Trichosurus Vulpecula Research Articles

Assessing Movements of Brushtail Possums (Trichosurus vulpecula) in Relation to Depopulated Buffer Zones for the Management of Wildlife Tuberculosis in New Zealand.

In New Zealand, managing the threat of bovine tuberculosis (TB) to livestock includes population reduction of potentially infectious wildlife, primarily the brushtail possum (Trichosurus vulpecula). Population control is often targeted on forested buffer zones adjacent to farmland, in order to limit movements of possums across the buffer and reduce the risk of disease transmission to livestock. To assess the effectiveness of buffers in protecting livestock we analysed GPS telemetry data from possums located in untreated forest adjacent to buffers, and used these data to characterise patterns of movement that could lead to possums reaching farmland during the season when most dispersal occurs. Analyses of movement data showed that the direction of dispersal by sub-adult and adult possums and the extent of long exploratory movements were not biased toward forest buffers, even though these provided vacant habitat as suitable for possums as untreated forest. Instead, dispersal and exploratory movements were uncommon even for sub-adult possums and such events typically lasted <10 days. Dispersing possums settled predominantly in river valleys. A simulation model was developed for the 3-6-month dispersal season; it demonstrated a probability of <0.001 that an infected possum, originating from a low-density population with low disease prevalence in untreated forest, would move across 3 km of recently controlled forest buffer to reach farmland. Our results indicate short-term reduction in the risk of TB transmission from possums to livestock in New Zealand by the use of depopulated buffer zones, while acknowledging that the threat of disease spread from untreated forest is likely to increase over time as possum population density and, potentially, TB prevalence among those possums, increase in the buffer zone.

Chemical characterization of milk oligosaccharides of the common wombat (Vombatus ursinus).

Previous structural characterizations of marsupial milk oligosaccharides have been performed in the tammar wallaby, red kangaroo, koala, common brushtail possum and the eastern quoll. To clarify the homology and heterogeneity of milk oligosaccharides among marsupial species, which could provide information on their evolution, the oligosaccharides of wombat milk carbohydrate were characterized in this study. Neutral and acidic oligosaccharides were isolated from the carbohydrate fractions of two samples of milk of the common wombat and characterized by (1) H-nuclear magnetic resonance spectroscopy. The structures of six neutral saccharides were found to be Gal(β1-4)Glc (lactose), Gal(β1-3)Gal(β1-4)Glc (3'-galactosyllactose), Gal(β1-3)Gal(β1-3)Gal(β1-4)Glc (3',3"-digalactosyllactose), Gal(β1-3)Gal(β1-3)Gal(β1-3)Gal(β1-4)Glc, Gal(β1-3)Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (galactosyl lacto-N-novopentaose I) and Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (lacto-N-novooctaose), while those of six acidic saccharides were Neu5Ac(α2-3)Gal(β1-3)Gal(β1-4)Glc. (sialyl 3'-galactosyllactose), Neu5Ac(α2-3)Gal(β1-3)Gal(β1-3)Gal(β1-4)Glc (sialyl 3',3"-digalactosyllactose), Neu5Ac(α2-3)Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (sialyl lacto-N-novopentaose a), Gal(β1-3)[Neu5Ac(α2-3)Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (sialyl lacto-N-novopentaose c), Neu5Ac(α2-3)Gal(β1-3)Gal(β1-3)Gal(β1-3)Gal(β1-4)Glc,, Neu5Ac(α2-3)Gal(β1-3)Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc and Gal(β1-3)Gal(β1-3)[Neu5Ac(α2-3)Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc. In addition, small amounts of sulfated oligosaccharides but no oligosaccharides containing Neu5Gc or α(2-6) linked Neu5Ac were detected.

Do nest boxes in restored woodlands promote the conservation of hollow‐dependent fauna?

