Common Brushtail Possum Trichosurus Vulpecula Research Articles

Bait uptake by free living brush-tailed phascogales Phascogale tapoatafa and other non-target mammals during simulated buried fox baiting.

Field trials were undertaken in box-ironbark woodland at Puckapunyal Military Area (PMA) in central Victoria between January 2000 and April 2001 to assess bait uptake by the brushtailed phascogale (Phascogale tapoatafa) and other small mammals during simulated fox baiting exercises. The systemic marker Rhodamine B was used in non-toxic fox baits (Foxoff®) to detect non-target bait consumption. The trials demonstrated that free-living brush-tailed phascogales, yellow-footed antechinus (Antechinus flavipes), sugar gliders (Petaurus breviceps) and common brushtail possums (Trichosurus vulpecula) were capable of accessing non-toxic fox baits buried under 10 cm of sand. Rhodamine B markings were detected in six (15%) of 40 P. tapoatafa captured during the study period. The implications of these results and future research needs are discussed.

Effects of two plant secondary metabolites, cineole and gallic acid, on nightly feeding patterns of the common brushtail possum.

We investigated effects of two plant secondary metabolites (PSMs), cineole and gallic acid, on the nightly feeding behavior of the common brushtail possum (Trichosurus vulpecula), a generalist folivore. We tested whether possums altered their feeding behavior in response to increasing levels of cineole, a dietary terpene. Possums were fed artificial diets containing three levels of cineole: zero (basal diet), medium (6.8% of total dry matter, DM), and high (15.3% DM). In another experiment, we introduced gallic acid, a dietary phenolic, into the diets. Possums were offered a Choice PSM diet (cineole and gallic acid diets simultaneously) or a No-Choice PSM diet (containing either cineole or gallic acid). Detoxification products of cineole and gallic acid were examined in urine to determine that different detoxification pathways were utilized in the elimination of each compound. With increasing cineole levels, possums ate less, had smaller feeding bouts, and had a lower rate of intake, but did not extend their total nightly feeding time. Possums offered the Choice PSM diet, compared with the No-Choice diets, ate more, had larger feeding bouts, and tended to increase their rate of intake. Results from the urinary analysis indicated that gallic acid and cineole were not involved in competing detoxification pathways in brushtail possums. There was also a significant sex effect: females ate more overall, ate more per feeding bout, and ate at a higher rate than males. These results indicate that PSMs not only constrain overall intake, but that possums alter their feeding behavior in response to them. Altered feeding patterns may reduce the negative influence of PSMs on intake.

Adaptive biases in offspring sex ratios established before birth in a marsupial, the common brushtail possum Trichosurus vulpecula

Offspring sex ratios in the common brushtail possum are male biased in many populations, and there is evidence that interpopulation differences in sex ratios represent adaptive responses to local conditions. However, how these biases are produced is not known. Using comparisons between populations with and without biased offspring sex ratios, we show that biases in this species are not produced by sex-differential mortality between birth and weaning or sex-selective termination of pregnancy. Rather, adjustment in the sex ratio of offspring are evidently due to shifts in the probability of conceiving male and female offspring. Key words: brushtail possums, local resource competition, Marsupialia, primary sex ratio, sex ratio mechanisms, Trichosurus vulpecula. [Behav Ecol 13:653–656 (2002)]

