Suchergebnisse

The diets of the fox, Vulpes vulpes, and feral cat, Felis catus, were studied at Yathong Nature Reserve in semi-arid western New South Wales. The overall occurrence of rabbit was 45.1% in stomachs of foxes and 54.0% in cats, representing 51.3 and 82.6% respectively of the weight of stomach contents. Both predators exhibited a functional response to rabbits, Oryctolagus cuniculus, (their staple prey) during the rabbit breeding season. Predation on rabbits was greatest on an increasing prey population during good pasture conditions and a decreasing population during drought. After the rabbit breeding season, diet changed to other prey and resulted in an annual prey cycle which was similar for foxes and cats. Both predators successfully co-exist in the semi-arid environment by primarily utilising different age groups of the same staple prey and to some extent different supplementary prey. Foxes mainly ate adult rabbits and cats young rabbits. During the drought foxes preyed heavily on adult rabbits; cats ate some rabbits but relied heavily on other food sources. The supplementary prey of foxes were invertebrates, birds, reptiles and carrion; small mammals and fruits opportunely eaten. Invertebrates, birds, reptiles and small mammals were supplementary prey for cats with carrion opportunely eaten.

The relationship between forest structure or habitat complexity and
distribution and abundance has been demonstrated for a variety of mammalian
species in the southern forests of Australia. Recently, studies that utilise
airborne videography data have predicted forest structure across forested
landscapes. This paper unites these two fields of research. Existing models of
species abundance were applied to spatial estimates of habitat complexity to
produce predictions of the distribution and abundance of two small
ground-dwelling mammals commonly found in eucalypt forests. The spatial
estimates of habitat complexity were extrapolated across the landscape from
videography at 2-m spatial resolution on four 1-km 2 study areas. To examine
the accuracy of the abundance predictions, trapping grids for the two species
were established across a range of abundances. Linear regression showed a
strong positive relationship between the predicted distribution and abundance
from the videography and the recorded distribution and abundance for the
species.

The distribution and abundance of ground-dwelling mammals in the major vegetation alliances in the eucalypt forests within an area of c. 24000 km2 in north-eastern New South Wales were examined. Data for 33 species of mammal from 21 areas containing 30 vegetation alliances were collected. Four notable aspects of the data were the absence or low abundance of the introduced fox (Vulpes vulpes), the widespread distribution and abundance of the cat (Felis catus), the diversity and abundance of medium-sized native mammals and the diversity of small mammals.

Although differences occurred between areas and alliances, there was no significant difference in the number of native and introduced species. The ground-dwelling mammals present in the eucalypt forests of north-eastern New South Wales were more diverse and in greater abundance than those found in forests of south-eastern New South Wales. However, some species, such as the spotted-tailed quoll (Dasyurus maculatus), appear to be in urgent need of protection and management if they are to persist.

Airborne videographic remote sensing is a relatively recent technology thatcan provide inexpensive and high-spatial-resolution imagery for forestmanagement. This paper presents a methodology that allows videographic data tobe modelled to predict habitat complexity in eucalypt forests.Within the eucalypt forests of south-eastern New South Wales, plots werelocated on the imagery, and the local variance of the videography within eachplot was computed on the assumption that changes in local variance provided anindication of forest structure, and thus the habitat complexity of the site.The near- infrared (NIR) channel demonstrated the most variation, as thatchannel provided an indication of photosynthetic activity and, as a result,the variation between canopy, understorey, ground cover, soil and shadowprovided a highly variable response in the video imagery. Habitat-complexityscores were used to record forest structure, and the relationship between theNIR variance and field habitat-complexity scores was highly significant(P < 0·001)(r2 = 0·75;n = 29). From this relationship, maps of thehabitat-complexity scores were predicted from the videography at 2-m spatialresolution. The model was extrapolated across a 1 1 km subset of the videodata and field verification showed that the predicted scores correspondedclosely with the field scores.Studies have demonstrated the relationship between habitat-complexity scoresand the distribution and abundance of different mammalian fauna. This methodallows predictions of habitat-complexity scores to be spatially extrapolatedand used to stratify the landscape into regions for both the modelling offaunal habitat and to predict the composition, distribution and abundance ofsome faunal groups across the landscape. Ultimately, the management of foresthabitats for wildlife will depend on the availability of accurate maps of thediversity and extent of habitats over large areas and/or in difficult terrain.

Vegetation undergoes a natural succession after wildfire. Following an initial
flush of vegetation, when light and other resources become limiting, the stand
structure rapidly reaches a maximum. As a result, vegetation structure does
not form an even distribution over the landscape, but rather a patchwork
pattern. The position and characteristics of a patch of habitat in the
landscape may be critical in determining the faunal composition. In this paper
a sequence of 'habitat complexity scores' (which describe
vegetation structure independently of plant species) collected over 20 years
following a wildfire was utilised to estimate vegetation structure in relation
to time since fire. This information was compared with data collected over the
same period on medium-sized and large grounddwelling mammals to examine the
response of mammals to changes in vegetation structure. Models are presented
of the response of ground-dwelling mammals to time since wildfire and to
changes in habitat complexity scores, with predictions up to 25 years after
wildfire.

