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Understanding wild animal responses to stressors underpins effective wildlife management. In order for responses to stressors to be correctly interpreted, it is critical that measurements are taken on wild animals using minimally invasive techniques. Studies investigating wild animal responses to stressors often measure either a single physiological or behavioural variable, but whether such responses are comparable and concordant remains uncertain. We investigated this question in a pilot study that measured responses of wild-caught urban brown and black rats (Rattus norvegicus, Rattus rattus) to fur-based olfactory cues from a predator, the domestic cat (Felis catus); a novel herbivore, the koala (Phascolarctos cinereus); and a familiar herbivore and competitor, the common brushtail possum (Trichosurus vulpecula). Physiological responses, measured by assaying faecal glucocorticoid metabolites, were compared to behavioural responses observed via video recordings. We found that physiological and behavioural responses to stressors were expressed concordantly. There was no sizeable physiological response observed, and the behavioural response when considered across the night was negligible. However, the behavioural response to the predator and competitor cues changed across the observation period, with activity increasing with increasing hours of exposure. Our results indicate that responses of wild rodents to cues are nuanced, with stress responses modulated by behaviour changes that vary over time according to the severity of the perceived threat as animals gather further information. If the physiological response alone had been assessed, this moderated response may not have been evident, and in terms of wildlife management, vital information would have been lost.

Wildlife disease surveillance requires accurate information on the proportion of managed populations sampled or their population density, parameters that are typically expensive to measure. However, these parameters can be estimated using spatially explicit modelling of capture probabilities, based on the distribution and deployment times of capture devices, given accurate information on the relationships between these variables. This approach is used in New Zealand's surveillance programme aimed at confirming areas free of bovine tuberculosis (bTB 1 ) in brushtail possums (Trichosurus vulpecula). However, there is uncertainty about the accuracy of the underpinning parameters characterizing possum trappability (g), given the distance between where a trap is placed and the possum home range centre. Sampling intensity (SI: the percentage of the population sampled during a population survey) and sigma (σ; 95% home range radius/2.45) were measured, using leg-hold traps deployed under a set protocol to standardize survey effort, at four sites containing previously radio- and GPS-collared individuals. Those data were used to derive an estimate of the nightly probability of capture of possums in a trap set at their home range centre (g 0 ). Those estimates were compared to the standard assumptions currently used as defaults in the day-to-day approach used by bTB managers. Home-range size (and therefore σ) varied widely between sites (range 3.6-49.4 ha), probably largely in response to differences in possum density. Field measured SI also varied widely between sites, and was closely positively correlated with home range size (R 2  = 0.967; P =  0.017); wide-ranging possums were more trappable than sedentary ones. We found that g 0 was inversely related to σ, but the magnitude of increases in g 0 with declining σ appeared to be insufficient to compensate for the fewer places at which each possum could be trapped when those home ranges were small. SI was, therefore, not constant across sites where a standard survey effort was applied. The assumed relationship between g 0 and σ in the current spatial model may, therefore, need reassessment. The management implication of these result is that the sampling effort required to attain a target sampling intensity is dependant on the target animal density, and for bTB management of possums in New Zealand, is under-estimated by the current default parameters in a model of freedom-from-disease for higher density possum populations., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Prey naiveté is a failure to recognize novel predators and thought to cause exaggerated impacts of alien predators on native wildlife. Yet there is equivocal evidence in the literature for native prey naiveté towards aliens. To address this, we conducted a meta-analysis of Australian mammal responses to native and alien predators. Australia has the world's worst record of extinction and declines of native mammals, largely owing to two alien predators introduced more than 150 years ago: the feral cat, Felis catus , and European red fox, Vulpes vulpes Analysis of 94 responses to predator cues shows that Australian mammals consistently recognize alien foxes as a predation threat, possibly because of thousands of years of experience with another canid predator, the dingo, Canis lupus dingo We also found recognition responses towards cats; however, in four of the seven studies available, these responses were of risk-taking behaviour rather than antipredator behaviour. Our results suggest that a simple failure to recognize alien predators is not behind the ongoing exaggerated impacts of alien predators in Australia. Instead, our results highlight an urgent need to better understand the appropriateness of antipredator responses in prey towards alien predators in order to understand native prey vulnerability., (© 2018 The Author(s).)

Ecologists have long been interested in how the nutritional composition of leaves changes as they age, and whether this affects herbivore feeding preferences. As a consequence, the literature abounds with reports that younger leaves contain higher concentrations of nitrogen and plant secondary metabolites (PSMs) than do older leaves. Most of these studies, however, base their conclusions on average values that often mean little to herbivores. We examined this issue in the well-studied marsupial-eucalypt system, using Eucalyptus melliodora and captive common brushtail possums (Trichosurus vulpecula) offered branches from individual trees containing both young and mature leaves. Like many plants, the concentrations of N and PSMs differed among individual E. melliodora. Although young leaves were, on average, "better defended" by the PSM sideroxylonal than were mature leaves, some trees produced leaves that were relatively undefended at both ages. In response, possums chose different proportions of young and mature leaves depending on the chemistry of the individual tree. Possums did not always prefer leaves with lower concentrations of sideroxylonal (mature leaves) or those with higher concentrations of available N (young leaves). Instead, the sideroxylonal concentration of young leaves dictated their choice: possums preferred young leaves with low sideroxylonal concentrations, but not with high concentrations. By skewing their feeding toward trees producing young leaves with low concentrations of PSMs, possums may influence plant fitness. Researchers will detect these potentially important interactions only if they are aware that measuring variation among plants discloses more information than do average relationships.

Pregnancy in mammals requires remodeling of the uterus to become receptive to the implanting embryo. Remarkably similar morphological changes to the uterine epithelium occur in both eutherian and marsupial mammals, irrespective of placental type. Nevertheless, molecular differences in uterine remodeling indicate that the marsupial uterus employs maternal defences, including molecular reinforcement of the uterine epithelium, to regulate embryonic invasion. Non-invasive (epitheliochorial) embryonic attachment in marsupials likely evolved secondarily from invasive attachment, so uterine defences in these species may prevent embryonic invasion. We tested this hypothesis by identifying localization patterns of Talin, a key basal anchoring molecule, in the uterine epithelium during pregnancy in the tammar wallaby (Macropus eugenii; Macropodidae) and the brush tail possum (Trichosurus vulpecula; Phalangeridae). Embryonic attachment is non-invasive in both species, yet Talin undergoes a clear distributional change during pregnancy in M. eugenii, including recruitment to the base of the uterine epithelium just before attachment, that closely resembles that of invasive implantation in the marsupial species Sminthopsis crassicaudata. Basal localization occurs throughout pregnancy in T. vulpecula, although, as for M. eugenii, this pattern is most specific prior to attachment. Such molecular reinforcement of the uterine epithelium for non-invasive embryonic attachment in marsupials supports the hypothesis that less-invasive and non-invasive embryonic attachment in marsupials may have evolved via accrual of maternal defences. Recruitment of basal molecules, including Talin, to the uterine epithelium may have played a key role in this transition., (© 2017 Wiley Periodicals, Inc.)

