Category Archives: Publications

Shifting public values and what they mean for increasing democracy in wildlife management decisions

Authors: Lily M van Eden, Chris R Dickman, Euan G Ritchie, and Thomas M Newsome

Published in: Biodiversity and Conservation

Abstract

Over the last century, changing public attitudes about the value of wildlife have triggered substantial changes in species management that have both benefited and hindered conservation efforts. Understanding and integrating contemporary public values is therefore critical for effective conservation outcomes.

Using historic and contemporary examples, we highlight how public attitudes—expressed through the media and campaigns—are shaping the management of introduced and native species, as values shift towards animal welfare and mutualism. We focus on the issue of deliberate human-caused killing of wildlife, because protests against such management have disrupted traditional political and management structures that favoured eradication of wildlife across many jurisdictions and ecological contexts. In doing so, we show that it is essential to work with multiple stakeholder interest groups to ensure that wildlife management is informed by science, while also supported by public values. Achieving this hinges on appropriate science communication to build a better-informed public because management decisions are becoming increasingly democratised.

van Eeden LM, Dickman CR, Ritchie EG, Newsome TM (2017) Shifting public values and what they mean for increasing democracy in wildlife management decisions. Biodiversity and Conservation, PDF DOI 

The Conversation: Thinking big gives top predators the competitive edge

By Thomas Newsome (Deakin University)

Dingoes could be the key to controlling red foxes and other invasive predators, but only if we encourage them in large enough numbers over a wide enough area, our research shows.

Dingoes can help manage devastating red fox and feral cat numbers, but only if we let enough of them live in key areas. Image credit Bobby Tamayo via The Conversation

Interest in re-introducing or restoring top predators, like dingoes and wolves, has been fuelled by recent studies demonstrating their important roles in their ecosystems. They can especially be vital in suppressing the abundance of lower-order competitors or “mesopredators”, like red foxes and possibly feral cats (which can have devastating effects on native species).

But researchers have found top predators aren’t always successful in reducing mesopredator numbers. Until now, such variation has been linked to human presence, land-use changes and environmental factors such as landscape productivity.

However, our research, published yesterday in Nature Communications, found that a key factor for success is high numbers of dingoes and wolves across their natural range.

The density effect

If you look at how species are typically distributed across a landscape – their range – ecological theory predicts there’ll be lower numbers at the outer edges of their range.

If you do need large numbers of top predators to effectively suppress mesopredators, the core of their range is potentially the best place to look.

We tested this idea, looking at the dingo in Australia and the grey wolf in North America and Europe. The mesopredators included the red fox in Australia, the coyote in North America and the golden jackal in Europe.

We used information from bounty hunting programs, as these provide data on predator numbers across a wide geographical area. In the case of Australia we used historic data from the 1950s, as this is the most recent reliable information about red fox and dingo distribution. The actual population numbers of red foxes and dingoes have changed substantially since then, but the nature of their interactions – which is what we were investigating – has not.

We determined that top predators exist in higher numbers at the core of their ranges in comparison to the edges. We then looked at mesopredator numbers across the range edges of their respective top predator.

The results, which were consistent across the three continents, suggest that top predators can suppress mesopredators effectively (even completely) but only in the core of their geographic range, where their numbers are highest.

In other words, abundant top predators can exert disproportionate mesopredator control once their numbers increase past a certain point.

The ‘enemy constraint hypothesis’

The relationship we uncovered is now formalised as the “Enemy Constraint Hypothesis”. It could apply to other predator dyads, where two animals compete for similar resources – even relationships involving parasites and pathogens.

Our findings are important for understanding species interactions and niches, as well as the ecological role of top predators. It could explain why other studies have found top predators have little influence on mesopredators: they were looking at the edge, not the core, of the top predators’ range.

How many top predators do we need?

Dingoes can be vital for reducing red fox and possibly feral cat numbers. In our case studies the ranges of each top predator were limited primarily by human use of the land and intensive shooting, trapping and poisoning.

Killing pack animals like dingoes can fracture social groups, potentially altering their natural behaviour and interactions with other species. Future studies on predator interactions therefore need to consider the extent to which the animals are acting in response to human intervention.

If we want to benefit from the presence of top predators, we need to rethink our approach to management – especially where they are subjected to broad-scale control, as the dingo is in some parts of Australia.

