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Abstract

From analysis of results from 93 studies on the frequency of occurrence of birds in cat dietary samples, and a recently published assessment of the population size of feral cats in largely natural landscapes, we estimate and map the number of birds killed annually in Australia by feral cats. We show that average rates of predation on birds by cats on islands are ca. 10 times higher than for comparable mainland areas. Predation rates on birds are also relatively high in hot, arid regions. Across Australia's natural landscapes, feral cats typically consume 272 million birds yr− 1 (95% confidence interval [CI]: 169–508 million). However, there is substantial inter-annual variation, depending on changes in the cat population that are driven by rainfall conditions: ranging between 161 million birds yr− 1 (95% CI: 114–284 million) following dry periods and 757 million birds yr− 1 (95% CI: 334–1580 million) following wet periods. On average, feral cats kill 35.6 birds km− 2 yr− 1 (95% CI: 22.2–66.6). About 99% of these mortalities are native bird species. With a much sparser evidence base, we also estimate that a further 44 million birds are killed annually by feral cats in highly modified landscapes, and 61 million birds are killed annually by pet cats, summing to 377 million birds killed yr− 1 (i.e., just over 1 million birds per day) by all cats. Feral cats include a significantly higher proportion of birds in their diet than do other main mammalian predators. The national tally of birds killed by cats in Australia is broadly comparable to recent assessments for Canada, but less than that reported for the United States (because the cat population is much higher there). However, it remains challenging to interpret this mortality tally in terms of population viability or conservation concern for Australian birds.

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... Even in small-scale studies, cats can have a significant impact on an impressive diversity of regional wildlife. Domestic cat predation is a direct cause of wildlife mortality, but cats can also affect bird populations through their role in disease transmission, resource competition, spatial exclusion of native species, and a fear induction (Louvrier et al. 2022), all of which compound their impact on biodiversity (Gehrt et al. 2013, Doherty et al. 2017, Loss and Marra 2017, Trouwborst et al. 2020. Pet cats, even wellfed individuals, are opportunistic meso-carnivores, which pose an additional threat to wildlife communities (Crooks andSoulé 1999, Hawkins et al. 2004). ...
... Pet cats, even wellfed individuals, are opportunistic meso-carnivores, which pose an additional threat to wildlife communities (Crooks andSoulé 1999, Hawkins et al. 2004). Cats have been associated in the extirpation of at least 367 species worldwide and they have been implicated in more than half of recent extinction events associated with the introduction of exotic mammals in sensitive areas (Doherty et al. 2017). It is important to stress that domestic cats may cause an unsustainable harvest in local populations (Smith et al. 1993, Crooks andSoulé 1999), as shown by computational simulations (van Heezik et al. 2010). ...
... Although prey selected by cats closely reflect prey availability (Flux 2017), our survey provides an incomplete sample of prey because taxa returned are likely to differ substantially from total preyed taxa (Loyd et al. 2013, McDonald et al. 2015, Mori et al. 2019, Seymour et al. 2020). In addition, several studies provide evidence that domestic cats also cause substantial mortality of reptiles (Mori et al. 2019), small mammals (Doherty et al. 2017), and amphibians (Loyd et al. 2013). Domestic cats affect a wide range of wildlife and this may be especially important in the northern Andes, where wildlife is available all year round as compared to changes in prey availability because of the seasonality in temperate regions (Krauze-Gryz et al. 2017). ...
... Although there exist numerous local-scale studies from several continents that document consequential impacts of cat predation of wildlife, large-scale studies that quantify total predation and thus allow inferences about the likelihood of cumulative impacts on wildlife populations and biodiversity are restricted to a few countries. For example, cats are estimated to annually kill approximately 100-300 million birds in Canada (Blancher, 2013), 2.4 billion birds and 12.3 billion mammals in the United States (Loss et al., 2013), 272 million birds and 1144 million mammals in Australia (Woinarski et al., 2017;Murphy et al., 2019), and 583 million mammals and 136 million birds in Polish farmsteads (Krauze-Gryz et al., 2019). Such large-scale evaluations help demonstrate the overall magnitude of domestic cat predation and relate it to other sources of wildlife mortality. ...
... For the first time, we estimated national-level predation on wildlife by free-ranging domestic cats in China. Such large-scale evaluations had also been lacking for Asia more broadly, and only a handful of studies worldwide have documented the cumulative magnitude of cat predation on wildlife at a national level, with all from countries having lower biodiversity and human population than China (Dunn and Tessaglia, 1994;Levy and Crawford, 2004;Blancher, 2013;Loss et al., 2013;Loss and Marra, 2017;Woinarski et al., 2017;Krauze-Gryz et al., 2019;Mori et al., 2019;Woolley et al., 2020). Our predation estimates suggest that cats in China depredate a substantial number of wildlife, with roughly 12.13-32.98 billion total animals killed annually by all owned and unowned cats. ...
... published literature documenting local predation rates (Blancher, 2013;Loss et al., 2013;Woinarski et al., 2017). Due to a lack of small-scale empirical research on cat predation in China, this study used a survey questionnaire approach to upscale per cat abundance and predation rate estimates by individual respondents to the entire country. ...
Article
Throughout much of the world, growing populations of free-ranging domestic cats pose an increasingly serious threat to biodiversity. However, no study has estimated the magnitude of wildlife mortality caused by cats in China, one of the largest and most biodiverse nations on earth. We used a novel, survey questionnaire-based approach to estimate annual predation on wildlife by cats in China; we separately considered predation rates in urban and rural areas and by both owned free-ranging cats and unowned cats (e.g., feral and semi-feral cats including those associated with feeding and trap-neuter-return (TNR) activities). Using statistical simulations based on 2187 questionnaire responses that included direct observations of prey returns to owners and predation events by unowned cats, we estimate that the minimum annual amount of predation by all free-ranging cats in China is: 1.61-4.95 billion invertebrates, 1.61 -3.58 billion fishes, 1.13-3.82 billion amphibians, 1.48-4.31 billion reptiles, 2.69-5.52 billion birds, and 3.61-9.80 billion mammals. Thus, we show that free-ranging cats cause a tremendous death that may be profoundly impacting China's wildlife populations and biodiversity. Our results indicate that there is an urgent need for increased research into the impacts of cats on wildlife in China, and for management and policy that reduces numbers of free-ranging cats and thus mitigates their harmful effects on China's wildlife.
... There are estimated to be somewhere around 1.4 to 3.4 million feral cats across Australia, around one feral cat per four square kilometers [160]. There is no doubt that feral cats eat large numbers of native fauna [161][162][163] but the studies are not conclusive on the actual effects on prey populations generally [162][163][164], and observed effects do not necessarily equate to causation [160]. It has been argued that feral cats have led to the demise of mammalian fauna [23,29,43,44,156,165], and an exclusion study in the Kimberley region suggested that feral cats can extirpate local populations of native mammals [35]. ...
... There are estimated to be somewhere around 1.4 to 3.4 million feral cats across Australia, around one feral cat per four square kilometers [160]. There is no doubt that feral cats eat large numbers of native fauna [161][162][163] but the studies are not conclusive on the actual effects on prey populations generally [162][163][164], and observed effects do not necessarily equate to causation [160]. It has been argued that feral cats have led to the demise of mammalian fauna [23,29,43,44,156,165], and an exclusion study in the Kimberley region suggested that feral cats can extirpate local populations of native mammals [35]. ...
... Hunting cats to protect threatened species, such as by Indigenous hunters, also needs to be examined further for effectiveness [181]. The monitoring of the outcomes of feral cat control is essential, including the benefits to the native species affected by feral cats [162,176,179,182]. ...
Article
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Northern Australian biomes hold high biodiversity values within largely intact vegetation complexes, yet many species of mammals, and some other taxa, are endangered. Recently, six mammal species were added to the 20 or so already listed in the Australian endangered category. Current predictions suggest that nine species of mammal in northern Australia are in imminent danger of extinction within 20 years. We examine the robustness of the assumptions of status and trends in light of the low levels of monitoring of species and ecosystems across northern Australia, including monitoring the effects of management actions. The causes of the declines include a warming climate, pest species, changed fire regimes, grazing by introduced herbivores, and diseases, and work to help species and ecosystems recover is being conducted across the region. Indigenous custodians who work on the land have the potential and capacity to provide a significant human resource to tackle the challenge of species recovery. By working with non-Indigenous researchers and conservation managers, and with adequate support and incentives, many improvements in species' downward trajectories could be made. We propose a strategy to establish a network of monitoring sites based on a pragmatic approach by prioritizing particular bioregions. The policies that determine research and monitoring investment need to be re-set and new and modified approaches need to be implemented urgently. The funding needs to be returned to levels that are adequate for the task. At present resourcing levels, species are likely to become extinct through an avoidable attrition process .
... Another Australian report described analyses of results from 93 studies on the frequency of occurrence of birds in cat dietary samples, combined with an estimate of the population size of feral cats and pet cats, and the authors concluded that just over 1 million birds per day are killed by cats in Australia (54). In that study, it was estimated that across Australia, 3.5% of the bird population was killed annually by cats, with the lowest numbers killed by cats in urban areas, and the highest numbers killed by feral cats in remote areas. ...
... If predation by cats removes unhealthy individuals unlikely to breed again, and likely to die shortly from other causes anyway, the magnitude and significance of any effect urban cats have on native bird populations is at the very least unclear. Furthermore, if the large numbers of birds killed by cats that some studies report (4,54) are misleading, they ought not to be the basis for imposing lethal control measures on urban cats unless and until more reliable measures of the impacts of cats on wildlife numbers become available. Prospective studies are urgently needed to evaluate the impact of owned dogs and cats on wildlife numbers and diversity in urban areas. ...
... The vegetation density was greater at this site, and the authors concluded it was vegetation density rather than cats or cat management legislation that had the greatest impact on susceptible populations. The results of this study provide evidence that determining the magnitude of effects of predation by urban domestic cats can be further complicated by contemporaneous confounding factors such as habitat loss (54,58,68). Further research is needed to examine the complex role pet cats now occupy in Australian urban ecosystems and their impact on populations of native wildlife and invasive species. ...
Article
Concerns about the impact of pet dogs and cats on native wildlife populations have shaped pet control legislation, despite there being scant research of their impact in urban areas. Using an online questionnaire, we obtained data from 662 Australian dog and cat owners who had observed their pets capture prey in the previous 6 months. Of the pets observed to catch prey, dogs caught a median of 2 mammals, 2 birds, 2 reptiles, and 3 amphibians, whereas cats caught a median of 3 mammals, 2 birds, 4 reptiles, and 2 amphibians. Of mammals caught by dogs and cats, 88 and 93%, respectively, were identifiable as introduced mice, rats, and rabbits. Of pets that caught prey, a substantial proportion caught native animals (62% of dogs and 47% of cats). However, median numbers of native animals caught per dog (2) or cat (3) over 6 months were low. Small skinks and lizards comprised the greatest proportion for dogs and cats, but dogs also caught larger native prey (e.g., possums, kangaroos, and wallabies). Most birds caught by dogs and cats were common or introduced (dogs: crested pigeons and lorikeets; cats: noisy miners and rosellas). To design measures that will effectively protect Australia's native wildlife, thorough understanding of the role dogs and cats play in Australian urban ecosystems is required. These findings can inform that understanding, and assist with development of management strategies for urban dogs and cats, and as well as directing resources to efforts that will most protect urban wildlife.
... Cats are opportunistic hunters and their predatory behavior is innate, and can persist even if the individuals are sufficiently fed (Adamec 1976;Spotte 2014). Their prey commonly includes wildlife, such as birds (Dauphiné and Cooper 2009;Woods et al. 2003;Woinarski et al. 2017), mammals (Loss et al. 2013;Krauze-Gryz et al. 2017;Murphy et al. 2019), reptiles (Arnaud et al. 1993;Barratt 1998;Woinarski et al. 2018), amphibians (Woods et al. 2003;Baker et al. 2005;Woinarski et al. 2020) and invertebrates (Gillies and Clout 2003;Medina and García 2007;Woolley et al. 2020), many of which are native. However, most cat predation studies have focused on the birds and mammals (Blancher 2013;Mella-Méndez et al. 2019;Murphy et al. 2019), with little attention paid to other groups like amphibians, reptiles and invertebrates (Seymour et al. 2020;Woinarski et al. 2020). ...
... Birds and invertebrates were the groups that presented the highest number of species depredated by hunting domestic cats, a finding that coincided with those of similar studies, in which birds are also reported as one of the groups most affected by cats (van Heezik et al. 2010;Thomas et al. 2012;Woinarski et al. 2017). At global level, birds constitute the group with the highest number of threatened and extinct species as a result of this predator (Doherty et al. 2016). ...
