Suchergebnisse

We conducted a broad-scale aerial survey between 20 August and 12 October 2001 to ascertain the distribution and abundance of feral camels in the southern part of the Northern Territory. There was a minimum of 80 533 feral camels in the Northern Territory at the time of the survey. This figure is corrected for perception bias (a result of observers missing animals that are potentially visible), but not for availability bias (a result of some animals being concealed from the observers). The population of feral camels in the Northern Territory increased at a mean annual exponential rate, r, of 0.093 between 1993 and 2001. This represents an increase of ~10% per year or an approximate doubling in population size every 8 years. This trend is likely to continue for the foreseeable future. We use the results of an earlier survey (which included the Northern Territory, South Australia and Western Australia) to give a minimum figure of 300 000 feral camels for Australia in 2001. We discuss what is known of the impacts of feral camels in Australia, the inadequacy of current management practices and issues to be considered in designing an effective long-term management strategy for the species.

Context Lethal control through the application of 1080 baits is widely used in Australia to manage the negative impacts of wild dogs (dingoes, wild domestic dogs and their hybrids) on cattle production, but its effectiveness in this regard is not well understood. Aims To evaluate the efficacy of once yearly 1080 baiting on dingoes and its effects in mitigating predation and sublethal impacts on beef cattle. Methods A replicated experiment with two paired treatments (1080 poisoned and non-poisoned) was conducted on each of four cattle stations of 3782–10 850 km2, over 2.5 years (2000–02) in the southern Northern Territory. The study was undertaken in relatively good rainfall years. Key results Track-based surveys indicated that dingo abundance declined on poisoned relative to non-poisoned areas immediately following a single baiting episode. However, there was no detectable difference about 8 months after baiting. No difference was detected in observed levels of calf damage or calf loss between poisoned and non-poisoned areas. Conclusions The results add to the growing body of consistent evidence that contemporary dingo control practices yield little benefit to rangeland beef producers most of the time. Implications Routine dingo baiting (as currently undertaken) may be largely unnecessary for beef cattle producers in arid and semiarid areas. Alternative strategies and practices to reduce dingo mauling and predation impacts should be investigated using replicated and controlled field studies.

Movement patterns of female feral camels were studied over four years
(February 1993 to December 1996) in central and northern Australia using
satellite telemetry. Areas used over 12-month periods (calculated using the
fixed kernel method) were large (449–4933 km 2 )
and increased with increasing aridity as measured by long-term mean annual
rainfall. No consistent pattern of variation was detected in movement rates of
camels across seasons. Data collected over several years are needed to
classify movements in feral camels. The only telemetered camel that has been
monitored for longer than two years (this study) appeared to move within a
large home range over the concluding 3.5 years that it was tracked. Because
the areas used are large, extensive buffer zones will be needed in arid
regions to protect environmentally sensitive areas from the impacts of feral
camels.

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.

Context
Helicopter shooting is an effective tool for reducing feral horse (Equus caballus) populations that are considered overabundant. However, this tool has been less commonly used in recent years because of concerns about animal-welfare outcomes, which have not previously been quantified.

Aims
The aims of the present study were to assess the helicopter shooting of feral horses to determine (1) the duration of stress, (2) the frequency of adverse animal-welfare events and (3) the influence of explanatory variables in determining welfare outcomes.

Methods
We quantified the welfare outcomes of three helicopter shooting programs in central Australia during 2013 and 2015. We conducted ante-mortem observations of 937 horses and post-mortem observations of 630 horses. We measured the following three parameters to estimate the duration of stress from pursuit and the mode of death: chase time (CT), time to death (TTD) and total time (TT; CT+TTD). We quantified the frequency of adverse animal-welfare events, namely instantaneous death rate (IDR; percentage of animals for which TTD was zero), the apparent frequency of non-fatal wounding, and the frequency of bullet-wound tracts in different anatomical locations. We investigated the role of explanatory variables in determining whether or not a horse had an inferred instantaneous death.

Key results
For all horses, the median CT was 42s, the median TTD was 0s (median TTD for horses not killed instantaneously was 15s), and median TT was 52s. At least 1% of horses were non-fatally wounded, IDR was 63% (60–66%), and 3% (2–5%) of horses were not shot in the cranium, neck or thorax. Shooter skill was the most important determinant of whether or not a horse had an instantaneous death.

Conclusions
The animal-welfare outcomes of helicopter shooting appear to be similar for feral horses and feral camels (Camelus dromedarius), the only other species that has been studied using these methods, and could be refined by improving shooter skill.

Implications
Quantifying animal-welfare outcomes is particularly important for contentious wildlife management techniques. Wildlife managers should integrate the results of welfare studies into decision-making processes rather than excluding contentious techniques from consideration on the basis of perception.

Abstract ContextRecent global concern over invertebrate declines has drawn attention to the causes and consequences of this loss of biodiversity. Feral cats, Felis catus, pose a major threat to many vertebrate species in Australia, but their effect on invertebrates has not previously been assessed. AimsThe objectives of our study were to (1) assess the frequency of occurrence (FOO) of invertebrates in feral cat diets across Australia and the environmental and geographic factors associated with this variation, (2) estimate the number of invertebrates consumed by feral cats annually and the spatial variation of this consumption, and (3) interpret the conservation implications of these results. MethodsFrom 87 Australian cat-diet studies, we modelled the factors associated with variation in invertebrate FOO in feral cat-diet samples. We used these modelled relationships to predict the number of invertebrates consumed by feral cats in largely natural and highly modified environments. Key resultsIn largely natural environments, the mean invertebrate FOO in feral cat dietary samples was 39% (95% CI: 31–43.5%), with Orthoptera being the most frequently recorded order, at 30.3% (95% CI: 21.2–38.3%). The highest invertebrate FOO occurred in lower-rainfall areas with a lower mean annual temperature, and in areas of greater tree cover. Mean annual invertebrate consumption by feral cats in largely natural environments was estimated to be 769 million individuals (95% CI: 422–1763 million) and in modified environments (with mean FOO of 27.8%) 317 million invertebrates year−1, giving a total estimate of 1086 million invertebrates year−1 consumed by feral cats across the continent. ConclusionsThe number of invertebrates consumed by feral cats in Australia is greater than estimates for vertebrate taxa, although the biomass (and, hence, importance for cat diet) of invertebrates taken would be appreciably less. The impact of predation by cats on invertebrates is difficult to assess because of the lack of invertebrate population and distribution estimates, but cats may pose a threat to some large-bodied narrowly restricted invertebrate species. ImplicationsFurther empirical studies of local and continental invertebrate diversity, distribution and population trends are required to adequately contextualise the conservation threat posed by feral cats to invertebrates across Australia.