Suchergebnisse

A general synthesis is presented of the key results of a series of studies of
den tree use by the mountain brushtail possum
(Trichosurus caninus) at Cambarville in the mountain ash
(Eucalyptus regnans) forests of the central highlands of
Victoria, south-eastern Australia. The project produced a range of unexpected
results including (1) the number of den trees used, (2) the extent of den
sharing, especially among adult males, (3) the overlap in denning ranges of
animals, and (4) the predictability of transitions between den trees. Possible
reasons for these findings are outlined. We also discuss the limitations of
our study, how it could be improved if it were to be repeated, and some of the
important implications of the findings for the management of forests where
T. caninus occurs.

Radio-tracking was used to examine the spatial configuration and co-occupancy
of large trees with hollows occupied by 16 mountain brushtail possums
(Trichosurus caninus) at Cambarville in the central
highlands of Victoria, south-eastern Australia. The distance that animals
moved between trees on successive days was also examined. Our analyses showed
that animals often remained in a given den tree on successive days. On nights
when animals did shift between den sites, they typically moved to a new tree
that was relatively nearby (< 200 m). Long-distance movements (e.g. >
300 m) between den trees were rare.
Considerable variation was found between individuals in the size of areas
encompassing trees used frequently (≥5 times) ('core denning
range') and those encompassing all occupied trees [i.e. including
those used infrequently (< 5 times)] ('total denning
range'). The mean area of the core denning range averaged about
1·1 ha for males and 0·7 ha for females. The mean value for the
total denning range was approximately 2·6 ha for males and females
respectively. Considerable overlap was found in the total denning ranges of
pairs of adult males and pairs of adult females. For most animals, the total
denning range was shared with the total denning ranges of several other
animals. There was substantial variation in the extent of this overlap,
ranging from complete enclosure to the sharing of a single tree. The extent of
overlap was more limited for the core denning ranges, particularly among
females. We observed differences in the extent of the overlap of the total
denning ranges of pairs of males and pairs of females in the breeding season
(January–March) and non-breeding season (the remaining months of the
year). Fewer instances of overlapping total denning ranges among pairs of both
males and females were found during the breeding season. The total denning
ranges in the breeding season were generally smaller than those in the non-
breeding season.
Simultaneous co-occupancy of a given den tree by
T. caninus was relatively common. Unexpectedly, there
was a number of instances of groups of three or four adult animals sharing the
same den site on the same night. We recorded several instances of sharing by
pairs of animals of the same sex, especially adult males. However, most
records of simultaneous tree use were by an adult male and an adult female
T. caninus.
The extent of overlap in the denning ranges of animals and the prevalence of
simultaneous co-occupancy of den trees indicate that the social behaviour of
T. caninus at Cambarville may be different from that
observed among populations of the species elsewhere in Australia. Possible
reasons for these differences are outlined.

As early morning bird vocalisation is a major feature of many bird communities, longitudinal profiles of vocal activity data, collected using sound recorders, were compared for a range of habitat types in the Tumut area of south-eastern Australia. There was a significant, and roughly linear, decline in vocal activity across the morning after an initial early peak of activity. Vocal activity persisted longer at sites located within large areas of continuous eucalypt forest than in the strip- and patch-shaped eucalypt remnants surrounded by extensive stands of radiata pine or at sites dominated by stands of radiata pine. There was evidence that the pattern of persistence of vocal activity differed among the different bird groups.

This paper presents the results of a study of the use of den trees by the greater glider (Petauroides volans) in five patches of remnant eucalypt forest embedded within an extensive radiata pine (Pinus radiata) plantation near Tumut in south-eastern Australia. Radio-tracking was used to identify 171 den trees occupied by 40 animals over 948 animal-tracking days between September 1997 and September 1998. All radio-tracked P. volans used multiple den trees. Males used significantly more den trees than females and a greater proportion of these were used for single visits. Males also used fewer new den trees over the study period in the smaller patches, although they still used more than females. In the larger patches, males and females used similar numbers of den trees.
Commonly used den trees tended to be situated in (or close to) core areas of an individual's home range. Den tree sharing, either concurrently or independently, was predominantly between adult males and females, or between adults and their young. Trees most likely to be used by more than one individual had the same characteristics as trees that had the highest probability of use per se – that is, they were of large 'average size'.

