Suchergebnisse

Foxes, wild dogs, feral cats, rabbits, feral pigs and feral goats are believed to have deleterious impacts on native biodiversity in Australia. However, although considerable resources have been expended controlling these six species, little is known about national patterns and costs of control and monitoring. We therefore conducted a survey of pest-control operations undertaken by conservation-focused organisations in Australia. A total of 1306 control operations were reported, with most conducted during 1998–2003: there was little information prior to 1990. Foxes and rabbits were the most, and feral cats the least, frequently controlled pest species. The total area on which control was undertaken in 2003, the year for which most information was available, ranged from ~0.4 × 104 km2 for feral cats to ~10.7 × 104 km2 for foxes. A wide range of techniques and intensities were used to control each of the six species. The estimated cost of labour expended on control in 2003 ranged from $0.4 × 106 for feral cats to $5.3 × 106 for foxes. Monitoring of the pest or biodiversity occurred in 50–56% of control actions in which foxes, wild dogs and feral cats were targeted, but only 22–26% of control actions in which rabbits, feral pigs and feral goats were targeted. Our results are discussed in relation to previous studies of pest animal control and monitoring in Australia.

Context Shooting is used to reduce the abundance of kangaroo (Macropus sp.) populations in many peri-urban areas in Australia, but there is uncertainty surrounding the animal welfare outcomes of this practice. Aim We assessed the animal welfare outcomes of night shooting for peri-urban eastern grey kangaroos (Macropus giganteus). We quantified the duration of stress for: (1) shot animals; (2) euthanased pouch young; and (3) other animals in the same social group. Methods An independent observer collected thermal imagery data, enabling four key animal welfare parameters to be quantified: instantaneous death rate, median time to death, wounding rate and flight duration of conspecifics. The duration between pouch removal and insensibility was recorded for pouch young. Post-mortem data were recorded to confirm the location and extent of pathology from shooting. Key results Of the 136 kangaroos that were shot at, two were missed. The wounding rate was zero, with a 98% instantaneous death rate. The median time to death for the three animals not killed instantaneously was 12 s. For pouch young considered sentient, the median stress time was 4 s. Kaplan–Meier survival analysis revealed that the median flight duration of conspecifics was 5 s. Conclusions Our results indicate that night shooting produces a very short duration of stress to shot kangaroos, their pouch young and their conspecifics. Implications When compared to other wildlife shooting methods, night shooting is a humane method for culling peri-urban kangaroos.

Effective management of sympatric mammalian herbivore populations requires an understanding of interspecific interactions. At Wilsons Promontory National Park, Victoria, sympatric native and introduced mammalian herbivores are thought to be contributing to modification of shrub-encroached Coastal Grassy Woodland. We estimated the diets of the five terrestrial mammalian herbivore species present using microhistological techniques. The diets of introduced hog deer (Axis porcinus) and native swamp wallabies (Wallabia bicolor) consisted mainly of dicots. The diet of introduced European rabbits (Oryctolagus cuniculus) contained similar proportions of monocots and dicots. The diets of native eastern grey kangaroos (Macropus giganteus) and native common wombats (Vombatus ursinus) consisted mainly of monocots but kangaroos also consumed moderate amounts of dicots. Deer and wallabies consumed more native plants than did the other species and rabbits consumed more exotic plants than did all other species except kangaroos. Diet breadth was narrowest for kangaroos and broadest for swamp wallabies and hog deer. Overlap in food use by the five herbivores was high, particularly between deer and wallabies, and between kangaroos and both rabbits and wombats. Our results suggest that the potential impacts of native and introduced species on the vegetation of Coastal Grassy Woodland are similar, and that the entire herbivore assemblage will need to be managed to increase fine fuel loads if fire is used as a restoration tool.

The principal method for estimating the abundance of bats in roosts is to count the number of bats exiting the roost at dusk ('flyout counts'). We hypothesised that the accuracy and precision of flyout counts decrease non-linearly as the number of bats moving per unit of time increases, and that accuracy increases with observer experience. To test these hypotheses, we filmed grey-headed flying-foxes (Pteropus poliocephalus) exiting a roost in Melbourne on three consecutive evenings. The film was slowed and the number of flying-foxes flying-out in 30-s intervals was counted and assumed to be the true abundance. Thirteen other observers independently counted the number of flying-foxes flying-out in real time. We formulated our hypotheses into candidate models and compared support for these models using information-theoretic methods. Non-linear models had much greater support than linear models for all three flyouts. There was undercounting in two flyouts and overcounting in the third. There was good support for an effect of observer experience in one of the flyouts, but less support in the others. Precision declined as the true abundance increased in all three flyout counts. Our results indicate that accuracy, precision and observer effects vary with the dynamics of each flyout, and suggest that under some conditions flyout counts will often provide both inaccurate and imprecise estimates of abundance.

