Category Archives: Research

Managing conflict between large carnivores and livestock

Authors: Lily M Van Eeden, Mathew S Crowther, Chris R Dickman, David W Macdonald, William J Ripple, Euan G Ritchie, and Thomas M Newsome

Published in: Conservation Biology (early view)


Large carnivores are persecuted globally because they threaten human industries and livelihoods. How this conflict is managed has consequences for the conservation of large carnivores and biodiversity more broadly. Mitigating human-predator conflict should be evidence-based and accommodate people’s values while also protecting carnivores.

Despite much research into human-large carnivore coexistence strategies, there have been limited attempts to document the success of conflict mitigation strategies on a global scale.

We present a meta-analysis of global research on conflict mitigation between large carnivores and humans, focusing on conflicts that arise from the threat that large carnivores pose to livestock industries.

Overall, research effort and focus varied between continents, aligning with the different histories and cultures that shaped livestock production and attitudes towards carnivores.

Of the studies that met our criteria, livestock guardian animals were most effective at reducing livestock losses, followed by lethal control, although the latter exhibited the widest variation in success and the two were not significantly different. Financial incentives have promoted tolerance in some settings, reducing retaliatory killings.

In future, coexistence strategies should be location-specific, incorporating cultural values and environmental conditions, and designed such that return on financial investment can be evaluated. Improved monitoring of mitigation measures is urgently required to promote effective evidence-based policy.

Van Eeden LM, Crowther MS, Dickman CR, Macdonald DW, Ripple WJ, Ritchie EG, Newsome TM (2017) Managing conflict between large carnivores and livestock. Conservation Biology, PDF DOI

The global impacts of domestic dogs on threatened vertebrates

Authors: Tim S Doherty, Chris R Dickman, Alistair S Glen, Thomas M Newsome, Dale G Nimmo, Euan G Ritchie, Abi T Vanak, Aaron J Wirsinge

Published in: Biological Conservation, volume 210 (June 2017)


Domestic dogs (Canis familiaris) have a near-global distribution. They range from being feral and free-ranging to owned and completely dependent on humans. All types of domestic dogs can interact with wildlife and have severe negative impacts on biodiversity.

Here, we use IUCN Red List data to quantify the number of threatened species negatively impacted by dogs, assess the prevalence of different types of dog impact, and identify regional hotspots containing high numbers of impacted species. Using this information, we highlight key research and management gaps and priorities.

Domestic dogs have contributed to 11 vertebrate extinctions and are a known or potential threat to at least 188 threatened species worldwide. These estimates are greater than those reported by previous assessments, but are probably conservative due to biases in the species, regions and types of impacts studied and/or reported.

Percentage of extinct or threatened vertebrate species that are, or were, affected by different types of dog impact.

Predation is the most frequently reported impact, followed by disturbance, disease transmission, competition, and hybridisation. Regions with the most species impacted are: South-east Asia, Central America and the Caribbean, South America, Asia (excluding SE), Micro/Mela/Polynesia, and Australia.

We propose that the impacts of domestic dogs can be better understood and managed through: taxonomic and spatial prioritisation of research and management; examining potential synergisms between dogs and other threatening processes; strategic engagement with animal welfare and human health campaigns; community engagement and education; and mitigating anthropogenic effects such as resource subsidies. Such actions are essential for threatened species persistence, especially given that human and dog populations are expected to increase both numerically and geographically in the coming decades.

Doherty TS, Dickman CR, Glen AS, Newsome TM, Nimmo DG, Ritchie EG, Vanak AT, Wirsing AJ (2017) The global impacts of domestic dogs on threatened vertebrates. Biological Conservation, PDF DOI 

Responses of invasive predators and native prey to a prescribed forest fire

Authors: Bronwyn A Hradsky, Craig Mildwaters, Euan G Ritchie, Fiona Christie, and Julian Di Stefano

Published in: Journal of Mammalogy (early view)


Fire shapes biome distribution and community composition worldwide, and is extensively used as a management tool in flammable landscapes. There is growing concern, however, that fire could increase the vulnerability of native fauna to invasive predators.

We developed a conceptual model of the ways in which fire could influence predator–prey dynamics.

Using a before–after, control–impact experiment, we then investigated the short-term effects of a prescribed fire on 2 globally significant invasive mesopredators (red fox, Vulpes vulpes, and feral cat, Felis catus) and their native mammalian prey in a fire-prone forest of southeastern Australia. We deployed motion-sensing cameras to assess species occurrence, collected predator scats to quantify diet and prey choice, and measured vegetation cover before and after fire. We examined the effects of the fire at the scale of the burn block (1,190 ha), and compared burned forest to unburned refuges.

