Category Archives: Research

Towards meaningful monitoring: A case study of a threatened rodent

Authors: Hayley M Geyle, Gurutzeta Guillera‐Arroita, Hugh F Davies, Ronald S C Firth, Brett P Murphy, Dale G Nimmo, Euan G Ritchie, John C Z Woinarski, and Emily Nicholson

Published in: Austral Ecology

Abstract

Detecting trends in species’ distribution and abundance are essential for conserving threatened species, and depend upon effective monitoring programmes. Despite this, monitoring programmes are often designed without explicit consideration of their ability to deliver the information required by managers, such as their power to detect population changes.

Here, we demonstrate the use of existing data to support the design of monitoring programmes aimed at detecting declines in species occupancy. We used single‐season occupancy models and baseline data to gain information on variables affecting the occupancy and detectability of the threatened brush‐tailed rabbit‐rat Conilurus penicillatus (Gould 1842) on the Tiwi Islands, Australia. This information was then used to estimate the survey effort required to achieve sufficient power to detect changes in occupancy of different magnitudes.

We found that occupancy varied spatially, driven primarily by habitat (canopy height and cover, distance to water) and fire history across the landscape. Detectability varied strongly among seasons, and was three times higher in the late dry season (July–September), compared to the early dry season (April–June). Evaluation of three monitoring scenarios showed that conducting surveys at times when detectability is highest can lead to a substantial improvement in our ability to detect declines, thus reducing the survey effort and costs.

Our study highlights the need for careful consideration of survey design related to the ecology of a species, as it can lead to substantial cost savings and improved insight into species population change via monitoring.

Geyle HM, Guillera-Arroita G, Davies HF, Firth RSC, Murphy BP, Nimmo DG, Ritchie EG, Woinarski JCZ, Nicholson E (2018) Towards meaningful monitoring: A case study of a threatened rodent. Austral Ecology, PDF DOI

Eradicating abundant invasive prey could cause unexpected and varied biodiversity outcomes: The importance of multispecies interactions

Authors: Miguel Lurgi, Euan G Ritchie, and Damien A Fordham

Published in: Journal of Applied Ecology

Abstract

Abundant and widely distributed invasive prey can negatively affect co‐occurring native species by competing for food and/or shelter, removing vegetation cover and reducing habitat complexity (changing predation risk), and by sustaining elevated abundances of invasive mesopredators. However, information regarding the community and trophic consequences of controlling invasive prey and their temporal dynamics remain poorly understood.

We used multispecies ecological network models to simulate the consequences of changing European rabbit Oryctolagus cuniculus abundance in an arid mammalian community. We quantified how changes in the dominant prey (rabbits) affected multiple trophic levels, examining changes in predator–prey interactions through time and how they affected native prey persistence.

Our results suggest that removal of rabbits can benefit native biodiversity immediately at removal rates between 30% and 40%. However, beyond these levels, densities of small native mammals will decline in the short term. The processes underpinning these declines are: (a) increased competition for resources (vegetation) with kangaroos Macropus spp., whose numbers increase due to their release from competition with rabbits and (b) increased predation (prey switching) by feral cats Felis catus. Both effects are mediated by dingoes Canis dingo, a native apex predator.

Importantly, native mammal abundance recovers after a time delay, which is prolonged when high rates of rabbit control are applied. This is likely due to a reduction in hyperpredation by invasive feral cats and red foxes Vulpes vulpes following rabbit removal.

Continued eradication of rabbits in arid Australia will benefit native species due to a decrease in apparent competition for resources and by alleviating hyperpredation from invasive mesopredators. Furthermore, ecosystem‐level conservation benefits of reducing invasive prey abundance are as important as direct control of invasive mesopredators.

Synthesis and applications: Multispecies ecological network models provide wildlife managers with tools to better understand and predict the complex effects of species removal and control on both intact and modified ecosystems. Our results show that management of the Australian arid zone can benefit from controlling invasive prey as well as invasive predators. However, invasive species control can cause unexpected outcomes on native biodiversity. This extends to other systems where dominant prey may play fundamental roles in ecosystem structure and function.

