Suchergebnisse

The northern hairy-nosed wombat,
Lasiorhinus krefftii, is a critically endangered grazing
herbivore, restricted to a single population of just 65 individuals in the
savanna of central Queensland. Lasiorhinus krefftii
shares its habitat with another grazing herbivore of similar body size, the
eastern grey kangaroo, Macropus giganteus. This study
investigated the potential for M. giganteus to compete
with L. krefftii for food. Analysis of faecal residues
demonstrated that both herbivores consumed grass almost exclusively, with the
exception of small quantities of sedges and dicotyledons. Dietary overlap
between M. giganteus and
L. krefftii was high, both in the consumption of plant
species (90%) and plant parts (99%), suggesting that there is
potential for dietary competition. Using the distribution of faecal deposits
for both herbivores, analysis of habitat usage by multiple linear regression
techniques indicated that M. giganteus exhibits clear
associations with some habitat features but proved inconclusive for
L. krefftii because of their use of defecation in social
marking. However, an examination of the population dynamics of
M. giganteus suggested that the densities reported in
this study, although highly seasonal, are sufficiently low that competition
with L. krefftii for food is currently negligible.

The short-term effect of radio-packages on the activity of the northern
hairy-nosed wombat, Lasiorhinus krefftii, was
investigated using activity data-loggers. Adjustment to the radio-package
occurred between 10 and 18 days following capture and fitting of the
radio-package. Following the adjustment period, activity levels were some
84–97% less than that of the initial activity level after the
attachment of the radio-package. We believe that the adjustment period needs
to be considered in studies involving the attachment of radio- packages.

Several indirect methods for measuring body composition in a large herbivore,
the southern hairy-nosed wombat (Lasiorhinus latifrons),
were evaluated. Body composition was determined by whole-body chemical
analysis of 15 wild-caught wombats, and compared with several indices of body
fat: total body water measured by isotope dilution, bioelectrical impedance
analysis (BIA), body-mass index, and a body- condition score. Total body water
and total body fat (by soxhlet analysis) were highly correlated
(r2 = 0.97, intercept s.e.
= 1.00). Total body water measured by desiccation was highly correlated
with isotope dilution space (r2
= 0.97, intercept s.e. = 0.43 for deuterium;
r2 = 0.95, intercept s.e.
= 0.44 for H218O).
Percentage body fat by soxhlet analysis was highly correlated with total body
water measured as deuterium dilution space
(r2 = 0.83, intercept s.e.
= 2.46). Multiple linear regression models using BIA plethysmograph
measurements (resistance and impedance) and total body mass, were successful
in predicting body fat (r2
= 0.90, s.e. = 1.99) and total body water
(r2 = 0.90, s.e. =
1.64). Isotope-dilution techniques are the most accurate means of indirectly
measuring total body water and total body fat, but at considerable expense of
time and money. BIA offers reduced accuracy but at less cost and may be useful
for measuring changes in body composition in populations of herbivores.
Body-condition indices and scores correlate poorly with body fat, suggesting
that their application as a means to predict body fat is limited.

Abstract
ContextSignificant resources have been devoted to the control of introduced mesopredators in Australia. However, the control or removal of one pest species, such as, for example, the red fox (Vulpes vulpes), may inadvertently benefit other invasive species, namely feral cats (Felis catus) and rabbits (Oryctolagus cuniculus), potentially jeopardising native-species recovery.
AimsTo (1) investigate the impact of a large-scale, long-term fox-baiting program on the abundance of foxes, feral cats and introduced and native prey species in the Flinders Ranges, South Australia, and (2) determine the effectiveness of a short time period of cat removal in immediately reducing feral cat abundance where foxes are absent.
MethodsWe conducted an initial camera-trap survey in fox-baited and unbaited sites in the Flinders Ranges, to quantify the impact of fox baiting on the relative abundance of foxes, feral cats and their prey. We then conducted a secondary survey in sites where foxes were absent, following an intensive, but short, time period of cat removal, in which 40 cats were shot and killed.
Key resultsNo foxes were detected within baited sites, but were frequently detected in unbaited sites. We found a corresponding and significant increase in several native prey species in fox-baited sites where foxes were absent. Feral cats and rabbits were also more frequently detected within baited sites, but fox baiting did not singularly predict the abundance of either species. Rather, feral cats were less abundant in open habitat where foxes were present (unbaited), and rabbits were more abundant within one predominantly open-habitat site, where foxes were absent (fox-baited). We found no effect of short-term cat removal in reducing the local abundance of feral cats. In both camera-trap surveys, feral cat detections were positively associated with rabbits.
ConclusionsLong-term fox baiting was effective in fox removal and was associated with a greater abundance of native and introduced prey species in the Flinders Ranges. To continue to recover and conserve regional biodiversity, effective cat control is required.
ImplicationsOur study showed fox removal has likely resulted in the local release of rabbits and an associated increase in cats. Because feral cat abundance seemingly fluctuated with rabbits, we suggest rabbit control may provide an alternative and more effective means to reduce local feral cat populations than short-term removal programs.