The formation of a placenta is critical for successful mammalian pregnancy and requires remodelling of the uterine epithelium. In eutherian mammals, remodelling involves specific morphological changes that often correlate with the mode of embryonic attachment. Given the differences between marsupial and eutherian placentae, formation of a marsupial placenta may involve patterns of uterine remodelling that are different from those in eutherians. Here we present a detailed morphological study of the uterus of the brushtail possum (Trichosurus vulpecula; Phalangeridae) throughout pregnancy, using both scanning and transmission electron microscopy, to identify whether uterine changes in marsupials correlate with mode of embryonic attachment as they do in eutherian mammals. The uterine remodelling of T. vulpecula is similar to that of eutherian mammals with the same mode of embryonic attachment (non-invasive, epitheliochorial placentation). The morphological similarities include development of large apical projections, and a decrease in the diffusion distance for haemotrophes around the period of embryonic attachment. Importantly, remodelling of the uterus in T. vulpecula during pregnancy differs from that of a marsupial species with non-invasive attachment (Macropus eugenii; Macropodidae) but is similar to that of a marsupial with invasive attachment (Monodelphis domestica; Didelphidae). We conclude that modes of embryonic attachment may not be typified by a particular suite of uterine changes in marsupials, as is the case for eutherian mammals, and that uterine remodelling may instead reflect phylogenetic relationships between marsupial lineages., (© 2017 Anatomical Society.)

Background: Introduced brushtail possums are controlled in New Zealand to mitigate their spread of bovine tuberculosis in livestock. Given the low rainfall and extreme variation in seasonal temperatures in dryland areas of the South Island, the habitats of possums in these areas differ in many respects from those in the rest of New Zealand. We investigated the movements and habitat preferences of possums at two dryland sites to identify where they aggregate following population control by using GPS collars and cards chewed by possums. At one site, possum numbers were reduced from high levels by 65%, and at the other site, possums had already been reduced to low levels for some time beforehand but were further reduced to maintain them at low levels. This resulted in different possum densities., Results: Possum home ranges were about 3 times smaller at the higher-density site, but average ranges expanded by 27% following initial control. Home ranges were already large at the lower-density site but did not expand further after maintenance control. No preference for habitat types was apparent at the higher-density site, but at the lower-density site possums selected rock and shrubby habitats and avoided open grassy areas., Conclusions: Home range sizes and habitat preferences were density dependent: the lower the density, the larger was the home range; and habitat preferences were highly variable between individuals, but less so for possums at low density. Preference for shrubs and rocks is likely to benefit population control if population control devices are focused on these habitat types. © 2016 Society of Chemical Industry., (© 2016 Society of Chemical Industry.)

Polyethylene glycol (PEG) has been used to study the intake and digestion of tannin-rich plants by mammalian herbivores because it preferentially binds to tannins. However, it is not clear whether the responses of herbivores to dietary PEG is due to increased protein availability from the release of tannin-bound protein, amelioration of tannin effects, or whether PEG also may bind to other compounds and change their activity in the gut. We used three native New Zealand tree species to measure the effect of PEG on the amount of foliage eaten by invasive common brushtail possums (Trichosurus vulpecula) and on in vitro digestible nitrogen (available N). The addition of PEG increased the in vitro available N content of Weinmannia racemosa foliage, and possums ate significantly more PEG-treated foliage than untreated foliage. However, possums also ate more PEG-treated Fuchsia excorticata foliage, even though PEG did not increase in vitro available N in this species. Possums ate very little Melicytus ramiflorus, regardless of PEG treatment, even though M. ramiflorus contained the highest concentration of in vitro available N. These results prompted us to use PEG and a protein supplement, casein, to manipulate the available N concentration of diets containing ground eucalypt foliage, a well-studied food species for possums. Again, the response of possums to PEG was independent of changes in in vitro available N. In addition, altering the protein content of the diet via the addition of casein did not affect how much food the possums consumed. We conclude that the effects of PEG on dry matter intake by mammalian herbivores are not due solely to the release of tannin-bound protein. There is need for a better understanding of PEG-tannin interactions in order to ensure that the use of PEG in nutritional studies does not outstrip an understanding of its mechanisms of action.

Introduced herbivores frequently inflict significant, yet patchy damage on native ecosystems through selective browsing. However, there are few instances where the underlying cause of this patchy damage has been revealed. We aimed to determine if the nutritional quality of foliage could predict the browsing preferences of an invasive mammalian herbivore, the common brushtail possum (Trichosurus vulpecula), in a temperate forest in New Zealand. We quantified the spatial and temporal variation in four key aspects of the foliar chemistry (total nitrogen, available nitrogen, in vitro dry matter digestibility and tannin effect) of 275 trees representing five native tree species. Simultaneously, we assessed the severity of browsing damage caused by possums on those trees in order to relate selective browsing to foliar nutritional quality. We found significant spatial and temporal variation in nutritional quality among individuals of each tree species examined, as well as among tree species. There was a positive relationship between the available nitrogen concentration of foliage (a measure of in vitro digestible protein) and the severity of damage caused by browsing by possums. This study highlights the importance of nutritional quality, specifically, the foliar available nitrogen concentration of individual trees, in predicting the impact of an invasive mammal. Revealing the underlying cause of patchy browsing by an invasive mammal provides new insights for conservation of native forests and targeted control of invasive herbivores in forest ecosystems.

Species distribution models (SDMs) are an effective way of predicting the potential distribution of species and their response to environmental change. Most SDMs apply presence data to a relatively generic set of predictive variables such as climate. However, this weakens the modelling process by overlooking the responses to more cryptic predictive variables. In this paper we demonstrate a means by which data gathered from an intensive animal trapping study can be used to enhance SDMs by combining field data with bioclimatic modelling techniques to determine the future potential distribution for the koomal (Trichosurus vulpecula hypoleucus). The koomal is a geographically isolated subspecies of the common brushtail possum, endemic to south-western Australia. Since European settlement this taxon has undergone a significant reduction in distribution due to its vulnerability to habitat fragmentation, introduced predators and tree/shrub dieback caused by a virulent group of plant pathogens of the genus Phytophthora. An intensive field study found: 1) the home range for the koomal rarely exceeded 1 km in in length at its widest point; 2) areas heavily infested with dieback were not occupied; 3) gap crossing between patches (>400 m) was common behaviour; 4) koomal presence was linked to the extent of suitable vegetation; and 5) where the needs of koomal were met, populations in fragments were demographically similar to those found in contiguous landscapes. We used this information to resolve a more accurate SDM for the koomal than that created from bioclimatic data alone. Specifically, we refined spatial coverages of remnant vegetation and dieback, to develop a set of variables that we combined with selected bioclimatic variables to construct models. We conclude that the utility value of an SDM can be enhanced and given greater resolution by identifying variables that reflect observed, species-specific responses to landscape parameters and incorporating these responses into the model.

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., (© 2015 The Author(s) Published by the Royal Society. All rights reserved.)

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.

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.

When conducting controlled laboratory studies with non-traditional laboratory animals it is important that methods for determining body weight stability are reliable. This helps ensure the health and welfare of animals when they are maintained during periods of free feeding or food restriction. This study compared different methods for determining body weight stability in six common brushtail possums (Trichosurus vulpecula) maintained on a free-feeding diet under laboratory conditions. A criterion of five consecutive weighings with less than ±2.5% change across days and no more than two consecutive days of weight loss or weight gain was judged to be the most suitable criteria for determining stability. It is important to study non-traditional animals, especially endangered or pest species, under controlled laboratory conditions and to have robust methods for establishing body weight stability., (© The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.)

Plant genetic and ontogenetic variation can significantly impact dependent fungal and arthropod communities. However, little is known of the relative importance of these extended genetic and ontogenetic effects within a species. Using a common garden trial, we compared the dependent arthropod and fungal community on 222 progeny from two highly differentiated populations of the endangered heteroblastic tree species, Eucalyptus morrisbyi. We assessed arthropod and fungal communities on both juvenile and adult foliage. The community variation was related to previous levels of marsupial browsing, as well as the variation in the physicochemical properties of leaves using near-infrared spectroscopy. We found highly significant differences in community composition, abundance and diversity parameters between eucalypt source populations in the common garden, and these were comparable to differences between the distinctive juvenile and adult foliage. The physicochemical properties assessed accounted for a significant percentage of the community variation but did not explain fully the community differences between populations and foliage types. Similarly, while differences in population susceptibility to a major marsupial herbivore may result in diffuse genetic effects on the dependent community, this still did not account for the large genetic-based differences in dependent communities between populations. Our results emphasize the importance of maintaining the populations of this rare species as separate management units, as not only are the populations highly genetically structured, this variation may alter the trajectory of biotic colonization of conservation plantings.

