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Dr Arian Wallach


My research investigates the ecological role of large predators on biodiversity and functioning of novel ecosystems. My fieldwork is mainly conducted across the Australian arid zone, where I am researching the influence of dingoes on biodiversity and native-non-native coexistence.

My research has challenged established paradigms on the cause and treatment of biodiversity decline in Australia, by showing that protecting dingoes enables species to thrive in modern ecosystems, and that lethal control of introduced species is both unnecessary and counterproductive.

My work on predators featured in the journals Nature and Science, and together with a collaborative research team has been awarded the 2013 Eureka Prize for Environmental Research.

I co-founded the Dingo for Biodiversity Project, an initiative that brings scientists and landholders together to transition to predator-friendly practices. The project has helped establish three large-scale dingo recovery programs in collaboration with the indigenous custodians and pastoral landowners.

During 2012-2014 I co-managed Evelyn Downs, a predator-friendly cattle station in northern SA. In 2014 I was awarded a Churchill Fellowship and travelled to Israel, India, southern Africa and North America to investigate the ecological effects of losing and recovering the Earth's largest predators. Since 2015 I have been based at the UTS Centre for Compassionate Conservation.

Image of Arian Wallach
Chancellor's Postdoctoral Research Fellow, School of Life Sciences
Member, Centre for Compassionate Conservation

Research Interests

Trophic cascades: large predators and their role as top-down regulators of ecosystems

Novel ecosystems: Evolutionary and ecological drivers that enable coexistence between native and non native species

Social stability: The influence of predator sociality and behavior on their ecological functioning

Biotic globalization: Conservation values of species outside their historic range

Compassionate conservation: promoting coexistence with wildlife in conservation and farming

Can supervise: Yes


Wallach, A. 2014, 'Strongly interactive carnivore species: maintaining and restoring ecosystem function' in Glen Alistair & Dickman Christopher (eds), Carnivores of Australia: Past, Present and Future, CSIRO, pp. 301-322.
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Journal articles

