Investigation of potential diseases associated with Northern Territory mammal declines

There is compelling evidence of broad-scale declines in populations of small terrestrial native mammals in northern Australia, including the Top End of the Northern Territory (NT) over the past 20 years. Causes under consideration include changed fire regimes, introduced fauna (including predators) and disease. To date information on health and disease in northern Australian mammals has been limited. Disease is increasingly recognised as a primary driver of some wildlife population declines and extinctions e.g., Tasmanian devil facial tumour disease, white nose syndrome in bats and chytrid fungus in amphibians. Disease has been identified as a risk factor for extinction in declining and fragmented wildlife populations globally, particularly in situations of increased environmental stressors, changing ecosystems, arrival of new vertebrate threats or climate change. Unless wild populations are studied in detail over long periods of time, the effects of disease are easily overlooked and may be difficult to determine. This study is the largest and most comprehensive study of health and disease in small mammals in northern Australia and is one of a small number of studies worldwide to have approached investigation of wildlife populations in this comprehensive manner

Prevalence, genetic diversity and potential clinical impact of blood-borne and enteric protozoan parasites in native mammals from northern Australia

A molecular survey was conducted to provide baseline information on the prevalence, genetic diversity and potential clinical impacts of blood-borne and enteric protozoans in native wild mammals from the Northern Territory (NT). A total of 209 blood and 167 faecal samples were collected from four target species; the northern brown bandicoot (Isoodon macrourus), common brushtail possum (Trichosurus vulpecula), northern quoll (Dasyurus hallucatus) and brush-tailed rabbit-rat (Conilurus penicillatus). Blood samples were screened by PCR at the 18S rRNA gene for trypanosomes, piroplasms and haemogregarines, with faecal samples tested for Cryptosporidium spp. at the 18S rRNA locus, and for Giardia spp. at the glutamate dehydrogenase (gdh) and 18S rRNA loci. The potential clinical impact was investigated by associating clinical, haematological and biochemical parameters with presence or absence of infection. Overall, 22.5% (95% CI: 17.0-28.8%) of the animals tested were positive for haemoprotozoans. Trypanosomes were found in 26.6% (95% CI: 18.7-35.7%) of the bandicoots and were identified as Trypanosoma vegrandis G6, except for one unique genotype, most similar to T. vegrandis G3 (genetic distance = 7%). The prevalence of trypanosomes in possums was 23.7% (95% CI: 11.4-40.2%), and the genotypes identified clustered within the T. noyesi clade. The presence of Babesia sp. and Hepatozoon sp. was confirmed in bandicoots only, both at a prevalence of 9.7% (95% CI: 2.7-9.2%). The total prevalence of intestinal protozoan parasites observed was relatively low (3%; 95% CI: 1.0-6.9%). No evidence of clinical disease associated with protozoan parasitic infection was observed, however bandicoots positive for Trypanosoma exhibited a significantly lower packed cell volume (PCV) compared to negative bandicoots (p = 0.046). To the authors' knowledge, this is the first research conducted in the NT to characterise protozoan parasites in threatened native mammals using both molecular and morphological tools; and to assess the potential clinical impacts of these agents. The absence of clear signs of major morbidity in infected animals seems to exclude a direct association between infections with these agents and possible population decline events in northern Australian native mammals. However until the cause(s) of population decline are ascertained for each individual mammal species, further studies are required. The outcome of the present investigation may be used to inform wildlife conservation and zoonotic disease programs

Europe's cross-border trade, human security and financial connections: A climate risk perspective

As the impacts of climate change begin to take hold, increased attention is being paid to the consequences that might occur remotely from the location of the initial climatic impact, where impacts and responses are transmitted across one or more borders. As an economy that is highly connected to other regions and countries of the world, the European Union (EU) is potentially exposed to such cross-border impacts. Here, we undertake a macro-scale, risk-focused literature and data review to explore the potential impact transmission pathways between the EU and other world regions and countries. We do so across three distinct domains of interest - trade, human security and finance - which are part of complex socio-economic, political and cultural systems and may contribute to mediate or exacerbate risk exposure. Across these domains, we seek to understand the extent to which there has been prior consideration of aspects of climate-related risk exposure relevant to developing an understanding of cross-border impacts. We also pro-vide quantitative evidence of the extent and strength of connectivity between the EU and other world regions. Our analysis reveals that - within this nascent area of research - there is uncer-tainty about the dynamics of cross-border impact that will affect whether the EU is in a relatively secure or vulnerable position in comparison with other regions. However, we reveal that risk is likely to be focused in particular ‘hotspots’; defined geographies, for example, that produce materials for EU consumption (e.g. Latin American soybean), hold financial investments (e.g. North America), or are the foci for EU external action (e.g. the Middle East and North Africa region). Importantly, these domains will also interact, and - via the application of a conceptual example of soybean production in Argentina based on a historical drought event - we illustrate that impact and response pathways linked to EU risk exposure may be complex, further heightening the challenge of developing effective policy responses within an uncertain climatic and socioeconomic future

Is disease contributing to terrestrial mammal declines in Australia's Top End?