Structural characterizations of marsupial milk oligosaccharides have been performed in only three species: the tammar wallaby, the red kangaroo and the koala. To clarify the homology and heterogeneity of milk oligosaccharides among marsupials, 21 oligosaccharides of the milk carbohydrate fraction of the common brushtail possum were characterized in this study. Neutral and acidic oligosaccharides were separated from the carbohydrate fraction of mid-lactation milk and characterized by (1)H-nuclear magnetic resonance spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The structures of the 7 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(β1-3)Gal(β1-3)Gal(β1-4)Glc, Gal(β1-3)Gal(β1-3)Gal(β1-3)Gal(β1-3)Gal(β1-4)Glc, 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). The structures of the 14 acidic oligosaccharides detected were Neu5Ac(α2-3)Gal(β1-3)Gal(β1-4)Glc (sialyl 3'-galactosyllactose), 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(β1-3)Gal(β1-4)Glc, Neu5Ac(α2-3)Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (sialyl lacto-N-novopentaose a), Gal(β1-3)(-3-O-sulfate)Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc, Gal(β1-3)Gal(β1-3)[Gal(β1-4)(-3-O-sulfate)GlcNAc(β1-6)]Gal(β1-4)Glc, Gal(β1-3)[Neu5Ac(α2-6)Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (sialyl lacto-N-novopentaose b), Neu5Ac(α2-3)Gal(β1-3)Gal(β1-3)Gal(β1-3)Gal(β1-4)Glc, Gal(β1-3)(-3-O-sulphate)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, Gal(β1-3)(-3-O-sulphate)Gal(β1-3)Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc, Gal(β1-3)Gal(β1-3)Gal(β1-3)[Gal(β1-4)(-3-O-sulphate)GlcNAc(β1-6)]Gal(β1-4)Glc and Gal(β1-3)Gal(β1-3)[Neu5Ac(α2-6)Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (galactosyl sialyl lacto-N-novopentaose b). No fucosyl oligosaccharides were detected. Galactosyl lacto-N-novopentaose II, lacto-N-novopentaose I sulfate a, lacto-N-novopentaose I sulfate b and galactosyl sialyl lacto-N-novopentaose b are novel oligosaccharides. The results are compared with those of previous studies on marsupial milk oligosaccharides.

We investigated the passive mechanical properties of villi in ex vivo preparations of sections of the wall of the distal ileum from the brushtail possum (Trichosurus vulpecula) by using a flow cell to impose physiological and supra-physiological levels of shear stress on the tips of villi. We directly determined the stress applied from the magnitude of the local velocities in the stress inducing flow and additionally mapped the patterns of flow around isolated villi by tracking the trajectories of introduced 3 µm microbeads with bright field micro particle image velocimetry (mPIV). Ileal villi were relatively rigid along their entire length (mean 550 µm), and exhibited no noticeable bending even at flow rates that exceeded calculated normal physiological shear stress (>0.5 mPa). However, movement of villus tips indicated that the whole rigid structure of a villus could pivot about the base, likely from laxity at the point of union of the villous shaft with the underlying mucosa. Flow moved upward toward the tip on the upper portions of isolated villi on the surface facing the flow and downward toward the base on the downstream surface. The fluid in sites at distances greater than 150 µm below the villous tips was virtually stagnant indicating that significant convective mixing in the lower intervillous spaces was unlikely. Together the findings indicate that mixing and absorption is likely to be confined to the tips of villi under conditions where the villi and intestinal wall are immobile and is unlikely to be greatly augmented by passive bending of the shafts of villi.

Dispersal costs need to be quantified from empirical data and incorporated into dispersal models to improve our understanding of the dispersal process. We are interested in quantifying how landscape features affect the immediately incurred direct costs associated with the transfer of an organism from one location to another. We propose that least-cost modelling is one method that can be used to quantify direct transfer costs. By representing the landscape as a cost-surface, which describes the costs associated with traversing different landscape features, least-cost modelling is often applied to measure connectivity between locations in accumulated-cost units that are a combination of both the distance travelled and the costs traversed. However, we take an additional step by defining an accumulated-cost dispersal kernel, which describes the probability of dispersal in accumulated-cost units. This novel combination of cost-surface and accumulated-cost dispersal kernel enables the transfer stage of dispersal to incorporate the effects of landscape features by modifying the direction of dispersal based on the cost-surface and the distance of dispersal based on the accumulated-cost dispersal kernel. We apply this approach to the common brushtail possum (Trichosurus vulpecula) within the North Island of New Zealand, demonstrating how commonly collected empirical dispersal data can be used to calibrate a cost-surface and associated accumulated-cost dispersal kernel. Our results indicate that considerable improvements could be made to the modelling of the transfer stage of possum dispersal by using a cost-surface and associated accumulated-cost dispersal kernel instead of a more traditional straight-line distance based dispersal kernel. We envisage a variety of ways in which the information from this novel combination of a cost-surface and accumulated-cost dispersal kernel could be gainfully incorporated into existing dispersal models. This would enable more realistic modelling of the direct transfer costs associated with the dispersal process, without requiring existing dispersal models to be abandoned.

The detoxification limitation hypothesis predicts that the metabolism and biotransformation of plant secondary metabolites (PSMs) elicit a cost to herbivores. There have been many attempts to estimate these costs to mammalian herbivores in terms of energy, but this ignores what may be a more important cost-increases in protein turnover and concomitant losses of amino acids. We measured the effect of varying dietary protein concentrations on the ingestion of two PSMs (1,8 cineole-a monoterpene, and benzoic acid-an aromatic carboxylic acid) by common brushtail possums (Trichosurus vulpecula). The dietary protein concentration had a small effect on how much cineole possums ingested. In contrast, protein had a large effect on how much benzoate they ingested, especially at high dietary concentrations of benzoate. This prompted us to measure the effects of dietary protein and benzoate on whole-body protein turnover using the end-product method following an oral dose of [(15)N] glycine. Increasing the concentration of dietary protein in diets without PSMs improved N balance but did not influence whole-body protein turnover. In contrast, feeding benzoate in a low-protein diet pushed animals into negative N balance. The concomitant increases in the rates of whole-body protein turnover in possums eating diets with more benzoate were indicative of a protein cost of detoxification. This was about 30 % of the dietary N intake and highlights the significant effects that PSMs can have on nutrient metabolism and retention.

Estimating the nutritional value of a herbivore's diet is difficult because it requires knowing what the animal eats, the relative quality of each component and how these components interact in relation to animal physiology. Current methods are cumbersome and rely on many assumptions that are hard to evaluate. We describe a new method for estimating relative diet quality directly from faeces that avoids the problems inherent in other methods. We combine this method with near infrared reflectance spectroscopy (NIRS) to analyse many samples and thus provide a technique with immense value in ecological studies. The method stems from the correlation between the concentrations of dietary and faecal nitrogen in herbivores eating a tannin-free diet, but a weaker relationship in browsers that ingest substantial amounts of tannins, which form complexes with proteins. These complexes reduce the availability of nitrogen and may increase faecal nitrogen concentrations. Using the tannin-binding compound, polyethylene glycol, we showed that tannin-bound nitrogen is a significant and variable part of faecal nitrogen in wild common brushtail possums (Trichosurus vulpecula). We developed a technique to measure faecal available nitrogen and found that it predicted the reproductive success of female brushtail possums in northern Australia. Faecal available nitrogen combined with NIRS provides a powerful tool for estimating the relative nutritional value of the diets of browsing herbivores in many ecological systems. It is a better indicator of diet quality than other commonly used single-nutrient measures such as faecal nitrogen and foliage analysis paired with observed feeding behaviour.

