Kangaroo ecology and ecological impacts

Control and monitoring of kangaroo populations in the Mallee Parks of semi-arid Northwest Victoria

(Morris, Duncan, & Vesk, 2018)

This report explores the kangaroo population programs in the Mallee National Parks of Victoria.  Kangaroo populations in the Parks are managed for two interdependent reasons: to prevent large die-offs of kangaroos during drought and to prevent kangaroo grazing from impeding the ecological restoration of degraded semi-arid woodland ecosystems.

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Remote sensing of trophic cascades: multi-temporal landsat imagery reveals vegetation change driven by the removal of an apex predator

(Fisher et al, 2021)

Trophic cascade theory predicts that predators indirectly benefit plants by limiting herbivore consumption. As humans have removed large predators from most terrestrial ecosystems the effect of their absence is unrecognized. A manipulation of dingo populations across Australia’s dingo-proof fence, within the Strzelecki Desert, was used to assess how predator absence has altered vegetation cover dynamics at landscape and site scales.

Landscape-scale analysis used Landsat fractional vegetation cover time series statistics to classify landforms and examine vegetation dynamics either side of the dingo fence. Generalised additive models were used to analyse the influence of predator absence on site-scale observations of fauna abundance and vegetation cover. The location of the dingo fence was visible as a change in both the standard deviation and maximum of non-photosynthetic vegetation (NPV) cover (e.g. wood and dry leaves) over 32 years (1988–2020). On average, NPV cover of swales decreased in the standard deviation by 1.4% and in the maximum by 5.0% where dingo abundance was reduced. The differences were consistent with suppressed vegetation growth following rainfall, due to high grazing pressure, where predators were rare. The landscape-scale analysis was supported by site-scale observations. The influence of the trophic cascade was observable at both the landscape and site scales, suggesting that apex predator removal has significantly affected the arid ecosystem’s responses to resource pulses. Analogous effects may exist across the large areas of the planet over which apex predators have been extirpated.

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Eaten out of house and home: impacts of grazing on ground-dwelling reptiles in Australian Grasslands and Grassy Woodlands

(Howland, et al., 2014)

Large mammalian grazers can alter the biotic and abiotic features of their environment through their impacts on vegetation. Grazing at moderate intensity has been recommended for biodiversity conservation. Few studies, however, have empirically tested the benefits of moderate grazing intensity in systems dominated by native grazers. Here we investigated the relationship between (1) density of native eastern grey kangaroos, Macropus giganteus, and grass structure, and (2) grass structure and reptiles (i.e. abundance, richness, diversity and occurrence) across 18 grassland and grassy Eucalyptus woodland properties in south-eastern Australia. There was a strong negative relationship between kangaroo density and grass structure after controlling for tree canopy cover. We therefore used grass structure as a surrogate for grazing intensity. Changes in grazing intensity (i.e. grass structure) significantly affected reptile abundance, reptile species richness, reptile species diversity, and the occurrence of several ground-dwelling reptiles. Reptile abundance, species richness and diversity were highest where grazing intensity was low. Importantly, no species of reptile was more likely to occur at high grazing intensities.

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Victoria’s rangelands: In Recovery or in Transition?

(Sandell, 2011)

The management of approach of the reserved rangeland areas in NW Victoria are more akin to “restoration ecology” than the move conventional concept of conservation management of parks and reserves. This report provides an extensive exploration of historical land use as well as the creation of the mallee parks.  Management plans include extensive rabbit and kangaroo population management strategies to prevent adverse impacts on regeneration and habitat restoration.

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Threatened plant translocation in Australia: A review

(Silcock, et al., 2019)

This project combined a literature review with extensive consultations with translocation practitioners to compile data on translocations of threatened Australian plants.  The evaluation highlights the need to consider translocation in the broad context of conservation actions for species recovery and the need for long-term commitment to monitoring, site maintenance and documentation. Macropod grazing and trampling was a significant factor in the survival rates of some species.

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Using evidence of decline and extinction risk to identify priority regions, habitats and threats for plant conservation in Australia

(Silcock & Fensham, 2018)

This project undertook to compile published information and best available field knowledge including 125 expert interviews to identify declining and at risk species of vascular plants. Grazing from kangaroos featured as a threat to many of these at risk species.

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Density and dispersion of two species of kangaroo in relation to habitat

(Caughey, 1963)

A seminal work which investigates the differences in dispersion of red and grey kangaroos which indicated that grey kangaroos are more dependent on cover than red kangaroos and suggests that grey kangaroos frequent areas where they feel safe from observation.

