17 resultados para Ehrlichia canis

em Deakin Research Online - Australia


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This essay discusses Bully (Canis Canem Edit), considering the game's antecedents (narratives involving young people in school settings) and the features which set it apart from other teen texts. It discusses the controversy surrounding the game and comes to the conclusion that the principal reason
for unease on the part of parents and educational authorities is that Bully's postmodernist ethic evades the binaries of liberal humanism and calls into question the foundations on which conventional ethical systems are based. Tbe paper considers several episodes from the game to flesh out its arguments about how the game manifests features of postmodernist textuality in its propensity for simultaneously deploying and interrogating references to historical and contemporary cultural practices.

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Top-order predators often have positive effects on biological diversity owing to their key functional roles in regulating trophic cascades and other ecological processes. Their loss has been identified as a major factor contributing to the decline of biodiversity in both aquatic and terrestrial systems. Consequently, restoring and maintaining the ecological function of top predators is a critical global imperative. Here we review studies of the ecological effects of the dingo Canis lupus dingo, Australia's largest land predator, using this as a case study to explore the influence of a top predator on biodiversity at a continental scale. The dingo was introduced to Australia by people at least 3500 years ago and has an ambiguous status owing to its brief history on the continent, its adverse impacts on livestock production and its role as an ecosystem architect. A large body of research now indicates that dingoes regulate ecological cascades, particularly in arid Australia, and that the removal of dingoes results in an increase in the abundances and impacts of herbivores and invasive mesopredators, most notably the red fox Vulpes vulpes. The loss of dingoes has been linked to widespread losses of small and medium-sized native mammals, the depletion of plant biomass due to the effects of irrupting herbivore populations and increased predation rates by red foxes. We outline a suite of conceptual models to describe the effects of dingoes on vertebrate populations across different Australian environments. Finally, we discuss key issues that require consideration or warrant research before the ecological effects of dingoes can be incorporated formally into biodiversity conservation programs.

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It has been postulated that the neuropeptide, oxytocin, is involved in human-dog bonding. This may explain why dogs, compared to wolves, are such good performers on object choice tasks, which test their ability to attend to, and use, human social cues in order to find hidden food treats. The objective of this study was to investigate the effect of intranasal oxytocin administration, which is known to increase social cognition in humans, on domestic dogs' ability to perform such a task. We hypothesised that dogs would perform better on the task after an intranasal treatment of oxytocin. Sixty-two (31 males and 31 females) pet dogs completed the experiment over two different testing sessions, 5-15 days apart. Intranasal oxytocin or a saline control was administered 45 min before each session. All dogs received both treatments in a pseudo-randomised, counterbalanced order. Data were collected as scores out of ten for each of the four blocks of trials in each session. Two blocks of trials were conducted using a momentary distal pointing cue and two using a gazing cue, given by the experimenter. Oxytocin enhanced performance using momentary distal pointing cues, and this enhanced level of performance was maintained over 5-15 days time in the absence of oxytocin. Oxytocin also decreased aversion to gazing cues, in that performance was below chance levels after saline administration but at chance levels after oxytocin administration.

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Population control of socially complex species may have profound ecological implications that remain largely invisible if only their abundance is considered. Here we discuss the effects of control on a socially complex top-order predator, the dingo (Canis lupus dingo). Since European occupation of Australia, dingoes have been controlled over much of the continent. Our aim was to investigate the effects of control on their abundance and social stability. We hypothesized that dingo abundance and social stability are not linearly related, and proposed a theoretical model in which dingo populations may fluctuate between three main states: (A) below carrying capacity and socially fractured, (B) above carrying capacity and socially fractured, or (C) at carrying capacity and socially stable. We predicted that lethal control would drive dingoes into the unstable states A or B, and that relaxation of control would allow recovery towards C. We tested our predictions by surveying relative abundance (track density) and indicators of social stability (scent-marking and howling) at seven sites in the arid zone subject to differing degrees of control. We also monitored changes in dingo abundance and social stability following relaxation and intensification of control. Sites where dingoes had been controlled within the previous two years were characterized by low scent-marking activity, but abundance was similar at sites with and without control. Signs of social stability steadily increased the longer an area was allowed to recover from control, but change in abundance did not follow a consistent path. Comparison of abundance and stability among all sites and years demonstrated that control severely fractures social groups, but that the effect of control on abundance was neither consistent nor predictable. Management decisions involving large social predators must therefore consider social stability to ensure their conservation and ecological functioning.