The introduced Australian brushtail possum is a major vertebrate pest in New Zealand, with impacts on conservation and agriculture being managed largely through poisoning operations. Cholecalciferol (vitamin D3) is registered for use in controlling possums and despite its many advantages it is expensive and relatively inhumane. Combination of a high proportion of aspirin with a low proportion of cholecalciferol was effective in killing high proportions of groups of acclimatised, caged possums: this is attributed to both an unexpectedly high toxicity of the type of cholecalciferol used, and a proposed synergistic mechanism between the two compounds. Death was caused by localised damage to heart ventricles by aspirin, and inhibition of tissue repair by both aspirin and cholecalciferol. The observed toxicosis had lower impact on the welfare of possums than either compound administered alone, particularly aspirin alone. Residue analyses of bait remains in the GI tract suggested a low risk of secondary poisoning by either compound. The combination of cholecalciferol and aspirin has the potential to meet key requirements of cost-effectiveness and humaneness in controlling possum populations, but the effect of the combination in non-target species has yet to be tested.

Multiple particle-tracking techniques were used to quantify the thermally driven motion of ensembles of naked polystyrene (0.5 µm diameter) microbeads in order to determine the microrheological characteristics around the gut mucosa. The microbeads were introduced into living ex vivo preparations of the wall of the terminal ileum and proximal colon of the brushtail possum (Trichosurus vulpecula). The fluid environment surrounding both the ileal villi and colonic mucosa was heterogeneous; probably comprising discrete viscoelastic regions suspended in a continuous Newtonian fluid of viscosity close to water. Neither the viscosity of the continuous phase, the elastic modulus (G') nor the sizes of viscoelastic regions varied significantly between areas within 20 µm and areas more than 20 µm from the villous mucosa nor from the tip to the sides of the villous mucosa. The viscosity of the continuous phase at distances further than 20 µm from the colonic mucosa was greater than that at the same distance from the ileal villous mucosa. Furthermore, the estimated sizes of viscoelastic regions were significantly greater in the colon than in the ileum. These findings validate the sensitivity of the method and call into question previous hypotheses that a contiguous layer of mucus envelops all intestinal mucosa and restricts diffusive mass transfer. Our findings suggest that, in the terminal ileum and colon at least, mixing and mass transfer are governed by more complex dynamics than were previously assumed, perhaps with gel filtration by viscoelastic regions that are suspended in a Newtonian fluid.

We present a new measure for analysing animal movement data, which we term a 'Multi-Scale Straightness Index' (MSSI). The measure is a generalisation of the 'Straightness Index', the ratio of the beeline distance between the start and end of a track to the total distance travelled. In our new measure, the Straightness Index is computed repeatedly for track segments at all possible temporal scales. The MSSI offers advantages over the standard Straightness Index, and other simple measures of track tortuosity (such as Sinuosity and Fractal Dimension), because it provides multiple characterisations of straightness, rather than just a single summary measure. Thus, comparisons can be made among different segments of trajectories and changes in behaviour can be inferred, both over time and at different temporal granularities. The measure also has an important advantage over several recent and increasingly popular methods for detecting behavioural changes in time-series locational data (e.g., state-space models and positional entropy methods), in that it is extremely simple to compute. Here, we demonstrate use of the MSSI on both synthetic and real animal-movement trajectories. We show how behavioural changes can be inferred within individual tracks and how behaviour varies across spatio-temporal scales. Our aim is to present a useful tool for researchers requiring a computationally simple but effective means of analysing the movement patterns of animals., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Invasive species are often favoured in fragmented, highly-modified, human-dominated landscapes such as urban areas. Because successful invasive urban adapters can occupy habitat that is quite different from that in their original range, effective management programmes for invasive species in urban areas require an understanding of distribution, habitat and resource requirements at a local scale that is tailored to the fine-scale heterogeneity typical of urban landscapes. The common brushtail possum (Trichosurus vulpecula) is one of New Zealand's most destructive invasive pest species. As brushtail possums traditionally occupy forest habitat, control in New Zealand has focussed on rural and forest habitats, and forest fragments in cities. However, as successful urban adapters, possums may be occupying a wider range of habitats. Here we use site occupancy methods to determine the distribution of brushtail possums across five distinguishable urban habitat types during summer, which is when possums have the greatest impacts on breeding birds. We collected data on possum presence/absence and habitat characteristics, including possible sources of supplementary food (fruit trees, vegetable gardens, compost heaps), and the availability of forest fragments from 150 survey locations. Predictive distribution models constructed using the programme PRESENCE revealed that while occupancy rates were highest in forest fragments, possums were still present across a large proportion of residential habitat with occupancy decreasing as housing density increased and green cover decreased. The presence of supplementary food sources was important in predicting possum occupancy, which may reflect the high nutritional value of these food types. Additionally, occupancy decreased as the proportion of forest fragment decreased, indicating the importance of forest fragments in determining possum distribution. Control operations to protect native birds from possum predation in cities should include well-vegetated residential areas; these modified habitats not only support possums but provide a source for reinvasion of fragments.

Generalist herbivores forage on a variety of plant species, allowing them to gain nutrients while limiting ingestion of harmful toxins. As the capacity to mix diets appears important for maximizing intake, the spatial scale in heterogeneity of food resources should influence the foraging behavior of herbivores. Our aim was to identify how the feeding strategy of a generalist mammalian herbivore, the common brushtail possum, responds to foods within a spatially defined environment. We evaluated foraging responses against increasing spatial separation between pairs of artificial diets that differed in flavor and toxin profile, to determine how distance and diet affect intake and behavior. Foraging responses were influenced by the type of diet or the degree of spatial separation between foods but not by their interaction. Diet influenced intake, time spent feeding, and feeding rate, but had no effect on nightly foraging interval, number of feeding bouts, or bout length. The number of switches between paired food resources and foraging efficiency (intake per unit distance, which accounts for the energetic costs of travelling), were influenced only by distance. Titrating foraging against a range of distances demonstrated how quickly foraging efficiency can decline in response to the spatial separation of food resources, highlighting the importance of spatial heterogeneity of plants within the home range of an herbivore.

The common brushtail possum (Trichosurus vulpecula) is the most widespread browsing marsupial in Australia, where it occupies woodland, agricultural, and urban environments. Following its introduction into New Zealand in the 19th century it has become a major feral pest, threatening native forests. The adaptability of the possum is thought to be due in part to its social organization, in which chemical communication is important. Possums have cloacal glands and exhibit related marking behavior. This study sought to characterize the chemicals involved in scent marking. Swabs were taken of the cloacal region of 15 possums (5 females, 10 males) from north-eastern Tasmania and analyzed by gas chromatography-mass spectrometry. There was a large number of compounds present, including 81 branched and unbranched, and saturated and unsaturated, fatty acids (C(4)-C(15)) and alcohols (C(6)-C(26)); 27 esters of 2,6- and 2,7-dimethyloctanol; 29 esters of formic acid; 39 sulfur compounds including S(8) and a series of dialkyl disulfides, trisulfides, and tetrasulfides (C(4)-C(10)); and several alkylglycerol ethers. Many of these cloacal compounds are new to biology. There was considerable individual variability in the relative amounts of compounds found, and no evident sex differences, although the study was not designed to test this. This pattern suggests that these compounds may be acting collectively as a signature mixture of semiochemicals, carrying information on the individual, its kinship, and physiological and social status. This is the first detailed description of putative semiochemicals in any marsupial species.