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Density Distributions and Habitat Associations of Red Kangaroos, Macropus rufus, and Western Grey Kangaroos, M. fuliginosus, in the South Australian Pastoral Zone

(Cairns, Pople, & Grigg, 1991)

Density distributions of red and western grey kangaroos in the South Australian pastoral zone were determined for the period 1978-1986. The habitat associations of these kangaroos were analysed.  Habitat heterogeneity and climatic factors including low evaporation and relatively high rainfall appeared to be the major determinants of the density distribution of western grey kangaroos. 

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Home ranges of sympatric red kangaroos Macropos rufus, and Western Grey Kangaroos M. fuliginosus, in Western New South Wales

(Priddel, Shepherd, & Wellard, 1988)

Kangaroos are the most significant herbivores on Kinchega National Park.  This research involved using radiotracking 48 individual kangaroos over 20 months to determine home ranges.  Based on diurnal locations (resting sites) only, home ranges of red kangaroos were larger than those of western greys, but home ranges of kangaroos on Kinchega were smaller than those on the adjacent pastoral leasehold.

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Is camera trap videography suitable for assessing activity patterns in eastern grey kangaroos?

(Green-Barber & Old, 2017)

This project assessed the suitability of using cameras to document the behaviour of eastern grey kangaroos by comparing activity patterns collected using cameras to published activity patterns for the species. The findings of this study suggest that camera traps are suitable for assessing the diurnal activity of eastern grey kangaroos and are useful tools for documenting their behaviour.

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Sixteen years of Eastern Barred Bandicoot Perameles gunnii reintroductions in Victoria: a review

(Winnard & Coulson, 2008)Examined characteristics affecting the success of Eastern Barred Bandicoot reintroductions, including competition from herbivores.  A combination of drought and grazing pressure from kangaroos and rabbits reduced the amount of available habitat and possibly led to population decline of Eastern Barred Bandicoots at one reintroduction site in Victoria.

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The Effects of Grazing by Kangaroos and Rabbits on the Vegetation and the Habitat of Other Fauna in the Tidbinbilla Nature Reserve, Australian-Capital-Territory

(Neave & Tanton, 1989)

Examined the status of grassland vegetation in three areas in which exclosures provided protection since 1979 and compared with 1982-1983.  Showed that some plants had declined while others increased under high kangaroo grazing and explored habitat implications for other wildlife.

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The impact of grazing by Eastern Grey Kangaroos (Macropus giganteus) on vegetation recovery after fire at Reef Hills Regional Park, Victoria

(Meers & Adams, 2008)

This project was aimed at determining the grazing patterns of Eastern Grey Kangaroos after fire and determine the impacts that grazing might have on post fire woody shrub recovery. Found preferential grazing occurred on small burnt plots compared to adjacent unburnt areas and significant reduction in shrub diversity on grazed plots compared to ungrazed plots.

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Bringing forward the benefits of coarse woody debris in ecosystem recovery under different levels of grazing and vegetation density. 

(Manning, Cunningham, & Lindenmayer, 2012)

Examined the effect of experimentally adding Course Woody Debris, in four different treatments, on reptile abundance in temperate woodlands in south-eastern Australia – one of the most highly degraded vegetation types on the continent. They investigated the influence that varying grazing pressure and vegetation density had on those effects.Found a reduction of grazing was the most effective way of increasing small skink abundance in high density vegetation.

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Birds of a feather flock together: Using trait-groups to understand the effect of macropod grazing on birds in grassy habitats

(Howland B. W., et al., 2016)

Investigated the relationship between (1) density of native eastern grey kangaroos and grass structure and (2) grass structure and reptiles.  Found reptile abundance, species richness and diversity were highest where grazing intensity was low.

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Habitat preference of the striped legless lizard: Implications of grazing by native herbivores and livestock for conservation of grassland biota

(Howland B. W., et al., 2016)

Investigated habitat preferences of Delma Impar at multiple spatial scales and found it was not affected by the size of grassland remnants, but was negatively related to the density of native grazers.

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Mitigating impacts of weeds and kangaroo grazing following prescribed fire in a Banksia woodland

(Brown, Paczkowska, & Gibson, 2016)

Investigated (i) how native and weed species richness and cover changed following autumn prescribed fire and (ii) effectiveness of management techniques at reducing the impacts of grazing by western grey kangaroos.  Found fencing significantly increased cover of native shrubs and grasses through prevention of kangaroo grazing. However, kangaroos also appeared to play a role in suppressing weedy annual grasses post-fire in the woodlands.