Vegetation restoration is considered as an important strategy for reversing biodiversity decline in agricultural areas. However, revegetated areas often lack key vegetation attributes like large old hollow‐bearing trees. As these trees take a long time to develop, artificial cavities such as nest boxes are sometimes provided to address lag effects. We conducted a 3‐year experiment using 150 nest boxes with 4 designs to quantify patterns of occupancy within 16 replanted areas and 14 patches of remnant old‐growth eucalypt woodland. We quantified patterns of occupancy of nest boxes in physically connected versus isolated remnants and plantings, and multiple covariate effects on nest box occupancy at the nest box, tree, patch, and landscape levels. Our analyses revealed a lower probability of nest box occupancy within remnants (vs. plantings) for 2 of the 6 response variables examined: any species and the Feral Honeybee. Nest boxes in connected remnants and plantings were more likely to be occupied than those in isolated plantings and remnants by any mammal and the Common Brushtail Possum. Nest boxes in restored woodlands are used by some hollow‐dependent fauna but principally already common species and not taxa of conservation concern. Nest boxes were also used by pest species. A key management consideration must be to create connected habitat to facilitate colonization of nest boxes by mammals. Approximately 15% of the cavity‐dependent vertebrates within the study area used next boxes, possibly because the diverse requirements of the array of other species were not met by the range of nest boxes deployed.

Comparative dietary ecology of two congeneric marsupial folivores

AbstractKnowledge of species diets is critical to assisting our understanding of their ecology. Using microhistological analysis of faecal samples, we described and compared the diets of sympatrically occurring folivorous congenerics, common and mountain brushtail possums (Trichosurus vulpecula and T. cunninghami, respectively). Throughout the 28‐month study period, common brushtails relied heavily on eucalypt foliage, particularly very young leaves, which is consistent with data from captive studies on their dietary physiology. In contrast, eucalypt foliage formed only a small part of the diet of mountain brushtails, which instead relied heavily on silver wattle foliage. The mean number of plant groups per faecal sample was significantly greater for common brushtails than mountain brushtails. No significant differences in diet between male and female mountain brushtails were detected. However, intraspecific differences in diet occurred for common brushtails: the diet of females included significantly less eucalypt foliage and significantly more foliage of the exotic, tree lucerne, than that of males during the Wet Season (April–November), but not during the Dry Season (December–March). Diets varied temporally for both species, with some individuals feeding on seasonally available resources. The diets described for common and mountain brushtails are consistent with those of a dry‐adapted and mesic‐adapted species, respectively. We discuss how our results contribute to our understanding of the evolutionary history of both study species, and more broadly the family Phalangeridae to which they belong. We also consider the diet of our study species in the context of recent advances in our understanding of interactions between plants that produce secondary metabolites, and mammals specialized to feed on them.

Landscape-scale analysis of nutritional traits of New Zealand tree foliage using near-infrared spectroscopy

Near-infrared reflectance spectroscopy (NIRS) was used to predict the nutritional quality of tree foliage from a New Zealand forest inhabited by the introduced common brushtail possum (Trichosurus vulpecula) as part of a study to understand the relationship between possum browsing and the nutritional quality of foliage. The traits of interest were the foliar concentrations of total nitrogen, in vitro dry matter digestibility, and available nitrogen (with and without incubation with polyethylene glycol to indicate the effect of tannins). A total of 1399 samples from five plant species were studied, with 650 included in a calibration set and 50 in a separate validation set. We evaluated the performance of classic (GLOBAL) and alternative (LOCAL) calibration techniques. Both were successful, although a GLOBAL equation incorporating all calibration samples was used for the final predictions. Modelling of the spectra enabled the nutritional quality of the foliage samples to be estimated with coefficients of determination (r2) of 0.83–0.99 using modified partial least-squares regression. Nutritional quality varied both within and between five tree species for which possums show varied preferences. The predictive models developed in this study facilitate landscape-scale ecological investigations into the role of plant nutrients on the behaviour and demography of introduced herbivores. This provides new opportunities to test theories on invasiveness and to prioritize landscapes for conservation and possum control.

