Suchergebnisse

In this study, fluorescent pigment tracking was used to determine the microhabitat use and foraging behaviour of a small insectivorous marsupial, Sminthopsis youngsoni (the lesser hairy-footed dunnart), in the dunefields of the Simpson Desert, south-western Queensland. In total, 25 successful trails were traced over the duration of this study, between March 1996 and April 1998. Nocturnal foraging trails were identified, then the distance travelled by the dunnart through each microhabitat type (nine in all) was measured and accumulated for each trail and compared with surrounding available microhabitats along control trails. This provided an index of selectivity of microhabitat use. Terrestrial invertebrates were collected from both actual and control trails to measure food availability. Dunnarts strongly selected open microhabitats when foraging, with the periphery of spinifex hummocks (up to 20 cm from the edge of a spinifex hummock) being favoured. Spinifex itself was avoided unless shelter was sought (i.e. immediately after release). Potential invertebrate prey captured along the actual trails travelled by dunnarts tended to occur in greater numbers and were larger than those captured along the control trails, indicating that dunnarts can accurately locate resource-rich areas in which to forage. Clearly, the foraging strategies used by this species enable it to successfully exploit patchy and unpredictable food resources, thereby ensuring its continued persistence and relative abundance in an unstable environment.

Field trials were conducted in central Australia to evaluate the ability of
various olfactory lures to attract feral cats
(Felis catus L.). Ten food-based lures, one plant
extract and two scent-based lures (anal-gland preparations from male and
female cats) were evaluated on the basis of visitation rates and elicited
behavioural responses. A visual lure composed of bird feathers was also tested
in conjunction with the scent-based lures. One food-based lure (sun-rendered
prawn) and both of the scent-based lures were found to attract feral cats. The
visual lure did not enhance the attractiveness of the scent-based lures. The
possible uses and relative advantages of these lures in control programmes and
in ecological studies of cats are discussed.

We evaluated the efficacy of spotlight surveys
and passive track surveys conducted along roads for assessing the relative
abundance of feral cats and dingoes in a semi-arid rangeland environment in
central Australia. Track surveys were more time-efficient than spotlight
surveys and offered higher precision. We cover a range of issues that need to
be considered when using track-based surveys to assess population change. We
also discuss the merits of other techniques used to monitor the abundance of
mammalian carnivores.

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.

Information on the movements, social structure and burrow use of the mulgara, Dasycercus cristicauda, was collected using radio-telemetry at two study areas in central Australia, one located near the Granites gold mine in the Tanami Desert and the other located on the edge of Uluru Kata Tjuta National Park. The average home-range size was not significantly different between the two study areas but home-range size was highly variable amongst individuals, with areas from 1.0 to 14.4 ha being used. The average maximum distance moved was significantly greater for males than for females. Overlap of home ranges was less than 20%, on average, but this was highly variable. There was an average overlap of 14% for females, with a maximum of 67%. The home ranges of males also overlapped, averaging 16.5%, as did those of females and males (19%). D. cristicauda is a solitary species that exhibits high site fidelity and a low propensity for dispersal once a home range has been established.

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.

In central Australia, most 1080 (sodium monofluoroacetate) meat baits placed
on soil in predator-proof cages remained toxic to dingoes, foxes and feral
cats for at least 8 months regardless of whether they were protected from rain
or not. Thus, untaken baits will remain a potential hazard to non-target
species, particularly farm dogs, for a considerable period. However, when
dingo-control programs were monitored (n = 3
stations), approximately 85% of meat baits were taken within 4 days.
Dingo-control programs were undertaken on three stations by placing 1080 meat
baits near water points (bores) with known dingo activity. Baiting was
effective on two stations but not on the third. Where successful, dingo
numbers were reduced by 50–70%. The failure on the third station
was not due to the lack of bait-take as approximately 80% of these
baits were taken within 4 days; it was probably caused by the presence of
ephemeral water-bodies that could not be baited. However, this technique was
effective in removing those dingoes that utilised the artificial water points,
and hence were likely to be interacting with cattle. Such an outcome has
benefits to both conservation and the pastoral industry, as problem dogs are
removed without placing the long-term survival of dingoes at risk.

We examined the diet of the barn owl in three bioregions of arid Northern Territory; two in upland areas, the other on the Barkly Tableland. Owls from the MacDonnell and Petermann Ranges fed predominantly on rodents. At both sites, Mus musculus was the dominant prey both in terms of frequency and prey units, with Pseudomys hermannsburgensis an important secondary item. Notomys alexis was an important secondary item in the MacDonnell Ranges. These results support previous research in highlighting the importance of plague rodents in the diet of barn owls in arid Australia. In contrast to the samples from the upland sites, the Barkly Tableland sample was composed mostly of the dasyurid marsupial Sminthopsis macroura, with only one rodent captured. The absence of the long-haired rat, Rattus villosissimus, from the sample, despite the species being a favoured prey item of the barn owl that undergoes population irruptions at the collection site, suggests that the sample was collected during a non-plague period. Our study is the first to record a marsupial species as the major prey of the barn owl. This finding suggests that barn owls can switch to other prey when populations of rodents crash.