Susceptibility of some Eucalyptus species and their hybrids to possum damage

Summary Common brushtail possums (Trichosurus vulpecula) are a significant vertebrate pest of eucalypt plantations in Tasmania; their browsing damage can cause loss in growth, reduced seedling survival and deformities. Possum damage could therefore become a serious problem in Australia's rapidly expanding eucalypt plantations. In addition, expansion of plantation areas is projected to include drier zones, where inter-specific eucalypt hybrids may play an important role. However, hybrids are currently being developed with little knowledge of their resistance to pests. This study examined the susceptibility to browsing by common brushtail possums of a range of eucalypts (Eucalyptus bicostata, E. globulus, E. gunnii, E. nitens, E. morrisbyi and E. ovata) and their F1 hybrids in four separate field trials in Tasmania. The Tasmanian endemics E. gunnii and E. morrisbyi were extremely susceptible to browsing whereas the other four species were relatively resistant. Within E. globulus, significant differences in damage between provenances were also detected. Field damage on interspecific F1 hybrids was generally intermediate in crosses between susceptible and resistant eucalypt species. While the exact degree of susceptibility varied, crossing a relatively resistant species with a highly susceptible species resulted in a significant increase in the susceptibility of the F1 hybrid compared with that of the resistant species. Only the hybrids between the two major plantation species E. nitens and E. globulus were significantly more susceptible to browsing than either the E. nitens or E. globulus controls, which were both relatively resistant. In practical terms, the present study indicated that possum susceptibility is an important factor to consider when investigating the potential of pure species and their hybrids for commercial use.

Inhibition of the microsomal metabolism of 1,8-cineole in the common brushtail possum (Trichosurus vulpecula) by terpenes and other chemicals

1. Brushtail possums (Trichosurus vulpecula) ingest large amounts of terpenes in their diet of Eucalyptus leaf. Previously, we showed that dietary terpenes induce the cytochrome P450 enzymes (CYPs) responsible for their metabolism. The present study examined the effects of various CYP inhibitors on the metabolism of 1,8-cineole, the major dietary terpene, by liver microsomes from the possum and rat. 2. Ketoconazole inhibited the major reactions of terpene-induced microsomes in both species: 9-hydroxylation in the possum and 2-hydroxylation in the rat. This suggests the involvement of CYP3A enzymes, although in the possum there was a lack of the expected inhibition by troleandomycin or activation by α -naphthoflavone, highlighting the differences between species in CYP forms. Diethyldithiocarbamate also inhibited 9-hydroxylation in the possum, indicating that a CYP2E1-like enzyme contributes to this reaction. 3. Three other dietary terpenes were potent competitive inhibitors of 9-hydroxylation in the possum. K i (µM) (mean ± SE, n = 4) were: α -pinene, 4.4 ± 1.1; limonene, 7.8 ± 2.1; p -cymene, 44.3 ± 11.2; cuminyl alcohol (a p -cymene metabolite), 6.0 ± 0.8. It appears likely that p -cymene acts via its metabolite to inhibit 1,8-cineole metabolism. 4. Inhibitory interactions between dietary terpenes, as well as other plant secondary compounds, may impose a significant constraint on foliage consumption in the common brushtail possum, therefore explaining the obligatory generalist nature of this browsing marsupial and other generalist herbivores.

Changes in mammal populations in relatively intact landscapes of Kakadu National Park, Northern Territory, Australia

AbstractA previous study (Braithwaite & Muller 1997) reported substantial declines in mammal abundance over the period 1986–1993 for a large study area (300 km2) within Kakadu National Park in the tropical savannas of northern Australia. This decline was reported as being a ‘natural’ response to fluctuating groundwater levels, driven by runs of poor wet seasons. We resampled mammals in this area in 1999, following a series of unusually good wet seasons, and examined the prediction that mammal numbers should have recovered. Increases in abundance were evident for four species: the smallest dasyurid (red‐cheeked dunnart Sminthopsis virginiae) and the three smallest rodents (delicate mouse Pseudomys delicatulus, western chestnut mouse Pseudomys nanus and grassland melomys Melomys burtoni). In contrast, the abundance of all mammals combined and that for seven individual mammal species (northern quoll Dasyurus hallucatus, fawn antechinus Antechinus bellus, common brushtail possum Trichosurus vulpecula, northern brown bandicoot Isoodon macrourus, dusky rat Rattus colletti, black‐footed tree‐rat Mesembriomys gouldii and pale field rat Rattus tunneyi) continued to decline. The decline in abundance of these mammal species is consistent with limited observations elsewhere in northern Australia. Although far from conclusive, these observations suggest that the biota of the vast relatively undisturbed tropical savannas can no longer be assumed to be intact nor safe. Further research is needed to test this possible pattern of decline and, if confirmed, to identify and ameliorate the processes contributing to it.