Wallach, A.D., Dekker, A.H., Lurgi, M., Montoya, J.M., Fordham, D.A. & Ritchie, E.G. 2017, 'Trophic cascades in 3D: network analysis reveals how apex predators structure ecosystems', Methods in Ecology and Evolution, vol. 8, no. 1.
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The role of apex predators as ecosystem regulators is now firmly embedded in ecological theory, suggesting that the world is green and biologically diverse in large part because predators suppress herbivore densities (Hairston, Smith & Slobodkin 1960; Estes et al. 2011; Ripple et al. 2014). Studies from across the globe show that apex predators limit the abundance and modify the behaviour of their prey and smaller mesopredators, suppressing grazing and predation pressure, and enhancing biodiversity and productivity (Ritchie & Johnson 2009; Ritchie et al. 2012). This top-down forcing cascades throughout ecosystems influencing a broad range of processes, both biotic and abiotic, including species abundances and richness, animal behaviour, disease dynamics, carbon sequestration and stream morphology (Estes et al. 2011; Ripple et al. 2014; Atwood et al. 2015). The rise and fall of apex predators not only affects the composition of species within ecological communities therefore, but also ecosystem functioning (Estes et al. 2011; Ripple et al. 2014; Standish et al. 2014). For example, wolves (Canis lupus) provide critical resource subsidies to scavenging species during warm months, thus enhancing their resilience to shortening winters due to global warming (Wilmers & Getz 2005). Similarly, dingoes (C. dingo) stabilize herbivore prey densities by dampening their population responses to rainfall in arid environments, thereby enabling plant biomass to accumulate during brief wet seasons (Letnic & Crowther 2013).
Wallach, A., Ramp, D. & O'Neill, A.J. 2017, 'Cattle mortality on a predator-friendly station in central Australia', Journal of Mammology, vol. 98, no. 1, pp. 45-52.
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Large predators are declining worldwide primarily due to hunting and persecution by humans, driven in large part by the livestock industry. Some ranchers are transitioning to 'predator-friendly farming by adopting nonlethal predator deterrents. On very large rangeland properties, such as the vast stations of the Australian arid zone, ending lethal control may in itself reduce livestock losses by enabling the predator's social structure to stabilize. The dingo (Canis dingo), Australia's apex predator, is commonly subjected to eradication campaigns to protect livestock. We analyzed causes of cattle (Bos taurus) deaths on Evelyn Downs, a 2,300-km2 predator-friendly station in central Australia, for 2 years after dingo protection was established. Husbandry-related challenges, associated with deteriorating environmental conditions, were the leading causes of deaths of cattle. Predation by dingoes was minor and declined as the indices of dingo abundance stabilized and social stability increased. Shifting from killing predators to improving husbandry standards is likely to improve livestock survival and welfare.
Johnson, C.N. & Wallach, A.D. 2016, 'The virtuous circle: predator-friendly farming and ecological restoration in Australia', Restoration Ecology, vol. 24, no. 6, pp. 821-826.
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Ripple, W.J., Abernethy, K., Betts, M.G., Chapron, G., Dirzo, R., Galetti, M., Levi, T., Lindsey, P.A., Macdonald, D.W., Machovina, B., Newsome, T.M., Peres, C.A., Wallach, A.D., Wolf, C. & Young, H. 2016, 'Bushmeat hunting and extinction risk to the world's mammals', Royal Society Open Science, vol. 3, no. 10, pp. 160498-160498.
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Ripple, W.J., Chapron, G., López-Bao, J.V., Durant, S.M., Macdonald, D.W., Lindsey, P.A., Bennett, E.L., Beschta, R.L., Bruskotter, J.T., Campos-Arceiz, A., Corlett, R.T., Darimont, C.T., Dickman, A.J., Dirzo, R., Dublin, H.T., Estes, J.A., Everatt, K.T., Galetti, M., Goswami, V.R., Hayward, M.W., Hedges, S., Hoffmann, M., Hunter, L.T.B., Kerley, G.I.H., Letnic, M., Levi, T., Maisels, F., Morrison, J.C., Nelson, M.P., Newsome, T.M., Painter, L., Pringle, R.M., Sandom, C.J., Terborgh, J., Treves, A., Van Valkenburgh, B., Vucetich, J.A., Wirsing, A.J., Wallach, A.D., Wolf, C., Woodroffe, R., Young, H. & Zhang, L. 2016, 'Saving the World's Terrestrial Megafauna', Bioscience, vol. 66, no. 10, pp. 807-812.
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Wallach, A.D., Bekoff, M., Nelson, M.P. & Ramp, D. 2015, 'Promoting predators and compassionate conservation', Conservation Biology, vol. 29, no. 5, pp. 1481-1484.
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Wallach, A.D., Izhaki, I., Toms, J.D., Ripple, W.J. & Shanas, U. 2015, 'What is an apex predator?', Oikos, vol. 124, no. 11, pp. 1453-1461.
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© 2015 Nordic Society Oikos. Large 'apex' predators influence ecosystems in profound ways, by limiting the density of their prey and controlling smaller 'mesopredators'. The loss of apex predators from much of their range has lead to a global outbreak of mesopredators, a process known as 'mesopredator release' that increases predation pressure and diminishes biodiversity. While the classifications apex- and meso-predator are fundamental to current ecological thinking, their definition has remained ambiguous. Trophic cascades theory has shown the importance of predation as a limit to population size for a variety of taxa (top-down control). The largest of predators however are unlikely to be limited in this fashion, and their densities are commonly assumed to be determined by the availability of their prey (bottom-up control). However, bottom-up regulation of apex predators is contradicted by many studies, particularly of non-hunted populations. We offer an alternative view that apex predators are distinguishable by a capacity