Article
Full-text available
Domestic cats are a potential risk for native fauna in the Neotropics. Intrinsic (age, weight, sex, color) and extrinsic (nocturnal confinement, time spent outside the home, distance to green areas, etc.) factors can influence the type and quantity of prey that cats take to their homes. The study goal was to evaluate domestic cat predation in a Neotropical city. We intend to answer the following questions: (1) Which is the richness, dominance and abundance of prey captured by domestic cats? (2) Which are the extrinsic or intrinsic factors that most influence prey capture by domestic cats? We predict that: (a) cats will capture a large diversity of native wildlife and (b) extrinsic factors will have a greater effect compared intrinsic factors due to the innate predatory cat’s behavior. We chose 120 cats from 44 households in the city of Xalapa, Veracruz, Mexico. We documented the richness, dominance and abundance of wildlife species captured and brought home by cats during March to August 2019 and those intrinsic and extrinsic factors that modulate their predatory behavior. The cats captured 246 prey items, 35.8% were reptiles, 23.2% invertebrates, 17.9% amphibians, 15.4% birds and 7.7% mammals. The prey items belonged to 64 taxa (17 birds, 17 invertebrates, 15 reptiles, nine mammals and six amphibians). The lizard Sceloporus variabilis was the most captured prey. Of the prey items, 93.5% were native and 6.5% non-native. Five intrinsic and 5 extrinsic factors contributed most to the predation events, of which cat stripe color, time spent by the cats outside of the home and nocturnal confinement were the most important. These results allow us to understand the harmful effect of cats on wildlife in a Neotropical city.
... Feral cats are regarded as one of the most destructive invasive mesopredators to arrive in Australia (Murphy et al., 2019;Woinarski et al., 2017Woinarski et al., , 2018. Even at low densities, feral cats can substantially impact prey species populations. ...
... APD, agricultural property dingo; CPP, cattle property Paluma; FLP, Fleurieu peninsula; KIR, Kirrama National Park; KOM, Koombooloomba National Park; MZT, mount zero-Taravale wildlife sanctuary; TNP, Taunton National Park; TUM, tumoulin forestry reserve; WOO, Wooroonooran National Park Previous studies have suggested that feral cats could be found in very low densities in the AWT. This suggestion was based on the continental scale feral cat density model, which has been used to infer how many invertebrates, reptiles, birds, amphibians, and small mammals are consumed by cats annually (Murphy et al., 2019;Woinarski et al., 2017Woinarski et al., , 2018Woinarski et al., , 2020Woolley et al., 2020). Cat density patterns in the continental models are probably accurate for semi-arid and arid Australia, due to multiple existing density estimates from these environments. ...
Article
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Invasive mesopredators are responsible for the decline of many species of native mammals worldwide. Feral cats have been causally linked to multiple extinctions of Australian mammals since European colonization. While feral cats are found throughout Australia, most research has been undertaken in arid habitats, thus there is a limited understanding of feral cat distribution, abundance, and ecology in Australian tropical rainforests. We carried out camera‐trapping surveys at 108 locations across seven study sites, spanning 200 km in the Australian Wet Tropics. Single‐species occupancy analysis was implemented to investigate how environmental factors influence feral cat distribution. Feral cats were detected at a rate of 5.09 photographs/100 days, 11 times higher than previously recorded in the Australian Wet Tropics. The main environmental factors influencing feral cat occupancy were a positive association with terrain ruggedness, a negative association with elevation, and a higher affinity for rainforest than eucalypt forest. These findings were consistent with other studies on feral cat ecology but differed from similar surveys in Australia. Increasingly harsh and consistently wet weather conditions at higher elevations, and improved shelter in topographically complex habitats may drive cat preference for lowland rainforest. Feral cats were positively associated with roads, supporting the theory that roads facilitate access and colonization of feral cats within more remote parts of the rainforest. Higher elevation rainforests with no roads could act as refugia for native prey species within the critical weight range. Regular monitoring of existing roads should be implemented to monitor feral cats, and new linear infrastructure should be limited to prevent encroachment into these areas. This is pertinent as climate change modeling suggests that habitats at higher elevations will become similar to lower elevations, potentially making the environment more suitable for feral cat populations. Feral cats are responsible for the decline of multiple native species both globally and in Australia. However, we know very little about their ecology in tropical rainforests. This study demonstrated despite predictions of cats being absent from wet complex habitats, feral cats were present in all national parks surveyed and prefer low elevation, rugged terrain in rainforests.
... However, in recent years a rapid increase in the population size of cats has been observed, and it is estimated to have doubled in France between 1990and 2015(FACCO, 2017, and increased by 200,000 in Belgium between (SPF Economie, 2016. Therefore, it is not surprising that such an exponential increase of their populations in many countries leads to 350 million birds being killed per year in Canada (Blancher, 2013), 148.9 million in Poland (Krauze-Gryz et al., 2017), 272 million in Australia Doherty et al., 2017b;Woinarski et al., 2017), as well as 12.3 billion small mammals in the United States (Loss et al., 2013), 631 million in Poland (Krauze-Gryz et al., 2017), and 466 million reptiles in Australia , just to give a few examples of the scale of cat predation. ...
... Despite the observed decreasing populations and extinction of many wild animals, especially small mammals and birds (Veitch, 1985;Dowding and Murphy, 2001;Medway, 2004;Hughes et al., 2008;Bonnaud et al., 2009;Faulquier et al., 2009) in closed island ecosystems (Liberg 1984;Woods et al., 2003;Bonnaud et al., 2011;Medina et al., 2011) and on the scale of a country and the continent (Barratt 1997;Beckerman et al., 2007;Baker et al., 2008;Dauphiné and Cooper, 2009;Bonnington et al., 2013;Legge et al., 2017;Woinarski et al., 2017) little is known about the niches overlaping between cats as predator and birds as potential prey. This is probably caused by difficulties in performing a joint assessment of cat and bird densities in spatially large domains. ...
Article
Ecological interactions between native species are often disturbed by invasive species. However, to understand their impact on wild native animal populations on a country scale it is necessary to develop a predictive model. Therefore, I followed the species density distribution modelling approach to explore how feral domestic cats (Felis catus) along with environmental predictors determined densities of two bird species, the Yellowhammer (Emberiza citrinella) and the Yellow Wagtail (Motacilla flava) on the whole area of Poland. As a modelling method, I used the Generalised Additive Model to develop two models for each of the two bird species: The first with the feral cat density as an additional predictor, and the second without it. As a result, I demonstrated the negative impact of cat density on native bird populations, illustrated by reduced density of the two studied species in their preferred habitats, in which cats reached a high density. Although it cannot be explicitly asserted that cats lead to a local extinction of the two bird species, these predators should not be underestimated. In many locations feral populations are fed with new individuals, and they do not follow the same internal mechanisms regulating their population as the native bird fauna. Thus, on a large spatial scale species density distribution models of birds should include cats’ population size as an additional predictor when this predator's environmental preferences overlap with preferences of the studied target groups.
... Many feral populations cause a severe impact in native wild species, like cats (Felis silvestris) (Oedin et al. 2021;Woinarski et al. 2017;Medina et al. 2009;Honegger 1981;Frank et al. 2014), or goats (Capra aeagrus) in some islands like Galapagos (Desender et al. 1999). However, many populations, even of species that generate a conservation problem in certain places, such as the above mentioned goats, may hold conservation value if, for instance, they fill the empty niche of an extinct species, represent the only surviving genetic material of extinct ancestors, or havestrong cultural importance. ...
... In numerous cases, feral populations pose an undeniable threat to biodiversity and human activities such as agriculture and livestock production, and need to be managed or controlled (Bonacic et al., 2019). A clear example is provided by feral cats (Felis silvestris catus), that prey on birds, reptiles, amphibians and small mammals (Honegger 1981;Medina et al. 2009;Frank et al. 2014;Woinarski et al. 2017;Oedin et al. 2021), having driven some to extinction, as with the island endemic and flightless Stephens Island wren (Traversia lyalli) in New Zealand (Galbreath & Brown 2004). In addition, free roaming domestic cats suppose a risk for disease transmission to threatened fauna (Duarte et al. 2012), or hybridization whit genuine wildcats Felis silvestris (Krüger et al. 2009). ...
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Feral animals are those that live wild but are descendants of domesticated populations. Although in many cases, possibly the majority, these populations suppose a risk to the environment and may conflict with wild local species and human activities, there are feral populations that are considered worth preserving hold and, in some cases, already enjoy protection from interest groups and even pubic authorities. In this review, we aimed to separate those valuable populations using model cases classified by three main criteria of interest: (a) the genetic conservation value in case of extinct wild ancestors, (b) the niche occupancy criterion and, finally, (c) a cultural criterion. We propose a detailed analysis of feral populations under scrutiny, supporting control measures when necessary, but also allowing for international protection at the same level as wild animals for feral taxa of special concern. Feral taxa which are already in the focus of conservation efforts and may be awarded extended recognition and protection include ancient lineages of feral dogs, horses, camels, goats and bees (as pollinators) in different parts of the world.
... Early observers reported on the impacts of these two predators on the Australian bird fauna, with severe and rapid decline of many native bird species mirroring the sequential spread of cats and foxes (e.g., Campbell 1915, Le Souef 1923, Abbott et al. 2014, although the separate and relative influence of these two predators has often been difficult to tease apart. Other evidence of the extent of predation and the impacts of cats (feral and pet) on Australian birds has been adduced in a series of recent publications (Woinarski et al. 2017a, Woinarski et al. 2017b, Legge et al. 2020. ...
... That fewer bird species are known to be consumed by foxes than by cats is also broadly consistent with previous Australian studies that have shown birds to be a less important component of fox diet than of cat diet. For example, across 22 Australian sites where both predators co-occurred, Woinarski et al. (2017a) reported that birds occurred in 17% of fox dietary samples and in 29% of cat dietary samples. ...
Article
Two introduced carnivores, the European red fox Vulpes vulpes and domestic cat Felis catus , have had extensive impacts on Australian biodiversity. In this study, we collate information on consumption of Australian birds by the fox, paralleling a recent study reporting on birds consumed by cats. We found records of consumption by foxes on 128 native bird species (18% of the non-vagrant bird fauna and 25% of those species within the fox’s range), a smaller tally than for cats (343 species, including 297 within the fox’s Australian range, a subset of that of the cat). Most (81%) bird species eaten by foxes are also eaten by cats, suggesting that predation impacts are compounded. As with consumption by cats, birds that nest or forage on the ground are most likely to be consumed by foxes. However, there is also some partitioning, with records of consumption by foxes but not cats for 25 bird species, indicating that impacts of the two predators may also be complementary. Bird species ≥3.4 kg were more likely to be eaten by foxes, and those <3.4 kg by cats. Our compilation provides an inventory and describes characteristics of Australian bird species known to be consumed by foxes, but we acknowledge that records of predation do not imply population-level impacts. Nonetheless, there is sufficient information from other studies to demonstrate that fox predation has significant impacts on the population viability of some Australian birds, especially larger birds, and those that nest or forage on the ground.
... In arid Australia, many ground nesting birds are threatened and in decline (Reid and Fleming, 1992). Habitat loss and fragmentation are important contributors to this decline, but ground nesting birds are also threatened by high nest predation rates from invasive predators including the red fox and feral cat, Felis catus (Reid and Fleming, 1992;Smith et al., 1994;Woinarski et J o u r n a l P r e -p r o o f J o u r n a l P r e -p r o o f Highlights  Carcass presence and proximity increased predation by scavengers on artificial bird nests  More artificial bird nest eggs were depredated in open habitat  Corvids depredated the most artificial nests and visited the most carcasses  Red foxes were the dominant predators of artificial night parrot nests  Carcass presence influenced artificial nest predation by red foxes but not corvids J o u r n a l P r e -p r o o f ...
... comm. Nick Leseberg; Woinarski et al., 2017). ...