Morning vocal activity data for birds were collected using automatic sound recorders at 165 sites in fragmented forests at Tumut in south-eastern Australia. A model was developed to describe the statistical properties of the vocal activity data and study the relationship between the number of 'elements' (or notes) broadcast by birds and the number of birds recorded by human observers. We discuss the practical issues of finding a model where variance heterogeneity and skewness is a feature of the data, while the context of the problem required that multiplicative relationships be preserved. A satisfactory fit to our vocal activity data was obtained by using a Gamma distribution.For most groups of birds, the observed relationships between vocal activity and the number of birds recorded by human point counts were weak but statistically significant.Our analysis suggests that these data provide limited useful information about vocal activity per bird. Automatic sound-recording data may be informative for drawing inferences about temporal patterns in vocal activity but do not seem useful as a method for estimating the abundance of birds. A significant relationship was identified between the number of species vocalising, as measured by sound recorders, and the number of species observed by point count method. However, the relationship was far from isometric and there were many more species detected by the sound recorders than by human observers.Results from analyses of vocal activity data gathered at Tumut were confirmed by additional data obtained in a subsequent, small calibration study in the Namadgi National Park in the Australian Capital Territory.

Night-time use of feed trees by 40 radio-collared individuals of the greater glider (Petauroides volans) was recorded within five remnant patches of eucalypt forest near Tumut in south-eastern Australia. Radio-collared animals were observed making 663 night-time visits to 433 trees. For these observations, we recorded the number of visits by an animal to each tree, the number of different animals using each tree, the characteristics of trees that animals used, and the category of activity or behaviour displayed by animals (classified as feeding, perching, and moving).
We found no evidence of a significant difference in patterns of behaviour between male and female P. volans in their night-time use of trees within remnant patches, regardless of patch size or population density. There were few records of animals (4%) from the radiata pine (Pinus radiata) plantation that surrounded the eucalypt remnants, although 20 observations were made of P. volans feeding on the young male cones and buds of this introduced tree species. There was evidence of preference for feeding in ribbon gum (Eucalyptus viminalis), mountain gum (E. dalrympleana) and narrow-leaved peppermint (E. radiata), with 72% of feeding observations of P. volans coming from these three tree species. Animals were generally solitary and spent most of the night feeding and perching in the upper canopy. Most trees were used by a single individual, with 96% of observations being of a single animal in a tree. The limited number of cases of sharing and co-use of trees were generally between an adult male and adult female (assumed mates), and females and their young. The probability that a tree was used increased with the average size of a tree (a composite measure of diameter, height and crown features) until approaching an asymptote of 1.0, i.e. all large trees were used. The number of visits a tree received from P. volans also was positively related to the measure of its size.

This paper examines home-range attributes of 40 greater gliders (Petauroides volans) in five patches of remnant eucalypt forest surrounded by stands of radiata pine (Pinus radiata) near Tumut in south-eastern Australia. Fixed-kernel smoothing methods were used to estimate home-range size for P. volans. For males, home-range size varied from 1.38–4.10 ha (mean = 2.6 ± 0.8 ha, n = 12) and was significantly larger (P < 0.05) than for females (1.26–2.97 ha, mean = 2.0 ± 0.6 ha, n = 11). Home-range size increased significantly with increasing patch size and reduced patch population density. Thus, small patches had more animals per unit area with smaller home ranges and greater home-range overlap.
Our findings illustrate flexibility in the use of space by P. volans. Such results have not previously been reported for P. volans or any other species of arboreal marsupial. Considerable home-range overlap (at 95th percentile isopleth level) was observed between male and female P. volans. Pairs of females also exhibited home-range overlap. Males tended to maintain home ranges exclusive of other males, although some shared common areas. Contrary to the large variations observed in home-range area, core areas (50th isopleth) remained relatively constant, regardless of patch size, population density or sex. This may indicate that core areas are an essential requirement for individuals and resources they contain cannot be shared with congeners.

Statistical models of the patterns of den-tree choice by the mountain
brushtail possum (Trichosurus caninus) at Cambarville in
the mountain ash (Eucalyptus regnans) forests of the
central highlands of Victoria, south-eastern Australia are presented. These
models enable us to predict, for a particular possum, the choice of den tree
on the basis of patterns of recent den-tree usage and are required for
individual-based simulation studies. The models show that the pattern of
den-tree use is more complicated than might have been expected, in the sense
that it is animal-specific, and that old animals exhibit more complicated
patterns of den-tree choice than young ones.