1. Foraging herbivores must deal with plant characteristics that inhibit feeding and they must avoid being eaten. Principally, toxins limit food intake, while predation risk alters how long animals are prepared to harvest resources. Each of these factors strongly affects how herbivores use food patches, and both constraints can pose immediate proximate costs and long-term consequences to fitness. 2. Using a generalist mammalian herbivore, the common brushtail possum (Trichosurus vulpecula), our aim was to quantitatively compare the influence of plant toxin and predation risk on foraging decisions. 3. We performed a titration experiment by offering animals a choice between non-toxic food at a risky patch paired with food with one of five toxin concentrations at a safe patch. This allowed us to identify the tipping point, where the cost of toxin in the safe food patch was equivalent to the perceived predation risk in the alternative patch. 4. At low toxin concentration, animals ate more from the safe than the risky patch. As toxin concentration increased at the safe patch, intake shifted until animals ate mainly from the risky patch. This shift was associated with behavioural changes: animals spent more time and fed longer at the risky patch, while vigilance increased at both risky and safe patches. 5. Our results demonstrate that the variation in toxin concentration, which occurs intraspecifically among plants, can critically influence the relative cost of predation risk on foraging. We show that herbivores quantify, compare and balance these two different but proximate costs, altering their foraging patterns in the process. This has potential ecological and evolutionary implications for the production of plant defence compounds in relation to spatial variation in predation risk to herbivores., (© 2011 The Authors. Journal of Animal Ecology © 2011 British Ecological Society.)

1.  The causes of juvenile sex-biased philopatry and space use in mammals remain poorly understood, and results of previous research have been conflicting. Experimental interventions and manipulations on wild populations are rare, but can play an important role in establishing the factors governing offspring space use. 2.  We experimentally removed mothers of independent juvenile brushtail possums from the maternal home range and examined changes in offspring space use with global positioning system collars. We examined the influence of mother absence on philopatric behaviour, and determined whether or not maternal presence affected offspring space use. 3.  We fitted a longitudinal linear mixed effects model to demonstrate a change over time in the home range size of juveniles following experimental treatment by the removal of their mothers. When mothers were removed from the natal range, juveniles occupied significantly larger home range areas, with average increases of 175% in 95% kernel density estimates and 289% in minimum convex polygon estimates. This increase occurred within the first month following mother absence and was independent of juvenile sex. Home ranges of control juveniles did not change during the same time period. 4.  Changes in the spatial structure of mammalian populations in response to removal of individuals have important implications for pest management. The impacts of management strategies which target particular individuals in a population may counteract conservation benefits through their effect on the space use of survivors. Studies involving experimental removals provide important information on consequences of control and also yield insights into the causes of mammalian space use, philopatric behaviours and ultimately dispersal., (© 2010 The Authors. Journal compilation © 2010 British Ecological Society.)

The main purpose of this review is to provide a comprehensive update on what is known about the regulatory mechanisms of the hypothalamic-pituitary-ovarian axis in the brushtail possum, and to report on the outcomes of attempts made to manipulate by hormonal means, these processes in the possum. Over the last 15 years, several unique features of possum reproductive physiology have been discovered. These include an extended follicular phase despite elevated concentrations of FSH during the luteal phase, and early expression of LH receptors on granulosa cells of small antral follicles, suggesting a different mechanism for the selection of a dominant follicle. The use of routine synchronisation protocols that are effective in eutherians has failed to be effective in possums, and so the ability to reliably synchronise oestrus in this species remains a challenge., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Foraging herbivores must satisfy their nutrient requirements in a world of toxic plants while also avoiding predators. Plant toxins and perceived predation risk at food patches should both reduce patch residency time, but the relative strengths of these factors on feeding decisions has rarely been quantified. Using an arboreal generalist herbivore, the common brushtail possum Trichosurus vulpecula, we tested the effects on food intake of the plant toxin, cineole, and regurgitated pellets from one of its predators, the powerful owl Ninox strenua at the small spatial scale of the food patch. We used the giving-up density (GUD) framework, with animals harvesting food items (sultanas) in an inedible matrix (small pebbles). We ran two consecutive field experiments in a eucalypt woodland in eastern Australia, 1 month apart in the same location. In experiment 1, there was a significant interaction between cineole [at 17% of dry matter (DM)] and owl pellets. The GUD was lowest in the absence of both cineole and owl pellet, intermediate in the presence of owl pellet; and highest with cineole ± owl pellet. The effect of owl pellet diminished over time. In experiment 2, only cineole (at 10% DM) increased the GUD significantly. The difference in effect of owl pellet was probably due to both habituation and freshness of the cue. Our study demonstrates the importance of synthesising predator-prey and plant-herbivore ecology to better understand the complex set of constraints influencing foraging herbivores. The greater effect of toxin than fear on possums is likely to be due to its high, but ecologically relevant concentration. This highlights the need to explore the relative and net impacts of a range of concentrations of plant toxins and predation risks.

Two examples of the introduction of non-indigenous invasive species are reviewed: the grey squirrel in Europe (United Kingdom, Ireland and Italy) and the brushtail possum in New Zealand. Both have become very successful in their respective non-native habitats since their introductions in the mid-to-late 19th Century. Both species impact extensively on native biodiversity, environmental sustainability, forestry, and agriculture through a range of direct and indirect mechanisms. Management is currently mainly by lethal control, namely poisoning, trapping and shooting. Such methods of control are, however, increasingly contentious for both species, and alternative, non-lethal methods of population control, e.g. fertility control, are being developed. The case studies highlight many of the issues in invasive animal control; for example, prevention being better than control, lack of good understanding of impacts and the success of control measures on reducing impacts, interactive impacts on native biodiversity and ecosystems, the telling influence of public opinion on management options and, lastly, the need to better inform and educate the public.

IGFs are known to be key regulators of ovarian follicular growth in eutherian mammals, but little is known regarding their role in marsupials. To better understand the potential role of IGFs in the regulation of follicular growth in marsupials, expression of mRNAs encoding IGF1, IGF2, IGF1R, IGF-binding protein 2 (IGFBP2), IGFBP4 and IGFBP5 was localized by in situ hybridization in developing ovarian follicles of the brushtail possum. In addition, the effects of IGF1 and IGF2 on granulosa cell function were tested in vitro. Both granulosa and theca cells synthesize IGF mRNAs, with the theca expressing IGF1 mRNA and granulosa cell expressing IGF2 mRNA. Oocytes and granulosa cells express IGF1R. Granulosa and theca cells expressed IGFBP mRNAs, although the pattern of expression differed between the BPs. IGFBP5 mRNA was differentially expressed as the follicles developed with granulosa cells of antral follicles no longer expressing IGFBP5 mRNA, suggesting an increased IGF bioavailability in the antral follicle. The IGFBP protease, PAPPA mRNA, was also expressed in granulosa cells of growing follicles. Both IGF1 and IGF2 stimulated thymidine incorporation but had no effect on progesterone production. Thus, IGF may be an important regulator of ovarian follicular development in marsupials as has been shown in eutherian mammals.