Lurgi M, Ritchie EG, Fordham DA (2018) Eradicating abundant invasive prey could cause unexpected and varied biodiversity outcomes: The importance of multispecies interactions, Journal of Applied Ecology, PDF DOI 

The Conversation: Killing sharks, wolves and other top predators won’t solve conflicts

Black tip sharks swim with tropical fish in a lagoon in French Polynesia.

By Robert Lennox (Carleton University), Austin Gallagher (University of Miami), Euan Ritchie (Deakin University) and Steven J Cooke (Carleton University).

This article was originally published on The Conversation. Read the original article.

In French Polynesia, fishing is an integral part of everyday life. The people living here fish on the flats and along the reef using nets, hooks and line, harpoons, spearguns and traditional artisanal traps.

They fish for food. They are also seeing the benefits of using their traditional knowledge to guide recreational fishing tourists — a business with potential to improve long term employment security.

Abundant sharks in the lagoon led to questions about their contribution to the fishery and whether it would help the fishery if they were targeted. This is a question that is often on the minds of humans when they encounter predators.

As an ecologist working with the fish populations in French Polynesia, I went looking for research about what happens to an ecosystem when a predator is removed. Are the responses predictable? Does it work? Can we make generalizations?

Our new study, published in Biological Conservation, surveyed the research on predator removal and identified several interesting — and perhaps unexpected — trends.

Humans and other predators

Predators are among the most charismatic animals on Earth — lions, eagles and sharks adorn many human symbols. On land, in the air and in water, predators fascinate and inspire, they are quintessential representations of nature’s majesty and might.

In spite of their ecological, economic and cultural significance, predators are among the most heavily persecuted animals, due to conflict with humans and their assets.

Predators attack and kill livestock, hunt economically important prey and can kill or injure people or be perceived as a threat to human safety. These conflicts may motivate humans to try to manage predators to lessen the damages.

One of the oldest and most rudimentary methods is to cull or remove them, even though predators are already rare and some are threatened with extinction.

The motivation to remove predators is easy to understand, but what if predator removal does not even achieve the desired outcomes?

In balance

Predators are essential to ecosystems because they regulate prey populations. Without predators, prey can become over-abundant. This can result in damage to local plants, as well as disease outbreaks that can spread to domesticated animals.

Top predators like wolves dominate small predators like coyotes, keeping those populations in check too. Without predators, ecosystems become unbalanced in many ways because plants, herbivores and small predators change in response to their loss.

In a perfect scenario, successful predator removal would strike a balance. It would reduce conflict and be sustainable, but not cause the predator population to disappear entirely. However, our review of 141 studies of predator removal revealed that success is rarely achieved.

Livestock attacks weren’t always reduced when predators were removed, and the human-wildlife conflict remained. On top of that, new predators often moved into vacated territory and recolonized areas where others had been removed. For example, when caracal (a type of wild cat) and leopard were culled in South Africa, predator conflicts on farms increased.

A small number of studies have shown successful removal of predators without harming the predator population, and led to increases in the prey population. However, these examples of success were generally from the Arctic where wolves were removed to increase caribou or moose numbers. In that scenario, there are fewer links in the food web, possibly making responses more predictable.

Generally, however, the responses were unpredictable and removing predators often failed for one reason or another.

Coexistence, not conflict

Ecosystems are complex networks of species. They include plants, decomposers, naturally subordinate predators (such as feral cats, foxes and coyotes), pathogens, predators and their prey. Together, they all play vital roles in regulating each other.

When humans remove predators, the effects are consistently negative. The action can, for example, fracture wolf packs into smaller units, or increase the reproductive rates of coyotes to produce even more offspring. This can have knock on effects, including an increase in disease, plant damage if herbivore populations explode and even an increase in the number of collisions between large herbivores, such as moose, and vehicles.

Instead of killing predators, there are other measures we can take to reduce conflict and learn to live with wildlife. In parts of Alberta, biologists are encouraging landowners to use electric fencing around bee hives and chicken coops to fend off bears. These types of non-lethal solutions can be tested and may often be more effective than removing the predator.