Article
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In addition to feeding on animal remains, many scavengers also function as predators. Carcasses may therefore affect local animal communities by attracting facultative scavengers and increasing predation risk for other species in the vicinity of the carcasses. This risk may be elevated in low productivity environments, especially where humans increase carcass production and where facultative scavengers include invasive species. In June and October 2018, we monitored experimentally placed red kangaroo (Osphranter rufus) carcasses and artificial bird nests in two different habitats in the Simpson Desert, Australia, to identify the nest predators attracted to the carcasses, and to determine how carcasses affect overall and predator-specific nest predation. We modelled our nests to approximate those of the ground nesting little buttonquail (Turnix velox) and the endangered night parrot (Pezoporus occidentalis). Native Corvus spp. and then invasive red foxes (Vulpes vulpes) were the top carcass visitors and nest egg predators. Carcass presence and open habitat increased overall nest predation and fewer artificial parrot nest eggs were depredated compared to those of quail. Open habitat and carcass presence only increased predator-specific nest predation by foxes, but corvid nest predation was highest in June 2018, and for the artificial quail nest types. Foxes were the main predator of eggs from night parrot nests. Our study shows that carcass provisioning by humans may have indirect, deleterious effects on ground nesting birds, and indicates that foxes might pose a greater threat to night parrot populations than previously recognised.
... Free roaming domestic and feral cats (Felis catus) are ubiquitous predators of birds in urban areas. An individual cat may kill 10 s to 100 s of birds per year [1,2]. This, in turn, may lead to millions of birds killed per year in cities, where high cat densities are supported by an abundance of anthropogenic food sources and reduced predator densities. ...
... It is surprising that empirical studies, including ours, have found weak and uncertain effects of owned outdoor cats on bird populations in urban landscapes, given the large estimates of the numbers of birds killed by cats [1,2,50]. It is possible that owned outdoor cats have stronger negative effects on bird populations than we and others have found, but that such effects are difficult to detect for several reasons. ...
Article
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Domestic cats (Felis catus) are ubiquitous predators of birds in urban areas. In addition to the lethal effect of predation, there can also be sublethal, negative effects of domestic cats on individual birds. These effects have led to the inference that reducing outdoor cat densities would benefit urban bird communities. Here we estimate the likely result of policies/programs designed to reduce densities of owned outdoor cats in urban areas, estimating relationships between bird richness/abundance and cat densities across 58 landscapes in Ottawa, Ontario, Canada. We estimate that we would most likely observe one additional bird species, and 0.003 additional individuals per species, if policies/programs reduced owned outdoor cat densities to zero in an average landscape in Ottawa (with 130.2 cats/km2). However, these effects of cat density on birds were uncertain, with 95% confidence intervals crossing zero. Our findings—in combination with those of previous studies—suggest a need for research to resolve the apparent disconnect between the strong, negative effects of cats on individual urban birds and the weak, uncertain effects of cats on bird populations. Although measures that reduce owned outdoor cat densities are justified based on the precautionary principle, evidence to date does not support prioritizing these measures over those addressing threats that have consistently strong effects on bird populations.
... In fact, feralization is an ongoing process due to the continual release or escape of domestic animals into the wild [5,6]. Many feral populations cause a severe impact on native wild species, like domestic cats (Felis silvestris) predating on songbirds and other fauna [7][8][9][10][11], or goats (Capra aegagrus hircus) feeding on endemic flora in some islands like Galapagos [12]. However, many populations, even of species that generate a conservation problem in certain places, such as the abovementioned goats, may hold conservation value if, for instance, they fill the empty niche of an extinct species, represent the only surviving genetic material of extinct ancestors, or have strong cultural importance. ...
... A dramatic example is provided by feral cats (F. silvestris catus), that prey on birds, reptiles, amphibians, and small mammals [7][8][9][10][11], having driven some to extinction, as with the island endemic and flightless Stephens Island wren (Traversia lyalli) in New Zealand [21]. In addition, free-roaming domestic cats suppose a risk of disease transmission to threatened fauna [22] or hybridization with genuine wildcats F. silvestris [23]. ...
Article
Full-text available
Feral animals are those that live in the wild but are descendants of domesticated populations. Although, in many cases, these feral populations imply a demonstrable risk to the ecosystems in which they live and may conflict with local wild species and human activities, there are feral populations that are considered worth preserving and, in some cases, they already enjoy protection by interest groups and even public authorities. In this review, we aim to identify valuable populations using three criteria: (a) Genetic conservation value (for instance, if the wild ancestor is extinct), (b) the niche occupancy criterion and, finally, (c) a cultural criterion. We propose a detailed analysis of feral populations under scrutiny, supporting control measures when necessary, but also allowing for international protection at the same level as wild animals for feral taxa of special concern. Feral taxa, which are already in the focus of conservation efforts, and should be awarded extended recognition and protection, mainly include ancient lineages with relevant genetic or cultural importance.
... Three of the greatest threats to Australian flora, fauna, and ecosystems are altered fire regimes, invasive species, and landclearing; all threats interact with and compound one another (Doherty et al. 2015). The approximately 3 billion vertebrates that we estimate to have been present within the burnt area is in addition to more than 2 billion frogs, lizards, birds, and mammals estimated to be killed annually by feral and domestic cats in Australia (Woinarski et al. 2017;Woinarski et al. 2018;Murphy et al. 2019;Woinarski et al. 2020b) and more again by red foxes (Saunders et al. 2010). These estimates of predation are derived for populations in the absence of a major fire event and many populations can potentially recover because of this. ...
... This illustrates that descriptor values reported for groups other than mammals may not reflect their importance in the diet. For this reason, even though we are aware that other vertebrate classes can comprise a considerable amount of resources used by carnivorans (Woinarski et al. 2017(Woinarski et al. , 2020, the available data are still insufficient to estimate how frequently those resources are consumed and how important predation by carnivorans is in regulating populations of non-mammalian prey. Future studies using other methods of dietary analyses that can identify items with greater detail, such as metagenomics or metabarcoding (Kartzinel et al. 2015), could help obtain more complete dietary information about prey that are hard to detect in scats. ...
Article
en • Mammalian carnivores (order Carnivora) perform important regulatory functions in terrestrial food webs. Building a comprehensive knowledge of the dietary patterns of carnivorans and the factors determining such patterns is essential for improving our understanding of the role of carnivorans in ecosystem functioning. • In the Neotropics, there are 64 extant species of terrestrial Carnivora, but information on their trophic ecology is diffuse. We compiled and analysed the available quantitative dietary data for Neotropical carnivorans, aiming to detect patterns of intraspecific and interspecific dietary variation at a large geographical scale. • The resulting database encompasses information on trophic interactions of 37 native carnivoran species from six families across 14 countries. There are clear geographical biases towards southern Brazil, Chile, and Argentina, and a noticeable knowledge gap within the Amazon. Also, most studies are focused on canids and felids, especially Puma concolor, Panthera onca, Cerdocyon thous, Leopardus pardalis, and Chrysocyon brachyurus, whereas for 27 native species, we found no quantitative dietary information. • Neotropical carnivorans consume species from at least 651 genera of vertebrates, invertebrates, and plants. We found clear species-specific dietary patterns and marked differences between Neotropical felids and canids. Although predators generally exhibit high levels of consistency in their diets regarding prey body mass, we detected significant intraspecific variation for all species analysed across study sites. • Body mass imposes strong constraints on prey use, but biogeographical differences in prey availability and human influence may drive the geographical variation we found. Overall, observed patterns show not only similarities with resource-use patterns found for carnivorans in other continents, such as nestedness driven by body mass, but also differences, such as high levels of frugivory and consumption of invertebrates by canids. Assessing resource-use patterns is the first step towards a better understanding of processes underlying the organisation of trophic interactions, and is imperative for addressing impacts of defaunation on ecosystems and for informing conservation efforts. RESUMO EM PORTUGUÊS es • Carnivoros mamíferos (ordem Carnivora) são responsáveis por manter funções regulatórias importantes em redes tróficas terrestres. Para que possamos entender o papel desempenhado por esses animais no funcionamento dos ecossistemas, é essencial construir um conhecimento abrangente no que diz respeito aos padrões de dieta e aos fatores que determinam esses padrões. • Na região neotropical, há 64 espécies nativas de Carnivora terrestres, mas as informações relativas à ecologia trófica dessas espécies são bastante difusas na literatura. Nós compilamos e analisamos dados quantitativos de dieta disponíveis para carnívoros neotropicais, com o objetivo de detectar padrões intraespecíficos e interespecíficos na dieta, além de variações numa escala geográfica extensa. • A base de dados resultante contém informações provenientes de estudos realizados em 14 países, acerca de interações tróficas de 37 espécies nativas de carnívoros de seis famílias diferentes. Há um viés geográfico evidente: as regiões Sul e Sudeste do Brasil, Chile e Argentina foram consideravelmente mais amostradas, enquanto há um vazio amostral na região da Amazônia, por exemplo. Além disso, a maioria dos estudos foca na dieta de canídeos e felídeos, principalmente Puma concolor, Panthera onca, Cerdocyon thous, Leopardus pardalis and Chrysocyon brachyurus, enquanto para 27 espécies, não encontramos dados quantitativos de dieta. • Carnívoros neotropicais consumem pelo menos 651 gêneros diferentes, entre vertebrados, invertebrados e plantas. Há um claro padrão de dieta espécie-específico e diferenças marcantes entre felídeos e canídeos neotropicais. Apesar de esses predadores geralmente exibirem altos níveis de consistência em suas dietas em termos da massa corpórea das presas, nós identificamos variações intraespecíficas significativas entre sítios para todas as espécies analisadas. • O tamanho corpóreo impõe limitações consideráveis aos padrões de uso de recursos, mas diferenças biogeográficas na disponibilidade de presas e influências antrópicas possivelmente levam às variações encontradas. De maneira geral, os padrões observados evidenciam similaridades com padrões de uso de recurso encontrados para carnívoros em outros continentes, como aninhamento relacionado a tamanho corpóreo, mas também divergências, como altos níveis de frugivoria e consumo de invertebrados por canídeos. Avaliar padrões de uso de recursos é o primeiro passo em direção a um entendimento mais completo dos processos que organizam interações tróficas, além de ser imprescindível para estimar os impactos da defaunação e orientar medidas de conservação.
... Cats are implicated in the extinction of 34 Australian native mammal species and are considered to pose an extinction risk to a further 123 species (Kearney et al., 2018;Woinarski, Burbidge, & Harrison, 2015). Feral and domestic cats are estimated to kill more than 2 billion frogs, lizards, birds, and mammals annually in Australia (Murphy et al., 2019;Woinarski et al., 2017;Woinarski et al., 2018;Woinarski et al., 2020). ...
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Free‐roaming domestic cats pose risks to wildlife, domestic animals, humans, and importantly, the cats themselves. Behavior change campaigns that seek to minimize these risks by increasing cat containment require an understanding of the factors that predict cat owners' containment behaviors. We conducted an online survey in Victoria, Australia (N = 1,024) to identify cat owners' (N = 220) behaviors in containing their cats, explore beliefs and attitudes that predict containment behavior, and compare attitudes about cat containment with respondents that do not own cats (N = 804). We found that 53% of cat owning respondents do not allow any roaming. These respondents were more likely to hold concerns about risks to cats' safety while roaming and less likely to perceive that cats have a right to roam. Concern about impacts to wildlife was not a significant predictor of containment behavior. Expectations that cat owners should manage cats' roaming behavior was a social norm among cat owners and other respondents, and cat containers were more likely to indicate that they would try to change behaviors of their peers that they perceived to be harmful to the environment. Cat containment campaigns could be improved by appealing to owners' concerns about cat well‐being, engaging respected messengers that align with these concerns, including owners who already contain their cats.
... Despite the apparent impacts of cats on bird populations, important information gaps continue to present challenges. For example, several basic aspects of cat-bird interactions remain poorly described in most locations, including which species are most often captured, the role of habitat differences in determining the identities of species attacked by cats, whether year-round residents or migrants are more susceptible, and which other traits (e.g., body size, propensity to forage on or near the ground) might influence the likelihood of birds being attacked by cats [7]. Furthermore, current estimates of cat-influenced mortality have been generated from a number of variables difficult to measure accurately. ...
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Depredation of birds by domestic cats is hypothesized to be one of many significant sources of mortality leading to global bird declines. Direct observations are relatively rarely documented compared with large numbers of birds hypothesized to be killed or wounded by cats. We analyzed data from two wildlife rehabilitation centers located in Salem and Grants Pass, Oregon USA, to understand which species were most likely to interact with a cat, and the species traits associated with cat interactions and habitats (urban vs. rural) of rescued birds. Interaction with a cat was the second-most commonly reported cause of admission, representing 12.3% of 6345 admissions. Half to two-thirds of birds were rescued from cats in urban settings and were usually species foraging on or near the ground. Most species were admitted to rehabilitation centers in direct proportion to their regional abundance. An exception was the absence of common species weighing less than 70 g, which we conclude is an effect of sampling bias. We conclude that cats most often interact with regionally common near-ground-dwelling bird species in both urban and rural habitats. Wildlife rehabilitation centers can provide valuable sources of data for cat-bird interactions but potential sources of uncertainty and bias in their data need to be considered carefully.