Changes in marsupial herbivore densities in relation to a forestry 1080-poisoning operation

Summary Tasmanian forestry companies commonly manage browsing damage to seedlings on plantations through the lethal control of native mammalian herbivores, using ‘1080’ (sodium monofluoroacetate). Although this practice is controversial, there is a lack of published quantitative data on its success in reducing animal numbers. We present the first published study quantifying the effects of a poisoning operation on the densities of mammalian herbivores both on a poisoned plantation and in the surrounding environment. Line transect surveys were used to monitor species densities before and after poisoning. The species targetted by the poisoning operation were the red-bellied pademelon (Thylogale billardierii), the red-necked wallaby (Macropus rufogriseus subspecies M. r. rufogriseus), the common brushtail possum (Trichosurus vulpecula) and European rabbit (Oryctolagus cuniculus). One non-target species, the common wombat (Vombatus ursinus), was also monitored. Poisoning significantly reduced pademelon density on the poisoned plantation (decline of 98%). A significant decrease in red-necked wallaby density was also detected at this time (decline of 60%) but a general declining trend was present within the data, so we interpret this result with caution. No significant effects were detected for possums, rabbits or wombats. The high kill-rate for pademelons may reflect the dominance of this species over others at bait stations and/or greater sensitivity to 1080. Six weeks after poisoning, the density of pademelons on the treated plantation had increased but was still significantly lower than before poisoning. At the same time, red-necked wallaby density on the treated plantation had increased, with animals moving onto the plantation from surrounding habitats. The decline of pademelons was hypothesized to enable an influx of red-necked wallabies onto the poisoned site, through reduced inter-specific dominance behaviour.

The conservation value of mesic gullies in dry forest landscapes: mammal populations in the box–ironbark ecosystem of southern Australia

Within the context of landscape variation in habitat quality, areas of unusually high productivity may serve as refuges for fauna during environmentally stressful periods and as sources of recruitment into less productive areas. In dry landscapes, water availability often defines habitat quality, so that drainages that concentrate run-off can facilitate relatively lush, and sometimes distinct, vegetation communities. The dry box–ironbark forests of south-eastern Australia may be such an ecosystem. Recent clearing of vegetation for agriculture and mining has eliminated 85% of the original vegetation in this area, with the fertile, alluvial soils being most affected. Fragmentation and degradation of remnant forest in this ecosystem has increased the potential importance of the remaining high-quality habitat to conservation. In this study, we tested the hypothesis that the abundance of mammals was higher in moist gullies than on dry hilltops, slopes and ridges in the box–ironbark forests of central Victoria. We compared 57 spatially paired gully and ridge sites. Habitat analyses indicated that gullies had a tree canopy height that was 51% taller than on ridges, 53% more trees with hollows in the upper bole and branches, and almost six times more very large trees. Ridges had 71% more small trees than gullies. Among marsupials surveyed, the common brushtail possum Trichosurus vulpecula and common ringtail possum Pseudocheirus peregrinus were significantly more abundant in gullies. Nearly all the reproduction observed in these two species occurred in gullies. The yellow-footed antechinus Antechinus flavipes was also significantly more abundant in gullies; numbers of the sugar glider Petaurus breviceps differed little. Whereas gullies occupy a very limited total area in this ecosystem, they may nonetheless be critical to some species of mammals that can survive in dry habitats but thrive only in mesic areas. Given the precariously degraded state of the box–ironbark ecosystem as a whole, protection of gullies from proposed alluvial gold mining and timber harvesting could have a disproportionate benefit to biodiversity conservation.

Spatial distribution of browsing damage and mammalian herbivores in Tasmanian eucalypt plantations