Mammals have four hypaxial muscle layers that wrap around the abdomen between the pelvis, ribcage, and spine. However, the marsupials have epipubic bones extending anteriorly into the ventral hypaxial layers with two additional muscles extending to the ventral midline and femur. Comparisons of South American marsupials to basal eutherians have shown that all of the abdominal hypaxials are active bilaterally in resting ventilation. However, during locomotion marsupials employ an asymmetrical pattern of activity as the hypaxial muscles form a crosscouplet linkage that uses the epipubic bone as a lever to provide long-axis support of the body between diagonal limb couplets during each step. In basal eutherians, this system shifts off the femur and epipubic bones (which are lost) resulting in a shoulder to pelvis linkage associated with shifts in both the positions and activity patterns of the pectineus and rectus abdominis muscles during locomotion. In this study, we present data on hypaxial function in two species (Pseudocheirus peregrinus and Trichosurus vulpecula) representing the two major radiations of possums in Australia: the Pseudocheiridae (within the Petauroidea) and the Phalangeridae. Patterns of gait, motor activity, and morphology in these two Australian species were compared with previous work to examine the generality of 1) the crosscouplet lever system as the basal condition for the Marsupialia and 2) several traits hypothesized to be common to all mammals (hypaxial tonus during resting ventilation, ventilation to step synchrony during locomotion, and bilateral transversus abdominis activity during locomotor expiration). Our results validate the presence of the crosscouplet pattern and basic epipubic bone lever system in Australian possums and confirm the generality of basal mammalian patterns. However, several novelties discovered in Trichosurus, reveal that it exhibits an evolutionary transition to intermediate eutherian-like morphological and motor patterns paralleling many other unique features of this species., ((c) 2009 Wiley-Liss, Inc.)

We fed common brushtail possums artificial diets containing a buffer and the plant secondary metabolite (PSM), orcinol, to test the hypothesis that organic acids, common products of PSM metabolism, limit feeding by common brushtail possums (Trichosurus vulpecula). We introduced several diets containing orcinol and a buffer (urinary alkalising agent) over a course of three experiments. A diet containing 2% orcinol (wet matter) caused possums to reduce their food intake immediately, but feeding returned to normal 1-2 days later. Even though possums excreted strongly acidic urine (pH 5.1) and had perturbed nitrogen metabolism, they maintained their food intake and body mass until the experiment terminated 9 days after the introduction of orcinol. Possums ate 52% less when the basal diet contained 4% orcinol. As expected, the acid loads caused a change in the composition of urinary nitrogen with possums excreting more ammonium than urea and a large amount of unidentified nitrogenous material. Supplementing the diet containing orcinol with buffer neutralised the metabolic acid load and partly restored normal nitrogen metabolism, but did not restore feeding. Also, animals eating orcinol excreted normal amounts of 3-methylhistidine, indicating no increase in muscle protein catabolism. This suggests that a limitation to the rate of detoxification or toxicosis, rather than acid loads, limits the ingestion of acid-inducing PSMs.

Adult survival is perhaps the fitness parameter most important to population growth in long-lived species. Intrinsic and extrinsic covariates of survival are therefore likely to be important drivers of population dynamics. We used long-term mark-recapture data to identify genetic, individual and environmental covariates of local survival in a natural population of mountain brushtail possums (Trichosurus cunninghami). Rainfall and intra-individual diversity at microsatellite DNA markers were associated with increased local survival of adults and juveniles. We contrasted the performance of several microsatellite heterozygosity measures, including internal relatedness (IR), homozygosity by loci (HL) and the mean multilocus estimate of the squared difference in microsatellite allele sizes within an individual (mean d (2)). However, the strongest effect on survival was not associated with multilocus microsatellite diversity (which would indicate a genome-wide inbreeding effect), but a subset of two loci. This included a major histocompatibility complex (MHC)-linked marker and a putatively neutral microsatellite locus. For both loci, diversity measures incorporating allele size information had stronger associations with survival than measures based on heterozygosity, whether or not allele frequency information was included (such as IR). Increased survival was apparent among heterozygotes at the MHC-linked locus, but the benefits of heterozygosity to survival were reduced in heterozygotes with larger differences in allele size. The effect of heterozygosity on fitness-related traits was supported by data on endoparasites in a subset of the individuals studied in this population. There was no apparent density dependence in survival, nor an effect of sex, age or immigrant status. Our findings suggest that in the apparent absence of inbreeding, variation at specific loci can generate strong associations between fitness and diversity at linked markers.

Plant secondary metabolites (PSMs) strongly influence diet selection by mammalian herbivores. Concentrations of PSMs vary within and among plant species, and across landscapes. Therefore, local adaptations may cause different populations of herbivores to differ in their ability to tolerate PSMs. Here, we tested the food intake responses of three populations of a marsupial folivore, the common brushtail possum (Trichosurus vulpecula Kerr), from different latitudes and habitat types, to four types of PSMs. We found clear variation in the responses of northern and southern Australian possums to PSMs. Brushtail possums from southern Australia showed marked decreases in food intake in response to all four PSMs, while the two populations from northern Australia were not as sensitive and their responses did not differ from one another. These results were unexpected, based on our understanding of the experiences of these populations with PSMs in the wild. Our results suggest that geographically separated populations of possums may have evolved differing abilities to cope with PSMs, as a result of local adaptation to their natural environments. Our results provide the basis for future studies to investigate the mechanisms by which populations of mammalian species differ in their ability to tolerate PSMs.

Fluid secretion is essential for intestinal function and, in eutherian mammals, is driven by electrogenic Cl(-) transport, which is dependent upon a bumetanide-sensitive, basolateral Na(+)/K(+)/2 Cl(-) cotransporter, NKCC1. However, ileal secretion in the brushtail possum, a marsupial, involves a fundamentally different process, since NKCC1 expression is low in this tissue and the secretagogue-induced short circuit current (I(sc)) is insensitive to bumetanide. In view of these differences we have investigated the basis of the secretory response of the possum ileum. In the Ussing chamber the secretory I(sc) is independent of Cl(-) but dependent upon Na(+) and serosal HCO(3)(-)/CO(2), suggesting that secretagogues stimulate electrogenic HCO(3)(-) secretion. In agreement with this, serosal DIDS (4,4'-diisothiocyano-stilbene-2,2'-disulfonate; 1 mmol l(-1)) inhibited the secretory response. However, acetazolamide (1 mmol l(-1)) and serosal amiloride (1 mmol l(-1)) had little effect, indicating that HCO(3)(-) secretion is driven by HCO(3)(-) transport from the serosal solution into the cell, rather than hydration of CO(2) by carbonic anhydrase. Consistent with this the pancreatic variant of the electrogenic Na(+)/HCO(3)(-) cotransporter (pNBC) is highly expressed in the ileal epithelium and is located in the basolateral membrane of the epithelial cells, predominantly in the mid region of the villi, with lower levels of expression in the crypts and no expression in the villous tips. We conclude that the secretory response of the possum ileum involves electrogenic HCO(3)(-) secretion driven by a basolateral pNBC and that the ileal HCO(3)(-) secretion is associated with a specialised function of the possum ileum, most probably related to hindgut fermentation.

Plants contain a variety of chemical defenses that strongly affect feeding rates in captive mammals, but their effects on the fitness of wild herbivores are largely unknown. This is because the complexity of defensive compounds, and herbivores' counteradaptations to them, make their effects in the wild difficult to measure. We show how tannins interact with protein to produce spatial variation in the nutritional quality of eucalypt foliage, which is related to demography in a wild population of a marsupial folivore, the common brushtail possum (Trichosurus vulpecula Kerr). Tannins reduced the digestibility of nitrogen (N) in vitro, creating variation in available N concentrations among the home ranges of individual possums in an otherwise homogeneous habitat. This was strongly correlated with reproductive success: females with better quality trees in their home range reproduced more often and had faster-growing offspring. These results demonstrate a powerful mechanism by which spatial variation in plant chemistry may control herbivore population dynamics in nature.