Context
Distance sampling is widely used to estimate the size of wildlife populations, including kangaroos. However, the performance of distance-sampling abundance estimates has seldom been evaluated for wild mammal populations of known size.

Aims
We evaluated the precision, accuracy, bias and interval coverage of abundance estimates from walked line-transect sampling, a commonly used distance-sampling method, for a marked free-ranging population of eastern grey kangaroos (Macropus giganteus) at Yanakie Isthmus, Wilsons Promontory National Park, south-eastern Australia.

Methods
In each of two study periods (November 2012 and May 2013) we first determined the true size of the uniquely marked kangaroo population by conducting 10 intensive searches of the study area. We then conducted distance sampling along six systematically spaced line transects. We walked each transect four times in November 2012 and seven times in May 2013. Data were analysed using Program DISTANCE.

Key results
Our intensive searches revealed that 141 and 124 collared kangaroos were present in the study area in November 2012 and May 2013, respectively. When transects were walked four or more times (i.e. ≥400 observations), maximum precision (coefficient of variation; CV of ~13%) was achieved in both survey periods. Walking transects twice (i.e. ~200 observations) produced abundance estimates with CVs of <20% in each study period. The accuracy (root mean square error) of abundance estimates varied from 1 to 13 (November 2012) and from 3 to 28 (May 2013). Bias ranged from −9% to +23%, but stabilised at between −1% and −9% when transects were walked four or more times in each study period. The 95% confidence intervals for the abundance estimates always included the true population size.

Conclusions
Our results indicated that walked line-transect distance sampling is a precise and accurate method for estimating eastern grey kangaroo abundance. The small negative biases that occurred when sample sizes were large were likely to be due to some animals moving outside the study area.

Implications
Provided that the key design elements and assumptions are met, estimates of kangaroo abundance from walked line-transect distance sampling should have good precision (CV < 20%) and minimal (<10%) bias.

Context
Despite large mammals being an important component of many ecosystems, there is little information on the impacts of fire on large mammal populations.

Aims
We evaluated the effects of the large-scale high-severity 'Black Saturday' fires of 7 February 2009 on occupancy and abundances of an invasive large mammal, the sambar deer (Cervus unicolor), in south-eastern Australia.

Methods
The effects of the Black Saturday fires on the abundance of sambar deer were assessed using repeated annual counts of faecal pellets during 2007–11 in Kinglake National Park, which was burnt, and in Mount Buffalo National Park, which was not burnt. Pre-fire occupancy was modelled from data collected at 80 4-km2 cells using three survey methods. The same survey methods were used at 15 burnt (n = 9 sampled pre-fire) and 15 unburnt (n = 5 sampled pre-fire) cells 16–24 months after Black Saturday. Because multiple surveys were performed in each cell, we used a Bayesian state–space site-occupancy model to partition changes in the probability of occupancy from changes in the probability of detection.

Key results
Counts of sambar deer pellets increased linearly during 2007–11 in the unburnt Mount Buffalo National Park. Pellet counts also increased linearly in Kinglake National Park from 2007 to 2008, and then decreased (to zero) following Black Saturday; pellet counts increased again in 2010 and 2011. Sambar deer occupancy was weakly reduced (from 0.99 to 0.88) in burnt cells 16–24 months after Black Saturday, but was little changed in unburnt cells (from 0.99 to 0.98).

Conclusions
We conclude that the abundance of sambar deer was substantially reduced by the large-scale high-severity Black Saturday fires, but that most burnt habitat was reoccupied 16–24 months later.

Implications
There is concern about the negative impacts of invasive sambar deer on native biodiversity, particularly immediately post-fire. Our study suggests that it takes at least 8 months before sambar deer recolonise areas burnt by a large-scale high-severity fire; however, a risk-averse approach would be to act (e.g. by erecting fences or culling) sooner than that.