Better food-based baits and lures for invasive rats Rattus spp. and the brushtail possum Trichosurus vulpecula: a bioassay on wild, free-ranging animals

Food-based baits and lures remain the mainstay of eradication and monitoring methodologies for invasive mammalian species. To date, however, best-practise baits and lures for rats and possums have not been systematically compared to alternative food-based products in ways that quantify their effectiveness on free-ranging, wild animals. We designed a rapid bioassay using chew-cards to present large numbers of food-based products to free-ranging rats and possums to assess their attractiveness and consumption compared to current standards. We used linear mixed-effects regression analysis and an information-theoretic model set to consider the nutritive drivers of consumption for each species with the aim of informing the design of, and future search for, baits. Current standards were statistically outperformed in our trials. For rats, cheese, milk chocolate, Nutella® and walnut were statistically more attractive than the peanut butter standard. For possums, apricot and almond were statistically more attractive that the cinnamon standard. Model comparisons indicate that energy, particularly from fats, is the most important determinant of consumption by rats, while protein is the most important determinant of consumption by possums. Our results demonstrate that current standard lures for both species could be more attractive whilst the inclusion of fat to rat baits and protein to possum baits could increase bait consumption and improve control operation outcomes. Further, our bioassay provides practitioners a cost effective and rapid methodology to systematically assess large numbers of food products on free-ranging, wild animals thus providing more realistic results than those obtained under pen or laboratory conditions.

Improving animal welfare standards while reducing disease exposure risk during euthanasia of trapped brushtail possums (Trichosurus vulpecula)

AbstractIn New Zealand there is a long history of research studies working with wild free-living brushtail possums (Trichosurus vulpecula) where euthanasia of large numbers of animals is frequently required. The most commonly used method for euthanising trapped possums is by blunt-force trauma. If possums being euthanised are potentially infected with bovine tuberculosis (TB), however, the blunt-force trauma method is associated with risks of researcher exposure to TB infection (eg risk of being scratched, bitten or blood-splattered). Here, we trial the use of a close-range shot to the head with a high-velocity air rifle as an alternative method for the euthanasia of cage-trapped possums. Our trial revealed that the air rifle method reduced the potential disease exposure risks to researchers by minimising blood-spatter area, and by completely avoiding the likelihood of both accidents due to animal handling and animal escapes. While both methods induced immediate unconsciousness leading to death, the air rifle method was quicker (ie shorter conscious handling and total time) and arguably had better animal welfare performance by significantly reducing the time to unconsciousness. Thus, we conclude that the air rifle method is suitably humane for possum euthanasia and should be considered when dealing with potentially TB-infected cage-trapped possums.

Place invaders: Identity, place attachment and possum control in the South Island West Coast of New Zealand

The pesticide 1080 (sodium fluoroacetate) is used in New Zealand as the primary means of controlling the Australian brushtail possum, a problem pest. This study identified place and its role in identity as an important mediator of the perspectives of those that either strongly supported or opposed its use. Individuals' differing constructions of place influenced the way they perceived ‘others’ as a threat to their place and their views on control of its management and protection. This study may contribute to a new understanding of the importance of place in this and other similar natural resource disputes.

Aerial Prefeeding Followed by Ground Based Toxic Baiting for More Efficient and Acceptable Poisoning of Invasive Small Mammalian Pests.