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Invasive species are regarded as one of the top five drivers of the global extinction crisis. In response, extreme measures have been applied in an attempt to control or eradicate invasives, with little success overall. We tested the idea that state shifts to invasive dominance are symptomatic of losses in ecosystem resilience, due to the suppression of apex predators. This concept was investigated in Australia where the high rate of mammalian extinctions is largely attributed to the destructive influence of invasive species. Intensive pest control is widely applied across the continent, simultaneously eliminating Australia’s apex predator, the dingo (Canis lupus dingo). We show that predator management accounts for shifts between two main ecosystem states. Lethal control fractures dingo social structure and leads to bottom-up driven increases in invasive mesopredators and herbivores. Where control is relaxed, dingoes re-establish top–down regulation of ecosystems, allowing for the recovery of biodiversity and productivity.

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1. Apex predators can benefit ecosystems through top–down control of mesopredators and herbivores. However, apex predators are often subject to lethal control aimed at minimizing attacks on livestock. Lethal control can affect both the abundance and behaviour of apex predators. These changes could in turn influence the abundance and behaviour of mesopredators.

2. We used remote camera surveys at nine pairs of large Australian rangeland properties, comparing properties that controlled dingoes Canis lupus dingo with properties that did not, to test the effects of predator control on dingo activity and to evaluate the responses of a mesopredator, the feral cat Felis catus.

3. Indices of dingo abundance were generally reduced on properties that practiced dingo control, in comparison with paired properties that did not, although the effect size of control was variable. Dingoes in uncontrolled populations were crepuscular, similar to major prey. In populations subject to control, dingoes became less active around dusk, and activity was concentrated in the period shortly before dawn.

4. Shifts in feral cat abundance indices between properties with and without dingo control were inversely related to corresponding shifts in indices of dingo abundance. There was also a negative relationship between predator visitation rates at individual camera stations, suggesting cats avoided areas where dingoes were locally common. Reduced activity by dingoes at dusk was associated with higher activity of cats at dusk.

5. Our results suggest that effective dingo control not only leads to higher abundance of feral cats, but allows them to optimize hunting behaviour when dingoes are less active. This double effect could amplify the impacts of dingo control on prey species selected by cats. In areas managed for conservation, stable dingo populations may thus contribute to management objectives by restricting feral cat access to prey populations.

6. Synthesis and applications. Predator control not only reduces indices of apex predator abundance but can also modify their behaviour. Hence, indicators other than abundance, such as behavioural patterns, should be considered when estimating a predator's capacity to effectively interact with lower trophic guilds. Changes to apex predator behaviour may relax limitations on the behaviour of mesopredators, providing enhanced access to resources and prey.

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Several authors have recently argued that dingoes could be used to help conserve biodiversity in Australia. Fleming et al. (2012) [Australian Mammalogy 34, 119–131] offer the alternative view that restoration of dingo predation is unlikely to help native species, and is more likely to do harm. We think many of the arguments used by Fleming et al. to reach that conclusion are either unsound or beside the point, and we explain why.

