Pinus contorta, Pseudotsuga menziesii), and native beech trees (Lophozonia menziesii) using faecal analyses, video monitoring and a bioassay experiment. Both European red deer (Cervus elaphus) and Australian brushtail possum (Trichosurus vulpecula) pellets contained spores and DNA from a range of native and non‐native ectomycorrhizal fungi. Faecal pellets from both animals resulted in ectomycorrhizal infection of pine seedlings with fungal genera Rhizopogon and Suillus, but not with native fungi or the invasive fungus Amanita muscaria, despite video and DNA evidence of consumption of these fungi. Native L. menziesii seedlings never developed any ectomycorrhizal infection from faecal pellet inoculation. Synthesis. Our results show that introduced mammals from Australia and Europe facilitate the co‐invasion of invasive North American trees and Northern Hemisphere fungi in New Zealand, while we find no evidence that introduced mammals benefit native trees or fungi. This novel tripartite ‘invasional meltdown’, comprising taxa from three kingdoms and three continents, highlights unforeseen consequences of global biotic homogenization.

Male-biased predation and its effect on paternity skew and life history in a population of common brushtail possums (Trichosurus vulpecula).

Differences in predation risk may exert strong selective pressures on life history strategies of populations. We investigated the potential for predation to shape male mating strategies in an arboreal folivore, the common brushtail possum (Trichosurus vulpecula Kerr). We predicted that possums in a tropical population exposed to high natural levels of predation would grow faster and reproduce earlier compared to those in temperate populations with lower predation. We trapped a population of possums in eucalypt woodland in northern Australia each month to measure life history traits and used microsatellites to genotype all individuals and assign paternity to all offspring. We observed very high levels of male-biased predation, with almost 60% of marked male possums being eaten by pythons, presumably as a result of their greater mobility due to mate-searching. Male reproductive success was also highly skewed, with younger, larger males fathering significantly more offspring. This result contrasts with previous studies of temperate populations experiencing low levels of predation, where older males were larger and the most reproductively successful. Our results suggest that in populations exposed to high levels of predation, male possums invest in increased growth earlier in life, in order to maximise their mating potential. This strategy is feasible because predation limits competition from older males and means that delaying reproduction carries a risk of failing to reproduce at all. Our results show that life histories are variable traits that can match regional predation environments in mammal species with widespread distributions.

Long-term and large-scale control of the introduced red fox increases native mammal occupancy in Australian forests

Management agencies commonly control non-native mammalian predators to protect native prey populations, but there are few robust examples of such control enhancing native prey populations. We conducted a 9-year landscape-scale management experiment to evaluate the benefits of controlling the invasive red fox (Vulpes vulpes) to low densities for three native ground-dwelling mammalian prey species—common brushtail possum (Trichosurus vulpecula), long-nosed potoroo (Potorous tridactylus) and southern brown bandicoot (Isoodon obesulus)—in south-east Australian forests. We hypothesized that sustained and spatially extensive fox control would reduce fox abundance and increase occupancy, colonization and persistence rates for all three prey species in three treatment areas relative to three non-treatment areas. There was a substantial decline in bait take by foxes in treatment areas from 2005 to 2013, and fox abundances were much lower in treatment than non-treatment areas throughout the experiment. Occupancy rates of all three native prey species increased in treatment areas relative to non-treatment areas, although the magnitude of the increase varied with species, treatment area, and time. Colonization and persistence rates were not always positive for all species and all treatment areas. Our experiment demonstrates that foxes can be reduced to, and maintained at, low abundances and that this has a generally positive effect on the occupancy by small native mammalian prey species.

Direct and indirect effects of marsupial browsing on a foundation tree species

Plant-mediated indirect effects can be important ecological drivers in plant communities, especially in systems where extended genetic effects of foundation species can shape communities and influence ecosystem dynamics. Here we investigate the direct and indirect effects of uncontrolled browsing by marsupial herbivores including the common brushtail possum Trichosurus vulpecula, Bennetts wallaby Macropus rufogriseus and the red-bellied pademelon Thylogale billardierii, in a Eucalyptus system known to have extended community and ecosystem genetic effects. In a common garden trial containing 525 full-sib families from an incomplete diallel crossing program located in northeastern Tasmania, Australia, we assessed the genetic basis to herbivore preferences, the impact of a single and repeated marsupial browsing event on tree fitness and morphological traits and the associated indirect plant-mediated effects on a subsequent herbivore, autumn gum moth Mnesampela privata. Marsupial browsing was not influenced by plant genetics, but spatial components instead affected the pattern of damage across the trial. Marsupial browsing had significant impacts on tree development, morphology and survival, resulting in reductions in survival, height and basal area, an increase proportion in multiple stems, delays in flowering as well as delays in phase change from juvenile to adult foliage. Fitness impacts were minimal in response to a once-off browsing event, but effects were exacerbated when trees suffered repeated browsing. We demonstrate clear plant-mediated indirect effects of marsupial browsing on subsequent tree use by an invertebrate herbivore, through induced changes in plant morphology. Such indirect effects have the potential to influence biotic community structure on a foundation species host-plant, and the evolutionary interactions that occur between organisms and the host-plant themselves.