Summary The Bennett's wallaby (Macropus rufogriseus), Tasmanian pademelon (Thylogale billardierii), common brushtail possum (Trichosurus vulpecula) and European rabbit (Oryctolagus funiculus) can damage eucalypt seedlings growing in forestry plantations. The browsing damage caused by these herbivores is spatially variable, both within and between plantations. This study tests the hypothesis that the severity of browsing damage and the relative abundance of herbivores within a plantation, declines with increasing distance from adjacent cover habitat (remnant bushland or established plantation) and windrows. Randomly located damage plots (five seedlings) and scat plots were established at 15 plantations at the time of planting. Browsing damage was assessed at six and 12 months after planting. Scat counts were carried out from planting to 320 days. Correlation analyses indicated that browsing damage levels were related to distance from cover habitat in some, but not all, plantations. Damage scores measured at six months were negatively correlated with distance from cover habitat at four plantations (r = 0.373). Damage scores measured at 12 months were negatively correlated with distance from cover habitat at five plantations (r = 0.456). Damage was never correlated with distance from windrows. There was very little evidence to suggest that herbivores used areas close to cover habitat or windrows in preference to areas that were far from these habitat features. Significant correlation between the number of scats that were found in a plot and the distance from cover habitat was observed at only one plantation (pademelon: r = 0.603). There was no correlation between scat numbers and distance from windrow. These results suggest that there will often be little scope for reducing the economic impact of browsing damage, using methods weighted towards reducing levels of damage at the perimeter of the plantation. However, it may occasionally be possible to target edges in certain plantations, provided that the site characteristics conducive to edge effects are identified.

Ultrastructural observations on in vivo fertilisation in the brushtail possum, Trichosurus vulpecula, following PMSG/LH superovulation and artificial insemination.

Information on the dynamics of gamete interaction in marsupials is very limited and not available for any species from the major Australian Order Diprotodontia which includes most of the more familiar animals such as kangaroos, possums and the koala. This study addressed this deficiency by examining the ultrastructure of in vivo fertilised eggs from common brushtail possums (Trichosurus vulpecula). Females were superovulated by treatment with 15 IU PMSG and then 4 mg porcine LH 3 days later, and inseminations were performed 910-13 h after LH) using epididymal spermatozoa. Between 33 and 39 h after LH injection females were killed, reproductive tracts excised and the oviduct ampulla segment flushed for eggs. Three of the six eggs examined were fertilised as judged by the presence of sperm remnants in the cytoplasm. On the basis of these eggs it was found that sperm penetration left a large hole in the zona pellucida (ZP), suggesting that sperm zona penetration occurs primarily by the enzymatic action of acrosomal enzymes. Sperm lying within the perivitelline space were lacking both an outer acrosomal membrane and the associated acrosomal contents, while both these structures were found on sperm embedded within the mucoid layer, which is consistent with induction of the acrosome reaction by binding to the ZP. Once inside the egg cytoplasm, the sperm head travelled only a short distance before chromatin decondensation occurred. Fertilised eggs showed signs of cytoplasmic activation including cytoskeleton association with apparently dividing mitochondria and prominent rough endoplasmic reticulum. Unfertilised eggs appeared to be undergoing degenerative changes and lacked any evidence of activation. This study was demonstrated that superovulation and laparoscopic intravaginal artificial insemination provide a system through which perifertilisation events in the possum and other monovular Australian marsupials can be examined experimentally.

Ecological example of conditioned flavor aversion in plant-herbivore interactions: Effect of terpenes of Eucalyptus leaves on feeding by common ringtail and brushtail possums

We investigated the hypothesis that feeding deterrence of common ringtail possums (Pseudocheirus peregrinus) and common brushtail possums (Trichosurus vulpecula) by Eucalyptus terpenes (in this case 1,8-cineole) is a result of a conditioned flavor aversion (CFA), due to the association of terpenes with postingestive effects of another group of Eucalyptus toxins, the diformylphloroglucinol compounds (DFPCs). Wild-caught common ringtail and common brushtail possums showed a dose-dependent reduction in food intake when 1,8-cineole was added to the diet. However, after continued exposure over 12 days to increasing amounts of cineole in the diet, both species substantially increased their intakes of cineole relative to control animals. This indicated that the aversion to cineole was a conditioned response rather than a physiological limitation in their ability to detoxify terpenes. Subsequent exposure to a diet including both cineole and jensenone (a simple DFPC also found in Eucalyptus and considered to cause postingestive emesis) in corresponding amounts was able to recondition the dose-dependent aversion. Consequently, animals that had been given jensenone showed an aversion to cineole-rich diets that matched the behavior of animals in the control group. This supported our hypothesis that the effect of terpenes on feeding of these marsupial folivores on Eucalyptus is due to a CFA. Possums can cope with levels of terpenes in the diet that far exceed those occurring naturally. The role of terpenes in marsupial folivore–Eucalyptus interactions appears to be to act as a cue to levels of toxic DFPCs in the leaves, rather than acting as toxins in their own right.