Other studies have suggested that “rewilding” an ecosystem — that is, reintroducing species into the ecosystem — can reduce conflicts. When their prey are abundant, the predators have less interest in nearby livestock. One study showed that lynx conflict with farmers increased when their natural prey, roe deer, were scarcer.

Essential elements

Instead of removing predators to manage human-wildlife conflict, we should be looking towards non-lethal alternatives. Using deterrent devices (lights, sounds or flapping material) can keep predators away from homes, fields and livestock.

The services that predators and functioning ecosystems provide to humans are of enormous value, and we would be wise to work hard to conserve and maintain them for the benefit of all.

Predators aren’t only symbols, they are essential parts of healthy terrestrial and aquatic landscapes. And beyond what we value, we should feel an imperative to preserve the diversity of life we share Earth with, most of which precedes our own evolution.

Of course, there will be times when predator removal may be necessary to protect people and their interests. Interventions that champion the principles of coexistence between humans and predators may be more successful and justifiable approaches to managing wildlife.

Efforts to protect predators or proactively promote their return, rather than continue contributing to their decline and extinction, are among the greatest conservation challenges we face.
The Conversation

Crowdfunding biodiversity conservation

Authors: Eduardo Gallo-Cajiao, Carla Archibald, Rachel Friedman, Richard A Fuller, Edward T Game, Tiffany Morrison, and Euan G Ritchie

Published in: Conservation Biology

Abstract

Raising funds is critical for conserving biodiversity and hence so too is scrutinizing emerging financial mechanisms that might help achieve this goal. In this context, anecdotal evidence indicates crowdfunding is being used to support a variety of activities needed for biodiversity conservation, yet its magnitude and allocation remain largely unknown.

We conducted a global analysis to help address this knowledge gap, based on empirical data from conservation‐focused projects extracted from crowdfunding platforms. For each project, we determined the funds raised, date, country of implementation, proponent characteristics, activity type, biodiversity realm, and target taxa.

We identified 72 relevant platforms and 577 conservation‐focused projects that have raised US$4,790,634 since 2009. Whilst proponents were based in 38 countries, projects were delivered across 80 countries, indicating a potential mechanism of resource mobilization. Proponents were from non‐governmental organizations (35%), universities (30%), or were freelancers (26%). Most projects were for research (40%), persuasion (31%), and on‐ground actions (21%). Projects have focused primarily on species (57.7%) and terrestrial ecosystems (20.3%), and less on marine (8.8%) and freshwater ecosystems (3.6%). Projects have focused on 208 species, including a disproportionate number of threatened bird and mammal species.

Crowdfunding for biodiversity conservation has now become a global phenomenon and presents signals for potential expansion, despite possible pitfalls. Opportunities arise from its spatial amplifying effect, steady increase over time, inclusion of Cinderella species, adoption by multiple actors, and funding of a range of activities beyond research.

Our study paves the way for further research on key questions, such as campaign success rates, effectiveness, and drivers of adoption. Even though the capital input of crowdfunding so far has been modest compared to other conservation finance mechanisms, its contribution goes beyond funding research and providing capital.

Embraced with due care, crowdfunding could potentially become an increasingly important financial mechanism for biodiversity conservation.

Gallo-Cajiao E, Archibald C, Friedman R, Steven R, Fuller RA, Game ET, Morrison TH, Ritchie EG (2018) Crowdfunding biodiversity conservation, Conservation Biology PDF DOI

Animal recognition and identification with deep convolutional neural networks for automated wildlife monitoring

Authors: Hung Nguyen, Sarah J Maclagan, Tu Dinh Nguyen, Thin Nguyen, Paul Flemons, Kylie Andrews, Euan G Ritchie, and Dinh Phung

Published in: 2017 IEEE International Conference on Data Science and Advanced Analytics

Abstract

Efficient and reliable monitoring of wild animals in their natural habitats is essential to inform conservation and management decisions. Automatic covert cameras or “camera traps” are being an increasingly popular tool for wildlife monitoring due to their effectiveness and reliability in collecting data of wildlife unobtrusively, continuously and in large volume. However, processing such a large volume of images and videos captured from camera traps manually is extremely expensive, time-consuming and also monotonous. This presents a major obstacle to scientists and ecologists to monitor wildlife in an open environment.

