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Context. Invasive predators are a key threat to biodiversity worldwide. In Australia, feral cats are likely to be responsible for many extinctions of native mammal species in the south and centre of the continent. Aims. Here we examine the effect of feral cats on native rodent populations in the second of two translocation experiments. Methods. In a wild-to-wild translocation, we introduced pale field rats, Rattus tunneyi, whose populations are declining in the wild, into two pairs of enclosures where accessibility by feral cats was manipulated. Key results. Individual rats translocated into enclosures accessible to cats were rapidly extirpated after cats were first detected visiting the enclosures. Rats in the enclosure not exposed to cats were 6.2 times more likely to survive than those exposed to cats. Two individual cats were responsible for the deaths of all but 1 of 18 cat-accessible rats. Rats in the site with denser ground cover persisted better than in the site with more open cover. Conclusions. These results are consistent with our previous study of a different native rat species in the same experimental setup, and provide further evidence that, even at low densities, feral cats can drive local populations of small mammals to extinction.

Decision triggers are defined thresholds in the status of monitored variables that indicate when to undertake management, and avoid undesirable ecosystem change. Decision triggers are frequently recommended to conservation practitioners as a tool to facilitate evidence-based management practices, but there has been limited attention paid to how practitioners are integrating decision triggers into existing monitoring programs. We sought to understand whether conservation practitioners’ use of decision triggers was influenced by the type of variables in their monitoring programs. We investigated this question using a practitioner-focused workshop involving a structured discussion and review of eight monitoring programs. Among our case studies, direct measures of biodiversity (e.g. native species) were more commonly monitored, but less likely to be linked to decision triggers (10% with triggers) than measures being used as surrogates (54% with triggers) for program objectives. This was because decision triggers were associated with management of threatening processes, which were often monitored as a surrogate for a biodiversity asset of interest. By contrast, direct measures of biodiversity were more commonly associated with informal decision processes that led to activities such as management reviews or external consultation. Workshop participants were in favor of including more formalized decision triggers in their programs, but were limited by incomplete ecological knowledge, lack of skilled staff, funding constraints, and/or uncertainty regarding intervention effectiveness. We recommend that practitioners consider including decision triggers for discussion activities (such as external consultation) in their programs as more than just early warning points for future interventions, particularly for direct measures. Decision triggers for discussions should be recognized as a critical feature of monitoring programs where information and operational limitations inhibit

Monitoring programmes are intended to inform effective biodiversity conservation and management (Legge et al. 2018). Well‐designed programmes can establish baseline conditions, determine trends in threatened species populations, quantify the effects of management, and provide warning of ecosystem changes (Magurran et al. 2010). For these reasons, biodiversity monitoring underpins the activities of land management agencies worldwide. However, it is not always possible to directly monitor key variables at ideal spatio‐temporal resolutions, due to resourcing or logistic constraints. For example, direct monitoring of koalas (Phascolarctos cinereus) can be cost‐ and time‐intensive as koalas are cryptic, occur at low densities, and are difficult to reliably observe in dense forest canopies (McAlpine et al. 2006).

Context: Many Australian mammal species are highly susceptible to predation by introduced domestic cats (Felis catus) and European red foxes (Vulpes vulpes). These predators have caused many extinctions and have driven large distributional and population declines for many more species. The serendipitous occurrence of, and deliberate translocations of mammals to, 'havens' (cat- A nd fox-free offshore islands, and mainland fenced exclosures capable of excluding cats and foxes) has helped avoid further extinction. Aims: The aim of this study was to conduct a stocktake of current island and fenced havens in Australia and assess the extent of their protection for threatened mammal taxa that are most susceptible to cat and fox predation. Methods: Information was collated from diverse sources to document (1) the locations of havens and (2) the occurrence of populations of predator-susceptible threatened mammals (naturally occurring or translocated) in those havens. The list of predator-susceptible taxa (67 taxa, 52 species) was based on consensus opinion from >25 mammal experts. Key results: Seventeen fenced and 101 island havens contain 188 populations of 38 predator-susceptible threatened mammal taxa (32 species). Island havens cover a larger cumulative area than fenced havens (2152 km2 versus 346 km2), and reach larger sizes (largest island 325 km2, with another island of 628 km2 becoming available from 2018; largest fence: 123 km2). Islands and fenced havens contain similar numbers of taxa (27 each), because fenced havens usually contain more taxa per haven. Populations within fences are mostly translocated (43 of 49; 88%). Islands contain translocated populations (30 of 139; 22%); but also protect in situ (109) threatened mammal populations. Conclusions: Havens are used increasingly to safeguard threatened predator-susceptible mammals. However, 15