Introduced brushtail possums (Trichosurus vulpecula) and rat species (Rattus spp.) are major vertebrate pests in New Zealand, with impacts on conservation and agriculture being managed largely through poisoning operations. Aerial distribution of baits containing sodium fluoroacetate (1080) has been refined to maximise cost effectiveness and minimise environmental impact, but this method is strongly opposed by some as it is perceived as being indiscriminate. Although ground based control enables precise placement of baits, operations are often more than twice as costly as aerial control, mainly due to the high labour costs. We investigated a new approach to ground based control that combined aerial distribution of non-toxic ‘prefeed’ baits followed by sparse distribution of toxic baits at regular intervals along the GPS tracked prefeeding flight paths. This approach was tested in two field trials in which both 1080 baits and cholecalciferol baits were used in separate areas. Effectiveness of the approach, assessed primarily using ‘chewcards’, was compared with that of scheduled aerial 1080 operations that were conducted in outlying areas of both trials. Contractors carrying out ground based control were able to follow the GPS tracks of aerial prefeeding flight lines very accurately, and with 1080 baits achieved very high levels of kill of possums and rats similar to those achieved by aerial 1080 baiting. Cholecalciferol was less effective in the first trial, but by doubling the amount of cholecalciferol bait used in the second trial, few possums or rats survived. By measuring the time taken to complete ground baiting from GPS tracks, we predicted that the method (using 1080 baits) would be similarly cost effective to aerial 1080 operations for controlling possums and rats, and considerably less expensive than typical current costs of ground based control. The main limitations to the use of the method will be access to, and size of, the operational site, along with topography and vegetation density.

Dental fluorosis and skeletal fluoride content as biomarkers of excess fluoride exposure in marsupials

Particulate and gaseous fluoride emissions contaminate vegetation near fluoride-emitting industries, potentially impacting herbivorous wildlife in neighboring areas. Dental fluorosis has been associated with consumption of fluoride-contaminated foliage by juvenile livestock and wildlife in Europe and North America. For the first time, we explored the epidemiology and comparative pathology of dental fluorosis in Australian marsupials residing near an aluminium smelter. Six species (Macropus giganteus, Macropus rufogriseus, Wallabia bicolor, Phascolarctos cinereus, Trichosurus vulpecula, Pseudocheirus peregrinus) demonstrated significantly higher bone fluoride levels in the high (n=161 individuals), compared to the low (n=67 individuals), fluoride areas (p<0.001). Necropsy examinations of all six species from the high-fluoride area near the smelter revealed dental lesions considered characteristic of dental fluorosis in eutherian mammals. Within the high-fluoride area, 67% of individuals across the six species showed dental enamel lesions, compared to 3% in the low-fluoride areas. Molars that erupted before weaning were significantly less likely to display pathological lesions than those developing later, and molars in the posterior portion of the dental arcade were more severely fluorotic than anterior molars in all six species. The severity of dental lesions was positively associated with increasing bone fluoride levels in all species, revealing a potential biomarker of excess fluoride exposure.

Relaxation of risk-sensitive behaviour of prey following disease-induced decline of an apex predator, the Tasmanian devil.

Apex predators structure ecosystems through lethal and non-lethal interactions with prey, and their global decline is causing loss of ecological function. Behavioural changes of prey are some of the most rapid responses to predator decline and may act as an early indicator of cascading effects. The Tasmanian devil (Sarcophilus harrisii), an apex predator, is undergoing progressive and extensive population decline, of more than 90% in long-diseased areas, caused by a novel disease. Time since local disease outbreak correlates with devil population declines and thus predation risk. We used hair traps and giving-up densities (GUDs) in food patches to test whether a major prey species of devils, the arboreal common brushtail possum (Trichosurus vulpecula), is responsive to the changing risk of predation when they forage on the ground. Possums spend more time on the ground, discover food patches faster and forage more to a lower GUD with increasing years since disease outbreak and greater devil population decline. Loss of top-down effects of devils with respect to predation risk was evident at 90% devil population decline, with possum behaviour indistinguishable from a devil-free island. Alternative predators may help to maintain risk-sensitive anti-predator behaviours in possums while devil populations remain low.

Chemical characterization of milk oligosaccharides of the eastern quoll (Dasyurus viverrinus).