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On most developed coastlines, dunes backing ocean beaches constitute an urbanised landscape mosaic containing remnant pockets of small conservation areas. Urbanised beaches are also prime sites for domestic dogs, known to be environmentally harmful in many other settings. It is unknown, however, whether small, protected parcels of dune are adequate for biological conservation and whether dogs compromise their functional conservation objectives. Here we examine, for two small (2 km ocean boundary) reserves in Eastern Australia abutting an urban area, whether such small reserves can continue to function as effective conservation instruments on ocean beaches, using scavenger community composition and efficiency to assess ecosystem function. Two non-native species of canids—domestic dogs (Canis lupus familiaris) and red foxes (Vulpes vulpes)—were ubiquitous and numerous inside conservation areas, to the point of having become the most abundant vertebrate scavengers at the beach-dune interface, outcompeting native scavengers for wave-cast carrion. Dogs and foxes have effectively supplanted raptors, normally abundant on non-urban beaches in the region, and other avian scavengers, as the principal consumers of animal carcasses both inside the declared reserves and at the urban beach. Whilst the ecological threats posed by foxes are widely and intensively addressed in Australia in the form of fox-control programs, dog controls are less common and stringent. Our data emphasize, however, that managing domestic dogs may be required to the same extent in order to maintain key forms and functions in coastal reserves situated close to urban areas.

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The presence of domestic dogs Canis familiaris in public open spaces is increasingly controversial. In our review of the literature, we located 133 publications of various types (papers, reports etc.) that examine some aspect of dogs in parks and open spaces (50 % focussed solely on dogs). There has been an exponential growth in the cumulative number of articles (R (2) = 0.96; 82 % published since 1997); almost all pertain to temperate latitudes (97 %) and most to the northern hemisphere (62 %). Most articles focus on impacts on wildlife (51 %), zoonotic diseases (17 %), and people's perceptions regarding dogs (12 %). Articles mostly describe problems associated with dogs, while reports of low compliance with dog regulations are common. We outline six major findings regarding dogs in parks: (1) there is a paucity of information on dogs in parks, particularly in relation to their interactions with wildlife and regarding their management; (2) published studies are mainly restricted to a handful of locations in developed countries; (3) sectors of societies hold different views over the desirability of dogs in parks; (4) the benefits and risks of dogs to humans and park values are poorly documented and known; (5) dogs represent a notable disease risk in some but not all countries; and (6) coastal parks are over-represented in the literature in terms of potential negative impacts. Park managers globally require better information to achieve conservation outcomes from dog management in parks.

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Dingoes/wild dogs (Canis dingo/familiaris) and red foxes (Vulpes vulpes) are widespread carnivores in southern Australia and are controlled to reduce predation on domestic livestock and native fauna. We used the occurrence of food items in 5875 dingo/wild dog scats and 11,569 fox scats to evaluate interspecific and geographic differences in the diets of these species within nine regions of Victoria, south-eastern Australia. The nine regions encompass a wide variety of ecosystems. Diet overlap between dingoes/wild dogs and foxes varied among regions, from low to near complete overlap. The diet of foxes was broader than dingoes/wild dogs in all but three regions, with the former usually containing more insects, reptiles and plant material. By contrast, dingoes/wild dogs more regularly consumed larger mammals, supporting the hypothesis that niche partitioning occurs on the basis of mammalian prey size. The key mammalian food items for dingoes/wild dogs across all regions were black wallaby (Wallabia bicolor), brushtail possum species (Trichosurus spp.), common wombat (Vombatus ursinus), sambar deer (Rusa unicolor), cattle (Bos taurus) and European rabbit (Oryctolagus cuniculus). The key mammalian food items for foxes across all regions were European rabbit, sheep (Ovis aries) and house mouse (Mus musculus). Foxes consumed 6.1 times the number of individuals of threatened Critical Weight Range native mammal species than did dingoes/wild dogs. The occurrence of intraguild predation was asymmetrical; dingoes/wild dogs consumed greater biomass of the smaller fox. The substantial geographic variation in diet indicates that dingoes/wild dogs and foxes alter their diet in accordance with changing food availability. We provide checklists of taxa recorded in the diets of dingoes/wild dogs and foxes as a resource for managers and researchers wishing to understand the potential impacts of policy and management decisions on dingoes/wild dogs, foxes and the food resources they interact with.