Context There is concern about potential competition between non-native fallow deer (Dama dama) and livestock for food, particularly during times of low rainfall when pasture is scarce. Aims We aimed to estimate the extent to which a high-density fallow deer population (~37 deer per km2) competed with livestock for food during a severe drought on pastoral properties on the Liverpool Plains, New South Wales, Australia. Methods We collected rumen contents from 125 fallow deer shot from helicopters during control operations in June and August 2018, and used microhistology to quantify their diets. We then used the diet data to adjust published estimates of stock unit equivalence from farmed fallow deer. Fallow deer sex and age class abundances and stock unit equivalences were multiplied to estimate the grazing pressure of the fallow deer population pre- and post-control relative to recommended sheep and cattle stocking rates. Finally, we estimated density–impact relationships for fallow deer. Key results Fallow deer diet was dominated by monocots (primarily grasses), but some individuals consumed large amounts of dicots (commonly Eucalyptus). Fallow deer were grazers to intermediate mixed feeders. Fallow deer dry-sheep equivalents (DSEs, based on a 50-kg merino wether) varied from 1.01 (juveniles) to 1.85 (adult females and adult males). Assuming complete diet overlap, the pre-control fallow deer population was equivalent to approximately 60.3 DSEs per km2 and reduced the potential stocking rate of domestic livestock by 50.2%. Discounting the fallow deer DSEs by the amount of browse in the diet resulted in a pre-control population of 45.7 DSEs per km2. The helicopter-based shooting reduced the fallow deer population by 26%, increasing the stocking rate in natural pasture by 22.0% (complete overlap) or 13.8% (discounting for browse). Conclusions When food is limiting, fallow deer at high density can exert strong competitive pressure on livestock, reducing carrying capacity. Browsing, including on Eucalyptus, likely helped fallow deer to persist at high densities during the severe drought of 2018, when properties had destocked. Implications Helicopter-based shooting reduced the competitive effects of fallow deer on livestock in our study area to only a small extent, but more intensive shooting would have led to a greater reduction. The helicopter-based shooting of deer was received positively by landholders at a time of severe stress, suggesting that deer control in agricultural areas can have other important benefits.

Context Vehicle-based shooting has been widely used to kill deer, but the animal-welfare outcomes of this technique have not been evaluated in Australasia. Aim To assess the animal-welfare outcomes of peri-urban deer culling by quantifying the fates of deer seen and shot at, the duration of procedures, and the number and location of bullet wounds in deer. Methods We assessed vehicle-based night shooting of peri-urban rusa deer (Cervus timorensis) by professional contractors in eastern Australia. Shooters targeted the heads of deer using .223 Remington® rifles and 55 grain bullets. Independent veterinarians conducted ante-mortem (i.e. from the shooting vehicle) and post-mortem (i.e. inspecting the carcass) observations. The ante-mortem data were used to estimate the proportion of deer seen that were shot at, killed, wounded, and escaped. The influence of variables predicted to affect shooting outcomes was assessed. The numbers and locations of bullet wounds were recorded post-mortem. Key results Of the 269 deer seen in 21 nights, 48% were shot at and 85% of those shot at were killed by either one (87%), two (10%) or three (3%) shots. The frequency of non-fatal wounding (i.e. escaping wounded) was 3.5% for those shot at and hit, and the median time to insensibility for the deer that were shot multiple times was 289 s. There was variation among shooters in their ability to hit a deer, and also to do so with a killing shot. The number of bullet wounds per deer ranged from 1 to 3 (mean = 1.1), with 83% of shots striking the brain and 17% striking the anterior skull, neck and jaw. Conclusions The animal welfare outcomes we observed were comparable to those reported from other professional ground-based shooting programs for ungulates, but were poorer than those reported for professional ground-based shooting of peri-urban kangaroos. Implications Our results suggest that one way to improve the animal welfare outcomes of vehicle-based shooting of peri-urban deer is by improving shooter training. Assessment of shooter performance should be a routine part of ground-based shooting programs.