Leveraging on recent advances in deep learning techniques in computer vision, we propose in this paper a framework to build automated animal recognition in the wild, aiming at an automated wildlife monitoring system. In particular, we use a single-labeled dataset from Wildlife Spotter project, done by citizen scientists, and the state-of-the-art deep convo- lutional neural network architectures, to train a computational system capable of filtering animal images and identifying species automatically.

Our experimental results achieved an accuracy at 96.6% for the task of detecting images containing animal, and 90.4% for identifying the three most common species among the set of images of wild animals taken in South-central Victoria, Australia, demonstrating the feasibility of building fully automated wildlife observation. This, in turn, can therefore speed up research findings, construct more efficient citizen science- based monitoring systems and subsequent management decisions, having the potential to make significant impacts to the world of ecology and trap camera images analysis.

Nguyen H, Maclagan SJ, Nguyen TD, Nguyen T, Flemons P, Andrews K, Ritchie EG, Phung D (2017) Animal recognition and identification with deep convolutional neural networks for automated wildlife monitoring, 2017 IEEE International Conference on Data Science and Advanced Analytics PDF DOI 

Don’t judge habitat on its novelty: Assessing the value of novel habitats for an endangered mammal in a peri-urban landscape

Authors: Sarah J Maclagan, Terry Coates, and Euan G Ritchie

Published in: Biological Conservation, volume 223 (July 2018)

Abstract

Novel ecosystems are increasingly common worldwide, particularly in areas heavily impacted by humans such as urban and peri-urban landscapes. Consequently, interest in their potential contribution to biodiversity conservation is growing, including their ability to sustain populations of threatened species. However, few studies have explored whether novel habitats can support viable populations over time and how they compare to less modified, remnant habitats.

We investigated the capacity for novel habitats to support an endangered mammal, the southern brown bandicoot (Isoodon obesulus obesulus: Peramelidae), in a highly-modified landscape near Australia’s second largest city, Melbourne. We compared bandicoot abundance and body condition between five novel and two remnant sites, and examined whether novel sites support residency and key demographic processes necessary for bandicoot population persistence. We found that bandicoot abundance was higher at novel than remnant sites, with the highest abundance at the novel site with the most urbanised surroundings. Female body condition was similar between novel and remnant sites. The majority of bandicoots at novel sites were resident, and breeding activity, recruitment of first-year adults, and survival of mature adults were observed at all novel sites.

Our results demonstrate the potential significance of novel habitats for conserving threatened species within heavily-modified landscapes, and encourage us not to judge the quality of habitats on their novelty alone. Broadening our appreciation of the potential value of novel ecosystems could increase off-reserve species conservation opportunities, a key priority within the context of the Anthropocene and unprecedented global change and biodiversity loss.

Maclagan SJ, Coates T, Ritchie EG (2018) Don’t judge habitat on its novelty: Assessing the value of novel habitats for an endangered mammal in a peri-urban landscape, Biological Conservation PDF DOI 

Testing the assumptions of the pyrodiversity begets biodiversity hypothesis for termites in semi-arid Australia

Authors: Hayley Davis, Euan G Ritchie, Sarah Avitabile, Tim Doherty, and Dale G Nimmo

Published in: The Royal Society Open Science (April 2018)

Abstract

Fire shapes the composition and functioning of ecosystems globally. In many regions, fire is actively managed to create diverse patch mosaics of fire-ages under the assumption that a diversity of post-fire-age classes will provide a greater variety of habitats, thereby enabling species with differing habitat requirements to coexist, and enhancing species diversity (the pyrodiversity begets biodiversity hypothesis). However, studies provide mixed support for this hypothesis.

