Suchergebnisse

Context
Central Australia has been a graveyard for native mammals, with many small and medium-sized species becoming extinct or persisting in reduced geographical ranges in this region since the advent of European settlement. Species in the critical weight range (35–5500 g) have been affected most dramatically.

Aims
We compared the dynamics of two geographically distant populations of a medium-sized surviving desert mammal, the brush-tailed mulgara (Dasycercus blythi, ~100 g), and tested the hypothesis that this species' persistence can be explained by its demographic plasticity.

Methods
Paired sampling grids, each 31.5 ha, were set up in the Tanami Desert on the northern edge of the species' geographical range and near Uluru Kata Tjuta National Park (UKTNP) on the southern boundary. Animals were live-trapped every 3 months between 1992 and 1995, and estimates made of population size, residency, reproduction, bodyweight and tail width; the latter was used as an index of condition.

Key results
The UKTNP site supported a larger population of D. blythi than did the Tanami Desert site. In both areas, the population fluctuated annually, declining during the breeding season (June to October) and increasing again following the influx of juveniles in spring. Females had one litter per year, with a median and maximum litter size of six; births in the Tanami occurred in July, at least a month earlier than they did at UKTNP. Bodyweights and tail widths peaked before breeding and then declined until spring, with animals retaining better body condition in the Tanami than at UKTNP. In both regions, individuals were resident for 1–2 years; daughters remained near their mother's home range but males moved to other areas.

Conclusions
The results provided little support for our initial expectation that populations of D. blythi would behave differently in disparate parts of the species' geographical range, and suggested instead that this mulgara exhibits a predictable life history, with limited demographic flexibility.

Implications
The persistence of D. blythi in central Australia is most likely a result of its striking flexibility in use of food resources, its ability to enter torpor and to tolerate large declines in bodyweight and condition, and its propensity to dig deep burrows. We suggest that these attributes buffer mulgaras from the impacts of introduced predators that have contributed to extinctions of other medium-sized marsupials, and from climatic and resource uncertainties that shape the dynamics of many smaller desert mammals.

The eastern pygmy-possum (Cercartetus nanus) occurs broadly but patchily in south-eastern Australia. It is a small, difficult-to-trap marsupial with poorly known resource and habitat preferences. This study investigated the structural and floristic habitat resources used and selected by C. nanus in Royal National Park (which was heavily burnt by bushfire in 1994) and Heathcote National Park (most of which had remained unburnt for over two decades at the time of study), in central-coastal New South Wales. Three different sampling methods were used – pitfall traps, Elliott traps and hair tubes – with pitfall trapping being by far the most effective method for detecting C. nanus. Live-trapping in different habitats revealed higher numbers of C. nanus in unburnt and burnt woodland, burnt heathland and burnt coastal complex than in unburnt coastal complex and burnt and unburnt rainforest. To identify the components of habitat contributing to this pattern, we first scored floristic and structural features of vegetation around trap stations and then quantified habitat components further by using spool- and radio-tracking. We found little evidence that C. nanus responded to any structural components of habitat, although arboreal activity was greater, not surprisingly, in wooded than in burnt heathland habitats. C. nanus was associated most strongly with the abundance of certain plants in the Proteaceae and Myrtaceae. In particular, the species prefers Banksia spp. (probably for food) and Eucalyptus and Xanthorrhoea spp. (probably for shelter).

The removal of non-toxic baits was monitored during a simulated trail-baiting programme for foxes and wild dogs in the central tablelands of New South Wales. Ninety-one buried baits were removed by a number of species including spotted-tailed quolls, Australian brush-turkeys, superb lyrebirds, small mammals, wild dogs and a red fox. Spotted-tailed quolls were significantly less likely to remove baits buried under the ground surface than baits buried in raised mounds of soil. By means of remote photography, individual quolls were identified removing 3–4 baits in one night from bait stations 400 m apart. The results of this study show that spotted-tailed quolls and other non-target species may face substantial risk of consuming baits intended for wild dogs and foxes. However, the risk of poisoning spotted-tailed quolls may be significantly reduced by appropriate planning. Recommendations are made to increase the target-specificity of baiting programmes in areas with populations of spotted-tailed quolls.

The removal of non-toxic fox baits was monitored simultaneously using identification of tracks in sand plots and an inexpensive method of remote photography. During 1126 bait-nights carried out using both methods at sites in the central and northern tablelands of New South Wales, 106 baits were removed by a variety of target and non-target animals. Whereas the results of sand plots may be inaccurate or unreliable, particularly during poor weather conditions, remote photography provides results that are less open to misinterpretation.