Abstract Context Helicopter darting has been used to capture wild deer, but this method has never been used for chital deer (Axis axis). Aim The aims of this study were to develop, assess and refine a helicopter darting technique for wild chital deer in northern Australia by quantifying: (1) reliable pharmacological doses for immobilisation; (2) the efficacy of the technique (including the duration of procedures); and (3) the frequency of adverse animal welfare events. Methods The study was conducted in three stages: an initial protocol (n = 25 deer captured) in July−August 2018; a refined second protocol implemented in June 2019 (n = 12 deer captured); and a further refined third protocol implemented in June 2019 (n = 12 deer captured). Parameters to estimate the duration of procedures were measured and the frequency of several adverse animal welfare events during capture were quantified: mortality (at the time of capture and within 14 days of capture), hyperthermia, hypoxaemia, dart inaccuracy and manual restraint. Finally, GPS location collars with a mortality-sensing function were used to monitor post-release mortality. Results Mortality within 14 days of capture was 40% for the first stage, 25% for the second stage and 17% for the third stage. Considerable refinement of procedures occurred between stages in consultation with an Animal Ethics Committee. One-third of all 15 mortalities occurred at the time of capture and were attributed to ballistic trauma from dart impact and acute capture myopathy. The majority (n = 10) of mortalities, however, occurred post-release and were only detected by mortality-sensing GPS location collars. These post-release mortalities were attributed to capture myopathy. Conclusions Helicopter darting of wild chital deer poses animal welfare risks, but these can be minimised through the selection of the most appropriate pharmacological agents and attempts at preventing factors such as hyperthermia and hypoxaemia that contribute to the development of capture myopathy. Further research into capture protocols is needed for helicopter-based immobilisation of chital deer. Fitting animals with GPS location collars enabled post-release mortality, which was significant, to be evaluated.

Combining abundance data collected in designed field surveys with biophysical data derived from geographic information systems is a powerful way to investigate predictors of spatial variation in the abundance of wildlife. We used such an approach to evaluate hypotheses about factors influencing the abundance of sambar deer (Cervus unicolour Kerr, 1792), a large non-native herbivore, in south-eastern Australia. We developed a spatial model for the abundance of sambar deer faecal pellets in a 3650-ha area in the Upper Yarra Ranges, Victoria. We counted the number of sambar deer faecal pellets along 100 randomly located transects and used a geographic information system to estimate biophysical variables around each transect. We formulated our hypotheses about how those variables might affect the abundance of sambar deer pellets into 22 candidate models and used the deviance information criterion to identify the 'best' model(s). Because five models had strong support we used model averaging to generate a predictive model. The three variables included in the predictive model were aspect (abundance of pellets declined with increasing 'northerliness' and increased with increasing 'easterliness'), distance to water and elevation; the latter two variables were positively correlated and had a negative effect on the abundance of pellets. In contrast to previous models of sambar deer abundance in south-eastern Australia, our spatial predictions of the abundance of faecal pellets can be easily tested and updated. Our approach would be useful for modelling the abundances of other wildlife species at a range of spatial scales.

Context Safe and effective capture methods are crucial for improving our understanding and management of many wildlife species. The adaptation of established capture methods to novel situations requires critical evaluation because differences in environmental conditions and species' susceptibility to trauma and capture myopathy can produce unexpected outcomes. Helicopter net-gunning has been a valuable tool for capturing wild deer in New Zealand and the Americas, but there are no practical records of its use in Australia and only one report of it being used to capture three fallow deer (Dama dama) elsewhere. Aims The present study aimed to evaluate the feasibility of a helicopter-based net-gun capture technique for wild fallow deer by quantifying the efficacy of the technique and the frequency of injuries and deaths. Methods We captured fallow deer over two 3-day operations at a 135 km2 site in eastern Australia. We collected data on operational efficiency and variables expected to affect animal health and welfare, such as injuries and the duration of stressful procedures. We used GPS tracking collars with an accelerometer and a mortality-sensing function to monitor post-release survival and activity of fallow deer. Key results In total, 127 deer were targeted for capture, with nets fired at 64 deer (50%) and 27 deer captured (21%). Mortality within 30 days of capture was zero. Mean chase time was 2 min 46 s and mean total time from start of chase until release was 11 min 19 s. No animals were severely injured or euthanased, but hyperthermia was observed in 33% of captured animals. Conclusions Helicopter net-gunning was an effective and safe method for capturing wild fallow deer when compared with alternative methods. Implications We recommend that researchers consider using helicopter net-gunning to capture fallow deer in Australia and elsewhere, and other deer species in Australia.