In this study, we use data drawn from a series of trapping events on four 0.5-ha trapping grids surveyed in the wet eucalypt forests of central Victoria, south-eastern Australia, to identify relationships between capture probabilities and several factors of interest for three species of small mammals that are common throughout the forests of this region: the agile antechinus (Antechinus agilis), the dusky antechinus (Antechinus swainsonii) and the bush rat (Rattus fuscipes). The design of our study – four regular trapping grids – generated spatio-temporal data with binary responses and many covariates. We used powerful and relatively new statistical methodology to deal with the spatio-temporal dependence patterns in the data – analytical problems that are common in trapping data such as these modelled here. Although A. agilis, A. swainsonii and R. fuscipes are among the best studied mammals in Australia, our data analysis produced new perspectives on their probability of being captured. In particular, we quantified how capture probability is affected by trap position within a trapping grid, day of capture in a sequence of trapping days, history of trap occupancy over time by different species and sexes of those species, time of the year or season, and microhabitat attributes. Our insights are discussed in terms of their consequences for trapping protocols that might be applied in the field.

Two methods of assessing body condition were examined for the mountain
brushtail possum, Trichosurus caninus (Ogilby) at a
single study site in central Victoria, south-eastern Australia. Condition
indices were derived from measures of skeletal size and body mass, and body
water composition was determined using isotopic dilution of tritiated water to
give an estimate of total body water space. There were significant negative
relationships between body water composition and the condition indices for
body length, total length and pes length. Body water composition of
T. caninus was significantly higher in spring than in
winter, and those animals with higher body water composition had lower
absolute neutrophil counts and higher urea values. The relative usefulness of
the two methods used for estimating body condition in
T. caninus is discussed.

Context Reintroductions can be an effective means of re-establishing locally extinct or declining faunal populations. However, incomplete knowledge of variables influencing survival and establishment can limit successful outcomes. Aim We aimed to examine the factors (e.g. sex, body mass, release order) influencing the survival, dispersal, home range and habitat selection of reintroduced southern brown bandicoots (eastern subspecies; Isoodon obesulus obesulus) into an unfenced, predator-managed environment in south-eastern Australia (Booderee National Park). Methods Over 2 weeks in May 2016, six female and five male bandicoots were wild-caught in state forest and hard released into the park. Release locations were approximately evenly distributed between three primary vegetation types assessed as suitable habitat: heath, woodland and forest. Bandicoots were radio-tracked day and night for 4 weeks from the initial release date. Key results No mortality was detected. Males dispersed more than twice as far as females (male 704 m, female 332 m), but there was no significant sex bias in home range size. At the landscape scale, bandicoots preferentially selected home ranges that contained heath and avoided forest. Within home ranges, heath and woodland were both favoured over forest. Conclusions Post-release dispersal is sex-biased, but more data are required to determine the influence of other predictors such as body mass and release order. Within the release area, bandicoots favoured non-forest vegetation types. Implications Our study outlines factors influencing the establishment of reintroduced bandicoots. We recommend that future bandicoot reintroductions to Booderee National Park occur within areas of heath and woodland, and that subsequent releases consider the potentially larger spatial requirements and conspecific avoidance among male bandicoots. Our findings contribute new knowledge for improving translocation methods of a nationally endangered medium-sized mammal.

Being able to recognise critical habitat features such as nesting and denning sites is essential for wildlife conservation. It is particularly true for the den trees of species threatened by habitat loss, such as the squirrel glider (Petaurus norfolcensis). Measurements of 146 den trees of the squirrel glider were made in fragmented woodlands of the South-west Slopes of New South Wales and data compared with random trees to quantify the key characteristics of den sites. The likelihood of use as a den tree increased with increasing numbers of visible tree hollows and tree size. Dieback was also a positive indicator of den use. However, when visible hollows within a tree are abundant, dieback-free trees were preferred. Measures of den tree context such as basal area, the number of neighbouring large trees and distance to the next nearest tree, were also found to be important determinants of the likelihood of usage. The above variables were combined into a multiple regression model. The squirrel glider favoured particular Eucalyptus species and some broader eucalypt groups. We believe such variations were most likely due to interspecific differences in hollow development and dieback among the various groups, rather than bark type, a factor previously cited as an important determinant of den tree usage. The 'best' model had high negative predictive power, suggesting it would be useful for identifying (1) trees that could be felled without a loss of this critical habitat resource (e.g. at development sites) and (2) areas unsuitable for potential squirrel glider relocation or habitat enhancement. Squirrel gliders show preference for a combination of tree and tree context features in selecting den trees. Understanding these features will help managers enhance and protect denning resources for this species.