Possible impacts and mechanisms of response by Australian rodents to fire are
identified and discussed in relation to the literature. Although there is
considerable information on patterns of population response, there is little
concerning the effect of fire on individual behaviour, mortality, or
interactions at the community level. The evidence that links observed
responses of rodents to habitat variables is largely correlative, and theories
on mechanisms of recovery are often simplified or speculative. Experimental
manipulations of resources, competitive interactions and predation rates are
proposed as the best way to clarify which factors are most influential upon
individuals, populations and communities in the post-fire environment.

The diet of the mulgara, Dasycercus cristicauda, from
the Simpson Desert in Queensland, was analysed using scats collected between
1990 and 1995. Insects, arachnids and rodents were the main classes of prey of
D. cristicauda, but reptiles, centipedes and small
marsupials were also consumed. Insects represented 92% by percentage
frequency of occurrence in scats, while rodents represented 33% by
percentage frequency. Invertebrate prey ≥6 mm in length and vertebrate prey
occurred frequently in scats, but small prey ( 1–5 mm), when present,
occurred in large numbers. D. cristicauda ate more
individual prey items in spring and winter than in autumn, and more
large-sized prey in spring than in autumn. In autumn,
D. cristicauda consumed mostly insects (100% by
frequency) and few rodents (8%), but in winter and spring, switched to
rodents (38% and 47% respectively) and insects (88% and
93% respectively). Seasonal shifts in diet may reflect changes in the
availability of different groups of prey, or changes in prey selectivity by
D. cristicauda in response to costs imposed by seasonal
reproduction. The dietary flexibility of D. cristicauda
may allow individuals to occupy stable ranges, and has perhaps also promoted
the persistence of the species in arid areas that have been subjected to
changes in land use since European settlement.

Populations of feral cats, foxes and dingoes were assessed at four sites in
the northern Simpson Desert from May 1995 to October 1996 using track counts.
Counts were based on presence/absence of footprints on sandplots placed
randomly throughout each of the four sites, with all habitats being sampled in
accordance with their availability. Sandplots were repositioned between
sampling periods so that data were temporally independent. This unbiased
method was used to assess the reliability of more conventional indices of
carnivore abundance based on spotlighting and counts of footprints on roads,
which were run concurrently with the random sandplot counts. The sandplot data
were also used to assess habitat use of the three study species.
Counts on regularly spaced sampling plots along roads were correlated with
random sandplot counts for foxes, but not for cats. Conversely, an index of
activity based on counting individual tracks along roads was correlated for
cats, but not for foxes. Spotlighting counts appeared to have little
relationship with random sandplot counts for either species, with random
sandplot counts and spotlight counts of foxes being correlated for only one of
the four sites and no correlations being apparent for cats.
The sandplot data showed that cats used dune crests preferentially over other
habitats, while foxes preferred both dune crests and roads. Dune crests are
probably used as natural runways by both species. Dingoes used roads
preferentially over other habitats. It was concluded that differences in the
use of roads and other runways by the carnivores can potentially lead to
biases in indices collected along roadways. In relation to the random sandplot
counts, foxes were overestimated by road counts and spotlighting relative to
cats, the latter bias being related possibly to temporal differences in the
activity patterns of the two species.

Populations of feral cats, foxes and dingoes were assessed at four sites in
the northern Simpson Desert from May 1995 to October 1996 using track counts.
Counts were based on presence/absence of footprints on sandplots placed
randomly throughout each of the four sites, with all habitats being sampled in
accordance with their availability. Sandplots were repositioned between
sampling periods so that data were temporally independent. This unbiased
method was used to assess the reliability of more conventional indices of
carnivore abundance based on spotlighting and counts of footprints on roads,
which were run concurrently with the random sandplot counts. The sandplot data
were also used to assess habitat use of the three study species.
Counts on regularly spaced sampling plots along roads were correlated with
random sandplot counts for foxes, but not for cats. Conversely, an index of
activity based on counting individual tracks along roads was correlated for
cats, but not for foxes. Spotlighting counts appeared to have little
relationship with random sandplot counts for either species, with random
sandplot counts and spotlight counts of foxes being correlated for only one of
the four sites and no correlations being apparent for cats.
The sandplot data showed that cats used dune crests preferentially over other
habitats, while foxes preferred both dune crests and roads. Dune crests are
probably used as natural runways by both species. Dingoes used roads
preferentially over other habitats. It was concluded that differences in the
use of roads and other runways by the carnivores can potentially lead to
biases in indices collected along roadways. In relation to the random sandplot
counts, foxes were overestimated by road counts and spotlighting relative to
cats, the latter bias being related possibly to temporal differences in the
activity patterns of the two species.