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Experimental reduction of native vertebrate grazing and addition of logs benefit beetle diversity at multiple scales.

(Barton, Manning, Gibb, Lindenmayer, & Cunningham, 2011)

Investigated whether the differences in vertebrate grazing affect the trophic structure of beetle assemblages and a number of other habitat factors.  Found a reduction in grazing level had benefits for the abundance and species richness of beetles at the site scale.

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The concept of overgrazing and its role in management of large herbivores

(Mysterud, 2006)

Detailed discussion of what overgrazing means under different land uses and impacts of overgrazing in conservation and production landscapes.  There are several different ways of defining overgrazing.  Native and exotic herbivores can result in overgrazing which can lead to new stable ecosystems states and these new states may be irreversible.

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Eating away at protected areas: total grazing pressure is undermining public land conservation

(Prowse, O’Connor, Collard, & Rogers, 2019)

Grazing by domestic and wild mammalian herbivores can have a significant impact on the condition of remnant native vegetation, even if it is formally protected.  This project evaluated the evidence for grazing pressure trends in native vegetation covering 180 000km² of South Australia and employed Bayesian linear mixed-effects modelling and over the 12 year period found grazing severity in protected areas increased to levels closely matching those on private, unprotected land. These researchers suggest that macropod densities have increased substantially over that time frame and this has contributed significantly to the grazing pressure issue.

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Resource use by the Eastern Grey Kangaroo and the Black Wallaby in a managed remnant woodland community

(de Munk, 1999)

This work studies the interactions and relationships that exist between Eastern Grey Kangaroos and Black Wallabies in their utilisation of spatial and trophic resources in a managed remnant woodland community.  The thesis provides a close understanding of the way in which these species impact upon their habitats. Both species contributed to ecological management problems including lack of shrub and tree recruitment.

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Sensitivity of soil organic carbon to grazing management in the semi-arid rangelands of south-eastern Australia

(Orgill, et al., 2017)

This study compared the effects of grazing management on soil organic carbon stocks in the semi-arid rangelands of NSW.  Field surveys were conducted at three locations with paired sites of rotational grazing and continuous grazing. In some parts of the landscape higher soil C was found with TGP control. Grazing pressure was determined by domestic livestock records and data from annual aerial surveys of goats and kangaroos.  

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Management of grazing intensity in the semi-arid rangelands of southern Australia – Effects on soil and biodiversity

(Waters, Orgill, Melville, & Douglas, 2016)

Overgrazing contributes to rangeland degradation altering plant community composition, erosion and biodiversity. This research provides evidence that the effects of grazing management on SOC are mediated by ground cover and increased organic matter supply and/or reduced soil carbon redistribution (erosion), which indicates that the management of grazing intensity may provide a tool to avoid soil carbon loss in rangelands.

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Overabundant kangaroo populations in Southeastern Australia

(Coulson G. , 2001)

Review of 5 reserve sites where kangaroos have become overabundant and the control methods adopted. The negative impacts of high kangaroo density include threats to humans, depression of threatened species, decline in body condition of kangaroos, and altered grazing equilibria. Population density has been reduced by culling at all sites, supplemented by fertility control at 3 sites.

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Spatial patterns of kangaroo density across the South Australian pastoral zone over 26 years: aggregation during drought and suggestions of long distance movement

(Pople, et al., 2007)

This research went beyond the usual focus of wildlife surveys that estimate population size by using spatial analysis techniques to explore the spatial patterns of density of red and western grey kangaroos over a 26 year period in an area exceeding 200 000km² in South Australia.  The research found considerable year-to-year variation in the spatial patterns of kangaroo density which were too high to be explained by vital rates alone, implying immigration from surrounding areas.  “These large shifts in distribution were occasionally to areas that had received better rainfall than the surrounding areas.” The research shows that the Kriged density surface approach allowed improved estimations of kangaroo density, especially on individual properties and also validated that the current divisions for harvest management were appropriate.