Personality affects the foraging response of a mammalian herbivore to the dual costs of food and fear

Predators attack and plants defend, so herbivores face the dilemma of how to eat enough without being eaten. But do differences in the personality of herbivores affect the foraging choices of individuals? We explored the ecological impact of personality in a generalist herbivore, the brushtail possum (Trichosurus vulpecula). After quantifying personality traits in wild individuals brought temporarily into captivity, we tested how these traits altered foraging by individuals when free-ranging in their natural habitat. To measure their responses to the dual costs of predation risk and plant toxin, we varied the toxin concentration of food in safe foraging patches against paired, non-toxic risky patches, and used a novel synthesis of a manipulative Giving-Up-Density (GUD) experiment and video behavioural analysis. At the population level, the cost of safe patches pivoted around that of risky patches depending on food toxin concentration. At the individual level, boldness affected foraging at risky high-quality food patches (as behavioural differences between bold and shy), and at safe patches only when food toxin concentration was low (as differences in foraging outcome). Our results ecologically validate the personality trait of boldness, in brushtail possums. They also reveal, for the first time, a nuanced link between personality and the way in which individuals balance the costs of food and fear. Importantly, they suggest that high plant defence effectively attenuates differences in foraging behaviour arising from variation in personality, but poorly defended plants in safe areas should be differentially subject to herbivory depending on the personality of the herbivore.

Bird-repellent effects on bait efficacy for control of invasive mammal pests.

Repellents to reduce crop damage from birds and mammals have been investigated extensively, but their efficacy in reducing risk to non-target birds in aerial poisoning operations for control of mammal pests is less known. We assessed the impact on bait acceptability, palatability and kill efficacy for captive wild rats (Rattus rattus L.) and possums (Trichosurus vulpecula Kerr) of adding bird repellents (anthraquinone and d-pulegone) to baits used for their control in food choice trials. For possums, anthraquinone at 0.25% reduced acceptability and palatability but not the efficacy of poison baits, whereas d-pulegone at 0.17% had no significant effects. Rats showed little response to d-pulegone, but developed a marked aversion to prefeed baits containing anthraquinone at both 0.1 and 0.25%, such that almost no exposed rats ate poison baits and mortality was reduced significantly. The aversion induced by anthraquinone was generalised to the bait, as anthraquinone-exposed rats did not eat bait with only d-pulegone. Anthraquinone is not suitable for inclusion in bait for rat control at the concentrations tested, and also presents some risk to efficacy for possum control. D-pulegone would be suitable for inclusion in bait for possums and rats, but problems related to its volatility in bait manufacture and storage would need to be overcome. Further studies should focus on an alternative secondary repellent, or on establishing the maximum anthraquinone concentration that does not reduce efficacy for rats and testing whether or not that concentration is sufficient to repel native birds from baits reliably.

Straddling the divide: den use by brushtail possums (Trichosurus vulpecula) in urban parklands

In Australia, brushtail possums (Trichosurus vulpecula) are declining in natural habitats but have adapted to urban environments so readily that some human residents consider them to be a nuisance. Although this situation represents a conundrum for management, the use of urban habitats by the species remains poorly studied. We conducted our study in six urban parklands, a setting that represents an intermediary between a fully-urban and fully-natural environment. To determine factors that influence the presence of hollows in trees and their use by brushtail possums, physical characteristics of 240 mature trees in six parks in the Adelaide Parklands, South Australia were assessed. To investigate hollow use more comprehensively, 18 possums were radio-tracked. Presence of hollows in trees was a function of tree species and tree size, with hollows formed in both exotic and native species. Tree form and number of hollows were significant predictors of the use of hollow-bearing trees by possums. Use of exotic trees was high, with only 34 % of recorded den trees being native (non-indigenous) species. Radio-tracked individuals were relatively sedentary, with an average daytime denning area of 0.08 ha. While the majority of animals used multiple den sites, all individuals favoured a single den. Use of a variety of anthropogenic structures was high, even when trees were available. On average, sites supported ~1.5 brushtail possums per hollow-bearing tree. A correlation between number of hollows per hectare and possum density (r =0.892, P =0.017) suggests that altering a given area’s density of hollows or anthropogenic structures could influence the density of possums within it.

Ectoparasite infestation patterns, haematology and serum biochemistry of urban‐dwelling common brushtail possums

Urban environments support high concentrations of humans, domestic pets and introduced animals, creating conditions conducive to the transmission of parasites. This study compared patterns of ectoparasite infestation of the common brushtail possum Trichosurus vulpecula in urbanised Sydney (n = 161) to those from a remote woodland site (n = 18) from February 2005 – November 2006. We found diff erences in ectoparasite species prevalence between the two groups: the flea Echidnophaga myrmecobii was only found on urban possums and the tick Ixodes trichosuri was much more prevalent in the urban habitat, while the mite Atellana papilio was more prevalent on woodland possums. E. myrmecobii and I. trichosuri diff ered from other ectoparasites by showing an association with host sex and host age. Potential physiological costs of ectoparasitism to urban‐dwelling possums were determined using multivariate analysis of haematology, serum biochemistry and body condition. Changes in serum iron levels were seen in the presence of both the tick Ixodes trichosuri and the flea E. myrmecobii, and E. myrmecobii was associated with elevated serum levels of the liver enzyme ALT. However, ectoparasite‐related changes in haematology and serum biochemistry were not indicative of long‐term pathology. In this urban possum population, the costs of ectoparasitism appear to be limited and unlikely to pose a major threat to the health of the population.