An extensive fauna survey of forest habitats in the Murwillumbah Forestry
Management Area of north-eastern New South Wales allowed us to examine and
compare the use of Elliott traps, wire cage traps, soil plots, hair tubes,
spotlighting, dry pitfall traps, sightings and vocalisations as methods to
determine the identity, distribution and abundance of ground-dwelling and
arboreal mammals. Transects were established in 10 areas in six State Forests
and one National Park.
The aim of this study was to examine each method to satisfy three criteria and
to determine the most efficient and effective method or combination of methods
to survey arboreal and ground-dwelling mammals in forests. The three criteria
were to identify the species present, to determine their distribution and to
establish an index of their abundance. In all, 35 species were identified by
the seven methods. However, the species recorded, and the usefulness of the
method to provide their distribution and/or an index of abundance,
differed markedly according to the method used.
Stratified sampling with Elliott traps for small mammals, spotlights for
arboreal mammals and soil plots for medium-sized and large ground-dwelling
mammals was the most labour-efficient and productive combination for recording
species present and their status comprehensively. If needed, other methods
such as hair tubes or cage traps may be used locally and intensively to assist
in the identification of species. Moreover, randomly gathered sight and
vocalisation records accumulated during the survey were found to be very
useful in corroborating species present and in helping to identify the tracks
recorded to genus or family by the soil-plot method.

Statistical models are presented of the distribution and abundance of ground-dwelling mammals in eucalypt forests in relation to environmental variables within an area of approximately 24 000 km2 in north-eastern New South Wales. Environmental variables are defined as climatic or topographic variables that may be useful to map the distribution of fauna. The environmental variables examined were season, temperature, rainfall, elevation, lithology, steepness of slope, position on slope, aspect and landform profile. The probability of recording some species was higher in spring than autumn and many species were in highest abundance in areas of low temperature (high elevation). Although aspect was a significant variable in a number of models, no species was absent from any aspect category. Mid-slopes down to and including creeks and drainage lines were particularly important for many species, as were areas with flatter terrain. Although we have modelled environmental variables only there will no doubt be longer-term interactions between habitat and environmental variables. Fundamentally, environmental variables will determine the type of habitat present at a site, and the distribution of canopy communities, at least, can be predicted from environmental variables. However, other studies have shown for ground-dwelling mammals that environmental variables contribute little and it is the state of the habitat locally, and particularly the understorey, that determines their presence and abundance at a site. The results are discussed in relation to similar models using habitat variables and in relation to the use of such models in the management of ground-dwelling fauna in forests.

We examined the distribution and abundance of ground-dwelling mammals in
eucalypt forests in relation to habitat variables within an area of
c. 24 000 km2 in north-eastern New
South Wales. Habitat variables are defined as vegetative variables that may be
altered or created by humans or natural disturbances and used for the
management and/or conservation of fauna. Statistical models of the
distribution and abundance of ground-dwelling mammals in relation to the
habitat variables are presented.
Generally, the ground-dwelling mammals in the region were more diverse and in
greater abundance, and the forest more complex, than in south-eastern New
South Wales. The models reflect a general preference of the ground-dwelling
fauna for forests that were least disturbed. However, some species were more
tolerant of disturbance than others.
Recent developments in remote sensing have allowed the mosaic of habitats for
ground-dwelling mammals to be mapped over large areas of the landscape. Such
maps and the models presented here are discussed with respect to the
management of wildlife species. The reduced disturbance during silvicultural
practices and the lower abundance of foxes are discussed in relation to the
greater diversity and abundance of the ground-dwelling mammals in the region
than in south-eastern New South Wales.

We examined the relationship between ground-dwelling mammals and the
environment within 500 000 ha of eucalypt forest in south-eastern New South
Wales. Ground-dwelling mammals were surveyed at 368 sites in 13 areas in
relation to four habitat variables/factors, seven environmental variables,
and two derived variables ('disturbance' and 'prey
abundance'). Habitat variables are vegetative variables such as eucalypt
community and forest structure that may be altered by man (e.g. logging) or
natural disturbances (e.g. wildfire). Environmental variables are climatic or
topographic variables such as rainfall or lithology that cannot be altered by
man or natural disturbances.
Statistical models are presented of the distribution and abundance of
ground-dwelling mammals in temperate eucalypt forests. From studies of the
prediction of eucalypt species from environmental variables and the
distribution of arboreal marsupials it has been possible previously to map the
predicted density of arboreal marsupials for a large area of south-eastern New
South Wales. It would be difficult to do the same for the ground-dwelling
mammals because of the importance of structural variables and the influence of
disturbance on structure. However, there appears to be a positive relationship
between the abundance of some ground-dwelling mammals and environmental
variables such as the lithology nutrient rating.
Many past studies of fauna have stratified sampling on broad climatic and
terrain variables and not included an adequate proportion of the structural
variation, which may remain concealed as a large part of the unexplained
variation. This may be the single most important problem facing reliable
modelling and prediction of patterns of biodiversity in eucalypt forests.

The range of the cane toad has expanded rapidly in the Northern Territory, and
there is growing concern that the species may have a detrimental effect on the
native fauna. The aim of this study, therefore, was to determine the
short-term effects of cane toads on populations of native fauna and,
specifically, to compare the species diversity and relative abundance of
native fauna before, during and after the invasion of an area by cane toads.
Five major groups of fauna (wingless invertebrates, amphibians, reptiles,
birds and mammals) were sampled over two years.
The study has provided little evidence that cane toads have a significant
adverse effect in the short-term on the diversity and abundance of the native
fauna examined. However, there was an indication that there may be a long-term
indirect effect on some fauna. In the short-term the dingo
(Canis lupus dingo) and one Order of insect (Coleoptera)
were affected negatively. The possible long-term negative effect was on the
small reptile fauna and particularly the small skinks. This may be an indirect
effect on their food supply, because the groups affected were those that were
considered neither to ingest cane toads nor to be eaten by cane toads.

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