Here, using termite communities in a semi-arid region of southeast Australia, we test four key assumptions of the pyrodiversity begets biodiversity hypothesis:

  1. that fire shapes vegetation structure over sufficient time frames to influence species’ occurrence,
  2. that animal species are linked to resources that are themselves shaped by fire and that peak at different times since fire,
  3. that species’ probability of occurrence or abundance peaks at varying times since fire, and
  4. that providing a diversity of fire-ages increases species diversity at the landscape scale.

Termite species and habitat elements were sampled in 100 sites across a range of fire-ages, nested within 20 landscapes chosen to represent a gradient of low to high pyrodiversity. We used regression modelling to explore relationships between termites, habitat and fire.

Fire affected two habitat elements (coarse woody debris and the cover of woody vegetation) that were associated with the probability of occurrence of three termite species and overall species richness, thus supporting the first two assumptions of the pyrodiversity hypothesis. However, this did not result in those species or species richness being affected by fire history per se. Consequently, landscapes with a low diversity of fire histories had similar numbers of termite species as landscapes with high pyrodiversity.

Our work suggests that encouraging a diversity of fire-ages for enhancing termite species richness in this study region is not necessary.

Davis H, Ritchie EG, Avitabile S, Doherty T, Nimmo DG (2018) Testing the assumptions of the pyrodiversity begets biodiversity hypothesis for termites in semi-arid Australia, Royal Society Open Science PDF DOI 

Human-modified habitats facilitate forest-dwelling populations of an invasive predator, Vulpes vulpes

Authors: Bronwyn A Hradsky, Alan Robley, Ray Alexander, Euan G Ritchie, Alan York, and Julian Di Stefano

Published in: Scientific Reports

Abstract

Invasive and over-abundant predators pose a major threat to biodiversity and often benefit from human activities. Effective management requires understanding predator use of human-modified habitats (including resource subsidies and disturbed environments), and individual variation within populations.

We investigated selection for human-modified habitats by invasive red foxes, Vulpes vulpes, within two predominantly forested Australian landscapes. We predicted that foxes would select for human-modified habitats in their range locations and fine-scale movements, but that selection would vary between individuals. We GPS-tracked 19 foxes for 17–166 days; ranges covered 33 to >2500 ha.

Approximately half the foxes selected for human-modified habitats at the range scale, with some ‘commuting’ more than five kilometres to farmland or townships at night. Two foxes used burnt forest intensively after a prescribed fire. In their fine-scale nocturnal movements, most foxes selected for human-modified habitats such as reservoirs, forest edges and roads, but there was considerable individual variation. Native fauna in fragmented and disturbed habitats are likely to be exposed to high rates of fox predation, and anthropogenic food resources may subsidise fox populations within the forest interior.

Coordinating fox control across land-tenures, targeting specific landscape features, and limiting fox access to anthropogenic resources will be important for biodiversity conservation.

Hradsky BA, Robley A, Alexander R, Ritchie EG, York, Di Stefano J (2017) Human-modified habitats facilitate forest-dwelling populations of an invasive predator, Vulpes vulpes. Scientific Reports PDF DOI 

Honours projects for 2018

Looking for an exciting honours project in ecology? I have three openings for 2018.

I also welcome other project ideas from students if they fit with my expertise and research priorities.

To find out more, please refer to the Deakin University website: Honours in Life and Environmental Sciences, or contact me.

Fox, cat and fire interactions in the Grampians National Park

Supervisor: Dr Euan Ritchie

External and co-supervisors: Dr Dale Nimmo (Charles Sturt University) and Dr Tim Doherty, (Deakin University)

Start date: February 2018

Foxes are invasive predators in the Grampians. Image credit: Dan Derrett via Flickr

This project, a research partnership between Parks Victoria and Deakin University, will examine fox and cat distribution across the Grampians National Park. Specifically, it will aim to examine:

  1. The effect of fire on fox and cat habitat use.
  2. Fox diet.

Experience with using R and/or ArcGIS will be advantageous but is not essential. A manual driver’s licence is essential for this project.