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Native vertebrate herbivores facilitate native plant dominance in old fields while preventing native tree invasion – implications for threatened species

(Ingram & Kirkpatrick, 2013)

In a world in which reconstruction of the ‘natural’ does not necessarily result in the best outcomes for biodiversity, it is important to consider the implications of management change on faunal populations in protected areas, and on the future of the species that are most in need of protecting. On the old fields of Maria Island National Park, Tasmania we use vegetation data from exclosure plots and adjacent controls to reveal that current populations of native vertebrate herbivores prevent tree and shrub invasion of marsupial lawns and reduce the abundance of introduced plants. This maintenance of marsupial lawns may be less effective after an insurance population of the endangered marsupial carnivore, the Tasmanian Devil Sarcophilus harrisii, is introduced to the island. Native vertebrate herbivores represent potential prey for the devils, impacting on grazing regimes and plant succession. Vegetation change is most likely to favour two threatened bird species, while reducing the prospects for the threatened Tasmanian Devil and potentially threatened Tasmanian Pademelon Thylogale billardierii.

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An adaptive management case study for managing macropods on Maria Island National Park, Tasmania, Australia: adding devils to the detail

(Ingram, 2018)

Adaptive management is driven by structured decision making and evidence from monitoring in a ‘learning’ framework that guides management actions. In a conservation context, this iterative approach includes evaluation of the impacts on natural processes. On Maria Island National Park, Tasmania, Australia, introduced Forester kangaroo, Bennetts wallaby and Tasmanian pademelon have been intensively managed by an annual cull since 1994. Management actions were triggered by high parasite loads, intense grazing pressure and high juvenile mortality during drought periods. Criticism of the annual cull from animal welfare groups initiated the development of an adaptive management approach for decision making that replaces the historic ‘trial and error’ process. Following a comprehensive review of the existing macropod management program in 2011, an integrated monitoring strategy was established to provide evidence for informed decision making. Assessments of animal health and estimates of population trends are the key indicators for management actions to occur. Maintaining viable macropod populations and protecting natural values form the basis of management objectives. Management actions in each year, for each species, represent ‘treatments’ as spatial replication is not possible at such a small scale. An adaptive management approach for macropod management on Maria Island has resulted in only one species being culled in 2014 and 2015 for the first time in almost 20 years. However the recent introduction of a major predator, the Tasmanian devil, has increased uncertainty for long-term macropod management on Maria Island with no cull occurring in 2016 and 2017.

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The impact of grazing by Eastern Grey Kangaroos (Macropus Giganteus) on vegetation recovery after fire at Reef Hills regional park, Victoria

(Adams & Meers, 2003-2008)

In southeastern Australia ecological burning is frequently used to maintain a number of plant and animal populations. However, many of these prescribed fires are small, and may focus intense grazing activity on new regrowth. At Reef Hills Regional Park, Victoria shrub species have senesced, presumably due to the absence of fire. Ecological burning may be necessary to promote regeneration, however, the population density of the Eastern Grey Kangaroo (Macropus giganteus) is high (approx 38 per km2), and grazing pressure presents a significant risk to postfire vegetation recovery. An assessment of grazing patterns and their effects on postfire recovery was carried out at Reef Hills Regional Park through grazing exclusion plots. Preferential grazing by Eastern Grey Kangaroos occurred on small burnt plots compared to adjacent unburnt areas as determined by faecal pellet counts. On burnt areas, there was a significant reduction in shrub diversity on grazed plots compared to ungrazed plots. Most observations of kangaroos were of animals grazing on farmland surrounding the Park, and it is likely that any burning might shift grazing from farmland to burnt areas when new growth occurs. This needs to be considered before any ecological burn plan is applied to manage vegetation communities, particularly if the plan requires small areas to be burnt. We recommended that a large area up to 200 ha area be burnt and monitored to determine whether burning larger areas disperses grazing pressure from macropods to a level where impacts on vegetation are reduced and localized plant extinctions do not occur.

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What does it take to do successful adaptive management? A case study highlighting Coastal Grassy Woodland restoration at Yanakie Isthmus

(Morgan, et al., 2018)

This case study illustrates the steps necessary to deliver a complex, long-term adaptive management project involving a range of stakeholders at a landscape scale.  Perspectives of the land manager, scientist and volunteer help to convey successes and lessons learned.