The domestic cat (Felis catus) is an invasive exotic in many locations around the world and is thought to be a key factor driving recent mammal declines across northern Australia. Many mammal species native to this region now persist only in areas with high topographic complexity, provided by features such as gorges or escarpments. Do mammals persist in these habitats because cats occupy them less, or despite high cat occupancy? We show that occupancy of feral cats was lower in mammal-rich habitats of high topographic complexity. These results support the idea that predation pressure by feral cats is a factor contributing to the collapse of mammal communities across northern Australia. Managing impacts of feral cats is a global conservation challenge. Conservation actions such as choosing sites for small mammal reintroductions may be more successful if variation in cat occupancy with landscape features is taken into account.

Recent studies at some sites in northern Australia have reported severe and rapid decline of some native mammal species, notwithstanding an environmental context (small human population size, limited habitat loss, substantial reservation extent) that should provide relative conservation security. All of the more speciose taxonomic groups of mammals in northern Australia have some species for which the conservation status has been assessed as threatened, with 53% of dasyurid, 46% of macropod and potoroid, 33% of bandicoot and bilby, 33% of possum, 31% of rodent, and 24% of bat species being assessed as extinct, threatened or Near Threatened. This paper reviews disparate recent and ongoing studies that provide information on population trends across a broader geographic scope than the previously reported sites, and provides some information on the conservation status and trends for mammal groups (bats, larger macropods) not well sampled in previous monitoring studies. It describes some diverse approaches of studies seeking to document conservation status and trends, and of the factors that may be contributing to observed patterns of decline. The studies reported provide some compelling evidence that predation by feral cats is implicated in the observed decline, with those impacts likely to be exacerbated by prevailing fire regimes (frequent, extensive and intense fire), by reduction in ground vegetation cover due to livestock and, in some areas, by ‘control’ of dingoes. However the impacts of dingoes may be complex, and are not yet well resolved in this area. The relative impacts of these individual factors vary spatially (with most severe impacts in lower rainfall and less topographically rugged areas) and between different mammal species, with some species responding idiosyncratically: the most notable example is the rapid decline of the northern quoll Dasyurus hallucatus due to poisoning by the introduced cane toad Rhinella marina, which continues to sp

Fire regimes are changing throughout the world. Changed fire patterns across northern Australian savannas have been proposed as a factor contributing to recent declines of small- and medium-sized mammals. Despite this, few studies have examined the mechanisms that underpin how species use habitat in fire-affected landscapes. We determined the habitats and resources important to the declining golden-backed tree-rat (Mesembriomys macrurus) in landscapes partially burnt by recent intense fire. We aimed to (i) compare the relative use of rainforest and savanna habitats; (ii) examine the effect of fire history on use of savanna habitats; and (iii) identify key foraging and denning resources. Habitat selection was examined by comparing the availability of eight habitat types around real (used) and generated (available) location points. Individuals used a range of habitats, but consistently selected long unburnt rainforest in preference to recently burnt savanna (1–12 months post-fire); however, recently burnt savanna was used in preference to long unburnt savanna. Tree-rats foraged in Terminalia hadleyana, Planchonia rupestris, Celtis philippensis and Owenia vernicosa, tree species that are found in a variety of habitat types. Individuals used a range of den sites, including cliffs, trees, logs, scree and stags found throughout the study area. Although multiple factors may have led to the decline of Mes. macrurus across its range, these results are consistent with the idea that changes in the savanna structure as a consequence of contemporary fire patterns could also have a role. The continued persistence of Mes. macrurus in the northwest Kimberley may be supported by land management strategies that conserve fruiting and hollow-bearing trees, and maintain the availability of fire-sensitive vegetation types.

The spread of the toxic cane toad Rhinella marina threatens populations of the endangered northern quoll Dasyurus hallucatus. We identified quoll populations at risk from toad invasion in the central Kimberley and explored whether free ranging quolls would consume ‘toad-aversion’ baits that induce aversions to live toads. A long-term study in Kakadu National Park showed that each generation of quolls learns to avoid toads, so one deployment of toad-aversion baits could protect quolls from toads. Encouragingly, 50% of wild quolls at Sir John Gorge, Mornington Wildlife Sanctuary (central Kimberley) consumed toad-aversion sausages. More research on captive quolls is necessary to develop long-lasting toad-aversion baits suitable for aerial deployment.

Small mammal species are declining across northern Australia. Predation by feral cats Felis sylvestris catus is one hypothesised cause. Most evidence of cat impacts on native prey comes from islands, where cat densities are often high, but cats typically