Pre-fire, invasive predators and large native herbivores were more likely to occur at sites with an open understory, whereas the occurrence of most small- and medium-sized native mammals was positively associated with understory cover. Fire reduced understory cover by more than 80%, and resulted in a 5-fold increase in the occurrence of invasive predators. Concurrently, relative consumption of medium-sized native mammals by foxes doubled, and selection of long-nosed bandicoots (Perameles nasuta) and short-beaked echidnas (Tachyglossus aculeatus) by foxes increased. Occurrence of bush rats (Rattus fuscipes) declined. It was unclear if fire also affected the occurrence of bandicoots or echidnas, as changes coincided with normal seasonal variations.

Overall, prescribed fire promoted invasive predators, while disadvantaging their medium-sized native mammalian prey. Further replication and longer-term experiments are needed before these findings can be generalized. Nonetheless, such interactions could pose a serious threat to vulnerable species such as critical weight range mammals. Integrated invasive predator and fire management are recommended to improve biodiversity conservation in flammable ecosystems.

Hradsky BA, Mildwaters C, Ritchie EG, Christie F, Di Stefano J (2017) Responses of invasive predators and native prey to a prescribed forest fire, Journal of Mammalogy PDF DOI

Enumerating a continental-scale threat: How many feral cats are in Australia?

Authors: S Legge, BP Murphy, H McGregor, JCZ Woinarski, J Augusteyn, G Ballard, M Baseler, T Buckmaster, CR Dickman, T Doherty, G Edwards, T Eyre, BA Fancourt, D Ferguson, DM Forsyth, WL Geary, M Gentle, G Gillespie, L Greenwood, R Hohnen, S Hume, CN Johnson, M Maxwell, PJ McDonald, K Morris, K Moseby, T Newsome, D Nimmo, R Paltridge, D Ramsey, J Read, A Rendall, M Rich, E Ritchie, J Rowland, J Short, D Stoked, DR Sutherland, AF Wayne, L Woodford and F Zewe.

Published in: Biological Conservation


Feral cats (Felis catus) have devastated wildlife globally. In Australia, feral cats are implicated in most recent mammal extinctions and continue to threaten native species. Cat control is a high-profile priority for Australian policy, research and management.

To develop the evidence-base to support this priority, we first review information on cat presence/absence on Australian islands and mainland cat-proof exclosures, finding that cats occur across >99.8% of Australia’s land area. Next, we collate 91 site-based feral cat density estimates in Australia and examine the influence of environmental and geographic influences on density.

We extrapolate from this analysis to estimate that the feral cat population in natural environments fluctuates between 1.4 million (95% confidence interval: 1.0–2.3 million) after continent-wide droughts, to 5.6 million (95% CI: 2.5–11 million) after extensive wet periods. We estimate another 0.7 million feral cats occur in Australia’s highly modified environments (urban areas, rubbish dumps, intensive farms).

Feral cat densities are higher on small islands than the mainland, but similar inside and outside conservation land. Mainland cats reach highest densities in arid/semi-arid areas after wet periods. Regional variation in cat densities corresponds closely with attrition rates for native mammal fauna.

The overall population estimate for Australia’s feral cats (in natural and highly modified environments), fluctuating between 2.1 and 6.3 million, is lower than previous estimates, and Australian feral cat densities are lower than reported for North America and Europe. Nevertheless, cats inflict severe impacts on Australian fauna, reflecting the sensitivity of Australia’s native species to cats and reinforcing that policy, research and management to reduce their impacts is critical.

Legge, S, et al (2016) Enumerating a continental-scale threat: How many feral cats are in Australia? Biological Conservation PDF DOI


Phylogeography of the antilopine wallaroos (Macropus antilopinus) across tropical northern Australia

Authors: Jessica J Wadley, Damien A Fordham, Vicki A Thomson, Euan G Ritchie and Jeremy J Austin

Published in: Ecology and Evolution (early view)


The distribution of antilopine wallaroo, Macropus antilopinus, is marked by a break in the species’ range between Queensland and the Northern Territory, coinciding with the Carpentarian barrier.