Does a sap feeding marsupial choose trees with specific chemical characteristics?

Only about 20 vertebrate species are known to feed regularly on tree sap. One of these is the yellow-bellied glider (Petaurus australis), a marsupial that obtains between 16% and 80% of its diet from eucalypt sap. We reviewed the literature on sap feeding by the yellow-bellied glider and identified 10 species from which it most frequently obtains sap. These species come mainly from a few sections of the subgenus Symphyomyrtus, which accounts for two-thirds of over 2000 sap trees reported, but more specifically sections Latoangulatae and Maidenii within this subgenus. Some of these key species contain relatively high concentrations of foliar nutrients and each is an important food tree for at least one of the arboreal folivores – koala (Phascolarctos cinereus), greater glider (Petauroides volans), and common ringtail (Pseudocheirus peregrinus) and brushtail possums (Trichosurus vulpecula). Because yellow-bellied gliders, like the arboreal folivores, prefer to feed from certain individuals within a species, we hypothesized that these trees possess a unique chemical signature that links sap-feeding with the concentrations of available nitrogen and formylated phloroglucinol compounds in leaves – the nutritive and defensive chemicals that influence feeding on these species by marsupial folivores. We tested this hypothesis in samples of leaves and bark collected from E. punctata and E. viminalis but found no link between chemistry and sap feeding and conclude that other aspects of an individual tree, such as sap flow or sap chemistry, determine whether gliders will target it for sap.

Variations in epithelial Na(+) transport and epithelial sodium channel localisation in the vaginal cul-de-sac of the brushtail possum, Trichosurus vulpecula, during the oestrous cycle.

The fluid in the vaginal cul-de-sac of the brushtail possum, Trichosurus vulpecula, is copious at ovulation when it may be involved in sperm transport or maturation, but is rapidly reabsorbed following ovulation. We have used the Ussing short-circuit current (Isc) technique and measurements of transcript and protein expression of the epithelial Na(+) channel (ENaC) to determine if variations in electrogenic Na(+) transport are associated with this fluid absorption. Spontaneous Isc (<20µAcm(-2) during anoestrus, 60-80µAcm(-2) in cycling animals) was inhibited by serosal ouabain. Mucosal amiloride (10µmolL(-1)), an inhibitor of ENaC, had little effect on follicular Isc but reduced luteal Isc by ~35%. This amiloride-sensitive Isc was dependent on mucosal Na(+) and the half-maximal inhibitory concentration (IC50)-amiloride (0.95μmolL(-1)) was consistent with ENaC-mediated Na(+) absorption. Results from polymerase chain reaction with reverse transcription (RT-PCR) indicate that αENaC mRNA is expressed in anoestrous, follicular and luteal phases. However, in follicular animals αENaC immunoreactivity in epithelial cells was distributed throughout the cytoplasm, whereas immunoreactivity was restricted to the apical pole of cells from luteal animals. These data suggest that increased Na(+) absorption contributes to fluid absorption during the luteal phase and is regulated by insertion of ENaC into the apical membrane of cul-de-sac epithelial cells.

Erratum to: Chemical characterization of milk oligosaccharides of the common brushtail possum (Trichosurus vulpecula).

Erratum to: Chemical characterization of milk oligosaccharides of the common brushtail possum (Trichosurus vulpecula).

First direct estimate of the detection probability of bovine tuberculosis in possums by possum transmission

We conducted a field trial to determine whether percutaneous challenge of wild brushtail possums (Trichosurus vulpecula) with virulent Mycobacterium bovis, the causative agent of bovine tuberculosis (TB), resulted in subsequent transmission of M. bovis to other possums. We then used our results to make a preliminary first direct estimate of the ‘TB detection probability’ or transmission rate in wild possums. Seven free-living adult possums in the Rimutaka Forest Park, New Zealand, were captured, GPS-collared, experimentally challenged and then released. Possum populations surrounding the challenged individuals were examined for secondary cases 4–8 months post-challenge. Of 37 possums caught within the home ranges of the challenged individuals, one had confirmed TB. As no TB was detected in 355 other possums examined in this study, or 659 possums in a concurrent study in the immediate vicinity, we conclude that this represents the first documented case of onward transmission of M. bovis from an experimentally challenged possum in the wild. This pilot trial therefore gives some confidence that the new percutaneous challenge model for TB in possums can be used to obtain empirical estimates of TB detection probabilities. The calculated probability of onward transmission (‘detection’) here was just 0.027; however, with the possibility that further transmission events would have occurred from the one challenged possum removed from the trial before it had died, or if our trapping missed secondary cases, this value could be an underestimate. The implications of this low preliminary estimate are discussed.