... To date, the most convincing demonstrations of the impacts of feral cats have come from islands where their introduction has unequivocally resulted in severe declines and in some cases extinctions of island fauna (Medina et al. 2011). Other demonstrations of the negative impacts of feral cats, not limited to islands, include mortalities of translocated threatened species caused by feral cat predation that ultimately result in the failure of reintroduction programs (Short et al. 1992, Moseby et al. 2011, population increases in potential prey associated with fencing feral cats and other predators out of specific areas (Risbey et al. 2000, Frank et al. 2014, Legge et al. 2018, extrapolation from feral cat predation rates to the numbers of individual prey killed (Loss et al. 2013, Woinarski et al. 2017, and dietary studies showing the frequency and range of prey taken by feral cats (Doherty et al. 2015, Murphy et al. 2019. The mechanism(s) by which feral cats affect other species include one or a combination of interactions such as competition with native carnivores for resources, hybridization, and/or transmission of disease; however, knowledge to date indicates that direct predation on prey is the single strongest deleterious effect of feral cats (Medina et al. 2014). ...
Article
Feral individuals of the cat Felis catus are recognised internationally as a threat to biodiversity. Open, non‐insular systems support a large proportion of the world’s biodiversity, but the population‐level impacts of feral cats in these systems are rarely elucidated. This limits prioritization and assessment of the effectiveness of management interventions. We quantified the predatory impact of feral cats on small mammals in open, non‐insular forest systems in Tasmania, Australia in the context of other factors hypothesized to affect small mammal densities and survival, namely the density of a native carnivore, co‐occurring small mammals, and rainfall. Change in feral cat density was the most important determinant of small mammal density and survival. We calculated that, on average, a 50% reduction in feral cat density could result in 25% and 10% increases in the density of the swamp rat Rattus lutreolus and long‐tailed mouse Pseudomys higginsi, respectively. Low‐level culling of feral cats that we conducted on two of our four study sites to experimentally alter feral cat densities revealed that swamp rat survival was highest when feral cat densities were stable. We conclude that feral cats exert downward pressure on populations of indigenous small mammals in temperate forest systems. However, alleviating this downward pressure on prey by culling a large proportion of the feral cat population is difficult as current methods for reducing feral cat populations in cool temperate forest systems are ineffective, and potentially even counter‐productive. We suggest using an adaptive approach that regularly and robustly monitors how feral cats and small mammals respond to management interventions that are intended to conserve vulnerable prey species.
... More so than elsewhere in the world, many separate studies have been gathered into a substantial evidence base on cat density and diet. This has allowed the following: robust analyses of cat distribution, population size and spatial variation in cat density across the Australian mainland and islands (Legge et al. 2017); estimates of the toll of predation of cats on animal groups; and identification of the native species most prone to cat predation (Woinarski et al. 2017a(Woinarski et al. , 2017bMurphy et al. 2019;Woolley et al. 2020). In this special issue, the final components of that series are presented, with estimates of the toll taken by cats in Australia on frogs ) and invertebrates . ...
... T he feral cat (Felis catus) (cat) is almost ubiquitous across the Australian mainland, occupying most habitats (West 2018), with recent studies suggesting there are an estimated 2.1-6.3 million feral cats residing in Australia Woinarski et al. 2017). They prey upon mammals, birds and reptiles and are identified as a major threat to many threatened fauna (Woinarski et al. 2015). ...
Article
The feral cat (Felis catus) is a key threat for many Australian native critical weight range animals (i.e. species of intermediate body mass between 35 and 5,500 g that are particularly susceptible to introduced predators) and estimates of cat abundance are required for assessing changes in population size. Camera trapping is a much used tool for monitoring and estimating population sizes, including with mark–resight techniques, for which the more robust estimators require individual identification. Many feral cats are individually marked, which potentially makes them suitable for such monitoring programmes. We sought to determine what proportion of cat images captured during a commonly used field deployment of camera traps could be individually identified, and whether aspects of camera trap deployment affected the rate of individual identification. Camera trap arrays were established in four conservation areas in south-west New South Wales, Australia, during 2017 (range 39–50 camera traps per site). The unlured camera traps were continuously deployed over 26 months, with five or 10 images captured per trigger. Where possible, cats were individually identified based on phenotypic characteristics. Over the deployment period (95,413 camera trap nights; CTN), we obtained 2.25 million images, of which 13,845 contained feral cats. Feral cat events (i.e. a series of images taken <5 minutes apart on the same camera trap) ranged from 0.004 to 0.047 events per CTN across the four conservation areas, with 85 individual cats identified. Depending on camera settings, few images could be assigned to a known individual (12.2–27.4% of feral cat events per site were of identifiable individuals). Minimum number known alive were 10–46 feral cats per site, with resultant quarterly densities ranging from 0.01 to 0.16 cats/km². With our current deployment, individual identification of feral cats was insufficient for estimating abundance or survival using individual mark–resight methods. Such deployment deficits limit the ecological conclusions that can be drawn from ours and similar studies.
... Recent work suggests that the decline of Australian fauna is on-going, with more than 27% of Australian species currently threatened with extinction (IUCN 2020). For example, a recent study suggested that 1 million birds are killed by feral cats every day (Woinarski et al. 2017), with unknown consequences to the population viability for Australian native birds. ...
Thesis
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Environmental changes caused or influenced by human activity have increased the current rate of extinction to 100-1000 times the standard background rate (Ceballos et al. 2015). The reduction or loss of habitat for conversion to extractive uses, urban development or resource production causes environmental change and is considered a key threat to the suite of values associated with intact forests (Kingsford et al. 2009). Important mechanisms for abating species decline in the face of such pressures include protected areas and vegetation management policy. Globally, protected area expansion is exponential (Steffen et al. 2011) and yet studies that test the effectiveness of protected areas in achieving biodiversity outcomes remain rare (Schleicher, Eklund, D. Barnes, et al. 2019). This is highly problematic because a lack of evaluation undermines society’s ability to address emergent declines in biodiversity or ecological integrity, and to adapt policy responses accordingly. Commonly adopted targets relating to the simple area of a region or representation of species or communities, are easy to count for reporting purposes but may be achieved with little value in terms of avoiding the loss of biodiversity. As previous studies have shown, strict adherence to these targets without a deep understanding of ecological and conservation science may threaten bona fide progress in terrestrial conservation because resources for nature conservation are limited and increasingly disproportionate to the magnitude of biodiversity loss. It is of the utmost importance to effectively prioritise conservation policies and programs to maximise the efficiency of limited funding. A failure to maximise the efficacy of programs and policies is problematic not only in terms from a scientific perspective but also because failing to adequately control threatening processes can have a disastrous impact on biological diversity and ecological integrity. Effectively designing policies and programs requires a deep understanding of social, cultural, economic and political values. This thesis contributes to filling gaps in political and socio-economic values by evaluating the effectiveness of policy responses to deforestation in Australia, a global deforestation hotspot (Cresswell and Murphy 2017). The goals of this thesis are to: 1) review policies and programs for retaining natural forested habitats in Australia; 2) estimate the impact of current protected areas in terms of preventing forest cover loss; 3) describe the impact of policy changes on vegetation; 4) develop evidence-based recommendations for retaining Queensland’s forests in the future. Owing to complex governance arrangements for forest retention policies and programs, I use a transdisciplinary mixed-methods approach to investigate the complexities, effectiveness and future directions for conservation policy in Queensland, Australia. I combine rigorous qualitative policy analysis 2 (Chapters 2 and 4) with robust quasi-experimental evaluation methods (Chapters 3) and frequentist modelling (Chapter 5) to produce policy-ready recommendations for the future security of Queensland’s native forests (Chapter 6). In my first chapter, I set the scene for the relevance of this work by broadly introducing the primary mechanisms for forest retention (protected areas and environmental impact assessment). In developing this chapter, it became clear that the Australian state of Queensland is characterised by high rates of clearing, low rates of formal protection and globally significant biodiversity. These characteristics make Queensland an ideal case study for evaluating the effectiveness of deforestation mechanisms. To do this, however, there is a clear need to understand how protected areas are established across Australia. That is, what are the fundamental principles which drive gazettal. In Chapter 2, I use thematic analysis to identify and describe these principles as they occur in Australian policy documents. I found that representativeness was the most common driving principle for protected areas. Representativeness refers to ensuring that each type of ecosystem is contained within a reserve network. Given Queensland’s high rates of clearing (established in Chapter 1), however, is it logical to consider the feasibility of meeting a representativeness target as ecosystems are increasingly threatened with extinction. The next logical question, then, is whether or not protected areas effectively reduce clearing. The aim of Chapter 3 is to assess Queensland’s protected area network for impact retrospectively. This establishes counterfactual scenarios to provide a robust estimate of the relative impact of Queensland’s protected area system. I found that the majority (89.5%) of strictly protected areas would not have been cleared even in the absence of protection. This means that protection made no difference to deforestation in these areas. It is equally important to understand how regulation which relates to vegetation management contributes to de facto protection. An area is considered to be de facto protected if policy interventions prevent or significantly limit clearing. In this context, the relevant policies are guidelines which support Queensland’s Vegetation Management Act, 1999 (the Act). In Chapter 4, I evaluate the spatially explicit criteria for each guideline, summarise and then describe policy changes, including those which result in de facto protection. I found that the majority of Queensland’s vegetation does not have spatial features which would trigger an assessment under the Act. Australia’s significant and mostly endemic biodiversity is in long-term decline. The single most significant factor which can be attributed to continued species decline is habitat loss as humans increasingly modify natural environments. The results of the Chapters described above suggest that the mechanisms for retaining forested habitats in Queensland could be bolstered by understanding potential future scenarios of land clearing. These future scenarios can be a critical guide for strategic directions by anticipating opportunities to avoid the loss of high-risk areas. In Chapter 5, I used a generalised estimating equation to predict deforestation in Queensland’s forested bioregions. I then combined these models with vegetation community mapping in Queensland and 3 calculated which communities were likely to migrate into a higher vulnerability status (ie a least concern community becoming endangered). Using scenarios which constituted the projected severity of land-clearing, I identified between 29 and 212 communities are likely to increase in their vulnerability status. Of these, between five and 20 communities are likely to go extinct if no action is taken. To prevent such loss, it is imperative that policy intervention target areas with high vulnerability to future loss. Recommendations for these targeting areas with a high vulnerability to future loss are provided in the final chapter (Chapter 6). I build on the information developed in the first five chapters of this work to provide recommendations which link conservation outcomes to biodiversity threats and the types of decisions required of governments to maximise impact. To ensure that these recommendations are practical and feasible, I have worked closely with decision-makers throughout this project. This collaboration ensures the policy relevance of the work useful while also maintaining robust scientific methods. By achieving the objectives listed above, my thesis provides an essential contribution to future protected area policy and the academic literature concerning conservation planning by assessing current forests retention mechanisms and providing strong recommendations for policy.
... In Australia, they are the single largest threat to biodiversity regardless of ecological context. Predation by feral cats has been identified as the top threatening process for many Australian mammal (Woinarski, Burbidge & Harrison 2014Woolley et al., 2019), reptile (Woinarski et al., 2018), bird (Woinarski et al., 2017a(Woinarski et al., , 2017b and amphibian species. Their threat to native species has warranted the substantial effort expended in control and management of the species. ...
Article
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Accurate determination of chronological age for cats (Felis catus) permits assessment of age at reproduction and growth measures, whilst understanding survivorship enables modelling of population dynamics underpinning many management questions. At present, the relative accuracy of different measures has not been compared, especially in relation to ageing live cats, where options are more limited. We tested relationships between nine ageing methods using a large database of 384 unowned, free‐roaming cats culled as part of wildlife conservation and unowned cat management. Cat heads were cleaned and scored for tooth eruption, development of the canines (root closure, length and width; proportion of pulp determined by radiography), canine tooth cementum lines, tooth wear (canine tip sharpness and breakage, or absence of the P2), diastema distance and closure of two cranial sutures. Tooth eruption is informative for cats up to about 8 months of age and closure of the canine root up to 12 months. In adults with closed‐rooted canine teeth, only the cementum lines and cranial sutures varied; these two sets of measures were strongly correlated. We conclude by developing a predictive table for ageing cat specimens using tooth and skull features. Animals can be aged reliably over the lifespan of the animal from cadaver material, potentially adding valuable information to ecological studies where cats are culled. However, there is no way to reliably age live cats over approximately 8 months of age in the field, after which time full adult dentition is established. Similarly, radiography (to determine pulp volume) has limited use as an ageing tool for cats older than 1–2 years of age. This reduces the number of potential applications for live cats, including, for example, ageing unowned cats in trap–neuter–release programmes. Accurate determination of chronological age for cats (Felis catus) permits assessment of age at reproduction and growth measures, whilst understanding survivorship enables modelling of population dynamics underpinning many management questions.