Context
Fire is a major ecological factor in many landscapes. Prescribed fires are often used in the management of vegetation for ecological values, wildlife habitat and reduction of risk of wildfire. However, debate continues over whether active fire management is beneficial to flora and fauna. Although bats comprise ~20% of the world's extant mammal fauna, they have been largely ignored in studies investigating ecosystem response to fire, especially in Australia.
Aims
In the present study, we aim to investigate the immediate responses of microbats to prescribed fires in a tropical eucalypt woodland.Methods
We used a replicated paired experimental design, consisting of burned and unburned treatment and control sites, to investigate how bat activity and community structure change following a prescribed fire.
Key results
Total bat activity increased significantly following fire. Fire also resulted in changes in the bat species assemblage. Changes in community structure were driven by the following five species: Saccolaimus spp., Chalinolobus nigrogriseus, Chaerephon jobensis, Rhinolophus megaphyllus and unidentified Species c35. Activity of C. nigrogriseus, Saccolaimus spp., C. jobensis and Species c35 increased in the burned sites, whereas changes in the activity of R. megaphyllus were uncorrelated with the effects of fire.
Conclusions
The effect of fire on these species is consistent with flight patterns and habitat use; species with higher wing aspect ratios, such as Saccolaimus spp., which are capable of fast flight but with limited manoeuvrability, became more active in the open conditions created by fire.
Implications
The results of the present study suggest that prescribed fire as an environmental management tool may be beneficial to bats, at least in the short term, because it increases habitat suitability for a wider range of species.

Experimental manipulations of food supply in wild populations are often confounded by a number of factors, such as induced immigration to local populations receiving food supplements and intraspecific competition for access to feed stations. Here, we describe newly developed automated feeding stations, designed to dispense weighed food supplements to specific experimental animals. The feeders incorporate a data logger that records the identification and weight of each animal and the time of the visit to the feeder.Using the common brushtail possum (Trichosurus vulpecula) as a model medium-sized mammal, we present results of an 18-month field trial. Each free-ranging experimental possum was fitted with a collar containing a transponder chip, allowing them access to a feeder. During the field trial, experimental possums were found to show a significant increase in body mass compared with control animals, which showed a slight decrease in mass. Body masses recorded by the feeders for experimental possums did not differ from mass data recorded during live-trapping sessions.The automated feeding stations represent an advance over previous methodology and the first time supplementary food has been delivered in a controlled automated fashion in a wild mammal population. The implications of the feeders to future studies of resource supplementation in mammals are discussed.

Abstract
ContextFenced reserves from which invasive predators are removed are increasingly used as a conservation management tool, because they provide safe havens for susceptible threatened species, and create dense populations of native wildlife that could act as a source population for recolonising the surrounding landscape. However, the latter effect might also act as a food source, and promote high densities of invasive predators on the edges of such reserves.
AimsOur study aimed to determine whether activity of the feral cat is greater around the edges of a fenced conservation reserve, Arid Recovery, in northern South Australia. This reserve has abundant native rodents that move through the fence into the surrounding landscape.
MethodsWe investigated (1) whether feral cats were increasingly likely to be detected on track transects closer to the fence over time as populations of native rodents increased inside the reserve, (2) whether native rodents were more likely to be found in the stomachs of cats caught close to the reserve edge, and (3) whether individual cats selectively hunted on the reserve fence compared with two other similar fences, on the basis of GPS movement data.
Key resultsWe found that (1) detection rates of feral cats on the edges of a fenced reserve increased through time as populations of native rodents increased inside the reserve, (2) native rodents were far more likely to be found in the stomach of cats collected at the reserve edge than in the stomachs of cats far from the reserve edge, and (3) GPS tracking of cat movements showed a selection for the reserve fence edge, but not for similar fences away from the reserve.
ConclusionsInvasive predators such as feral cats are able to focus their movements and activity to where prey availability is greatest, including the edges of fenced conservation reserves. This limits the capacity of reserves to function as source areas from which animals can recolonise the surrounding landscape, and increases predation pressure on populations of other species living on the reserve edge.
ImplicationsManagers of fenced conservation reserves should be aware that increased predator control may be critical for offsetting the elevated impacts of feral cats attracted to the reserve fence.