Previous work on M. antilopinus revealed limited genetic differentiation between the Northern Territory and Queensland M. antilopinus populations across this barrier. The study also identified a number of divergent lineages in the Northern Territory, but was unable to elucidate any geographic structure.

Here, we re-examine these results to (1) determine phylogeographic patterns across the range of M. antilopinus and (2) infer the biogeographic barriers associated with these patterns.

The tropical savannahs of northern Australia: from the Cape York Peninsula in the east, to the Kimberley in the west. We examined phylogeographic patterns in M. antilopinus using a larger number of samples and three mtDNA genes: NADH dehydrogenase subunit 2, cytochrome b, and the control region. Two datasets were generated and analyzed: (1) a subset of samples with all three mtDNA regions concatenated together and (2) all samples for just control region sequences that included samples from the previous study. Analysis included generating phylogenetic trees based on Bayesian analysis and intraspecific median-joining networks.

The contemporary spatial structure of M. antilopinus mtDNA lineages revealed five shallow clades and a sixth, divergent lineage. The genetic differences that we found between Queensland and Northern Territory M. antilopinus samples confirmed the split in the geographic distribution of the species. We also found weak genetic differentiation between Northern Territory samples and those from the Kimberley region of Western Australia, possibly due to the Kimberley Plateau–Arnhem Land barrier. Within the Northern Territory, two clades appear to be parapatric in the west, while another two clades are broadly sympatric across the Northern Territory. MtDNA diversity of M. antilopinus revealed an unexpectedly complex evolutionary history involving multiple sympatric and parapatric mtDNA clades across northern Australia.

These phylogeographic patterns highlight the importance of investigating genetic variation across distributions of species and integrating this information into biodiversity conservation.

Wadley JJ, Fordham DA, Thomson VA, Ritchie EG, Austin JJ (2016) Phylogeography of the antilopine wallaroo (Macropus antilopinus) across tropical northern Australia. Ecology and Evolution PDF DOI 


The Conversation: Invasive predators are eating the world’s animals to extinction – and the worst is close to home

By Tim Doherty (Deakin University), Chris Dickman (University of Sydney), Dale Nimmo (Charles Sturt University),  Euan Ritchie (Deakin University) and Al Glen (Landcare Research, New Zealand).

Feral cats are a major driver of global biodiversity loss, contributing to 26% of bird, mammal and reptile extinctions. Image credit: Mark Marathon via Wikimedia Commons

Feral cats are a major driver of global biodiversity loss, contributing to 26% of bird, mammal and reptile extinctions. Image credit: Mark Marathon via Wikimedia Commons

Invasive species are a threat to wildlife across the globe – and invasive, predatory mammals are particularly damaging.

Our research, recently published in Proceedings of the National Academy of Sciences, shows that these predators – cats, rats and foxes, but also house mice, possums and many others – have contributed to around 60% of bird, mammal and reptile extinctions. The worst offenders are feral cats, contributing to over 60 extinctions.

So how can we stop these mammals eating away at our threatened wildlife?

Counting the cost

Our study revealed that invasive predators are implicated in 87 bird, 45 mammal and 10 reptile extinctions — 58% of these groups’ contemporary extinctions worldwide.

Invasive predators also threaten 596 species classed as vulnerable, endangered or critically endangered on the International Union for the Conservation of Nature Red List. Combined, the affected species include 400 birds, 189 mammals and 149 reptiles.

Twenty-three of the critically endangered species are classed as “possibly extinct”, so the number of extinctions above is likely to be an underestimate.

Until now, these shocking statistics have been unknown, and the heavy toll of invasive predators on native biodiversity grossly underappreciated. Species extinctions attributed to invasive predators include the Hawaiian rail (Zapornia sandwichensis) and Australia’s lesser bilby (Macrotis leucura).

Who are the worst offenders?

We found that three canids (including the red fox and feral dogs), seven members of the weasel family or mustelids (such as stoats), five rodents, two primates, two mongooses, two marsupials and nine species from other families negatively impact threatened species. Some of these species, such as hedgehogs and brushtail possums, don’t immediately spring to mind as predators, yet they are known to prey on many threatened species.

Feral cats threaten the most species overall (430), including 63 that have become extinct. This equates to one-quarter of all bird, mammal and reptile extinctions – making the feral cat arguably the most damaging invasive species for animal biodiversity worldwide.

Five species of introduced rodent collectively threaten 420 species, including 75 extinctions. While we didn’t separate out the impacts of individual rodent species, previous work shows that black rats (Rattus rattus) threaten the greatest number of species, followed by brown rats (R. norvegicus) and Pacific rats (R. exulans).