The introduced brushtail possum is a serious pest in New Zealand and there is much interest in the development of an immunocontraceptive vaccine for population control. Immunisation of female possums against recombinant possum zona pellucida protein-2 (ZP2) is known to reduce embryo production by 72-75% but successful development of fertility control will depend on a delivery system that is effective for field use. Bacterial ghost vaccine technology is a promising system to formulate a non-living vaccine for bait or aerosol delivery. The N-terminal (amino acid residues 41-316, ZP2N) and C-terminal (amino acid residues 308-636, ZP2C) regions of possum ZP2 were fused to maltose-binding protein and expressed in the periplasmic space of Escherichia coli NM522 bacterial ghosts. Female possums (n=20 per treatment group) were immunised with 20mg of either plain ghosts, ZP2N ghosts, or ZP2C ghosts in phosphate-buffered saline applied to the nostrils and eyes (nasal/conjunctival mucosa) at weeks 0, 2 and 4. Effects of immunisation on fertility were assessed following superovulation and artificial insemination. Both constructs evoked humoral (antibody) and cell-mediated immune responses in possums and significantly fewer eggs were fertilised in females immunised against ZP2C ghosts. Results in this study indicate that bacterial ghosts containing possum ZP antigens can reduce possum fertility when delivered by mucosal immunisation and offer a promising delivery system for fertility control of wild possum populations.

1. Sex allocation theory predicts that where dispersal is sex biased, the fitness consequences of producing male or female offspring are mediated by resource availability and maternal competitive ability. Females in poorer condition are expected to favour dispersing offspring to minimize resource competition with kin. Environmental heterogeneity may drive spatial variation in sex allocation through resource competition-related benefits to females and territory quality benefits to dispersing or philopatric offspring. 2. Here, we demonstrate that microhabitat heterogeneity can drive extremely fine-scale spatial heterogeneity in offspring sex allocation. Female bobucks (Trichosurus cunninghami) in temperate rainforest were more likely to produce male offspring than those in surrounding Eucalyptus forest. 3. A maternal physiological effect was identified, in that females of lower body mass were more likely to produce male offspring. This finding is consistent with resource competition predictions, in that smaller females are expected to have poorer competitive ability. 4. Genetic spatial autocorrelation analysis identified males as the more dispersing sex. Furthermore, overproduction of males by mothers in the rainforest habitat was geographically concordant with reduced philopatry, as inferred from spatial genetic analysis. This provides empirical validation of dispersal-related explanations of offspring sex allocation: that production of offspring of the dispersing sex minimizes the potential for resource competition with kin. 5. Spatial variation in dispersal via sex allocation responses to environmental heterogeneity can potentially contribute to spatial patterns in population dynamics.

To better understand the effects of ambient relative humidity (RH) on physiological variables and the implications of RH-correcting evaporative water loss (EWL) data for marsupials, we examined the effect of RH on EWL, body temperature (Tb), metabolic rate (MR) and thermal conductance (C) of the brushtail possum (Trichosurus vulpecula), a medium-sized marsupial. Correcting EWL data for 27 species of marsupial for water vapour pressure deficit (DeltaWVP) in the chamber during measurement significantly increased, rather than decreased, the variability of the allometric relationship for EWL. For the brushtail possum, both ambient temperature (Ta) and RH significantly affected EWL. At Ta=25 degrees C, EWL was independent of RH at "63% RH, but decreased linearly at higher RH values. At Ta=30 degrees C, EWL was significantly related to RH from 26% to 92% RH. There was a significant effect of Ta on Tb and dry thermal conductance (Cdry; higher at 30 degrees C), but no effect of RH. For MR and wet thermal conductance (Cwet) there was a significant effect of Ta (MR higher and Cwet lower at 25 degrees C), and RH at Ta=30 degrees C (MR higher and Cwet lower at the lowest RH) but not at 25 degrees C. Our results indicate that brushtail possums do not necessarily show the linear relationship between ambient RH and EWL expected for an endotherm, possibly because of behavioural modification of their immediate microclimate. This may account for the failure of WVP deficit correction to improve the allometric EWL relationship for marsupials. Chamber RH is an important environmental factor to be considered when measuring standard physiological variables such as MR and Cwet.

Beta1,4-galactosyltransferase-I (GalTase-I) is one of the key molecules on the sperm surface of eutherian mammals that is likely to be involved in binding to the egg coat, the zona pellucida, to mediate sperm-egg interaction. In laboratory mice, the species for which most data are available, this protein functions as a receptor for the zona pellucida protein ZP3 of the oocyte and, upon binding, triggers the sperm acrosome reaction. In the present study, we investigated the presence and abundance of GalTase-I in epididymal sperm extracts of a marsupial, the brushtail possum, Trichosurus vulpecula. For this, spermatozoa were collected from cauda epididymides and the amount of beta1,4-galactosyltransferase activity in washed sperm extracts was compared with that of porcine spermatozoa. Overall beta1,4-galactosyltransferase enzyme activity was found to be more abundant in possum sperm extracts than those from porcine spermatozoa (P<0.05). Immunoblots with an antibody to mouse GalTase-I revealed that the molecular weight of possum spermatozoa GalTase-I was 66 kDa, which is similar to the molecular weight of GalTase-I in spermatozoa from eutherian mammals. The molecular weight of GalTase-I was the same in sperm extracts collected from the caput and cauda epididymides. These results demonstrate that GalTase-I is indeed present in possum spermatozoa and thus it may be a gamete receptor molecule on the sperm surface of marsupials as well as those of eutherian mammals.

Mammalian mating systems are thought to be shaped by the spatial distribution and abundance of key resources, which in turn influence the spacing behaviour of individuals. In particular, female home range size is predicted to reflect the availability of key resources. We documented the availability and distribution of food and shelter resources for two neighbouring populations of bobucks, or mountain brushtail possums, Trichosurus cunninghami, that were characterised by different mating systems: our "forest population" was socially monogamous, whereas the "roadside population" was polygynous. Both silver wattle, Acacia dealbata, the main food resource for bobucks, and den-trees, which provided shelter, occurred at significantly higher density at the roadside site. The pattern of distribution of these two resources also differed between the sites. Both food and den-trees were scattered evenly throughout the roadside habitat. In contrast, den-trees were located predominantly at one end of the forest site, while silver wattle trees were located at the other. There was no significant difference in the amount of silver wattle, or in the number of den-trees, located within the home ranges of individual females at the two sites. However, forest females had home ranges, on average, almost three times the size of those of roadside females. At the roadside site, the size of female home ranges varied inversely with the density of silver wattle, indicating that these females ranged over as large an area as necessary to gain access to sufficient silver wattle trees. There was no such relationship among forest females. These populations provide a clear example of resource distribution determining female home range size. This influenced the number of female home ranges a male's home range overlapped with, which in turn determined the mating system. Such clear links between resource availability and mating system have not previously been established in a marsupial.

Oral formulations are typically based on studies from eutherian animal models. This review introduces information relating to oral formulations for a marsupial species, the Australian brushtail possum (Trichosurus vulpecula) that has arisen from research into new methods for controlling this species - a major vertebrate pest in New Zealand. Morphologically, the gastrointestinal tract of the brushtail possum is similar to that of hindgut fermenting eutherian species, but there are some striking differences in function. Limited data suggests that the pharmacokinetics and bioavailability of administered drugs are similar to that in eutherian species, but there is some evidence that possums may have specific mechanisms for handling the intake of plant toxins and xenobiotics. The development of oral formulations for a free-ranging pest species presents several challenges above those encountered in the development of therapeutic formulations for humans and domestic animals. Use of a marsupial animal model may lead to new strategies for oral formulations in humans.