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Vegetation responses to stratified kangaroo grazing pressure at Hattah-Kulkyne National Park, 1992-96

(Sluiter, Allen, Morgan, & Walker, 1997)

Many landscapes worldwide are degraded. Restoration ecology offers a variety of tools to enable managers to restore valued processes to landscapes. One such tool is state-and-transition (S-T) modelling, which provides a way to summarise knowledge of vegetation dynamics, tools for restoration and the impact of restoration activities. A theoretical S-T framework was developed and used to organise the history of degradation and restoration in the semi-arid woodlands of Hattah Kulkyne National Park, north-west Victoria. This process highlighted four main opportunities to enhance restoration success including: exploring where, when and why natural recruitment of key species was occurring, utilising the artificial stimulation of root suckers as an alternative tool to enhance the regeneration of desirable species, understanding and developing techniques to enable regenerating or partially restored woodlands to move to the desirable state of a self-perpetuating, restored woodland and a need to monitor and manage the threat posed by emerging weeds.

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Town roo, country roo: a comparison of behaviour in eastern grey kangaroos (Macropus giganteus) in developed and natural landscapes

(Green-Barber & Old, 2018)

Many species have adapted their behaviour to survive in anthropogenically developed environments (hereafter referred to as developed). Eastern grey kangaroos Macropus giganteus are common in developed areas, however very few studies have evaluated their behavioural adaptations to developed landscapes. This study compared the behaviour of eastern grey kangaroos in a developed environment to those surrounded by a natural environment. i Knowledge of the behavioural differences of kangaroos in developed areas will assist in designing management strategies.

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Water use and the thermoregulatory behaviour of kangaroos in arid regions: insights into the colonisation of arid rangelands in Australia by the Eastern Grey Kangaroo (Macropus giganteus)

(Dawson, McTavish, Munn, & Holloway, 2005)

The Eastern Grey Kangaroo (Macropus giganteus) occurs mostly in the wetter regions of eastern Australia. However, in the past 30-40 years it has moved into more arid regions (rainfall < 250 mm), thus increasing its overlap zone with the xeric adapted Red Kangaroo (Macropus rufus). An increased access to water (supplied for domestic stock) may explain this range extension, but changes in the availability of preferred feed could also be involved. The water use, drinking patterns and thermoregulatory behaviour of these two species of kangaroo have been examined in a semi-free range study, during summer at an arid rangeland site. Foraging was largely nocturnal in both species and during the day they behaved to reduce heat loads.

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Vegetation change, erosion risk and land management on the Nullarbor Plain, Australia

(Gillieson, Wallbrink, & Cochrane, 1996)

Arid karst landscapes that have been degraded by human activities provide a challenge for rehabilitation and an opportunity to test ideas about the stability and resilience of limestone ecosystems. The Nullarbor Plain is the largest arid karst area in Australia (220 000 km2) and is divided into extensive closed karstic depressions separated by low rocky ridges, while the dominant vegetation is chenopod shrubland. Since European settlement there has been considerable change in the vegetation, with significant reduction in shrub and grass cover over large areas of the plain. These changes are related to a state and transition model of vegetation dynamics which incorporates climatic variability, fire history and grazing pressure from sheep, kangaroos and rabbits.

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Are the faecal pellets of kangaroos (Macropus spp.) a source of nutrients and carbon in an inland floodplain wetland during flooding? A preliminary experimental inundation study in the Macquarie Marshes, New South Wales

(Kobayashi, Iles, & Knowles, 2011)

Kangaroos (Macropus spp.) are one of the most abundant native macrofauna on Australian floodplains with a positive relationship between their density and the deposition of faecal pellets that contain nutrients and carbon. This project tested whether kangaroo faecal pellets are a source of nutrients and carbon during flooding in the Macquarie Marshes, an inland floodplain wetland, in south-eastern Australia. Nutrient and carbon depositions to floodplains in the form of faecal pellets from large terrestrial animals such as kangaroos are an important process of cycling these elements in inland floodplain wetlands, especially where large populations of these animals occur.

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Disentangling chronic regeneration failure in endangered woodland ecosystems

(Bennett, Duncan, Rumpff, & Vesk, 2020)

Ecological restoration of degraded ecosystems requires the facilitation of natural regeneration by plants, often augmented by large-scale active revegetation. The success of such projects is highly variable. Risk factors may be readily identifiable in a general sense, but it is rarely clear how they play out individually, or in combination. We addressed this problem with a field experiment on the survival of, and browsing damage to, 1275 hand-planted buloke (Allocasuarina luehmannii) seedlings in a nationally endangered, semi-arid woodland community.

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Can threatened species survive where the top predator is absent?