... In this situation, multi-stakeholder participation, knowledge cultures and Indigenous resource management are equally relevant. High and growing numbers of dogs and cats in rAcs live in close proximity to humans [27][28][29], generating animal health problems, risks to human health [30][31][32][33], wildlife [34][35][36][37], and a potential reservoir for rabies should the disease become established in Australia [38]. The cultural connections between Australian Aboriginals and dogs [39,40] intensifies the wickedness of this issue. ...
Article
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Companion animal management in Australian remote Aboriginal communities (rAcs) is a complex problem, with multiple stakeholders involved with differing needs, knowledge, power and resources. We present our CoMM4Unity approach, a participatory systemic action research process designed to address such problems. In the first step, frame analysis is used to analyse stakeholders’ perspectives, knowledge types and power dynamics to determine their relative roles in animal management. Twenty individuals were interviewed from stakeholder groups involved in animal management in the remote, island rAc of Wurrumiyanga, Tiwi Islands. Frame analysis indicated that stakeholders aligned into four groups with distinct identity frames, knowledge types and power frames: Indigenous Locals, Indigenous Rangers, Non-Indigenous Locals and Animal Managers. All four groups shared overlapping perceptions about companion animals in Wurrumiyanga, and agreed that dog overpopulation was the primary issue. However, the groups differed in their strength of opinions about how dogs should be managed. Therefore, the situation is not one of diametrically opposing frames but more a misalignment of goals and values. Our application showed that frame analysis can reveal subtle variations in stakeholder groups’ identities, goals and values, and hence how they prioritise management measures.
... Since these introductions, they have established populations across the entire continent with islands and predator-fenced reserves forming the only Feral Cat-free areas (Rolls 1969;Legge et al. 2017). The impacts of Feral Cat predation on Australian native fauna are widely reported (Dickman 1996;Hilmer et al. 2010a;Doherty et al. 2015Doherty et al. , 2017Woinarski et al. 2017a;2017b;2018) and there is increasing concern about the impact of cat-mediated disease transmission on both wildlife and agricultural livestock (Groenewegen 2018;Taggart et al. 2019). Removal of Feral Cat populations from islands is a pragmatic solution to reduce the threats to insular fauna (Twyford et al. 2000;Campbell et al. 2011;Parkes et al. 2014;Hanson et al. 2015;Robinson et al. 2015). ...
Article
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Feral Cats (Felis catus) impact native wildlife species through direct predation and transmission of parasites. In July 2018, the Government of Victoria declared Feral Cats to be a pest in specific Crown land tenures and subsequently made changes to regulations to provide opportunity for use of additional control tools. This coincided with an Australian Government initiative to create Feral Free Safe Havens on islands and fenced exclosures. French Island was one of the islands nominated in this strategy and has had over 1100 Feral Cats removed since 2010. In conjunction, there has been increased awareness throughout the island community about the responsibilities of Domestic Cat owners. This paper presents the current regulatory environment and discusses how it impacts on a proposal to eradicate the Feral Cat population on French Island, Victoria.
... In northern Australia, companion animal management is posing a growing problem. Domestic free-roaming dogs and cats in remote Aboriginal communities (rAcs) pose health risks to humans [15,[18][19][20] and threaten local wildlife [21][22][23][24]. They are also likely to become a primary vector of rabies transmission to humans and wildlife populations should the virus enter Australia [25]. ...
Article
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Companion animal management in Australian remote Aboriginal communities (rAcs) is a complex problem with multiple stakeholders involved, with differing needs, knowledge, power and resources. The Comm4Unity (Cycle of Multiple Methods for Unity—For Community) approach was designed to address such problems. This study represents the second step of the Comm4Unity framework, where a causal loop analysis (CLA) was adapted and tested as a tool to address the issue of dog overpopulation in Wurrumiyanga, and in particular the systemic causes of the problem and necessary transformational management solutions. Ten focus group discussions (FGDs) were held amongst three of the four stakeholder groups identified during the first step in the analysis. The CLA identified 13 positive feedback loops, which drive vicious cycles and perpetuate the dog overpopulation issue. All three groups agreed and developed 22 solutions to address the causes of dog overpopulation. Despite the differences in the framings of the three groups, “training” and “education” were both the top priority solutions for all three groups. The majority of the solutions discussed by the groups were not only transformational but also social, requiring collaboration. This study was successful in so far as transformational actions were co-developed by all FGDs, which may have also built capacity and agency amongst the local community to implement them as a cohesive group.
... Cats were linked to more than 15% of the bird extinctions cases, a group which composes more than half of the endemic species affected by invasive ones (Doherety et al., 2016). Another study showed that the average frequency of birds present in cat's diet is at least twice as large on Australian islands than on the mainland (Woinarski et al., 2017). On Fernando de Noronha, Gaiotto et al. (2020) showed that about 20% of all feral cat dietary components were composed of endemic species from the archipelago, which leads to an even greater concern regarding the negative impacts of the feral cats on native fauna present on this island. ...
Article
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Fernando de Noronha is an inhabited Brazilian oceanic island, located on an archipelago with the same name. One of the biggest challenges for the archipelago’s conservation is the presence of invasive species (IS), such as cats (Felis catus). IS are responsible for many extinctions in insulars environments due to predation of native and endangered species. This study focused on estimating the size and density of feral cat population inside the National Park area on Fernando de Noronha island, evaluating feral cats capture success using tomahawk live traps and a set of different baits, and discussing the impacts of cats on native species and possible strategies for its control or eradication on the archipelago. Field data was collected during September and October 2018, and from January to March 2019, using linear transects, concomitantly with live trapping. The population was estimated in 439 animals (CI95%: 283-680), with a density of 46 animals/km2 (CI95%: 30-72). No cats were captured after 5,376 hours of trapping efforts. The results presented here update the existing information about this IS on the island and suggest an average increase of 41,1% in the cat population on Fernando de Noronha’s National Park in the last four years. It also justifies the urgent need for this species’ population control and eradication to promote the conservation of endemic and native wildlife, on this human heritage site (UNESCO), and important stop and reproduction habitat for threatened marine birds, as well as several endemic species. Keywords: Protected area; invasive fauna; island; adaptive management; ecology.
... Future studies of the effectiveness of antipredation measures must include all prey, regardless of age or time of day. This is not least because cat advocates often seek to undermine the scientific credibility of detrimental findings through blogs and other websites (Loss et al., 2018), claiming that published research over-emphasizes numbers of prey taken annually, now known to number millions (Woinarski et al., 2017) or billions (Loss et al., 2013;Zhang et al., 2022) of individuals. We hope that our critique of Geiger et al. (2022)'s conclusion of an "overestimation" of bird prey allows a more accurate assessment of this preventative measure. ...
Article
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Domestic cats take a huge toll on native wildlife and colourful collars are one way of reducing their hunting efficiency. Dr Seymour and I challenge some of the findings of a European study suggesting that such collars are as effective as Geiger et al suggest (This is partly because they removed after-dark bird kills, and nestling birds from their kill samples, and mainly because our own research indicates that most prey are not returned to the home.
... There is a view that mesic ecosystems of eastern Australia support lower feral cat densities compared to their xeric counterparts ) and therefore the impact of cats on biodiversity may be lower in mesic ecosystems (Doherty et al. 2017;Woinarski et al. 2017). However, our finding that feral cat occupancy increased with elevation has not been identified previously and raises concern that cats may potentially have more severe impacts on fauna in forested high-elevation areas than previously recognised. ...
Article
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Invasive predators, land clearing and altered fire regimes have been implicated in species decline and extinction worldwide. Enhanced knowledge of how these factors interact and influence medium-sized mammals is warranted. We tested three hypotheses using occupancy data for a diverse mammal assemblage including three threatened species, five common species, two introduced mesopredators and an apex predator in eastern Australia. We hypothesised that occupancy of mammal species within the assemblage would be influenced by (i) the physical environment (rainfall, vegetation type and elevation), (ii) habitat disturbance (number of fires and habitat fragmentation) and (iii) mesopredator release, whereby occupancy and/or detection of medium-sized mammals are influenced by mesopredators, the feral cat ( Felis catus ) and the red fox ( Vulpes vulpes ), which are influenced by an apex predator, the dingo ( Canis familiaris ). We utilised camera-trapping data from 173 sites (692 camera locations) across a north–south gradient spanning ~ 1500 km in eastern Australia. Although hypotheses i (physical environment) and ii (habitat disturbance) are not mutually exclusive, we show that the variables considered in each were only weakly correlated. We conducted occupancy modelling to investigate the physical environment and habitat disturbance hypotheses. We conducted co-occurrence modelling to investigate interactions between species. The physical environment hypothesis best supported occupancy models for six mammal species: red-necked pademelon ( Thylogale thetis ), bandicoots ( Isoodon macrourus and Perameles nasuta ), swamp wallaby ( Wallabia bicolor ), red-necked wallaby ( Macropus rufogriseus ), eastern grey kangaroo ( Macropus giganteus ) and feral cat. The disturbance hypothesis best supported occupancy models for four mammal species: long-nosed potoroo ( Potorous tridactylus ), red-necked pademelon and both mesopredators. Support for the mesopredator release hypothesis was equivocal. Large macropods showed site avoidance towards the red fox. Four species showed higher detection at sites where mesopredators were not detected. The fox showed a negative detection interaction to the dingo and the cat did not. Our study highlights how factors such as rainfall, land clearing, elevation and number of fires influence the occupancy of species within a diverse mammal assemblage at the macroecological scale. Our findings have implications for the conservation of threatened species in managed landscapes and suggestions for further research following the recent 2019–2020 wildfires.
... Future studies of the effectiveness of antipredation measures must include all prey, regardless of age or time of day. This is not least because cat advocates often seek to undermine the scientific credibility of detrimental findings through blogs and other websites (Loss et al., 2018), claiming that published research over-emphasizes numbers of prey taken annually, now known to number millions (Woinarski et al., 2017) or billions (Loss et al., 2013;Zhang et al., 2022) of individuals. We hope that our critique of Geiger et al. (2022)'s conclusion of an "overestimation" of bird prey allows a more accurate assessment of this preventative measure. ...
... Bird species are particularly susceptible to human-caused disturbances, including urbanization, land cover changes, collisions with artificial structures (buildings, vehicles, and powerlines), electrocution, predation by feral or domestic animals, contamination from pesticides and oil spills, and hunting ( Brabant et al., 2015 ;Woinarski et al., 2017 ). A high proportion of individuals die in the sites where they were injured, but a proportion of individuals that survive these traumatic events are moved to wildlife rehabilitation centers to start a careful medical and ethological care program ( Nichols et al., 2018 ). ...
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Captive animals that have experienced traumatic events require a high range of care prior to reintroducing them into their natural habitat; and this care should ensure their welfare in captivity. This report shows the ethological evolution of beneficial effects attributed to environmental enrichment. Specifically, the report focuses on the recovery of a white-throated toucan (Ramphastos tucanus: Rampastidae) affected by a collision trauma resulting in a skull fracture, which received treatment and care in the Taricaya wildlife rescue center (Madre Selva, Peru). An environmental enrichment protocol was implemented for 30 days, recording all activities during this period. We performed generalized linear models to identify significant trends in the observed activities. We showed that inactive time and self-mutilation significantly decreased, while walking, eating, and washing activities increased during the study period. Temporal improvement in toucan welfare may be associated with higher energy (walking), better nutrition (eating), and decreased stress, as shown by reduced self-mutilation. Our report provides evidence on the favorable outcome of environmental enrichment in a toucan, raising its importance as a management tool for veterinary practitioners in wildlife rescue centers.
... Introduced species like feral cats (Felis catus) and rats (Rattus sp.) are potential predators (Lorenzo and Barone 2007). In addition to effects as direct predators, introduced mammals might also cause a negative impact on breeding success because of disturbance effects (Woinarski et al. 2017;Greenwell et al. 2019;Kays et al. 2020). ...