Structural characterizations of marsupial milk oligosaccharides have been performed in four species to date: the tammar wallaby (Macropus eugenii), the red kangaroo (Macropus rufus), the koala (Phascolarctos cinereus) and the common brushtail possum (Trichosurus vulpecula). To clarify the homology and heterogeneity of milk oligosaccharides among marsupials, the oligosaccharides in the carbohydrate fraction of eastern quoll milk were characterized in this study. Neutral and acidic oligosaccharides were separated and characterized by (1)H-nuclear magnetic resonance spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The structures of the neutral oligosaccharides were Gal(β1-3)Gal(β1-4)Glc (3'-galactosyllactose), Gal(β1-3)Gal(β1-3)Gal(β1-4)Glc (3",3'-digalactosyllactose), Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (lacto-N-novopentaose I), Gal(β1-3)Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (galactosyl lacto-N-novopentaose I), Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-3)Gal(β1-4)Glc (galactosyl lacto-N-novopentaose II), Gal(β1-3)[Gal(β1-3)Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (galactosyl lacto-N-novopentaose III) and Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (lacto-N-novooctaose). The structures of the acidic oligosaccharides detected are Neu5Ac(α2-3)Gal(β1-4)Glc (3'-sialyllactose), Gal(β1-3)(O-3-sulfate)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (lacto-N-novopentaose I sulfate a), Gal(β1-3)[Gal(β1-4)(O-3-sulfate)GlcNAc(β1-6)]Gal(β1-4)Glc (lacto-N-novopentaose I sulfate b), Neu5Ac(α2-3)Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (sialyl lacto-N-novopentaose a), Gal(β1-3)[Neu5Ac(α2-3)Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (sialyl lacto-N-novopentaose c), Neu5Ac(α2-3) Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc, and Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc with an α(2-3) Neu5Ac linked to β(1-4)Gal residue of either branch of Gal(β1-4)GlcNAc(β1-6) units. The most predominant oligosaccharides in the carbohydrate fraction of mid-lactation milk were found to be lacto-N-novopentaose I and lacto-N-novooctaose, i.e., branched oligosaccharides that contain N-acetylglucosamine. The predominance of these branched oligosaccharides, rather than of a series of linear β(1-3) linked galacto oligosaccharides, appears to be the main feature of the eastern quoll milk oligosaccharides that differentiates them from those of the tammar wallaby and the brushtail possum.

Cost-Effective Large-Scale Occupancy-Abundance Monitoring of Invasive Brushtail Possums (Trichosurus Vulpecula) on New Zealand's Public Conservation Land.

There is interest in large-scale and unbiased monitoring of biodiversity status and trend, but there are few published examples of such monitoring being implemented. The New Zealand Department of Conservation is implementing a monitoring program that involves sampling selected biota at the vertices of an 8-km grid superimposed over the 8.6 million hectares of public conservation land that it manages. The introduced brushtail possum (Trichosurus Vulpecula) is a major threat to some biota and is one taxon that they wish to monitor and report on. A pilot study revealed that the traditional method of monitoring possums using leg-hold traps set for two nights, termed the Trap Catch Index, was a constraint on the cost and logistical feasibility of the monitoring program. A phased implementation of the monitoring program was therefore conducted to collect data for evaluating the trade-off between possum occupancy–abundance estimates and the costs of sampling for one night rather than two nights. Reducing trapping effort from two nights to one night along four trap-lines reduced the estimated costs of monitoring by 5.8% due to savings in labour, food and allowances; it had a negligible effect on estimated national possum occupancy but resulted in slightly higher and less precise estimates of relative possum abundance. Monitoring possums for one night rather than two nights would provide an annual saving of NZ$72,400, with 271 fewer field days required for sampling. Possums occupied 60% (95% credible interval; 53–68) of sampling locations on New Zealand’s public conservation land, with a mean relative abundance (Trap Catch Index) of 2.7% (2.0–3.5). Possum occupancy and abundance were higher in forest than in non-forest habitats. Our case study illustrates the need to evaluate relationships between sampling design, cost, and occupancy–abundance estimates when designing and implementing large-scale occupancy–abundance monitoring programs.