(Wallach, Murray, & O’Neill, 2008)

Top predators have been described as highly interactive keystone species. Their decline has been linked to secondary extinctions and their increase has been linked to ecological restoration. Several authors have recently argued that the dingo Canis lupus dingo is another example of a top predator that maintains mesopredators and generalist herbivores at low and stable numbers, thereby increasing biodiversity and productivity. Due to the sensitivity of many Australian species to introduced mesopredators and herbivores, the top predator hypothesis predicts that threatened species will not survive where dingoes are rare or absent. However, several threatened species have survived inside the Dingo Barrier Fence (DBF). We present a new view on the survival of the yellow-footed rock-wallaby Petrogale xanthopus xanthopus and the malleefowl Leipoa ocellata inside the DBF where the dingo is considered very rare, or in areas where the dingo is believed to have been eradicated several decades ago.

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Novel trophic cascades: apex predators enable coexistence

(Wallach, Ripple, & Carroll, 2015)

Novel assemblages of native and introduced species characterize a growing proportion of ecosystems worldwide. Some introduced species have contributed to extinctions, even extinction waves, spurring widespread efforts to eradicate or control them. We propose that trophic cascade theory offers insights into why introduced species sometimes become harmful, but in other cases stably coexist with natives and offer net benefits. Large predators commonly limit populations of potentially irruptive prey and mesopredators, both native and introduced. This top-down force influences a wide range of ecosystem processes that often enhance biodiversity. We argue that many species, regardless of their origin or priors, are allies for the retention and restoration of biodiversity in top-down regulated ecosystems.

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Fire and grazing influence food resources of an endangered rock-wallaby

(Tuft, Crowther, & McArthur, 2012)

Fire and grazing have complex and interacting impacts on food resources available to endangered herbivores and can potentially be manipulated as part of conservation strategies. Aims. We examined the interacting impacts of fire and grazing on the food resources available to a colony of endangered brush-tailed rock-wallabies (Petrogale penicillata) to test fire as a potential management tool. Methods. We conducted two manipulative experiments using a repeated-measures split-block design. We measured the effects of grazing and strategic burning on total vegetation biomass and on particular plants selected by rock-wallabies.

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Foraging behaviour and dispersion of eastern grey kangaroos (Macropus giganteus) in an ideal free framework

(Maguire, Ramp, & Coulson, 20016)

Ideal free distribution (IFD) theory predicts that animals in competitive situations should distribute themselves among available habitat patches according to the density of conspecifics and its regulatory effect on resources. To investigate the applicability of IFD models to free-ranging herbivores, we quantified the disper-sion and foraging behaviour of eastern grey kangaroos Macropus giganteus among habitat patches of differing suitability, within and outside a reservoir catchment in southern Victoria, Australia. Kangaroo densities within the catchment had a regulatory effect on resource density, while surrounding farmland maintained a higher standing crop despite higher densities of competitors.

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Large herbivore distribution and abundance: intra and interspecific niche variation in the tropics

(Ritchie, et al., 2008)

Determining the biological and environmental factors that limit the distribution and abundance of organisms is central to our understanding of the niche concept and crucial for predicting how species may respond to large-scale environmental change, such as global warming. However, detailed ecological information for the majority of species has been collected only at a local scale, and insufficient consideration has been given to geographical variation in intraspecific niche requirements. To evaluate the influence of environmental and biological factors on patterns of species distribution and abundance, we conducted a detailed, broadscale study across the tropical savannas of northern Australia on the ecology of three large, sympatric marsupial herbivores (family Macropodidae): the antilopine wallaroo (Macropus antilopinus), common wallaroo (M. robustus), and eastern grey kangaroo (M. giganteus).

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Macroecological patterns in mammal abundances provide evidence that an apex predator shapes forest ecosystems by suppressing herbivore and mesopredator abundance

(Colman, Crowther, & Letnic, 2015)

Apex predators often exert strong, top‐down effects on ecosystems, and their removal can result in the dramatic reorganization of ecosystems owing to herbivores and smaller predators becoming the dominant trophic‐regulating species. However, field studies designed to understand the influence that apex predators have on ecosystems are hampered by the large spatial and temporal scales required. Here, we use pre‐existing datasets to test predictions on the direct and indirect effects of apex predators on mammals and vegetation generated from trophic cascade theory and the mesopredator release hypothesis.