to limit their own population densities (self-regulation). We tested this idea using a set of life-history traits that could contribute to self-regulation in the Carnivora, and found that an upper limit body mass of 34 kg (corresponding with an average mass of 13-16 kg) marks a transition between extrinsically- and self-regulated carnivores. Small carnivores share fast reproductive rates and development and higher densities. Large carnivores share slow reproductive rates and development, extended parental care, sparsely populated territories, and a propensity towards infanticide, reproductive suppression, alloparental care and cooperative hunting. We discuss how the expression of traits that contribute to self-regulation (e.g. reproductive suppression) depends on social stability, and highlight the importance of studying predator-prey dynamics in the absence of predator persecution. Self-regulation in large carnivores may ensure that the lar...
Newsome, T.M., Ballard, G.A., Crowther, M.S., Dellinger, J.A., Fleming, P.J.S., Glen, A.S., Greenville, A.C., Johnson, C.N., Letnic, M., Moseby, K.E., Nimmo, D.G., Nelson, M.P., Read, J.L., Ripple, W.J., Ritchie, E.G., Shores, C.R., Wallach, A.D., Wirsing, A.J. & Dickman, C.R. 2015, 'Resolving the value of the dingo in ecological restoration', Restoration Ecology, vol. 23, no. 3, pp. 201-208.
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© 2015 Society for Ecological Restoration. 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.
Wallach, A.D., Ripple, W.J. & Carroll, S.P. 2015, 'Novel trophic cascades: apex predators enable coexistence.', Trends in ecology & evolution, vol. 30, no. 3, pp. 146-153.
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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.
Johnson, C.N., Crowther, M.S., Dickman, C.R., Letnic, M.I., Newsome, T.M., Nimmo, D.G., Ritchie, E.G. & Wallach, A.D. 2014, 'Experiments in no-impact control of dingoes: Comment on Allen et al. 2013', Frontiers in Zoology, vol. 11, no. 1.
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There has been much recent debate in Australia over whether lethal control of dingoes incurs environmental costs, particularly by allowing increase of populations of mesopredators such as red foxes and feral cats. Allen et al. (2013) claim to show in their recent study that suppression of dingo activity by poison baiting does not lead to mesopredator release, because mesopredators are also suppressed by poisoning. We show that this claim is not supported by the data and analysis reported in Allen et al.'s paper. © 2014 Johnson et al.; licensee BioMed Central Ltd.
Ripple, W.J., Estes, J.A., Beschta, R.L., Wilmers, C.C., Ritchie, E.G., Hebblewhite, M., Berger, J., Elmhagen, B., Letnic, M., Nelson, M.P., Schmitz, O.J., Smith, D.W., Wallach, A.D. & Wirsing, A.J. 2014, 'Status and ecological effects of the world's largest carnivores.', Science (New York, N.Y.), vol. 343, no. 6167, p. 1241484.
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Large carnivores face serious threats and are experiencing massive declines in their populations and geographic ranges around the world. We highlight how these threats have affected the conservation status and ecological functioning of the 31 largest mammalian carnivores on Earth. Consistent with theory, empirical studies increasingly show that large carnivores have substantial effects on the structure and function of diverse ecosystems. Significant cascading trophic interactions, mediated by their prey or sympatric mesopredators, arise when some of these carnivores are extirpated from or repatriated to ecosystems. Unexpected effects of trophic cascades on various taxa and processes include changes to bird, mammal, invertebrate, and herpetofauna abundance or richness; subsidies to scavengers; altered disease dynamics; carbon sequestration; modified stream morphology; and crop damage. Promoting tolerance and coexistence with large carnivores is a crucial societal challenge that will ultimately determine the fate of Earth's largest carnivores and all that depends upon them, including humans.
Keysary, A., Eremeeva, M.E., Leitner, M., Din, A.B., Wikswo, M.E., Mumcuoglu, K.Y., Inbar, M., Wallach, A.D., Shanas, U., King, R. & Waner, T. 2011, 'Spotted Fever Group Rickettsiae in Ticks Collected from Wild Animals in Israel', American Journal of Tropical Medicine and Hygiene, vol. 85, no. 5, pp. 919-923.
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Wallach, A.D., Johnson, C.N., Ritchie, E.G. & O'Neill, A.J. 2010, 'Predator control promotes invasive dominated ecological states.', Ecology letters, vol. 13, no. 8, pp. 1008-1018.
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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.
Wallach, A.D., Shanas, U. & Inbar, M. 2010, 'Feeding activity and dietary composition of roe deer at the southern edge of their range', European Journal of Wildlife Research, vol. 56, no. 1, pp. 1-9.
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We studied feeding activity and dietary components of hand-reared European roe deer (Capreolus capreolus) in Israel. Our ultimate goal was to assess habitat suitability for future reintroduction of the species, which has been locally extinct for nearly a century. Activity patterns, diet composition, and body mass of four does were monitored in two (fenced) typical east Mediterranean habitats: mature forest and scrubland recovering from fire. Food supplements were provided between trials. Throughout the year, the deer exhibited diurnal and nocturnal activity, mostly at dawn and dusk. Diet composition varied considerably between seasons and habitats, demonstrating the opportunistic flexibility of the deer. In both habitats, the deer fed on over 85% of the plant species but preferred a particular plant species or parts. In summer and early autumn, fruits and seeds became the dominant portion of their diet. In our semi-natural experimental setup, deer maintained body mass through the winter and spring. Weight loss occurred as the dry season advanced, but the animals rapidly regained mass when annuals and grasses became available following the first rains. In the east Mediterranean habitats, water availability seems more problematic for deer survival than food availability. © Springer-Verlag 2009.