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The increase of the tourism and urbanization of vast areas of dunes and beaches has been accompanied by an increase in the level of disturbances to many shorebirds, especially on those species which depend on such habitats to breed. The European Kentish plover (Charadrius alexandrinus) population is declining, also in the Canarian archipelago, one of the most important touristic destinations worldwide. Using data from an intense monitoring program on Lanzarote Island and the nearby La Graciosa islet (hereafter, both referred as Lanzarote), we aimed to (1) estimate the breeding output and survival and (2) use these parameter estimates to build a population model to assess the long-term growth rate of the population and evaluate, accordingly, its conservation status. Our studied population presents a relatively high breeding success although, thereafter, the first-year apparent survival is low. Even though adult apparent survival rates are reasonably high, these seem insufficient to compensate for the low survival rates of the first-year birds. In this sense, we found a negative growth rate according to a population model estimating an annual loss equivalent to 20% (95% confidence interval: 6–35%). Local studies to account for the effects of human disturbance caused by tourist industry on survival, breeding rates, and demography are required to develop precise conservation actions for the Kentish plover population in Lanzarote.
... Feral predators such as the cat (Felis catus) are a significant threat to biodiversity, and can annually kill a remarkable number of birds (Woinarski et al. 2017a). Ground-nesting species are particularly at risk, and night parrots (Pezoporus occidentalis) have life history traits that may make them especially vulnerable (Woinarski et al. 2017b). ...
Preprint
Context. Night parrots (Pezoporus occidentalis) are one of Australia's most endangered birds, and there is evidence suggesting feral cats (Felis catus) are a major cause of decline. However, because night parrots currently have a restricted distribution, little is known of the ecology of feral cats around their remaining populations. This limits the development of effective management strategies. Aims. The aims of this study were to understand feral cat movement and habitat selection around night parrots, and to then estimate the effectiveness of possible management actions. Methods. Research was conducted around the only confirmed night parrot population in eastern Australia. In 2019 and 2020, we obtained GPS data from nine feral cats, and used step selection functions to assess preferred habitats. Management options were then simulated based on cat movement data, including altering trap numbers and layout, and changing routes for night spotlight shooting (using existing roads, random walking or creating new roads in preferred habitats). Key results. Feral cats preferred alluvial and riparian habitats and avoided rocky woodlands and roads. Simulated control efforts were more successful if traps are placed at 'pinch points' where drainage lines converged, and if new roads were created near to creek lines and alluvial habitats. Conclusions. Feral cats move around the last known population of night parrots in eastern Australia, travelling through and using many shared habitats. Targeting creek lines and alluvial areas in cat control operations would improve effectiveness and potentially reduce predation impacts on night parrots. Implications. Conservation of endangered birds like night parrots can be enhanced through understanding the ecology of threats such as feral cats to develop locally tailored control operations.
... Feral predators such as the cat (Felis catus) are a significant threat to biodiversity, and can annually kill a remarkable number of birds (Woinarski et al. 2017a). Ground-nesting species are particularly at risk, and night parrots (Pezoporus occidentalis) have life history traits that may make them especially vulnerable (Woinarski et al. 2017b). ...
... The role of domestic and feral cats in the decline and extinction of vertebrate species is of major concern in conservation [120,121]. According to Medina et al. [122], domestic cats have contributed to 14% of the 238 global bird, mammal, and reptile extinctions. ...
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Although forest-dependent, tropical island endemic birds are particularly at risk of extinction, they remain largely understudied. In this context, we assessed the spatial occupancy, local abundance, and diel activity in three forest columbid species of hunting interest, the Ruddy Quail-Dove (RQD), Geotrygon montana; the Bridled Quail-Dove (BQD), Geotrygon mystacea; and the Zenaida Dove (ZD), Zenaida aurita, in Guadeloupe (French West Indies), using 5 camera-traps over 14 days on 24 survey stations, resulting in 1680 trap days. The number of observed RQD was too small to allow for a statistical comparison between habitats. BQD were more frequently observed at camera-trap stations that were dominated by tropical rainforest than those that were dominated by flooded forest. Conversely, ZD were more frequently observed at stations that were dominated by flooded forest and dry forest than at those that were dominated by tropical rainforest. High temperatures negatively affected the abundance of BQD, while the abundance of ZD was significantly lower in tropical rainforests compared to dry and flooded forests and tended to increase with canopy openness. The three species were diurnal. BQD significantly positively co-occurred spatially and temporally with small Indian mongooses, Urva auropunctata, whereas the temporal and spatial distribution of ZD overlapped significantly with that of domestic dogs, Canis familiaris, and domestic cats, Felis catus. Our results provide firm evidence that RQD remains scarce and is largely outnumbered by BQD in Guadeloupe which is in contrast with has been reported for other Caribbean islands.
... Domestic cat distribution and densities are thought to reflect human densities and their penchant for keeping them as pets (Sims et al., 2008). Domestic cats are often left free to roam and explore (Mori et al., 2019) and, in addition, the number of feral cats is rising (Trouwborst et al., 2020) in many countries including Canada (Blancher, 2013), the United States (Loss et al., 2013), Australia (Woinarski et al., 2018;Woinarski et al., 2017), New Zealand (Loss and Marra, 2017), the Netherlands (Knol, 2015;as in Trouwborst, 2010), the United Kingdom (Woods et al., 2003), Poland (Krauze-Gryz et al., 2019), Belgium, and France (Pavisse et al., 2019). These populations are still being poorly managed (cfr. ...
Article
Human activities severely impact the distribution and behaviour of apex predators in numerous terrestrial and aquatic ecosystems, with cascading effects on several species. Mesopredator outbreaks attributable to the removal of an apex predator have often been recorded and described in the literature as “mesopredator release”. During recent decades several examples of the phenomenon have been observed and studied in many different parts of the world. In this paper, we quantitatively reviewed the existing literature on mesopredator release using two software packages (VOSviewer and CiteSpace) to investigate patterns and trends in author keywords through occurrences and temporal analyses, and creating relative network maps. The results showed that even though the general scientific interest in mesopredator release has increased in recent decades, the vast majority of studies focus on canid species, leaving many other species or entire taxa (e.g., reptiles) understudied and under-described. The connection between invasive species and mesopredator release has only recently been more extensively explored and also the effects of apex predators declining in aquatic ecosystems are still only partially investigated. Due to the increasing effect of biological invasions, overfishing, and either the decline or the rise of apex predators in different parts of the world, we expect an even higher increase in interest and number of published documents on the subject. We also encourage widening the research focus beyond canids to include other important taxa.
... Other causes of the high incidence of bird mortality due to human activity are bird strikes to windows, strikes to buildings, and cats. Previous research has indicated that these three combined causes may account for 99% of bird mortalities, with wind turbines contributing less than 0.1% [94][95][96]. However, it has been indicated that bird deaths at wind turbines have an impact on high-conservation-value species. ...
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Significantly growing wind energy is being contemplated as one of the main avenues to reduce carbon footprints and decrease global risks associated with climate change. However, obtaining a comprehensive perspective on wind energy considering the many diverse factors that impact its development and growth is challenging. A significant factor in the evolution of wind energy is technological advancement and most previous reviews have focused on this topic. However, wind energy is influenced by a host of other factors, such as financial viability, environmental concerns, government incentives, and the impact of wind on the ecosystem. This review aims to fill a gap, providing a comprehensive review on the diverse factors impacting wind energy development and providing readers with a holistic panoramic, furnishing a clearer perspective on its future growth. Data for wind energy was evaluated by applying pivot data analytics and geographic information systems. The factors impacting wind energy growth and development are reviewed, providing an overview of how these factors have impacted wind maturity. The future of wind energy development is assessed considering its social acceptance, financial viability, government incentives, and the minimization of the unintended potential negative impacts of this technology. The review is able to conclude that wind energy may continue growing all over the world as long as all the factors critical to its development are addressed. Wind power growth will be supported by stakeholders’ holistic considerations of all factors impacting this industry, as evaluated in this review.
... Since their domestication approximately 9,000 years ago (Vigne et al. 2009), cats (Felis catus) have accompanied humans in their movements, reaching a large number of territories, disturbing the environments in which they settle and preying on native species. This has occurred and has been observed in both continental (Woods et al. 2003;Loss et al. 2013;Woinarski et al. 2017Woinarski et al. , 2018Mori et al. 2019) and island territories (Nogales et al. 2006;Bonnaud et al. 2011;Medina et al. 2011Medina et al. , 2014. Island environments are often more vulnerable to biological invasions, as the species that inhabit them are often more vulnerable to alien predators, competitors, pathogens, and parasites. ...
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Cats have accompanied humans since they were domesticated, spreading and settling in a large number of islands where they modify environments and prey on native species. In the Canary Islands, several studies have shown that cat’s prey on native species, including Critically Endangered species such as the giant lizards of Tenerife (Gallotia intermedia), La Gomera (G. bravoana) and El Hierro (G. simonyi). This study focuses on the trophic ecology of the cat in Montaña de Guaza, where a population of the giant lizard of Tenerife is located. The current results show important changes in the diet of this alien species at this area in relation to the obtained by others author in 2004. The main changes detected are the low level of consumption of mammals and the high levels of birds and lizards. These changes seem to be a direct consequence of a low density of rabbit (Oryctolagus cuniculus), the main prey at the different habitats of Canary Islands, probably due to the rabbit hemorrhagic disease virus (RHDV) incidence. The high consumption of reptiles detected in this study could explain the reduction of both distribution area and number of giant lizards at this locality.
... Globally, one in eight bird species are under threat of extinction (Birdlife International 2018). Australian bird species mirror these trends, showing national population declines under well-documented threats from a range of anthropogenic-related activities, including invasive species, fire, habitat loss and degradation (Nebel et al. 2008;Woinarski et al. 2017;Lindenmayer et al. 2018;Bayraktarov et al. 2021). Within the context that Australia's birds have never been more threatened, BirdLife Australia's primary aim is to promote and conserve Australian bird populations and their habitats, to stop extinction (Birdlife Australia 2017). ...
... Because cats live at high densities around human settlements, estimates of the total numbers of wild animals that might be killed by domestic cats tend also to be very high (Blancher, 2013;Lepczyk, Mertig, & Liu, 2003;Murphy et al., 2019;Woods et al., 2003). This leads to cumulative adverse effects on prey populations at local (Baker et al., 2005;Baker, Molony, Stone, Cuthill, & Harris, 2008;Sims, Evans, Newson, Tratalos, & Gaston, 2008;Thomas et al., 2012) up to continental scales (Blancher, 2013;Loss et al., 2013;Murphy et al., 2019;Woinarski et al., 2017). In many ecological contexts, the direct (Medina, Bonnaud, Vidal, & Nogales, 2014) and indirect (Beckerman, Boots, & Gaston, 2007;Bonnington, Gaston, Evans, & Whittingham, 2013) effects of cats can be detrimental to biodiversity conservation (Doherty, Glen, Nimmo, Ritchie, & Dickman, 2016), as well as to wild animal welfare (Baker, Thompson, & Grogan, 2018). ...
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Domestic cats (Felis catus) that roam outdoors have increased exposure to hazards to their health and welfare. Outdoor cats can themselves present a hazard to biodiversity conservation and wild animal welfare. Approaches to reducing predation of wildlife by cats might also bring benefits to cats by reducing their roaming and associated risks. We investigated ranging behaviors of domestic cats that regularly captured wild prey, and that had restricted or unrestricted outdoor access. We tested whether interventions aimed at reducing predation also affected their spatial behavior. We evaluated cat bells, Birdsbesafe collar covers, using a “puzzle feeder”, provision of meat‐rich food, object play, and a control group. Seventy‐two cats in 48 households in England completed the 12‐week trial in spring 2019. Home ranges were small (median AKDE95 = 1.51 ha). Cats with unrestricted outdoor access had 75% larger home ranges, 31% greater daily distances traveled, and reached 46% greater maximum distances from home, than cats with restricted outdoor access. None of the treatments intended to reduce predation affected cat ranges or distances traveled. While owners might use interventions to reduce predation, the only effective means of reducing cat roaming and associated exposure to outdoor hazards was restriction of outdoor access. While some interventions, like object play and dietary changes, can reduce domestic cat predation of wildlife, we found that these measures do not affect cat roaming behavior. Restricting access to the outdoors, even partially, does reduce the extent of cat ranging and likely reduces associated exposure to outdoor hazards.
... 8,23,24 Scientific research is cited in policy deliberations about FRCs primarily to quantify or characterize cat predation on wildlife or concerns about disease. 8,[25][26][27][28][29][30] It is less often utilized to determine the viability of a proposed action, or to define that action's critical implementation parameters or likely outcomes. In part, this may be because potentially relevant studies tend to focus on geographically specific case studies or closed demographic environments where there is no immigration or abandonment of cats, 3,31-35 which may constrain their broader utility. ...