Detailed studies of how endangered species use their environments at varied habitat scales are crucial if they are to be conserved and managed effectively. In this study, we used spool-and-line tracking to investigate the microhabitats used by the brush-tailed bettong (Bettongia penicillata) and the burrowing bettong (B. lesueur), two species with geographical ranges that have been dramatically reduced since European settlement in Australia. The study was carried out at Scotia Sanctuary, in semiarid western New South Wales, where both species have been recently reintroduced. The nocturnal movements and foraging of bettongs were associated with sites containing more canopy cover (mean 10–25%) than was available on average (0–10%). Models generated to predict the probability of bettong movements or activity points showed positive correlations with ground vegetation cover and ground vegetation height. Other microhabitat components of varying importance, including sand cover, litter cover, litter depth, crust cover, and distance to shrub/tree, were incorporated into these models. Species comparisons indicated that, although slight differences occurred in the way each species moved through the habitat, both species foraged in areas with similar microhabitat characteristics. While the models should have broad utility for the selection of favourable habitat for future release sites for B. penicillata and B. lesueur, further studies of diet and food availability are recommended to refine them further.

Abstract
ContextCats are the definitive or primary host for pathogens that cause diseases in people and livestock. These cat-dependent diseases would not occur in Australia if cats had not been introduced, and their ongoing persistence depends on contacts with cats. Toxoplasma gondii is a protozoan parasite that cycles between cats and any other warm-blooded animals. People infected by T. gondii may appear asymptomatic, or have a mild illness, or experience severe, potentially lethal symptoms; the parasite may also affect behaviour and mental health. T. gondii is also a major contributor to spontaneous abortion in sheep and goats. Two species of Sarcocystis, another genus of protozoan parasite, cycle through cats and sheep, causing macroscopic cysts to form in sheep tissues that reduce meat saleability. Toxocara cati, the cat roundworm, causes minor illnesses in humans and livestock, and the bacterium Bartonella henselae causes cat scratch disease, an infection that can be contracted by people when scratched or bitten by cats carrying the pathogen.
AimsWe estimated the economic costs of cat-dependent pathogens in Australia.
MethodsWe collated national and global data on infection rates, health and production consequences.
Key resultsWe estimated the costs of two cat-dependent diseases (toxoplasmosis, cat scratch disease) in people at AU$6.06 billion (plausible range AU$2.11–10.7 billion) annually, and the costs to livestock production from toxoplasmosis and sarcocystosis at AU$11.7 million (plausible range AU$7.67–18.3 million). Most of the human health costs are due to the associations between T. gondii and higher rates of traffic accidents and mental illness in people. The causality behind these associations remains uncertain, so those costs may be overestimated. Conversely, our estimates are incomplete, infections and illness are under-reported or misdiagnosed, and our understanding of disease outcomes is still imperfect, all of which make our costs underestimated.
ConclusionsOur analysis suggests that substantial benefits to public health and livestock production could be realised by reducing exposure to cats and breaking parasite transmission cycles.
ImplicationsReducing feral cat populations in farming and urban areas, reducing the pet cat population and increasing rates of pet cat containment could help reduce the burden of cat-dependent diseases to people and livestock.

Abstract ContextPredation by feral cats (Felis catus) threatens a range of vertebrate species across Australia, and cat-free islands increasingly act as safe havens for biodiversity. A feral cat eradication program has begun on Kangaroo Island (4405km2) in South Australia, and poison baiting is likely to be one of the main methods used. Aims Here, we trial a non-toxic version of a cat bait, 'Eradicat', on western Kangaroo Island, to examine its potential impact on non-target species. MethodsNon-toxic baits containing the biomarker Rhodamine B were deployed across four sites in early August and late November in 2018, with bait take and consumption assessed both by remote cameras and by the presence of Rhodamine B in mammalian whisker samples taken post-baiting. Key resultsCats encountered baits on very few occasions and took a bait on only one occasion in August (<1% of 576 baits deployed). Non-target species accounted for over 99% of identifiable bait takes. In both seasons, >60% of all baits laid was taken by either the common brushtail possum (Trichosurus vulpecula), bush rat (Rattus fuscipes) or Australian raven (Corvus coronoides). In November, Rosenberg's goanna (Varanus rosenbergi) and southern brown bandicoot (south-eastern subspecies; Isoodon obesulus obesulus), listed nationally as Endangered, also took baits (3% and 1% respectively). The Kangaroo Island dunnart (Sminthopsis fuliginosus aitkeni), listed nationally as endangered, approached a bait on only one occasion, but did not consume it. Evidence of bait consumption was visible in the whiskers of captured common brushtail possums (100% of post-baiting captured individuals in August, 80% in November), bush rats (59% in August and 50% in November), house mice (Mus musculus) (45% in November) and western pygmy-possums (Cercartetus concinnus) (33% in November). ConclusionsAlthough feral cat baiting has the potential to significantly benefit wildlife on Kangaroo Island, impacts on non-target species (particularly the bush rat and common brushtail possum) may be high. ImplicationsAlternative cat baits, such as those containing a toxin to which native species have a higher tolerance or that are less readily consumed by native wildlife, will be more appropriate.