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Management of apex predators is among the most controversial wildlife management issues globally. In Australia, some ecologists have advocated using the dingo, Canis dingo, as a tool for conservation management, due to evidence that they suppress invasive mesopredators. Hayward & Marlow (Journal of Applied Ecology, 51, 2014 and 835) questioned the capacity of dingoes to provide benefits to native biodiversity due to their inability to eradicate foxes and cats. They also argued that indices of abundance commonly used in studies of mesopredator release by dingoes (namely, track-based indices) invalidate the conclusions of the studies. Hayward & Marlow caution conservation practitioners against incorporating dingoes into conservation programmes. Counter to their claims, we summarise research showing that the suppression of invasive mesopredators (cf. eradication) can enhance populations of native species and is therefore a meaningful conservation objective. We highlight literature supporting the hypothesis that dingoes suppress mesopredator abundance and activity, which in turn benefits native biodiversity. We show that Hayward & Marlow overlook many studies of carnivores that show track indices capture a large amount of the variation in the density of medium- and large-sized carnivores. Synthesis and applications. Practitioners cannot afford to wait to act given the perilous state of Australia's mammal species, and we argue that the evidence is sufficiently strong to justify managing dingoes for biodiversity conservation.

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There is global interest in restoring populations of apex predators, both to conserve them and to harness their ecological services. In Australia, reintroduction of dingoes (Canis dingo) has been proposed to help restore degraded rangelands. This proposal is based on theories and the results of studies suggesting that dingoes can suppress populations of prey (especially medium- and large-sized herbivores) and invasive predators such as red foxes (Vulpes vulpes) and feral cats (Felis catus) that prey on threatened native species. However, the idea of dingo reintroduction has met opposition, especially from scientists who query the dingo's positive effects for some species or in some environments. Here, we ask 'what is a feasible experimental design for assessing the role of dingoes in ecological restoration?' We outline and propose a dingo reintroduction experiment-one that draws upon the existing dingo-proof fence-and identify an area suitable for this (Sturt National Park, western New South Wales). Although challenging, this initiative would test whether dingoes can help restore Australia's rangeland biodiversity, and potentially provide proof-of-concept for apex predator reintroductions globally.

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Apex predators perform important functions that regulate ecosystems worldwide. However, little is known about how ecosystem regulation by predators is influenced by human activities. In particular, how important are top-down effects of predators relative to direct and indirect human-mediated bottom-up and top-down processes? Combining data on species' occurrence from camera traps and hunting records, we aimed to quantify the relative effects of top-down and bottom-up processes in shaping predator and prey distributions in a human-dominated landscape in Transylvania, Romania. By global standards this system is diverse, including apex predators (brown bear and wolf), mesopredators (red fox) and large herbivores (roe and red deer). Humans and free-ranging dogs represent additional predators in the system. Using structural equation modelling, we found that apex predators suppress lower trophic levels, especially herbivores. However, direct and indirect top-down effects of humans affected the ecosystem more strongly, influencing species at all trophic levels. Our study highlights the need to explicitly embed humans and their influences within trophic cascade theory. This will greatly expand our understanding of species interactions in human-modified landscapes, which compose the majority of the Earth's terrestrial surface.

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Abstract. The diet of sympatric dingoes and feral cats was studied in the semiarid southern rangelands of Western Australia. A total of 163 scats were collected over a period of 19 months. Rabbit remains were the most common food item in cat scats, followed by reptiles, small mammals and birds. Macropod remains were the most common food item in dingo scats, followed by rabbits and birds. Dingo scats did not contain small mammal remains, and infrequently contained arthropod and reptile remains. Cat and dingo scats contained remains from 11 and six mammal species, respectively. Of the small mammals, cat scats contained rodent remains more frequently than those of dasyurids. Dietary diversity of cats was higher than for dingoes and dietary overlap between the two species was relatively low.