Article
Objectives: This study used computer simulation modeling to estimate and compare costs of different free-roaming cat (FRC) management options (lethal and non-lethal removal, trap-neuter-return, combinations of these options and no action) and their ability to reduce FRC population abundance in open demographic settings. The findings provide a resource for selecting management approaches that are well matched for specific communities, goals and timelines, and they represent use of best available science to address FRC issues. Methods: Multiple FRC management approaches were simulated at varying intensities using a stochastic individual-based model in the software package Vortex. Itemized costs were obtained from published literature and expert feedback. Metrics generated to evaluate and compare management scenarios included final population size, total cost and a cost efficiency index, which was the ratio between total cost and population size reduction. Results: Simulations suggested that cost-effective reduction of FRC numbers required sufficient management intensity, regardless of management approach, and greatly improved when cat abandonment was minimized. Removal yielded the fastest initial reduction in cat abundance, but trap-neuter-return was a viable and potentially more cost-effective approach if performed at higher intensities over a sufficient duration. Of five management scenarios that reduced the final population size by approximately 45%, the three scenarios that relied exclusively on removal were considerably more expensive than the two scenarios that relied exclusively or primarily on sterilization. Conclusions and relevance: FRCs present a challenge in many municipalities, and stakeholders representing different perspectives may promote varying and sometimes incompatible population management policies and strategies. Although scientific research is often used to identify FRC impacts, its use to identify viable, cost-effective management solutions has been inadequate. The data provided by simulating different interventions, combined with community-specific goals, priorities and ethics, provide a framework for better-informed FRC policy and management outcomes.
... The threat which free-ranging cats pose to native wildlife cannot be understated. Proponents of free-ranging cats on the landscape argue that predation by such cats on wildlife is negligible when compared to other sources of mortality, however many studies have shown that cats are a major, if not the greatest, source of mortality to native birds, mammals, reptiles, and amphibians (Lepczyk et al. 2003;Beckerman et al. 2007;Van Heezik 2010;Lloyd et al. 2013;Loss et al. 2013 andWoinarski et al. 2017 andLi et al. 2021). While loss of habitat is the primary cause of species extinctions, cats have contributed to the extinction of at least 63 species in the wild around the world (Doherty et al. 2016). ...
Article
Domestic cats (Felis catus) are a common household pet in the United States, with an estimated 25.4% of households owning cats (American Veterinary Medical Association 2018). While an increasing number of cat owners keep their pet cats exclusively indoors, a portion of society maintains that domestic cats are entitled to a free-ranging lifestyle and may even consider unowned domestic cats to be wildlife. Although wildlife managers recognize the beliefs of many concerned stakeholders, including advocates who use strong emotional appeals on behalf of cats, it remains that free-ranging and feral domestic cats are an invasive species spread by humans (Lowe et al. 2000) (Figure 1). Free-ranging cats are associated with a number of sociological and ecological conflicts. They impact people directly through the spread of parasites and diseases, damage to gardens and property, and noise nuisances. Cats also cause conflict through their direct and indirect impacts on native wildlife through predation, competition, spread of disease, and impacts on species survival (e.g., nest failure, injury, behavioral changes). Removing free-ranging cats is the most effective strategy for addressing cat-caused damage. Such removals could include adoption, placement in a long-term holding facility (e.g., cat sanctuary), or euthanasia. Owned cats should be kept indoors or otherwise under their owner’s control. Up to 164 million cats reside in the United States, of which an estimated 30 to 80 million are unowned (Loss et al. 2013) (Figure 2). A large portion of owned cats are also free-ranging (Loss et al. 2013). The threat which free-ranging cats pose to native wildlife cannot be understated.
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Aim Introduced predators negatively impact biodiversity globally, with insular fauna often most severely affected. Here, we assess spatial variation in the number of terrestrial vertebrates (excluding amphibians) killed by two mammalian mesopredators introduced to Australia, the red fox (Vulpes vulpes) and feral cat (Felis catus). We aim to identify prey groups that suffer especially high rates of predation, and regions where losses to foxes and/or cats are most substantial. Location Australia. Methods We draw information on the spatial variation in tallies of reptiles, birds and mammals killed by cats in Australia from published studies. We derive tallies for fox predation by (i) modelling continental‐scale spatial variation in fox density, (ii) modelling spatial variation in the frequency of occurrence of prey groups in fox diet, (iii) analysing the number of prey individuals within dietary samples and (iv) discounting animals taken as carrion. We derive point estimates of the numbers of individuals killed annually by foxes and by cats and map spatial variation in these tallies. Results Foxes kill more reptiles, birds and mammals (peaking at 1071 km⁻² year⁻¹) than cats (55 km⁻² year⁻¹) across most of the unmodified temperate and forested areas of mainland Australia, reflecting the generally higher density of foxes than cats in these environments. However, across most of the continent – mainly the arid central and tropical northern regions (and on most Australian islands) – cats kill more animals than foxes. We estimate that foxes and cats together kill 697 million reptiles annually in Australia, 510 million birds and 1435 million mammals. Main conclusions This continental‐scale analysis demonstrates that predation by two introduced species takes a substantial and ongoing toll on Australian reptiles, birds and mammals. Continuing population declines and potential extinctions of some of these species threatens to further compound Australia's poor contemporary conservation record.
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Protected areas are important for preventing biodiversity declines, yet indicators of species' trends in protected areas rarely include threatened species. We use data from the first national Threatened Species Index developed in Australia to report on trends for threatened and near‐threatened birds inside and outside terrestrial and marine protected areas. We adopted the Living Planet Index to calculate trends for 39 bird taxa at 16,742 monitoring sites (11,539 inside and 5,203 outside PAs) between 1985 and 2016. At a continental scale, the overall decline in the national index was smaller inside protected areas (66% decrease in average population abundance) than outside (77%), although after 2000 declines were greater within (36%) versus outside (26%) protected areas. Five out of seven jurisdictions showed similar switching in patterns over time. Protected areas initially had a greater net positive effect on trends of more imperiled birds than less imperiled birds, but between 2000 and 2016 declines of the most imperiled birds were greater inside protected areas than outside. Our analyses suggest that the effectiveness of Australia's protected area network at improving trends in threatened species has weakened, and support the hypothesis that trends for terrestrial birds outside PAs might be improving due to increased conservation efforts on private land. Although this study represents the most comprehensive collation of threatened species population time series and trends ever for Australia, the number of monitoring sites inside PAs was double that outside PAs, even though on average, more than 70% of threatened bird distributions occur outside PAs, with important gaps in monitoring across space, time and taxa that need to be filled to fully understand the effectiveness of public and private conservation actions at a national level. The results underline the importance of active management plus monitoring to track and report on long‐term trends across species.
Technical Report
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This Glovebox Guide for Managing Feral Cats is a general guide to provide background information to support the control of feral cat populations in Australia. This guide adopts the definition of ‘feral cat’ as those that live and reproduce in the wild (e.g. forests, woodlands, grasslands, deserts) and survive by hunting or scavenging; none of their needs are satisfied intentionally by humans. It is recognised that this categorisation of life cycles is artificial and that individual cats may transition between classes, such as stray and domestic, throughout their lifecycle. However, these other classes are not considered in this guide unless specifically mentioned.
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en • Cats Felis catus, in all their forms (domestic, free‐roaming/stray and feral), have been identified as a major global threat to biodiversity, especially birds and small mammals. However, there has been little previous consideration of the extent and impact of predation of bats by cats, or of whether specific characteristics make certain species of bats particularly vulnerable to predation by cats. • We reviewed the impact of cats on bats, based on a collation of scientific literature and the International Union for Conservation of Nature (IUCN) Red List database. Our aim was to produce a synthesis of the extent to which cats prey upon and threaten bats. We also collated available data on cat diet, which provide information on predation rates of bats by cats. • Few studies (n = 44) have identified bat species preyed upon or threatened by cats, with a disproportionate number of studies from islands. In these studies, 86 bat species (about 7% of the global extant tally) are reported as preyed upon or threatened by cats, and about one quarter of these species are listed as Near Threatened or threatened (IUCN categories Critically Endangered, Endangered, or Vulnerable). In IUCN Red List assessments, cats are more frequently mentioned as a threat to threatened or Near Threatened bat species than to non‐threatened species (IUCN category Least Concern). • In studies reporting on the incidence of bats in cat dietary samples (scats, stomachs and guts), the frequency of occurrence of bats in samples averaged 0.7 ± 2.1% (mean ± standard deviation; n = 102). Many studies had sample sizes that were too small to be likely to detect bats. • All forms of cat are reported to kill bats, and such predation has been reported in all major terrestrial habitats. We conclude that predation by cats is an under‐appreciated threat to the world’s bat species. Abstract fr RESUMÉ EN FRANÇAIS • Les chats Felis catus, sous toutes leurs formes (domestiques, errants ou harets), ont été identifiés comme une menace mondiale majeure pour la biodiversité, en particulier pour les oiseaux et les petits mammifères. Cependant, l'ampleur de ce phénomène et l'impact de la prédation exercée sur les chauves‐souris par les chats n'ont guère été pris en compte jusqu'à présent. En particulier la question de savoir si des caractéristiques spécifiques rendent certaines espèces de chauves‐souris particulièrement vulnérables à la prédation par les chats reste en suspens. • Nous avons examiné l'impact des chats sur les chauves‐souris, en croisant les informations issues de la littérature scientifique sur le sujet et celles disponibles dans la base de données de la liste rouge de l'Union Internationale pour la Conservation de la Nature (UICN). Notre objectif était de produire une synthèse mondiale visant à estimer dans quelle mesure les chats s'attaquent aux chauves‐souris et constituent une menace. Nous avons également rassemblé les données disponibles sur le régime alimentaire des chats, qui fournissent des informations sur les taux de prédation des chauves‐souris par les chats. • Peu d'études (n = 44) ont permis d’identifier des espèces de chauves‐souris prédatées et/ou menacées par les chats, un nombre disproportionné d’entre elles concernent les écosystèmes insulaires. Ces études ont permis d’identifier 86 espèces de chauves‐souris (environ 7 % des espèces mondiales) représentant des proies ou étant directement menacées par les chats ; environ un quart de ces espèces sont classées comme "quasi menacées" ou "menacées" (catégories de l'UICN : En danger critique d'extinction, En danger ou Vulnérable). Dans les évaluations de la Liste rouge de l'UICN, les chats sont plus fréquemment mentionnés comme une menace pour les espèces de chauves‐souris menacées ou quasi menacées que pour les espèces non menacées (catégorie de l'UICN "Préoccupation mineure"). • Dans les études analysant le régime alimentaire des chats (excréments, estomacs et tubes digestifs) la fréquence d'occurrence des chauves‐souris dans les échantillons était en moyenne de 0.7 ± 2.1 % (moyenne ± écart‐type ; n = 102). Dans de nombreux travaux, la taille des échantillons était trop petite pour permettre de détecter la prédation sur des chauves‐souris. • Toutes les formes de chats s'attaquent aux chauves‐souris, et cette prédation a été signalée dans tous les principaux habitats terrestres. En conclusion, la prédation des chauves‐souris par les chats apparait être une menace sous‐estimée au niveau mondial.