Fire impacts recruitment more than survival of small‐mammals in a tropical savanna

The frequency and spatial patterning of fire for optimal biodiversity conservation is often poorly understood by managers, in part due to a lack of understanding of the mechanisms responsible for altering population dynamics of individual species. We investigated changes in the vital rates (survival and recruitment) of four small mammal species (three marsupials and one rodent) in a tropical savanna under four different experimental fire treatments applied at a landscape scale. Apparent survival declined in all fire treatments for only one of four small mammal species (northern brown bandicootIsoodon macrourus). Recruitment was reduced in three of four species in multiple fire treatments. The suppression of recruitment in the northern brown bandicoot and the brushtail possumTrichosurus vulpeculapopulations was greatest immediately after the initial fire treatment was applied, compared to remaining treatment applications in successive years, possibly due to an elevated fire intensity as a result of higher initial fuel loads. The results suggest that higher intensity fire impacted recruitment more than survival for small mammals at this site. To assist fire managers to conserve small mammal populations in tropical savannas, we recommend fire regimes that optimise habitat resources for recruitment. This may be achieved by a reduction in fire frequency and managing fuel loads to prevent an increase in fire intensity.

Primary possum macrophage cultures support the growth of a nidovirus associated with wobbly possum disease

The objective of the study was to establish a system for isolation of a recently described, thus far uncultured, marsupial nidovirus associated with a neurological disease of possums, termed wobbly possum disease (WPD). Primary cultures of possum macrophages were established from livers of adult Australian brushtail possums (Trichosurus vulpecula). High viral copy numbers (up to 6.9×108/mL of cell lysate) were detected in infected cell culture lysates from up to the 5th passage of the virus, indicating that the putative WPD virus (WPDV) was replicating in cultured cells. A purified virus stock with a density of 1.09g/mL was prepared using iodixanol density gradient ultracentrifugation. Virus-like particles approximately 60nm in diameter were observed using electron microscopy in negatively stained preparations of the purified virus. The one-step growth curve of WPDV in macrophage cultures showed the highest increase in intracellular viral RNA between 6 and 12h post-infection. Maximum levels of cell-associated viral RNA were detected at 24h post-infection, followed by a decline. Levels of extracellular RNA increased starting at 9h post-infection, with maximum levels detected at 48h post-infection. The establishment of the in vitro system to culture WPDV will facilitate further characterisation of this novel nidovirus.

From Leaf Metabolome to In Vivo Testing: Identifying Antifeedant Compounds for Ecological Studies of Marsupial Diets.

Identifying specific plant secondary metabolites that influence feeding behavior can be challenging, but a solid understanding of animal preferences can guide efforts. Common brushtail possums (Trichosurus vulpecula) predominantly eat Eucalyptus species belonging to the subgenus Symphyomyrtus, and avoid eating those belonging to the Monocalyptus subgenus (also called subgenus Eucalyptus). Using an unbiased (1)H NMR metabolomics approach, a previous study identified unsubstituted B ring flavanones in most species of monocalypts examined, whereas these compounds were absent from symphyomyrtles. We hypothesised that unsubstituted B ring flavanones act as feeding deterrents for common brushtail possums. In the current study, we tested this hypothesis by comparing how much possums ate of a basal diet, with diets containing one of four structurally related compounds; pinocembrin, flavanone (unsubstituted B ring flavanones), chrysin (the flavone analogue of pinocembrin), and naringenin (a flavanone with B ring substitution). We found that pinocembrin and flavanone deterred feeding relative to the basal diet, but that chrysin and naringenin did not at equivalent concentrations. Thus, unsubstituted B-ring flavanones may explain why brushtail possums avoid eating monocalypt species. Furthermore, small differences in the structure of secondary compounds can have a large impact on antifeedant properties. These results demonstrate that metabolomics can be a valuable tool for ecologists seeking to understand herbivore feeding preferences.

Effect of stimulus and response separation in a matching-to-sample task in the brushtail possum (Trichosurus vulpecula)

This study seeks to investigate the impact of changing the proximity of stimulus and response manipulanda on matching-to-sample performance in possums. Possums were presented with five rows of blue and yellow stimuli arranged vertically 25mm apart above response levers. Generally, peak performance occurred at the distance from the lever currently being trained. Performance generalized to distances close to the currently trained distance and decreased in accuracy at distances further from the trained level. The findings from this experiment provide evidence for placing stimuli and response manipulanda close together to improve acquisition of a task, and increase the responding accuracy in MTS experiments. This suggests that spatial contiguity in the relative location of stimuli and response manipulanda is critical to animals performing complex operant tasks.