There has been an alarming and dramatic decline in small to medium sized native mammal species in northern Australia over the past 20 years. The causes of this decline are currently under investigation. There is limited historical and/or current information on health and disease in northern Australian mammal species and it is not known what role disease may be playing in the decline of mammals in northern Australia. The project objective is to investigate the potential role of disease in the declines of mammal species in northern Australia, focussing on the Top End of the Northern Territory. If species declines continue, then mammal populations will become more isolated; genetic diversity of species will diminish and faunal communities will change. Under these circumstances, the negative impacts of disease will increase. It is therefore vital to understand not only the role that disease may be playing in mammal declines at present, but also to gain understanding of the likely impacts of disease into the future. The disease investigation project will focus field research efforts on four main sites within the Top End: Kakadu National Park, Bathurst Island, Garig Gunak Barlu National Park on the Cobourg Peninsula and peri-urban areas around Darwin. Other potential study sites include remote islands, west Amhern Land and collaborative northern quail study sites in Kakadu NP. Logistics dictate an initial focus on one species from each major taxonomic group undergoing decline: Brush-tailed possum (Trichosurus vulpecula); Northern brown bandicoot (Isoodon macrourus); Northern quail (Dasyurus hallucatus ); Brush-tailed rabbit-rat (Conilurus penicillatus). Golden bandicoots (Isoodon auratus) may be targeted however sample size is likely to be limited. Feral species such as black rats (Rattus rattus) and cats (Felis catus), as well as abundant native species, will also be tested including fresh carcasses. Compromised individuals of any native species will be sampled, including post mortem examination of carcases. Animals will be trapped during routine fauna surveys and examined and sampled. A wide range of biological samples will be collected (generally under field anaesthesia) and submitted for health and disease screening. This is a strongly collaborative project drawing on support from a wide range of researchers across Australia. Results of the first two surveys (Cobourg Peninsula July 2013 and Bathurst Island September 2013) will be presented

Variation in feral cat density between two large adjacent islands in Australia's monsoon tropics

Despite contributing to the ongoing collapse of native mammal populations across northern Australian savannas, we have limited understanding of the ecological constraints of feral cat population density in this system. Addressing such knowledge gaps is a crucial step towards mitigating the impacts of feral cats, and is particularly important for the large islands off northern Australia that remain as strongholds for numerous species vulnerable to cat predation. Here, we investigated cat density across Melville and Bathurst Island, two large islands in Australia’s monsoon tropics. We deployed large grids (~13 km2) of 70 camera-traps at four locations to investigate how feral cat density varies under different combinations of fire frequency, and feral herbivore presence. Using spatially-explicit capture-recapture models, we estimated feral cat density on Melville Island to be 0.15 cats km−2. We did not record any cat detections on Bathurst Island. Using simulations, we predicted that if cat density on Bathurst Island was equal to that on Melville Island, we would have expected to record 27.9 detections of 9.9 individual cats. Our results, coupled with other recent surveys, suggest that the density of cats is much lower on Bathurst Island than the adjacent Melville Island. The absence of feral herbivores on Bathurst Island may have contributed to this variation in cat density. Management that enhances understorey vegetation density, through feral herbivore control, as well as fire management, could help mitigate the impact of feral cats on northern Australian savanna biodiversity

How many reptiles are killed by cats in Australia?

Published online 15 June 2018Context. Feral cats (Felis catus) are a threat to biodiversity globally, but their impacts upon continental reptile faunas have been poorly resolved. Aims.Toestimate the number of reptiles killed annually in Australia by cats and to list Australian reptile speciesknownto be killed by cats. Methods.Weused (1) data from>80 Australian studies of cat diet (collectively>10 000 samples), and (2) estimates of the feral cat population size, to model and map the number of reptiles killed by feral cats. Key results. Feral cats in Australia’s natural environments kill 466 million reptiles yr⁻¹ (95% CI; 271–1006 million). The tally varies substantially among years, depending on changes in the cat population driven by rainfall in inland Australia. The number of reptiles killed by cats is highest in arid regions.Onaverage, feral cats kill 61 reptileskm⁻²year⁻¹, and an individual feral cat kills 225 reptiles year⁻¹. The take of reptiles per cat is higher than reported for other continents. Reptiles occur at a higher incidence in cat diet than in the diet of Australia’s other main introduced predator, the European red fox (Vulpes vulpes). Based on a smaller sample size, we estimate 130 million reptiles year⁻¹ are killed by feral cats in highly modified landscapes, and 53 million reptiles year⁻¹ by pet cats, summing to 649 million reptiles year⁻¹ killed by all cats. Predation by cats is reported for 258 Australian reptile species (about one-quarter of described species), including 11 threatened species. Conclusions. Cat predation exerts a considerable ongoing toll on Australian reptiles. However, it remains challenging to interpret the impact of this predation in terms of population viability or conservation concern for Australian reptiles, because population size is unknown for most Australian reptile species, mortality rates due to cats will vary across reptile species and because there is likely to be marked variationamongreptile species in their capability to sustain any particular predation rate. Implications. This study provides a well grounded estimate of the numbers of reptiles killed by cats, but intensive studies of individual reptile species are required to contextualise the conservation consequences of such predation.J. C. Z. Woinarski, B. P. Murphy, R. Palmer, S. M. Legge, C. R. Dickman, T. S. Doherty, G. Edwards, A. Nankivell, J. L. Read and D. Stokel