Longitudinal and radial movements during spontaneous contractions of isolated segments of terminal ileum of the brushtail possum, a species of arboreal folivore, were studied using high definition spatiotemporal maps. Segments obtained from specimens were continuously perfused with solutions of various apparent viscosities at 3 cm and 5 cm hydrostatic pressure. A series of sustained tetrodotoxin-sensitive peristaltic events occurred during perfusion. The leading edge of each peristaltic event progressed by a succession of rhythmic surges of circular contraction with concerted concurrent phasic longitudinal contractions. Three types of peristaltic event were observed, with differing durations of occlusion and patterns of cyclic, in phase, circular and longitudinal contractions. Each peristaltic event was preceded by a change of shade on the D map that indicated circumferential dilatation. Differences in the slopes of these phasic shade changes from those occurring during peristalsis indicate that this distension is passive and likely results from aboral displacement of fluid. Tetradotoxin insensitive longitudinal contraction waves of frequency 9.2 min(-1) occurred during and in the absence of peristalsis, originating at a variety of sites, and propagating either in an orad or aborad direction but predominantly in the latter. Perfusion with 1% guar gum, at 5 cm hydrostatic pressure caused the lumen to become distended and the generation of peristaltic events to cease pending reduction of the hydrostatic head to 3 cm but longitudinal contractile activity was preserved. Neither the frequencies nor the rates of progression of circular and longitudinal contractile events, nor the temporal coordination between these events, varied with the apparent viscosity of the perfusate or altered in a manner that could facilitate mixing.

Exploring the spatial distribution of variation in plant secondary metabolites is critical for understanding the evolutionary ecology of biochemical diversity in wild organisms. In the present study, concentrations of foliar sideroxylonal, an important and highly heritable defense chemical of Eucalyptus melliodora, displayed strong, fine-scale spatial autocorrelation. The spatial patterns observed could promote associational effects on herbivore foraging decisions, which may influence the selection pressures exerted on sideroxylonal content. Multiple chemical traits have roles in certain eucalypt-herbivore interactions, and the spatial characteristics of the herbivore foraging environment are therefore determined by these different factors. We used a model of E. melliodora intake by common brushtail possums (Trichosurus vulpecula), based on the combined effects of two chemical traits, to explore this idea and found that the spatial patterns were different to those of sideroxylonal alone. Spatial genetic autocorrelation, examined using microsatellites, was strong and occurred at a fine scale, implying that restricted gene flow might allow genetic patches to respond to selection relatively independently. Local two-dimensional genetic autocorrelation, explored using a new heuristic method, was highly congruent with the pattern of local phenotypic variation observed for sideroxylonal, suggesting that the genetic variance underlying the sideroxylonal variation is similarly structured. Our results suggest that the spatial distribution of genetic and phenotypic variation could influence both the selective pressure imposed by herbivores on eucalypt defenses and the potential of populations to respond to natural selection. Spatial context should be considered in future studies of plant-herbivore interactions.

Artificial insemination of brushtail possums (Trichosurus vulpecula) is being developed as an assisted breeding model for endangered marsupials, as well as a bioassay for testing fertility control vaccines to manage overabundant populations. Procedures were optimised in animals superovulated with pregnant mare serum gonadotrophin (PMSG) and porcine luteinising hormone (pLH). Of three intervals examined, yields were maximal following uterine insemination at 27-29.5 h after pLH treatment (four eggs, two to three embryos per female). Compared with no insemination, uterine-inseminated animals ovulated 30-36 h rather than 28-34 h after pLH treatment. For the vaginal route, yields were maximal following insemination at 10-13 h after pLH treatment (six to seven eggs, four embryos per female) than at five other intervals, and when using acclimatised females during the autumn breeding season. This protocol was suitable for testing fertility control vaccines in April-June and was influenced by the housing location of animals, the presence of an active corpus luteum and PMSG batch, but not other factors (year of trial, Freund's adjuvant treatment, changes in bodyweight, dose of PMSG kg(-1)). Embryos developed to the eight- to 16-cell or unilaminar blastocyst stage after uterine or vaginal insemination, respectively. With the timing of artificial insemination optimised, new methods to synchronise or induce oestrus and ovulation are required to achieve year-round testing of fertility control vaccines or birth of offspring.

1. The aim of this study was to compare the effect of exogenous ATP and adenosine on spontaneous motility of the proximal and distal regions of the possum sphincter of Oddi (SO). 2. ATP or adenosine (1 microm-1 mm) was applied to distal-SO or proximal-SO muscle rings in organ baths in the absence or presence of tetrodotoxin (TTX) or P1/P2 antagonists. 3. Both ATP and adenosine altered spontaneous activity, predominantly in proximal-SO rings. 4. Exogenous ATP induced a bi-phasic response consisting of a brief TTX-sensitive excitatory component, and a longer-lasting TTX-insensitive inhibitory component. 5. The excitatory ATP response likely involves P2X receptors, whereas the late inhibitory response likely involves P2Y receptors. 6. Exogenous adenosine decreased spontaneous SO activity, via a TTX-insensitive mechanism. 7. Exogenous purines modulate SO motility, acting primarily in the proximal region of the SO, via neural and non-neural mechanisms and multiple purine receptor subtypes.

This study assessed how the palatability of leaves of different age classes (young, intermediate and older) of Eucalyptus nitens seedlings varied with plant nutrient status, based on captive feeding trials with two mammalian herbivores, red-bellied pademelons (Thylogale billardierii), and common brushtail possums (Trichosurus vulpecula). Seedlings were grown under three nutrient treatments (low, medium and high), and we determined how palatability was related to chemical and physical characteristics of the leaves. Pademelons ate more older leaves than young and intermediate leaves for all treatments. This pattern was best explained by sideroxylonals (formylated phloroglucinol compounds known to deter herbivory by other marsupials), and/or essential oil compounds that were present in lower concentrations in older leaves. In the low-nutrient treatment, possums also ate more of the older leaves. However, in the medium- and high-nutrient treatments, possums ate more intermediate leaves than older leaves and showed a behavioural preference for young leaves (consuming younger leaves first) over intermediate and older leaves, in spite of high levels of sideroxylonals and essential oils. The young leaves did, however, have the highest nitrogen concentration of all the leaf age classes. Thus, either sideroxylonals and essential oils provided little or no deterrent to possums, or the deterrent was outweighed by other factors such as high nitrogen. This study indicates that mammalian herbivores show different levels of relative use and damage to leaf age classes at varying levels of plant nutrient status and, therefore, their impact on plant fitness may vary with environment.

Generalist mammalian browsers and folivores feed on a range of chemically different plant species, which may assist them in diluting toxins and diversifying nutrient consumption. The frequency and order in which their diets are mixed are important determinants of intake. As a result, the degree of plant heterogeneity in an environment, and the spatial scale at which this occurs, should directly influence herbivore foraging decisions. We tested whether altering the Spatial scale of plants, and thus plant secondary metabolites (PSMs), affected foraging efficiency of a generalist folivore, the common brushtail possum (Trichosurus vulpecula). First, we demonstrated that possums were able to consume more from a mixed diet of two chemically different species, Eucalyptus globulus and E. tenuiramis, than when either of these species was offered alone. We then tested whether altering the spatial scale between E. globulus and E. tenuiramis, as small- or large-scale plant heterogeneity "patches," affected possum foraging behavior and, ultimately, their foraging efficiency. Possums increased their foraging efficiency when the spatial scale of plant heterogeneity was small rather than large. We argue that the ability to regularly switch diets, when plant spatial distribution is at a small scale, reduces the negative effects of PSM ingestion. We predict that the heterogeneity of plant patches, in relation to PSM distribution, and the scale at which this occurs across a landscape, are critical factors that influence foraging efficiency and, ultimately, fitness of mammalian herbivores. This research provides a fundamental link between plant chemistry, foraging, and habitat heterogeneity.