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Mammals of particular conservation concern in the Western Division of New South Wales

(Dickman, Pressey, Lim, & Parnaby, 1996)

The Western Division of New South Wales is an administrative region of 325 000 km2 on the eastern fringe of the Australian arid zone. Since European settlement in 1788, 71 species of native mammals have been recorded in the Division, seven more have been documented only as subfossils, and a further 15 species occur within 100 km of the Divisional boundary. At least 27 of the original species have become regionally extinct, and a further 11 have declined in distribution. As in other regions of Australia, species losses have been greatest for rodents and marsupials in a critical weight range of 35–5500 g, and least for bats. However, percentage losses among the terrestrial fauna are high relative to other regions, and probably reflect both the early settlement of New South Wales and the marginal distribution in the Division of 49% of the original fauna. Feral cats are implicated in the regional extinction of up to ten species of native mammals prior to 1857.

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National Recovery Plan for the Brush-tailed Rock-wallaby Petrogale penicillate

(Menkhorst & Hynes, 2011)

The Brush-tailed Rock-wallaby (Petrogale penicillata) is a medium-sized marsupial macropod that was formerly widely distributed in south-eastern Australia, from south-eastern Queensland through eastern and central New South Wales and the Australian Capital Territory to western Victoria.  It has suffered a widespread decline in range and abundance, with a major range contraction and local extinctions in many areas, especially in the south and west of its distribution.  The species now survives mostly on isolated rocky escarpments along the Great Dividing Range from south-eastern Queensland through eastern New South Wales to eastern Victoria.  Historical and current threats include hunting, predation, habitat loss, competition with other species and loss of genetic diversity.  The Brush-tailed Rock-wallaby is listed as Vulnerable under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999.  It is also listed as Vulnerable under the Queensland Nature Conservation Act 1992, Endangered under the New South Wales Threatened Species Conservation Act 1995, Endangered under the Australian Capital Territory Nature Conservation Act 1980, and Threatened under the Victorian Flora and Fauna Guarantee Act 1988.  This Recovery Plan for the Brush-tailed Rock-Wallaby is the first national recovery plan for the species, and details its distribution, habitat, threats and recovery objectives and actions necessary to ensure its long-term survival.

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Is the removal of domestic stock sufficient to restore semi-arid conservation areas?

(Page & Beeton, 2000)

Increasingly, conservation areas are proclaimed in non-pristine environments that have biodiversity values and the issue of how to change the management regime to restore such landscapes arises. Before gazettal in 1992, Currawinya National Park (28°52’S, 144°30’E) in south-west Queensland’s mulga lands was grazed by domestic stock for over 130 years. Following gazettal, the area was destocked and a monitoring programme initiated to determine the response by the vegetation. This paper describes the grass dynamics in three vegetation communities on Currawinya National Park with three different grazing regimes. Data are presented for an on-park site (native and feral herbivores present), an off-park site (domestic, native and feral herbivores were present), and an exclosure (no mammalian herbivores present). The results show that removal of domestic livestock alone is not sufficient to promote rapid recovery of grass populations and suggest that conservation area managers must reduce native herbivore numbers as well if the desired outcome is a return to the supposed “natural” condition.

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Predation risk and competitive interactions affect foraging of an endangered refuge-dependent herbivore

(Tuft K. D., Crowther, Connell, Muller, & McArthur, 2011)

Predators can have non-lethal effects on prey by causing animals to restrict their foraging in order to avoid predation risk. These effects can be of conservation concern when an introduced predator constrains the foraging behaviour of a threatened species, and therefore its access to resources. We examined the spatial response of foraging in endangered brush-tailed rock-wallabies to predation risk and food while taking into account the potentially competitive role of sympatric herbivores.

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Resolving the value of the dingo in ecological restoration

(Newsome, et al., 2015)

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?’

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Resource pulses and mammalian dynamics: conceptual models for hummock grasslands and other Australia desert habitats

(Letnic & Dickman, 2009)

Resources are produced in pulses in many terrestrial environments, and have important effects on the population dynamics and assemblage structure of animals that consume them. Resource-pulsing is particularly dramatic in Australian desert environments owing to marked spatial and temporal variability in rainfall, and thus primary productivity. Here, we first review how Australia’s desert mammals respond to fluctuations in resource production, and evaluate the merits of three currently accepted models (the ecological refuge, predator refuge and fire-mosaic models) as explanations of the observed dynamics. We then integrate elements of these models into a novel state-and-transition model and apply it to well-studied small mammal assemblages that inhabit the vast hummock grassland, or spinifex, landscapes of the continental inland.