Context Temporal reduction in shelter is an indirect primary impact of fire. Removal of animal refugia has implications for shelter site selection and fidelity – factors that have been largely overlooked in studies of Australian rodent fauna. This information is critical for guiding species conservation and appropriate land management including prescribed burning practices. Aims We sought to determine which features of burnt heath were selected as shelter sites by the eastern chestnut mouse, whether there was sex and/or seasonal variation in shelter site selection and whether we could identify primary refugia. Methods We completed a radio-telemetry study to identify diurnal refuge sites and compare habitat attributes with those of a matched set of control sites. We then used habitat features and fidelity parameters to classify refuge site use. Key results We found the eastern chestnut mouse selected shelters with the presence of specific structures and had taller, denser vegetation than randomly selected control sites. There were no differences in habitat selection between the sexes. Shelter sites in the non-breeding season had greater vegetation density compared with those used in the breeding season. In the breeding season, the eastern chestnut mouse showed no evidence of increased fidelity to particular refuges. Vegetation density in winter was the best predictor of a primary refuge compared with whether or not an animal returned to a shelter site or the amount of time spent in a shelter site. Mice were ephemeral and non-gregarious in their refuge use. There was some evidence for inheritance of refuge sites from a parent, as well as inter-season shelter site fidelity. Conclusions The eastern chestnut mouse selected refugia that had habitat attributes offering maximum protection. Seasonality in refuge site selection is likely to reflect the reproductive and environmental trade-offs in critical resources during different seasons. The maintenance of multiple, rarely occupied shelters by the eastern chestnut mouse is consistent with data for other mammals. Implications Fire management should ensure retention of vegetation structure on the ground layer, dense habitat patches in burned areas, and be carefully planned during the winter season to maintain shelter and refuge sites to assist population persistence.

Comparative trials of different survey methods were conducted in the southern jarrah (Eucalyptus marginata) forest to determine the most efficient means of detecting koomal (common brushtail possum, Trichosurus vulpecula hypoleucus) and ngwayir (western ringtail possum, Pseudocheirus occidentalis). In particular, we examined different trapping and spotlighting methods and compared these with scat surveys. Six different trapping methods (derived by combining three bait types and two trap positions) were compared at six sites. Significantly fewer koomal were caught on 'universal' bait (i.e. peanut butter, rolled oats and sardines) than on flour-based baits using rose oil or Eucalyptus oil as lures. Significantly more individuals of both possum species were caught in arboreal traps than in ground traps (P < 0.001 in both cases). Recapture rates of koomal were high, whereas ngwayir were rarely retrapped. There were no detection differences between six different spotlighting methods (derived by combining three spotlight intensities with two filter colours) for koomal. Significantly more ngwayir were detected using 50-W or 100-W lights than 20-W lights (P = 0.01). There were no significant differences in the detection rates for ngwayir using red or white light. There were, however, significant observer differences in the number of possums of both species detected (koomal, P = 0.025; ngwayir, P = 0.004). Spotlighting detected, on average, only 4.9% of the koomal 'known to be alive' by trapping. However, spotlighting with a 50-W or 100-W spotlight detected more ngwayir than did trapping. Koomal abundance measures derived from scat surveys were not related to trapping or spotlight abundance estimates. For ngwayir, however, scat counts were strongly related to spotlight counts and there were no significant observer differences for the former. We conclude that koomal are more effectively surveyed using arboreal trapping with rose or Eucalyptus lures. Ngwayir are best surveyed using scat surveys or 50-W spotlights.

The results are reported of a nest-box study conducted in two locations in the mountain ash (Eucalyptus regnans) forests of the Central Highlands of Victoria (south-eastern Australia) to compare usage of different nest-box designs located at different heights in trees. A total of 96 nest boxes was established using a rigorous experimental design – two regions (Powelltown and Toolangi State Forests), two forest age classes (20-year post-logging regrowth and 60-year fire- and salvage-logging regrowth), two nest-box designs (large boxes with large entrance holes and small boxes with small entrance holes), and two heights at which nest boxes were attached to trees (3 m and 8 m above the ground). The study entailed setting out four nest boxes at each of 24 sites to meet the design criteria. Evidence of occupancy by vertebrates was recorded in a total of 19 of 96 boxes on 11 of 24 sites site during regular inspections over more than three years. Thirteen boxes were used by Leadbeater's possum (Gymnobelideus leadbeateri), six by the mountain brushtail possum (Trichosurus cunninghami) and seven by the common ringtail possum (Pseudocheirus peregrinus). The common ringtail possum and mountain brushtail possum were seen only in high–large boxes but Leadbeater's possum used all but the low–large boxes. There was evidence of spatial dependence in usage patterns, with all four boxes at a given site showing signs of eventually being occupied. Only two nest boxes located in mountain ash forest regenerating after the 1939 wildfires were occupied. Relatively limited use of nest boxes supports concerns about the use of a nest box over large scales and long timeframes as an effective recovery tool for species threatened by the loss and subsequent shortage in the numbers of naturally occurring hollows.