The ecological role of eastern barred bandicoots in a newly established island population

Principal Supervisor: Dr Euan Ritchie

External and co-supervisors: Dr Duncan Sutherland (Phillip Island Nature Parks) and Dr Amy Coetsee (Zoos Victoria)

Start date: February or July 2018

Eastern barred bandicoots persist only in captivity or within fox-free nature reserves. Image credit JJ Harrison via Wikimedia Commons

Mainland eastern barred bandicoots (EBBs) are listed as extinct in the wild, persisting only in captivity or within fox-free fenced reserves.

Phillip Island Nature Parks, together with Zoos Victoria and the Eastern Barred Bandicoot Recovery Team, have established an EBB population on fox-free Churchill Island, adjacent to Phillip Island.

This project forms part of a broader effort to bring EBBs back from the brink of extinction and off the threatened species list. We seek an honours student for a project to experimentally determine the role of EBBs as ecological engineers, in particular their effect on invertebrate communities.

Experience with using R and/or ArcGIS will be advantageous but is not essential. Field accommodation on Phillip Island is available.

Large herbivore impacts on alpine ecosystems

Principal Supervisor: Dr Euan Ritchie

External and co-supervisors: Professor Don Driscoll and Dr Tim Doherty (Deakin University)

Start date: July 2018

Large, introduced herbivores, such as deer, threaten alpine ecosystems. Image credit: Rexness via Flickr

Large feral herbivores, such as horses and deer, threaten alpine ecosystems through overgrazing and trampling of vegetation, spreading weeds, elevated nutrients, and breaking down stream banks and reducing water quality.

This project will examine the impacts of large herbivores on alpine vegetation communities, and in turn on smaller, native vertebrate species.

Experience with using R and/or ArcGIS will be advantageous, but is not essential. A manual driver’s licence is essential for this project.

Bayesian networks elucidate interactions between fire and other drivers of terrestrial fauna distributions

Authors: Bronwyn A Hradsky, Trent D Penman, Dan Ababei, Anca Hanea, Euan G Ritchie, Alan York, and Julian Di Stefano

Published in: Ecosphere, volume 8, issue 8 (August 2017)

Abstract

Fire is a major driver of community composition and habitat structure and is extensively used as an ecological management tool in flammable landscapes. Interactions between fire and other processes that affect animal distributions, however, cause variation in faunal responses to fire and limit our ability to identify appropriate fire management regimes for biodiversity conservation.

Bayesian networks (BNs) have not previously been used to examine terrestrial faunal distributions in relation to fire, but offer an alternative statistical framework for modeling complex environmental relationships as they explicitly capture interactions between predictor variables.

We developed a conceptual model of the interactions between drivers of faunal distributions in fire-affected landscapes, and then used a non-parametric BN modeling approach to describe and quantify these relationships for a suite of terrestrial native mammal species. We also tested whether BNs could be used to predict these species’ distributions using only remote-sensed or mapped variables.

Data were collected at 113 sites across 47,000 ha of continuous eucalypt forest in the Otway Ranges, southeastern Australia; time-since-fire (TSF) ranged from six months to 74 years.

Habitat complexity increased with TSF and forest wetness. Critical-weight-range (35–5500 g) marsupials and rodents were generally more likely to occur at long unburnt sites with high habitat complexity, and in wetter forest types. In contrast, large grazers and browsers preferred less complex habitats and younger or drier forest. Species occurrences were more strongly affected by habitat complexity than TSF, coarse woody debris cover, or invasive predator (Vulpes vulpes or Felis catus) occurrence.

Bayesian network models effectively discriminated between the presence and absence of most native mammal species, even when only provided with data on remote-sensed or mapped variables (i.e., without field-assessed data such as habitat complexity). Non-parametric BNs are an effective technique for explicitly modeling the complex and context-dependent influence of fire history on faunal distributions, and may reduce the need to collect extensive field data on habitat structure and other proximate drivers.