A survey of mammalian browsing damage in Tasmanian eucalypt plantations

Summary Eucalypt seedlings growing in Tasmanian forestry plantations can be damaged by the Bennett's wallaby (Macropus rufogriseus), Tasmanian pademelon (Thylogale billardierii), common brushtail possum (Trichosurus vulpecula) and rabbit (Oryctolagus cuniculus). This paper reports the results of damage surveys carried out during 1994 to 1997 at 32 Eucalyptus nitens and 3 Eucalyptus globulus plantations. Browsing damage was evident at all 35 plantations. The percentage of seedlings damaged ranged from 14 to 97% at six months after planting and from 17 to 100% at 12 months. Mean browse score (MBS) ranged from 0.2 to 3.8 at six months and from 0.2 to 4.7 at 12 months. There was a strong exponential relationship between these two measures of damage. Browsing damage was estimated to have reduced first-year E. nitens growth rates by between 12 and 100% (mean = 36, sd = 22.9). The mean percentage of seedlings recorded with browsing damage at plantations where 1080 poisoning operations had been carried out (12 months: mean = 50, sd = 26.7) was significantly lower (P <0.01) than for plantations where 1080 was not used (mean = 84, sd = 18.5). The mean browse score recorded at poisoned plantations (12 months: mean = 1.2, sd = 1.14) was also significantly lower (P < 0.05) than that recorded for unpoisoned plantations (mean = 2.1, sd = 0.70). Seedling survival to 12 months was generally high (mean = 88%, sd = 10.7) and there was little evidence to suggest that survival of E. nitens during the first year following planting was strongly influenced by browsing damage.

Arboreal Marsupial Incidence in Eucalypt Patches in South-Eastern Australia: A Test of Hanski's Incidence Function Metapopulation Model for Patch Occupancy

The results of field tests are described of a simple model for the occupancy of habitat patches developed by Hanski. Patch occupancy was predicted for several species of arboreal marsupials in a system of fragmented patches of Eucalyptus forest in the Tumut region of southern New South Wales (NSW) in south-eastern Australia. The species of arboreal marsupials for which the model was tested were: common brushtail possum (Trichosurus vulpecula), mountain brushtail possum (Trichosurus caninus), common ringtail possum (Pseudocheirus peregrinus), and greater glider (Petauroides volans). Predictions of the model were compared against actual data on patch occupancy gathered from extensive field surveys. Four sub-models were tested for each of the four species of arboreal marsupials: with and without rescue effects and with and without mainland effects (i.e. dispersal from large population source areas). These sub-models were tested by deriving model parameters from a subset of 40 patches and then applying the model to make predictions of patch occupancy in an array of 86 other patches of remnant Eucalyptus forest habitat. Comparisons were then made between the actual values for patch occupancy found during field surveys and the probabilities of patch occupancy predicted by the model. Our analyses revealed large differences in the results for different species. In the case of P. peregrinu there were several models for which it was not possible to derive the parameter estimates required by the model (i.e. relationships for extinction and colonisation as a function of patch size and patch isolation). The ability of the species to persist at low density in the surrounding landscape matrix may have precluded the calculation of these estimates. There was reasonable congruence between predictions and actual field data for patch occupancy for P. volans and also for most sub-models for T. vulpecula. Conversely, none of the sub-models for T. caninus produced results that were consistent with the observed data on patch occupancy for this species. The reasons for the marked differences in results for T. caninus and T. vulpecula are not clear, but they indicate that knowledge of the response of one species to disturbance (e.g. habitat fragmentation) may not necessarily provide a useful guide to the possible response of other taxa, including those that are very closely related.