Changing our relationship with top predators would not come without its challenges, but high extinction rates around the world (and especially in Australia) clearly indicate that we urgently need to change something. If this includes restoring top predators, then we need to think big.

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

The Conversation

The Conversation

Top predators constrain mesopredator distributions

Authors: Thomas M Newsome, Aaron C Greenville, Duško Ćirović, Christopher R Dickman, Chris N Johnson, Miha Krofel, Mike Letnic, William J Ripple, Euan G Ritchie, Stoyan Stoyanov and Aaron J Wirsing

Published in: Nature Communications, volume 8

Abstract

Top predators can suppress mesopredators by killing them, competing for resources and instilling fear, but it is unclear how suppression of mesopredators varies with the distribution and abundance of top predators at large spatial scales and among different ecological contexts.

We suggest that suppression of mesopredators will be strongest where top predators occur at high densities over large areas. These conditions are more likely to occur in the core than on the margins of top predator ranges.

We propose the Enemy Constraint Hypothesis, which predicts weakened top-down effects on mesopredators towards the edge of top predators’ ranges.

Using bounty data from North America, Europe and Australia we show that the effects of top predators on mesopredators increase from the margin towards the core of their ranges, as predicted.

Continuing global contraction of top predator ranges could promote further release of mesopredator populations, altering ecosystem structure and contributing to biodiversity loss.

Newsome TM, Greenville AC, Ćirović D, Dickman CR, Johnson CN, Krofel M, Letnic M, Ripple WJ, Ritchie EG, Stoyanov S, Wirsing AJ (2017) Top predators constrain mesopredator distributions. Nature Communications, 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 

Making a new dog?

Authors: Thomas M Newsome, Peter J S Fleming, Christopher R Dickman, Tim S Doherty, William J Ripple, Euan G Ritchie, and Aaron J Wirsing

Published in: BioScience (early view)

Abstract

We are in the middle of a period of rapid and substantial environmental change. One impact of this upheaval is increasing contact between humans and other animals, including wildlife that take advantage of anthropogenic foods. As a result of increased interaction, the evolution and function of many species may be altered through time via processes including domestication and hybridization, potentially leading to speciation events.

We discuss the ecological and management importance of such possibilities, using gray wolves and other large carnivores as case studies.

Image caption: A hypothetical comparison of gray wolf (Canis lupus) ecological effects in wilderness areas (left) and human-modified systems (right) where there are abundant anthropogenic foods.

We identify five main ways that carnivores might be affected: changes to social structures, behavior and movement patterns, changes in survivorship across wild- to human-dominated environments, evolutionary divergence, and potential speciation.

As the human population continues to grow and urban areas expand while some large carnivore species reoccupy parts of their former distributions, there will be important implications for human welfare and conservation policy.

Thomas M Newsome, Peter J S Fleming, Christopher R Dickman, Tim S Doherty, William J Ripple, Euan G Ritchie, Aaron J Wirsing (2017) Making a New Dog? BioScience 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

Communication: Science censorship is a global issue

Authors: Euan G Ritchie, Don A Driscoll and Martine Maron

Published in: Nature, volume 542, number 7640 (February 2017)

Government gagging of scientists is a slippery slope towards removing evidence from public debate.

Government gagging of scientists is a slippery slope towards removing evidence from public debate.

President Donald Trump issued an order on 23 January to effectively gag US government scientists at the Environmental Protection Agency and the Department of Agriculture from communicating with the media and the public (see Nature 54210112017). Regrettably, suppression of public scientific information is already the norm, or is being attempted, in many countries (see, for example, go.nature.com/2kr5dnd). We fear that such gagging orders could encourage senior bureaucrats to use funding as a tool with which to rein in academic freedoms.

In Australia, public servants must abide by codes of conduct for communication that restrict them from contributing scientific evidence to public debates. Allegations emerged in 2011 that an Australian state government had threatened to stop funding university scientists who spoke out against cattle grazing in national parks, despite peer-reviewed evidence that this could damage a fragile alpine ecosystem and was unlikely to reduce fire risk as claimed (see also Nature 4714222011).

The response of scientists to this type of coercion has been to share scientific information widely and openly using such legal means as social media to defend facts and transparency (see Nature 5414352017). Academics and scientific associations are among the last still free to speak, so must continue to do so to protect open discussion of government policies.

Ritchie EG, Driscoll DA, Maron M (2017) Communication: Science censorship is a global issue, Nature 542 PDF DOI