Hradsky BA, Penman TD, Ababei D, Hanea A, Ritchie EG, York A and Di Stefano J (2017) Bayesian networks elucidate interactions between fire and other drivers of terrestrial fauna distributions. Ecosphere PDF DOI 

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)

Abstract

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)

Abstract

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)

Abstract

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

Abstract

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)

Abstract

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)

Abstract

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

 

Fire severity and fire-induced landscape heterogeneity affect arboreal mammals in fire-prone forests

Authors: Evelyn K Chia, Michelle Bassett, Dale G Nimmo, Steve W J Leonard, Euan G Ritchie, Michael F Clarke and Andrew F Bennett

Published in: Ecoshere, volume 6, issue 10 (October 2015)

EucFires

We examined the role of topography, fire history and fire sensitivity on the occurrence of arboreal mammals 2 to 3 years after wildfire in temperate Eucalypt forests. Image credit: Elizabeth Donoghue via Flickr.

Abstract

In fire-prone regions, wildfire influences spatial and temporal patterns of landscape heterogeneity. The likely impacts of climate change on the frequency and intensity of wildfire highlights the importance of understanding how fire-induced heterogeneity may affect different components of the biota.

Here, we examine the influence of wildfire, as an agent of landscape heterogeneity, on the distribution of arboreal mammals in fire-prone forests in south-eastern Australia.

First, we used a stratified design to examine the role of topography, and the relative influence of fire severity and fire history, on the occurrence of arboreal mammals 2–3 years after wildfire. Second, we investigated the influence of landscape context on the occurrence of arboreal mammals at severely burnt sites. Forested gullies supported a higher abundance of arboreal mammals than slopes.

Fire severity was the strongest influence, with abundance lower at severely burnt than unburnt sites. The occurrence of mammals at severely burned sites was influenced by landscape context: abundance increased with increasing amount of unburnt and understorey-only burnt forest within a one kilometre radius.

These results support the hypothesis that unburnt forest and moist gullies can serve as refuges for fauna in the post-fire environment and assist recolonization of severely burned forest. They highlight the importance of spatial heterogeneity created by wildfire and the need to incorporate spatial aspects of fire regimes (e.g. creation and protection of refuges) for fire management in fire-prone landscapes.

Chia EK, Bassett M, Nimmo DG, Leonard SWJ, Ritchie EG, Clarke MF, Bennett AF (2015) Fire severity and fire-induced landscape heterogeneity affect arboreal mammals in fire-prone forests, Ecosphere, 6:10 PDF DOI

Fire affects microhabitat selection, movement patterns, and body condition of an Australian rodent (Rattus fuscipes)

Authors: Amber Fordyce, Bronwyn A Hradsky, Euan G Ritchie, And Julian Di Stefano

Published in: Journal of Mammalogy, October 2015 (online)

Abstract

Resource selection by animals influences individual fitness, the abundance of local populations, and the distribution of species. Further, the degree to which individuals select particular resources can be altered by numerous factors including competition, predation, and both natural- and human-induced environmental change. Understanding the influence of such factors on the way animals use resources can guide species conservation and management in changing environments.

In this study, we investigated the effects of a prescribed fire on small-scale (microhabitat) resource selection, abundance, body condition, and movement pathways of a native Australian rodent, the bush rat (Rattus fuscipes). Using a before-after, control-impact design, we gathered data from 60 individuals fitted with spool and line tracking devices.

In unburnt forest, selection of resources by bush rats was positively related to rushes, logs and complex habitat, and negatively related to ferns and litter. Fire caused selection for spreading grass, rushes, and complex habitat to increase relative to an unburnt control location. At the burnt location after the fire, rats selected patches of unburnt vegetation, and no rats were caught at a trapping site where most of the understory had been burnt. The fire also reduced bush rat abundance and body condition and caused movement pathways to become more convoluted. After the fire, some individuals moved through burnt areas but the majority of movements occurred within unburnt patches.

The effects of fire on bush rat resource selection, movement, body condition, and abundance were likely driven by several linked factors including limited access to shelter and food due to the loss of understory vegetation and heightened levels of perceived predation risk.

Our findings suggest the influence of prescribed fire on small mammals will depend on the resulting mosaic of burnt and unburnt patches and how well this corresponds to the resource requirements of particular species.

Fordyce A, Hradsky BA, Ritchie EG, Di Stefano J (2015) Fire affects microhabitat selection, movement patterns, and body condition of an Australian rodent (Rattus fuscipes), Journal of Mammalogy PDF DOI