Wallach, A., Murray, B. & O'neill, A. 2009, 'Can threatened species survive where the top predator is absent?', Biological Conservation, vol. 142, no. 1, pp. 43-52.
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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. We found that dingoes co-occurred with both threatened species. Dingoes were present at all wallaby colonies surveyed and occurred throughout their range. The most common predator detected in areas inhabited by the wallabies was in fact the dingo, and we found no significant difference between dingo abundance inside compared to outside the DBF. Malleefowl nests were found to be scent marked by dingoes at the three sites that we surveyed, despite these sites being close to human settlement and sheep farms, and in small and fragmented patches of wilderness. These findings provide further evidence for an association between the presence of dingoes and the survival of threatened species, which is in agreement with the top predator hypothesis.
Wallach, A.D. & O'neill, A.J. 2009, 'Artificial water points: Hotspots of extinction or biodiversity?', Biological Conservation, vol. 142, no. 7, pp. 1253-1254.
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Wallach, A.D., Ritchie, E.G., Read, J. & O'Neill, A.J. 2009, 'More than mere numbers: the impact of lethal control on the social stability of a top-order predator.', PloS one, vol. 4, no. 9, p. e6861.
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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.
Wallach, A., Inbar, M. & Shanas, U. 2009, 'Roe deer and decapitated Anemone flowers', Israel Journal of Plant Sciences, vol. 57, no. 1-2, pp. 103-106.
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The roe deer (Capreolus capreolus) has been locally extinct from the East Mediterranean since the beginning of the 20th century. A reintroduction program has been initiated in Israel where several deer have been released in the southern Carmel Mountains. The diet of roe deer is markedly different from that of other local ungulates. Their unique dietary preference for the generally unpalatable geophyte Anemone coronaria is especially notable. They typically consume anemone by "decapitating" the flowers, leaving the rest of the stem intact. We studied the consumption rate of anemone in four hand-reared deer in the Hai Bar Nature Reserve. During the flowering season, each deer consumed 65.5 ± 13.13 and 37.6 ± 13.85 anemone flowers/day in 2003 and 2004, respectively. These results indicate that roe deer may have a profound influence on anemone populations. Being secretive and flighty animals, roe deer are hard to detect. A preliminary survey conducted in Ramat HaNadiv Park, where a roe deer population of an unknown size exists, suggested that with proper calibration, the typical, easy-to-detect decapitated anemone flower might be used for monitoring roe deer presence and density. © 2009 Science From Israel/LPPLtd., Jerusalem.
Wallach, A.D. & O'Neill, A.J. 2009, 'Threatened species indicate hot-spots of top-down regulation', Animal Biodiversity and Conservation, vol. 32, no. 2, pp. 127-133.
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Wallach, A.D., Shanas, U., Mumcuoglu, K.Y. & Inbar, M. 2008, 'Ectoparasites on Reintroduced Roe Deer Capreolus capreolus in Israel', Journal of Wildlife Diseases, vol. 44, no. 3, pp. 693-696.
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Wallach, A.D., Inbar, M., Scantlebury, M., Speakman, J.R. & Shanas, U. 2007, 'Water requirements as a bottleneck in the reintroduction of European roe deer to the southern edge of its range', Canadian Journal of Zoology, vol. 85, no. 11, pp. 1182-1192.
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Success rates of reintroduction programs are low, often owing to a lack of knowledge of site-specific ecological requirements. A reintroduction program of European roe deer (Capreolus capreolus (L., 1758)) in a dry Mediterranean region in Israel provides an opportunity to study the bottleneck effect of water requirements on a mesic-adapted species. Four does were hand-reared and released in a 10 ha site consisting of an early succession scrub land and a mature oak forest. We measured daily energy expenditure (DEE) and water turnover (WTO) using the doubly labeled water technique during summer and winter. DEE was similar in the summer and winter, but there was a significant difference in WTO and in the source of gained water. In winter, WTO was 3.3 L/day, of which 67% was obtained from vegetation. In summer, WTO dropped to 2.1 L/day, of which only 20% was obtained from the diet and 76% was gained from drinking. When the water source was moved to a nonpreferred habitat, drinking frequency dropped significantly, but water consumption remained constant. In a dry Mediterranean environment, availability of free water is both a physiological contraint and a behavioral constraint for roe deer. This study demonstrates the importance of physiological and behavioral feasibility studies for reintroduction programs. © 2007 NRC.
WALLACH, A., INBAR, M., LAMBERT, R., COHEN, S. & SHANAS, U. 2007, 'Hand-rearing Roe deer: practice and research potential', International Zoo Yearbook, vol. 41, no. 1, pp. 183-193.
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Keysary, A., Massung, R.F., Inbar, M., Wallach, A.D., Shanas, U., Mumcuoglu, K.Y. & Waner, T. 2007, 'Molecular evidence for Anaplasma phagocytophilum in Israel', Emerging Infectious Diseases, vol. 13, no. 9, pp. 1411-1412.
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