Context Feral cats (Felis catus) pose a significant threat to biodiversity in Australia, and are implicated in current declines of small mammals in the savannas of northern Australia. Basic information on population density and ranging behaviour is essential to understand and manage threats from feral cats. Aims In this study, we provide robust estimates of density and home range of feral cats in the central Kimberley region of north-western Australia, and we test whether population density is affected by livestock grazing, small mammal abundance and other environmental factors. Methods Densities were measured at six transects sampled between 2011 and 2013 using arrays of infrared cameras. Cats were individually identified, and densities estimated using spatially explicit capture–recapture analysis. Home range was measured from GPS tracking of 32 cats. Key results Densities were similar across all transects and deployments, with a mean of 0.18 cats km–2 (range = 0.09–0.34 km–2). We found no evidence that population density was related to livestock grazing or abundance of small mammals. Home ranges of males were, on average, 855 ha (±156 ha (95% CI), n = 25), and those of females were half the size at 397 ha (±275 ha (95% CI), n = 7). There was little overlap in ranges of cats of the same sex. Conclusions Compared with elsewhere in Australia outside of semiarid regions, feral cats occur at low density and have large home ranges in the central Kimberley. However, other evidence shows that despite this low density, cats are contributing to declines of small mammal populations across northern Australia. Implications It will be very difficult to reduce these already-sparse populations by direct control. Instead, land-management practices that reduce the impacts of cats on prey should be investigated.

Ancylostoma ceylanicum is the common hookworm of domestic dogs and cats throughout Asia, and is an emerging but little understood public health risk in tropical northern Australia. We investigated the prevalence of A. ceylanicum in soil and free-ranging domestic dogs at six rainforest locations in Far North Queensland that are Indigenous Australian communities and popular tourist attractions within the Wet Tropics World Heritage Area. By combining PCR-based techniques with traditional methods of hookworm species identification, we found the prevalence of hookworm in Indigenous community dogs was high (96.3% and 91.9% from necropsy and faecal samples, respectively). The majority of these infections were A. caninum. We also observed, for the first time, the presence of A. ceylanicum infection in domestic dogs (21.7%) and soil (55.6%) in an Indigenous community. A. ceylanicum was present in soil samples from two out of the three popular tourist locations sampled. Our results contribute to the understanding of dogs as a public health risk to Indigenous communities and tourists in the Wet Tropics. Dog health needs to be more fully addressed as part of the Australian Government's commitments to "closing the gap" in chronic disease between Indigenous and other Australians, and encouraging tourism in similar locations.

Ancylostoma ceylanicum is the common hookworm of domestic dogs and cats throughout Asia, and is an emerging but little understood public health risk in tropical northern Australia. We investigated the prevalence of A. ceylanicum in soil and free-ranging domestic dogs at six rainforest locations in Far North Queensland that are Indigenous Australian communities and popular tourist attractions within the Wet Tropics World Heritage Area. By combining PCR-based techniques with traditional methods of hookworm species identification, we found the prevalence of hookworm in Indigenous community dogs was high (96.3% and 91.9% from necropsy and faecal samples, respectively). The majority of these infections were A. caninum. We also observed, for the first time, the presence of A. ceylanicum infection in domestic dogs (21.7%) and soil (55.6%) in an Indigenous community. A. ceylanicum was present in soil samples from two out of the three popular tourist locations sampled. Our results contribute to the understanding of dogs as a public health risk to Indigenous communities and tourists in the Wet Tropics. Dog health needs to be more fully addressed as part of the Australian Government's commitments to "closing the gap" in chronic disease between Indigenous and other Australians, and encouraging tourism in similar locations.

Context
Changes in abundance following fire are commonly reported for vertebrate species, but the mechanisms causing these changes are rarely tested. Currently, many species of small mammals are declining in the savannas of northern Australia. These declines have been linked to intense and frequent fires in the late dry season; however, why such fires cause declines of small mammals is unknown.

Aims
We aimed to discover the mechanisms causing decline in abundance of two species of small mammals, the pale field rat, Rattus tunneyi, and the western chestnut mouse, Pseudomys nanus, in response to fire. Candidate mechanisms were (1) direct mortality because of fire itself, (2) mortality after fire because of removal of food by fire, (3) reduced reproductive success, (4) emigration, and (5) increased mortality because of predation following fire.