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Eating away at protected areas Total grazing pressure is undermining public land conservation

(Prowse T. A., O’Connor, Collard, & Rogers, 2019)

Protected areas are critical for the long-term conservation of biodiversity globally. Across agricultural landscapes, protected areas serve as refuges for threatened and declining species and provide valuable ecosystem services that support broader landscape function. However, increasing pressure on protected areas from a range of sources is undermining their unique conservation values. Much of the native vegetation remaining in southern Australia is now protected from broad-scale clearing, but the management of threats within these areas could be inadequate to maintain their biodiversity. In particular, grazing by domestic and wild mammalian herbivores can have a significant impact on the condition of remnant native vegetation, even if it is formally protected. We evaluated the evidence for grazing-pressure trends in native vegetation in both protected and unprotected areas across an agricultural landscape covering c. 180 000 km2 of South Australia.

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Stemming the tide: progress towards resolving the causes of decline and implementing management responses for the disappearing mammal fauna of northern Australia

(Ziembicki, et al., 2015)

Recent studies at sites in northern Australia have reported severe and rapid decline of several native mammal species, notwithstanding an environmental context (small human population size, limited habitat loss, substantial reservation extent) that should provide relative conservation security. All of the more speciose taxonomic groups of mammals in northern Australia have some species for which their conservation status has been assessed as threatened, with 53 % of dasyurid, 47 % of macropod and potoroid, 33 % of bandicoot and bilby, 33 % of possum, 30 % of rodent, and 24 % of bat species being assessed as extinct, threatened or near threatened. However, the geographical extent and timing of declines, and their causes, remain poorly resolved, limiting the application of remedial management actions.

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Trophic cascades and dingoes in Australia: Does the Yellowstone wolf-elk-willow model apply?

(Morgan, Hunter, Ballard, Reid, & Fleming, 2016)

Wolves are widely regarded as top-down regulators of prey and trophic cascades in North America. Consequent expectations of biodiversity benefits from canid-driven trophic cascades have driven debate around reintroduction plans for dingoes in south-eastern Australia. The biophysical characteristics of Yellowstone National park predispose that environment to trophic cascades but it is not clear that Australia provides a comparative context for dingoes. The wolf–elk–willow trophic cascade in Yellowstone National Park provides a key case study for understanding the broader system controls on trophic interactions. Here, we compare similarities and dissimilarities of the Yellowstone National Park model and the south-eastern Australian environments where dingo reintroductions have been proposed.

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Top predators as biodiversity regulators: the dingo Canis lupus dingo as a case study

(Letnic, Ritchie, & Dickman, 2012)

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.

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Predation by red foxes limits recruitment in populations of eastern grey kangaroos

(Banks, Newsome, & Dickman, 2000)

We investigated the impact of red fox (Vulpes vulpes Linnaeus 1758) predation on juvenile eastern grey kangaroos (Macropus giganteus Shaw 1790) using a replicated predator removal experiment. In two sites in Namadgi National Park, south-eastern Australia, a persistent 1080 poisoning campaign over 18 months reduced fox density by more than 85%, and to less than 10% of the fox density in two other sites with no fox baiting. Changes in the mother : young ratios and densities of kangaroo populations were monitored twice monthly along 2-km transects in each site from July 1993 to February 1995. Compared to nonremoval sites, where foxes were controlled, 25–40% more females retained juveniles over the period when these young became emergent from the pouch. This higher survival of emergent pouch young resulted in a significantly higher proportion of juveniles in kangaroo populations at fox control sites, which resulted in a significantly higher annual growth rate. We conclude that predation upon juveniles is an important limiting factor for kangaroo populations in Namadgi NP

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Linking modelling, monitoring and management: an integrated approach to controlling overabundant wildlife

(Chee & Wintle, 2010)

Overabundant wildlife can cause economic and ecological damage. Therefore population control typically seeks to maintain species’ abundance within desired control limits. Efficient control requires targets, methods for estimating population size before and after control, and reliable means of forecasting population size. Demographic stochasticity, environmental variability and model uncertainty complicate these tasks. Monitoring provides critical feedback in the control process, yet examples of integrated monitoring and management are scarce. Synthesis and applications. We provide a general and flexible framework for integrated monitoring and culling when the objective is to keep a species’ abundance within control limits. Our framework explicitly deals with uncertainty arising from demographic stochasticity, ecological complexity and lack of knowledge, and provides the foundation for maximizing efficiency and cost‐effectiveness of control operations. Our approach could be applied in any instances where control is effected via culling.

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