Administration of a 5HT 3 receptor antagonist increases the intake of diets containing Eucalyptus secondary metabolites by marsupials

The effect of a naturally occurring plant phenolic constituent (the acylphloroglucinol derivative, jensenone, derived from Eucalyptus jensenii) on the food intake of two folivorous marsupials, the common ringtail (Pseudocheirus peregrinus) and the common brushtail possum (Trichosurus vulpecula) was studied. When fed diets containing varying concentrations of jensenone, both species regulated their intake of jensenone so as not to exceed a ceiling intake. This ceiling was about twice as high for common ringtails as for common brushtails from northern Australia. Southern populations of common ringtails showed greatly reduced capacities to tolerate jensenone. When common brushtails were injected (0.5 mg.kg-0.75 body mass) with ondansetron (a selective antagonist of serotonin 5HT3 receptors), they ate significantly more jensenone than animals injected with physiological saline. The same pattern was observed when common ringtails were fed diets containing both jensenone and ondansetron (0.0035 mg.g-1 wet mass of diet). Ondansetron injection had no effect on food intake when the food did not contain jensenone while the addition of higher doses of ondansetron to diets of common ringtails very slightly reduced food intakes of a non-jensenone diet. When common brushtails were given 50 mg of jensenone by gastric lavage, their average subsequent intake of dietary jensenone matched the difference between the daily threshold and the dose given, although the response of individuals was highly variable. Lavage with water alone had no effect on subsequent jensenone intake compared with the pre-dose period. We interpret these results as evidence that the antifeedant effects of jensenone and related compounds are partly mediated by serotonin action on 5HT3 receptors most likely via "nausea" to condition a food aversion.

Methaemoglobin formation in the koala and the possum

Measurements were made of glutathione (GSH) levels, catalase activity and the oxidant sensitivity of the erythrocytes from the koala (Phascolarctos cinereus) and the common brushtail possum (Trichosurus vulpecula). The oxidant sensitivity was tested by treating the haemolysates with either 0.55 him H2O2 or 1.4mm NaNO2. The erythrocytes of the koala had greater levels of GSH and catalase and yet were found to be more susceptible to oxidation induced by both these oxidants.

The effect of manipulating population density on the probability of den-sharing among common brushtail possums, and the implications for transmission of bovine tuberculosis

Common brushtail possums (Trichosurus vulpecula) act as a reservoir of bovine tuberculosis (Mycobacterium bovis) in New Zealand and the simultaneous sharing of dens may result in the transmission of Tb between possums. The effect of manipulating population density on the per capita probability of simultaneous den-sharing among possums was investigated at a site near Dunedin, New Zealand. Den characteristics that could affect the probability of simultaneous sharing were also investigated, though none were found to be significant. The daily probability of a possum sharing a den was estimated to be 0.07 for possums denning within uncontrolled areas of the study area. Den-sharing was most common between female pairs, though sharing was also recorded between male–female and male–male pairs. The highest number of possums recorded sharing a single den was four. Reducing population density significantly lowered the probability of possums simultaneously sharing dens within the study area, with greater than 60% reductions estimated to eliminate simultaneous den-sharing altogether. The relationship between the contact rate arising from den-sharing and population density was convex-down, rather than convex-up, as often hypothesised for animal–animal disease contact processes. The implications of simultaneous den-sharing for the transmission and control of bovine tuberculosis in brushtail possum populations are discussed.

The follicle-stimulating hormone beta-subunit gene of the common brushtail possum (Trichosurus vulpecula): analysis of cDNA sequence and expression.

Reverse transcription-PCR has been used to obtain a cDNA sequence from the follicle-stimulating hormone (FSH) beta-subunit gene of the Australian brushtail possum (Trichosurus vulpecula). Comparisons of the possum FSHbeta-mRNA coding region nucleotide sequence with that of six eutherian mammal homologues reveals a mean percent identity of 77.3% and 76.8% at the nucleotide and predicted amino acid-sequence levels respectively. Furthermore, the predicted amino acid sequence of the possum FSHbeta mature protein shows evolutionary conservation of twelve cysteine residues and two potential N-linked glycosylation sites. The protein lacks the CAGY motif present in most reported glycoprotein beta-subunit sequences. The translation termination codon and consensus polyadenylation sequence overlap, a feature observed in other mammalian FSHbeta genes. Northern hybridization of total RNA from adult female possum pituitary revealed three hybridizing transcripts of approximately 2.8, 1.2 and 0.5 kb which may arise from utilizing alternative polyadenylation signals. In situ hybridization localized the FSHbeta transcripts to a sub-population of anterior pituitary cells interpreted as being gonadotropes. In summary the results indicate considerable evolutionary conservation of the structure of the FSH beta-subunit gene between the marsupial and eutherian mammalian lineages.