There is increasing evidence that the Dingo Canis lupus dingo plays an important ecological role as a trophic regulator in Australian ecosystems. However, there is sufficient runcertainty about the nature of this role as to hinder the development of effective management policies. This review defines strategic directions for future research on the trophic role of Dingoes by developing a national Dingo research framework. The framework aims to increase our knowledge of the influence that Dingoes have on the maintenance of biodiversity, thereby encouraging Dingo conservation and the refinement of current land-use practices. The framework begins by identifying four major bioclimatic zones across Australia that pose different questions and challenges for Dingo research. For each zone we construct a model that identifies major interactions between Dingoes and key prey or competitor species, and then used the models to identify key research needs, the possible advantages of maintaining Dingo populations within each zone, and ways to tease out unstudied interactions. Important questions identified in the review include the effects of Dingoes on native marsupial populations, vegetation communities, herbivore diets, the use of structural refugia by mesopredators, predator and prey behaviour, and the effect of habitat modification on these interactions. We briefly review legislative constraints and other factors, such as the ongoing hybridization of Dingo populations with domestic dog breeds, that may impede future studies. If research activities follow this framework, we believe that policy and management will be better informed, benefiting both the Dingo and the natural ecosystems and production systems where it occurs.

There is increasing evidence that the Dingo Canis lupus dingo plays an important ecological role as a trophic regulator in Australian ecosystems. However, there is sufficient runcertainty about the nature of this role as to hinder the development of effective management policies. This review defines strategic directions for future research on the trophic role of Dingoes by developing a national Dingo research framework. The framework aims to increase our knowledge of the influence that Dingoes have on the maintenance of biodiversity, thereby encouraging Dingo conservation and the refinement of current land-use practices. The framework begins by identifying four major bioclimatic zones across Australia that pose different questions and challenges for Dingo research. For each zone we construct a model that identifies major interactions between Dingoes and key prey or competitor species, and then used the models to identify key research needs, the possible advantages of maintaining Dingo populations within each zone, and ways to tease out unstudied interactions. Important questions identified in the review include the effects of Dingoes on native marsupial populations, vegetation communities, herbivore diets, the use of structural refugia by mesopredators, predator and prey behaviour, and the effect of habitat modification on these interactions. We briefly review legislative constraints and other factors, such as the ongoing hybridization of Dingo populations with domestic dog breeds, that may impede future studies. If research activities follow this framework, we believe that policy and management will be better informed, benefiting both the Dingo and the natural ecosystems and production systems where it occurs.

Research and management attention on the impacts of the introduced domestic cat (Felis catus) on Australian fauna have focussed mainly on the feral population. Here, we summarise the evidence for impacts of predation by pet cats on Australian wildlife. We collate examples of local wildlife population decline and extirpation as a result, at least in part, of predation by pet cats. We assemble information across 66 studies of predation by pet cats worldwide (including 24 Australian studies) to estimate the predation toll of pet cats in Australia, plus the predation pressure per unit area in residential areas. We compared these estimates to those published for feral cats in Australia. The per capita kill rate of pet cats is 25% that of feral cats. However, pet cats live at much higher densities, so the predation rate of pets per square kilometre in residential areas is 28–52 times larger than predation rates by feral cats in natural environments, and 1.3–2.3 times greater than predation rates per km2 by feral cats living in urban areas. Pet cats kill introduced species more often than do feral cats living in natural environments, but, nonetheless, the toll of native animals killed per square kilometre by pet cats in residential areas is still much higher than the toll per square kilometre by feral cats. There is no evidence that pet cats exert significant control of introduced species. The high predation toll of pet cats in residential areas, the documented examples of declines and extirpations in populations of native species caused by pet cats, and potential pathways for other, indirect effects (e.g. from disease, landscapes of fear, ecological footprints), and the context of extraordinary impacts from feral cats on Australian fauna, together support a default position that pet cat impacts are serious and should be reduced. From a technical perspective, the pet cat impacts can be reduced more effectively and humanely than those of feral cats, while also enhancing pet cat welfare. We review the management options for reducing predation by pet cats, and discuss the opportunities and challenges for improved pet cat management and welfare.