The humble house mouse (Mus musculus) is another interesting case. Despite their small size, house mice have been recorded eating live chicks of albatrosses, petrels and shearwaters.

Other predators that threaten large numbers of species are the domestic dog (Canis familiaris), pig (Sus scrofa), small Indian mongoose (Herpestes auropunctatus), red fox (Vulpes vulpes) and stoat (Mustela erminea).

Island species most at risk

Species found only on islands (insular endemics) account for 81% of the threatened species at risk from predators.

The isolation of many islands and a lack of natural predators mean that insular species are often naive about new predators and lack appropriate defensive responses. This makes them highly vulnerable to being eaten and in turn suffering rapid population decline or, worse, extinction. The high extinction rates of ground-dwelling birds in Hawaii and New Zealand — both of which lack native mammalian predators — are well-known examples.

Accordingly, the regions where the predators threatened the greatest number of species were all dominated by islands – Central America and the Caribbean, islands of the Pacific, the Madagascar region, New Zealand and Hawaii.

Conversely, the continental regions of North and South America, Europe, Africa and Asia contain comparatively few species threatened by invasive predators. While Australia is a continent, it is also an island, where large numbers of native birds and mammals are threatened by cats and foxes.

Managing menacing mammals

Understanding and mitigating the impact of invasive mammal predators is essential for reducing the rate of global biodiversity loss.

Because most of the threatened species studied here live on islands, managing invasive predators on islands should be a global conservation priority. Invasive predators occur on hundreds of islands and predator control and eradication are costly exercises. Thus, it is important to prioritise island eradications based on feasibility, cost, likelihood of success and potential benefits.

On continents or large islands where eradications are difficult, other approaches are needed. This includes predator-proof fencing, top-predator restoration and conservation, lethal control, and maintenance of habitat structure.

Despite the shocking statistics we have revealed, there remain many unknowns. For example, only around 40% of reptile species have been assessed for the Red List, compared to 99% for birds and mammals. Very little is known about the impact of invasive predators on invertebrate species.

We expect that the number of species affected by invasive predators will climb as more knowledge becomes available.

This article was originally published on The Conversation. Read the original article, including reader comments.
The Conversation
The Conversation

Concordance in phylogeography and ecological niche modelling identify dispersal corridors for reptiles in arid Australia

Authors: Jane Melville, Margaret L Haines, Joshua Hale, Stephanie Chapple and Euan G Ritchie

Published in: Journal of Biogeography (early access)


Using the rock-specialist agamid Ctenophorus caudicinctus as a model, we test hypothesized biogeographical dispersal corridors for lizards in the Australian arid zone (across the western sand deserts), and assess how these dispersal routes have shaped phylogeographical structuring in arid and semi-arid Australia.

We sequenced a c. 1400 bp fragment of mtDNA (ND2) for 134 individuals of C. caudicinctus as well as a subset of each of the mtDNA clades for five nuclear loci (BDNF, BACH1, GAPD, NTF3, and PRLR). We used phylogenetic methods to assess biogeographical patterns within C. caudicinctus, including relaxed molecular clock analyses to estimate divergence times. Ecological niche modelling (Maxent) was employed to estimate the current distribution of suitable climatic envelopes for each lineage.

Phylogenetic analyses identified two deeply divergent mtDNA clades within C. caudicinctus – an eastern and western clade – separated by the Western Australian sand deserts. However, divergences pre-date the Pleistocene sand deserts. Phylogenetic analyses of the nuclear DNA data sets generally support major mtDNA clades, suggesting past connections between the western C. c. caudicinctus populations in far eastern Pilbara (EP) and the lineages to the east of the sand deserts. Ecological niche modelling supports the continued suitability of climatic conditions between the Central Ranges and the far EP for C. c. graafi.

Estimates of lineage ages provide evidence of divergence between eastern and western clades during the Miocene with subsequent secondary contact during the Pliocene. Our results suggest that this secondary contact occurred via dispersal between the Central Ranges and the far EP, rather than the more southerly Giles Corridor. These events precede the origins of the western sand deserts and divergence patterns instead appear associated with Miocene and Pliocene climate change.

Melville J, Haines ML, Hale J, Chapple S, Ritchie EG (2016) Concordance in phylogeography and ecological niche modelling identify dispersal corridors for reptiles in arid Australia. Journal of Biogeography PDF DOI