Triacylglycerol estolides, a new class of mammalian lipids, in the paracloacal gland of the brushtail possum (Trichosurus vulpecula).

The paracloacal glands are the most prevalent scent glands in marsupials, and previous investigation of their secretions in the brushtail possum (Trichosurus vulpecula) has identified many odorous compounds together with large amounts of neutral lipids. We have examined the lipids by LC-MS, generating ammonium adducts of acylglycerols by electrospray ionisation. Chromatograms showed a complex mixture of coeluting acylglycerols, with m/z from about 404 to 1048. Plots of single [M + NH4](+) ions showed three groups of lipids clearly separated by retention time. MS-MS enabled triacylglycerols and diacylglycerol ethers to be identified from neutral losses and formation of diacylglycerols and other product ions. The earliest-eluting lipids were found to be triacylglycerol estolides, in which a fourth fatty acid forms an ester link with a hydroxy fatty acid attached to the glycerol chain. This is the first report of triacylglycerol estolides in animals. They form a complex mixture with the triacylglycerols and diacylglycerol ethers of lipids with short- and long-chain fatty acids with varying degrees of unsaturation. This complexity suggests a functional role, possibly in social communication.

Lean‐season primary productivity and heat dissipation as key drivers of geographic body‐size variation in a widespread marsupial

Geographic body‐size variation characterises many mammal species. Hypotheses centring around heat conservation, heat dissipation, primary productivity and seasonality have been advanced to explain geographic body‐size patterns. However, identification of the primary body‐size drivers has often been hampered by a paucity of data for broadly distributed species and the application of regression models that have not explicitly accounted for the spatial clustering inherent in such datasets. We used Australia's most widespread marsupial, the common brushtail possum Trichosurus vulpecula, as a model species with which to test five proposed drivers of geographic body‐size variation. Using geo‐referenced skull measurements from 588 specimens and a suite of putative environmental covariates, we employed spatial simultaneous autoregressive models, together with information criteria, to evaluate these different hypotheses. Our analysis identified a strong, positive relationship between possum body size and primary productivity during the least productive season, whereas the relationship with mean annual productivity received less support. Consistent with the heat‐dissipation hypothesis, T. vulpecula body size also decreased with increasing mean summer maximum temperature. Spatial autoregression coefficients estimated from the simultaneous autoregressive models were always high, suggesting that additional abiotic or biotic factors might contribute to the spatial patterns observed. We argue that the analysis of geographic body‐size variation should consider multi‐causal possibilities rather than treating the numerous hypotheses as competing, mutually exclusive alternatives.

Palatability and efficacy to possums and rats of pest control baits containing bird repellents

Repellents used to reduce by-kill of birds during pest control must not compromise acceptance by target species. Two repellents combined, anthraquinone (AQ; 0.4 g kg−1) and d-pulegone (DP; 1.0) did not reduce the palatability of blue-coloured carrot baits to laboratory rats (Rattus norvegicus); nor did DP (2.0). Green-coloured carrot baits coated with AQ, DP or AQ + DP were taken from bait stations by wild possums (Trichosurus vulpecula) and rats. Toxic (1080) bait coated with AQ (0.4) and peanut oil (0.1) had reduced palatability but was accepted by laboratory rats. However, laboratory rats did not consume enough baits coated with AQ and bacon, peanut butter, cinnamon or DP to be killed. Anthraquinone (0.4 or 0.8) plus cinnamon and DP (0.5) did not affect palatability or lethality to captive ship rats (R. rattus) or possums. Anthraquinone and DP as surface coatings on baits are therefore acceptable to possums and possibly rats, at concentrations that deter some bird species.