Methods
We used live trapping to monitor populations of these two species under the following three experimental fire treatments: high-intensity fire that removed all ground vegetation, low-intensity fire that produced a patchy burn, and an unburnt control. We also radio-tracked 38 R. tunneyi individuals to discover the fates of individual animals.

Key results
Abundance of both species declined after fire, and especially following the high-intensity burn. There was no support for any of the first four mechanisms of population decline, but mortality owing to predation increased after fire. This was related to loss of ground cover (which was greater in the high-intensity fire treatment), which evidently left animals exposed to predators. Also, local activity of two predators, feral cats and dingoes, increased after the burns, and we found direct evidence of predation by feral cats and snakes.

Conclusions
Fire in the northern savannas has little direct effect on populations of these small mammals, but it causes declines by amplifying the impacts of predators. These effects are most severe for high-intensity burns that remove a high proportion of vegetation cover.

Implications
To prevent further declines in northern Australia, fire should be managed in ways that limit the effects of increased predation. This could be achieved by setting cool fires that produce patchy burns, avoiding hot fires, and minimising the total area burnt.

Abstract Context Home-range size and population density characteristics are crucial information in the design of effective wildlife management, whether for conservation or control, but can vary widely among populations of the same species. Aims We investigate the influence of site productivity on home-range size and population density for Australian populations of the native, threatened spotted-tailed quoll (Dasyurus maculatus) and the alien and highly successful feral cat (Felis catus). Methods We use live trapping and fine-scale GPS tracking to determine the home-range size and population density for both species across five sites in Tasmania. Using these data, as well as published estimates for both species from across Australia, we model how these parameters change in response to productivity gradients. We also use the telemetry data to examine the energetic costs of increasing home-range size for both species. Key results For both species, decreasing site productivity correlates with lower population density, and in spotted-tailed quolls and female feral cats, it also correlates with larger home-range sizes. However, the relative magnitude of these changes is different. Feral cats show smaller increases in home-range size but larger decreases in population density relative to spotted-tailed quolls. Our results suggest that these differences may be because increases in home-range size are more costly for feral cats, demonstrated by larger increases in nightly movement for the same increase in home-range area. Conclusions We suggest that knowledge of both home-range size and population density is needed to accurately determine how species respond to habitat productivity, and inform effective management across their geographic range. Implications These results have clear management implications; for example, in our low-rainfall sites, an adult female spotted-tailed quoll requires up to five times the amount of habitat expected on the basis of previous studies, thus dramatically increasing the costs of conservation programs for this threatened native species. Conversely, productivity-driven differences of up to four-fold in feral cat population density would influence the resources required for successful control programs of this invasive species.

Deer are among the world's most successful invasive mammals and can have substantial deleterious impacts on natural and agricultural ecosystems. Six species have established wild populations in Australia, and the distributions and abundances of some species are increasing. Approaches to managing wild deer in Australia are diverse and complex, with some populations managed as 'game' and others as 'pests'. Implementation of cost-effective management strategies that account for this complexity is hindered by a lack of knowledge of the nature, extent and severity of deer impacts. To clarify the knowledge base and identify research needs, we conducted a systematic review of the impacts and management of wild deer in Australia. Most wild deer are in south-eastern Australia, but bioclimatic analysis suggested that four species are well suited to the tropical and subtropical climates of northern Australia. Deer could potentially occupy most of the continent, including parts of the arid interior. The most significant impacts are likely to occur through direct effects of herbivory, with potentially cascading indirect effects on fauna and ecosystem processes. However, evidence of impacts in Australia is largely observational, and few studies have experimentally partitioned the impacts of deer from those of sympatric native and other introduced herbivores. Furthermore, there has been little rigorous testing of the efficacy of deer management in Australia, and our understanding of the deer ecology required to guide deer management is limited. We identified the following six priority research areas: (i) identifying long-term changes in plant communities caused by deer; (ii) understanding interactions with other fauna; (iii) measuring impacts on water quality; (iv) assessing economic impacts on agriculture (including as disease vectors); (v) evaluating efficacy of management for mitigating deer impacts; and (vi) quantifying changes in distribution and abundance. Addressing these knowledge gaps will assist the development and prioritisation of cost-effective management strategies and help increase stakeholder support for managing the impacts of deer on Australian ecosystems.