Morphology and Function of the Gastrointestinal Tract of Australian Folivorous Possums

Museum specimens of seven Australian Pseudocheiridae (ringtail possums and greater glider) and six Australian Phalangeridae (brushtail possums and cuscuses) were examined to assess the extent of possible differences in gastrointestinal tract morphology and function within and between these two families of Australian folivorous possums. Although there were no differences between the two families in gut segment lengths, the Pseudocheiridae had less relative tissue mass in the small intestine (P &lt; 0·05) and greater relative tissue mass in the caecum (P &lt; 0·05) than the Phalangeridae. Total nitrogen concentrations of stomach, caecum and proximal colon digesta were greater in the Pseudocheiridae than in the Phalangeridae (P &lt; 0·05), but in the distal colon they were similar. These differences suggest that the colonic separation mechanism previously documented in two pseudocheirid species is probably characteristic of the family Pseudocheiridae, but not of the Phalangeridae. They also reflect the more folivorous nature of the Pseudocheiridae, as leaves are generally higher than fruit in total nitrogen concentration. Among members of the Phalangeridae, there were no significant differences in any of the parameters measured, and it is concluded that the digestive strategy of the common brushtail possum (Trichosurus vulpecula) is probably representative of the family. In contrast, there were several notable differences among members of the Pseudocheiridae, indicating that the common ringtail possum (Pseudocheirus peregrinus) is not representative of all pseudocheirids. In particular, the digestive strategy of the rock ringtail possum (Petropseudes dahli) should be examined in relation to its unusual habitat, to its relatively simple caecum, and to the unusually low nitrogen concentrations found throughout its gastrointestinal tract.

Role of Catalase in H2O2-induced oxidant stress in marsupial erythrocytes

We have examined the catalase activity and H2O2-induced oxidant stress on methaemoglobin formation and haemolysis in eight species of marsupials: the black striped wallaby (Macropus dorsalis), bridled nailtail wallaby (Onychogalea fraenata), proserpine rock wallaby (Petrogale persephone), red legged pademelon (Thylogale stigmatica), spectacled hare wallaby (Lagorchestes conspicillatus), whiptail wallaby (Macropus parryi), common brushtail possum (Trichosurus vulpecula), and the koala (Phascolarctos cinereus). The results indicate a significant relationship between the activity of catalase and methaemoglobin formation by H2O2.

Lithium and Cyanide-Induced Conditioned Food Aversions in Brushtail Possums

Bait shyness through conditioned food aversion (CFA) by the common brushtail possum (Trichosurus vulpecula) may reduce the effectiveness of sodium cyanide (NaCN) poisoning operations in New Zealand. Thus, we compared the relative effectiveness of 2 toxins (NaCN and lithium chloride [LiCl]) in establishing CFA in this species. Once a week, for 30 minutes, we presented 27 individually caged wild possums with a novel raspberry-flavored food. Within 74 minutes of feeding they received an intraperitoneal injection of either 414 mg/kg sodium chloride, 200 mg/kg LiCl, or 4 mg/kg NaCN (weeks 0, 1, and 2), or 300 mg/kg LiCl (weeks 0 and 1). We presented flavored food alone at weekly intervals for 8 more weeks. Following the first injection, possums reduced (P < 0.05) intake of flavored food, relative to the saline control, for 2 weeks (NaCN group) or for 9 weeks (both LiCl groups). The demonstration of a NaCN-induced CFA in some possums contrasts with previous failures to establish aversions in laboratory rats (Rattus norvegicus), and suggests that modifications to current toxin-control practices for possums are required to limit the development of bait shyness.