Feral goats in the 34 169 ha Egmont National Park (North Island, New Zealand) have been subject to sustained ground-based hunting with dogs since 1925. We analysed trends in hunting success from 1961 to 1999. During 1961–86 the catch per unit effort (CPUE) declined from 7 kills hunter–1 day–1 to <1 kill hunter–1 day–1. Since 1987 the CPUE has been maintained at low levels. The key impediment to switching from a strategy of sustained control to eradication is whether or not all goats can be put at risk. We suggest that managers test this experimentally in part of the park before embarking on an eradication programme. On the basis of an empirical estimate of rm and an assumption of logistic growth, we estimated the current population to be ~1047 animals. Removing 50% or 90% of the population annually would eradicate the population in >50 years or 12 years, respectively. Annual immigration of goats would prevent eradication under all scenarios.

Abstract Context Helicopter-based shooting has been widely used to kill deer in Australasia, but the animal welfare outcomes of this technique have not been evaluated. Aim To assess the animal welfare outcomes of helicopter-based shooting of deer in Australia by quantifying the fates of deer seen and shot at, the duration of procedures and the number and location of bullet wounds in deer. Methods Three deer control operations were assessed. These operations targeted: (1) chital deer (Axis axis) in Queensland, (2) fallow deer (Dama dama) in Australian Capital Territory and (3) fallow deer in New South Wales. For each operation, an independent veterinarian conducted ante-mortem (i.e. from the helicopter as shooting occurred) and post-mortem (i.e. from the ground after shooting had ceased) observations. The ante-mortem data were used to estimate the proportion of deer seen that were shot, chase time (CT), time to insensibility (TTI) and total time (TT; CT + TTI). The numbers and locations of bullet wounds were recorded post-mortem. Key results Ante-mortem and post-mortem observations were performed for 114–318 and 60–105 deer, respectively, in the three operations. Shots were fired at 69–76% of deer that were observed. Median CT ranged from 73 to 145 s. Median TTI ranged from 17 to 37 s and median TT ranged from 109 to 162 s. The mean number of bullet wounds per deer ranged from 1.43 to 2.57. Animal welfare outcomes were better in the two fallow deer operations than in the chital deer operation. In both fallow deer operations, most deer were shot multiple times and at least once in the head or thorax. In contrast, chital deer were shot fewer times and less often in the head or thorax, and non-fatal wounding was observed. Conclusions The best animal welfare outcomes were achieved when helicopter-based shooting operations followed a fly-back procedure and mandated that multiple shots were fired into each animal. Implications Animal welfare outcomes for helicopter-based deer shooting in Australia could be improved with a national-level standard operating procedure requiring helicopters to fly back over shot animals and repeatedly shoot animals in the head or thorax.

Context Feral pigs (Sus scrofa) have a wide global distribution that includes large parts of Australia and New Zealand. There is concern about the impacts of feral pigs on above- and below-ground flora and fauna, but little is known about their habitat use and feeding activity in temperate rainforests. Aims We evaluated the importance of abiotic and biotic variables hypothesised to influence seasonal and annual feral pig habitat use and feeding activity in a montane conifer–angiosperm rainforest in Te Urewera, North Island, New Zealand. Methods We used a grid of 25 remote-camera locations to collect feral pig images in a 100-ha area during the winters and summers of 2010 and 2011. Plant composition, solar radiation and soil fertility variables were determined for each camera-image area. Multiseason, multistate occupancy models and information-theoretic methods were used to evaluate how these variables related to feral pig occupancy and feeding. Key results Feral pigs occupied more camera locations in summer than in winter, and detection probabilities increased if piglets were present and with increasing soil phosphorus (P). Piglets were detected only in summer, and their detection probability increased with increasing soil P. The probability of detecting feral pigs feeding also increased with soil P and was higher in 2010 than 2011. Conclusions Feral pigs selected locations with high soil P, probably because those sites had more food than did locations with low soil P. Mast fruiting of tawa (Beilschmiedia tawa) has been hypothesised to increase feral pig recruitment, and the higher detection probability of piglets in summer 2010 followed a heavier tawa fruit fall. Implications Our study highlighted the usefulness of camera traps and occupancy models for understanding seasonal and annual dynamics of cryptic ungulate species in remote, rugged forests, and suggests that the impacts of feral pigs will be greatest in areas of high soil P following widespread tawa masting.