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en • Domestic cats Felis catus are distinct from other domesticated animals because their phenotype and genotype are relatively unchanged. While they live with people as pets or pest controllers, they retain capacity for survival independent of human support and readily persist as feral animals. Most cats retain some propensity to express hunting behaviours, even if hunting is not required for nutrition. In some settings, depredation by cats is a threat to biodiversity conservation, leading to attempts to mitigate their impacts. • We characterise drivers and facilitators of the hunting behaviour of domestic cats: evolutionary origins, diet, life history, personality and environment. Hunting is driven particularly by evolutionary constraints and associated physiological and nutritional requirements. Proximate causes of variation in hunting behaviours relate to prey availability, husbandry and degree of domestication, while early life history and personality play further roles. • We review cat management approaches in terms of effectiveness, feasibility and welfare. Amongst lethal, large‐scale methods of population control, poisoning is most frequently used in cat eradications from islands. Because poisoning is challenged on welfare grounds, euthanasia is used at smaller scales and in inhabited, mainland settings. Non‐lethal approaches, primarily surgical sterilisation, are favoured by cat advocates but entail challenging logistics and scale. In attempts to inhibit predation of wild species by pet cats, owners restrict outdoor access and use collar‐mounted devices, including bells, sonic devices, collar covers and bibs. Other individual‐level interventions, such as dietary and behavioural enrichment, some of which may improve cat welfare, have potential, but effects on hunting remain untested. • Understanding and managing the hunting behaviour of cats are complex challenges. We highlight drivers and facilitators of this behaviour, representing starting points for formulating solutions that might be acceptable to cat owners and wider groups of people who value cat welfare, while also being effective for wildlife conservation. RIASSUNTO IN ITALIANO it • I gatti domestici Felis catus si distinguono dagli altri animali domestici poiché i loro fenotipo e genotipo sono rimasti relativamente invariati. Nonostante vivano con le persone come animali domestici o vengano impiegati per il controllo dei roditori infestanti, i gatti domestici hanno mantenuto la capacità di sopravvivere indipendentemente dal supporto umano, e possono facilmente persistere come animali ferali (rinselvatichiti). La maggior parte dei gatti ha mantenuto una certa propensione alla caccia, nonostante questa non sia necessaria a sopperire a esigenze nutrizionali. In determinati ecosistemi la massiccia predazione da parte dei gatti rappresenta una minaccia per la conservazione della biodiversità, determinando quindi la necessità di adottare soluzioni per mitigare i possibili effetti negativi. • In questo studio vengono caratterizzati i fattori chiave che inducono i gatti domestici a cacciare, nonché quelli che ne facilitano l’espressione: le origini evolutive, il regime alimentare, le esperienze fatte nel corso della vita, la personalità e l’ambiente. Il comportamento di caccia è primariamente determinato da vincoli evolutivi e da fabbisogni fisiologici e nutrizionali ad esso associati. Le cause prossime coinvolte nelle variazioni di tale comportamento sono legate alla disponibilità di prede, dal metodo di allevamento del gatto e dal suo grado di addomesticamento; le esperienze fatte nei primi mesi di vita e la personalità del gatto ricoprono anch’essi un ruolo importante. • Abbiamo revisionato i diversi approcci impiegati nella gestione dei gatti in termini di efficacia, fattibilità e benessere. Tra i metodi letali impiegati su larga scala nel controllo di popolazione, l’avvelenamento è risultato essere quello più frequentemente utilizzato per l’eradicazione dei gatti dalle isole. Poiché l’avvelenamento è contestato per motivi legati al benessere, su scala più piccola e in posti abitati sulla terraferma viene preferita l’eutanasia. Gli approcci non letali, in particolare la sterilizzazione chirurgica, sono favoriti dai sostenitori dei diritti dei gatti, ma implicano complicazioni sul piano logistico e risultano comunque essere di portata più limitata. Nel tentativo di inibire la predazione dei gatti domestici sulle specie selvatiche, i proprietari ne limitano l’accesso all’esterno e utilizzano dispositivi che si attaccano ai collari, come campanelle, dispositivi sonori, copri collari colorati e bavagli ingombranti. Altri interventi a livello individuale come, ad esempio, l’arricchimento alimentare e quello comportamentale hanno un potenziale (alcuni potrebbero incrementare il benessere del gatto stesso), ma gli effetti sul comportamento di caccia non sono stati ancora testati. • La comprensione e la gestione del comportamento di caccia dei gatti rappresentano delle sfide complesse. Il presente lavoro evidenzia i fattori che guidano e quelli che facilitano tale comportamento, che rappresentano i punti di partenza per formulare soluzioni che potrebbero essere accettate dai proprietari dei gatti e da tutte le persone che ne valorizzano il benessere, e che al contempo siano efficaci nel salvaguardare gli animali selvatici.
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Habitat degradation, invasive species and overexploitation are currently the three main threats to biodiversity. Here we present a study on the population status of two sympatric flying fox species, Pteropus ornatus (endemic) and P. tonganus (native), and the impact of hunting and predation by the feral cat Felis catus in New Caledonia. The study of flying fox roost occupancy in the North Province shows a 33% disapearance in 40 years. The flying fox population on Grande Terre is estimated at about 735,000 individuals (of both species) and the annual hunting rate at 7%. Integrated stochastic modelling of this population suggests that current harvesting levels could lead to a decline of up to 80% in the next 30 years. Temporary hunting ban and/or protected areas appear, in addition to being combinable, to be the most acceptable and effective management options for hunters. An analysis of the data available worldwide shows that all forms of cats prey on bats in all habitats and that this threat is probably largely underestimated. Finally, initial results suggest that flying fox predation by feral cats in New Caledonia is of the same order of magnitude as hunting. This study proposes a framework for assessing the sustainability of hunting game species in an integrated adaptive management approach, taking into account other threat factors such as invasive species.
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Invasive species are a major threat to biodiversity worldwide, causing many of the recent declines and extinctions of native species. Competition is a common mechanism through which invasive species impact the native biota. In particular, exploitative competition results when the invader outcompetes native species for essential resources, such as food and shelter sites. Despite being pervasive invaders, the ecological impacts of invasive lizards are understudied and it is often unknown whether these invaders have detrimental impacts. The plague skink (Lampropholis delicata), native to eastern Australia, has invaded several locations throughout the Pacific region (Hawaiian Islands, New Zealand, Lord Howe Island). However, no studies have documented the plague skink as having a negative impact on native species anywhere throughout its introduced range. Here, we conducted a mark‐recapture study in northern New Zealand (Shakespear Regional Park) to investigate whether the plague skink competes with native skink species (Oligosoma aeneum, O. ornatum, O. moco). Though the plague skink has a broader distribution within the study region and occurred across a broader range of habitats, there was substantial range and niche overlap between the plague skink and the three native skink species. Both the absolute capture rates and estimated population size of the plague skink were significantly higher than the three native skink species. Although plague skinks have smaller body sizes well as shorter and narrower heads than the native skink species, there was still considerable scope for dietary overlap among the species. While our study does not provide definitive evidence for competition between the plague skink and native skink species in New Zealand, we clearly demonstrate the presence of the core components required for exploitative competition to occur. Further field‐ and laboratory‐based studies will be required to confirm the existence of exploitative or interference competition by the plague skink in its introduced range.
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Invasive species can reach high abundances and dominate native environments. One of the most impressive examples of ecological invasions is the spread of the African sub‐species of the honey bee throughout the Americas, starting from its introduction in a single locality in Brazil. The invasive honey bee is expected to more negatively impact bee community abundance and diversity than native dominant species, but this has not been tested previously. We developed a comprehensive and systematic bee sampling scheme, using a protocol deploying 11,520 pan traps across regions and crops for three years in Brazil. We found that invasive honey bees are now the single most dominant bee species. Such dominance has not only negative consequences for abundance and species richness of native bees but also for overall bee abundance (i.e., strong “numerical” effects of honey bees). Contrary to expectations, honey bees did not have stronger negative impacts than other native bees achieving similar levels of dominance (i.e., lack of negative “identity” effects of honey bees). These effects were remarkably consistent across crop species, seasons and years, and were independent from land‐use effects. Dominance could be a proxy of bee community degradation and more generally of the severity of ecological invasions.
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The effective control of wild dogs, feral cats and foxes is of primary interest to land managers, both for biodiversity conservation and for the protection of livestock. Control programs primarily target single species within the context of biodiversity conservation or livestock practices, but their effectiveness in depressing predator densities is unclear because monitoring is limited or not conducted. Here, we review and discuss the outcomes of a workshop to identify research priorities for managing predation on native fauna by introduced predators in the Pilbara bioregion in Western Australia. We suggest that the control of introduced predators will be most effective if it is implemented at a landscape-scale comprising integrated predator management that considers interspecific (predator) interactions combined with standardised monitoring to measure the effectiveness and benefits of control. Four research themes were identified: (1) collation and collection of baseline data, (2) effective monitoring of introduced predators, (3) understanding functional (ecological) roles of introduced predators within the different ecosystem contexts, and (4) identifying novel complementary approaches to protect threatened species. These themes collectively include research areas that invest in foundational, ecological and alternative biological parameters in research to close knowledge gaps related to the functional roles of introduced predators in the landscape. Addressing these research themes will assist land managers to achieve outcomes that address the needs of both biodiversity conservation and pastoral production. This framework is timely given the ongoing investment in offset funding being mobilised in the region.
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Apex predators are subject to lethal control in many parts of the world to minimize their impacts on human industries and livelihoods. Diverse communities of smaller predators—mesopredators—often remain after apex predator removal. Despite concern that these mesopredators may be 'released' in the absence of the apex predator and exert negative effects on each other and on co-occurring prey, these interactions have been little studied. Here, we investigate the potential effects of competition and intraguild predation between red foxes (Vulpes vulpes) and feral cats (Felis catus) in south-eastern Australia where the apex predator, the dingo (Canis dingo), has been extirpated by humans. We predicted that the larger fox would dominate the cat in encounters, and used a fox-removal experiment to assess whether foxes affect cat abundance, diet, home-range and habitat use. Our results provide little indication that intraguild predation occurred or that cats responded numerically to the fox removal, but suggest that the fox affects some aspects of cat resource use. In particular, where foxes were removed cats increased their consumption of invertebrates and carrion, decreased their home range size and foraged more in open habitats. Fox control takes place over large areas of Australia to protect threatened native species and agricultural interests. Our results suggest that fox control programmes could lead to changes in the way that cats interact with co-occurring prey, and that some prey may become more vulnerable to cat predation in open habitats after foxes have been removed. Moreover, with intensive and more sustained fox control it is possible that cats could respond numerically and alter their behaviour in different ways to those documented herein. Such outcomes need to be considered when estimating the indirect impacts of fox control. We conclude that novel approaches are urgently required to control invasive mesopredators at the same time, especially in areas where apex predators are absent.
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The threat that domestic cats pose to wildlife has gained increased recognition by researchers and conservationists, and in this study, we investigated the seasonal variability and the effects of environment type (rural vs. urban) on the prey composition of free-ranging house cats in Poland. We analysed the variability in 307 monthly prey samples of different prey items killed by cats and brought to their owners (i.e., prey brought home by cats living in one home in one month) between 2002 and 2007 at 26 rural and urban sites. The variability in prey composition over time was analysed using additive models and canonical correspondence analysis. In total, we recorded 1348 prey items. Rodents were the most common prey in both environments, but shrews and reptiles were killed by cats more often in the rural environment while birds (mainly sparrows and pigeons) were more common in the urban environment. Additionally, prey composition changed seasonally. The pooled number of vertebrates killed by cats was largest in September and lowest in January, and rodents were killed most often in September, shrews and birds in June, and reptiles in April. The seasonal variation in the prey composition of cats was relatively high in the rural environment and more stable in the urban environment. Prey composition seemed to follow temporal and spatial variations in prey availability, thus confirming a facultative feeding strategy in free-ranging house cats.
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Feral cats are among the most damaging invasive species worldwide, and are implicated in many extinctions, especially in Australia, New Zealand and other islands. Understanding and reducing their impacts is a global conservation priority. We review knowledge about the impacts and management of feral cats in Australia, and identify priorities for research and management. In Australia, the most well understood and significant impact of feral cats is predation on threatened mammals. Other impacts include predation on other vertebrates, resource competition, and disease transmission, but knowledge of these impacts remains limited. Lethal control is the most common form of management, particularly via specifically designed poison baits. Non-lethal techniques include the management of fire, grazing, food, and trophic cascades. Managing interactions between these processes is key to success. Given limitations on the efficacy of feral cat management, conservation of threatened mammals has required the establishment of insurance populations on predator-free islands and in fenced mainland enclosures. Research and management priorities are to: prevent feral cats from driving threatened species to extinction; assess the efficacy of new management tools; trial options for control via ecosystem management; and increase the potential for native fauna to coexist with feral cats.
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Invasive species threaten biodiversity globally, and invasive mammalian predators are particularly damaging, having contributed to considerable species decline and extinction. We provide a global metaanalysis of these impacts and reveal their full extent. Invasive predators are implicated in 87 bird, 45 mammal, and 10 reptile species extinctions-58% of these groups' contemporary extinctions worldwide. These figures are likely underestimated because 23 critically endangered species that we assessed are classed as "possibly extinct." Invasive mammalian predators endanger a further 596 species at risk of extinction, with cats, rodents, dogs, and pigs threatening the most species overall. Species most at risk from predators have high evolutionary distinctiveness and inhabit insular environments. Invasive mammalian predators are therefore important drivers of irreversible loss of phylogenetic diversity worldwide. That most impacted species are insular indicates that management of invasive predators on islands should be a global conservation priority. Understanding and mitigating the impact of invasive mammalian predators is essential for reducing the rate of global biodiversity loss.
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This report provides an overview of the impact of feral cats Felis catus on native fauna of the Pacific region, with particular reference to Australia and its island territories. In Australia, cats take a wide variety of native species of mammals, birds and reptiles, but show evident preference for young rabbits or small marsupials where these are available. Reptiles are taken primarily in arid habitats, while birds often feature predominantly in the diet of cats on islands. Despite their catholic diet, population-level impacts of feral cats on native fauna have been poorly documented. There is considerable potential for competition to occur between cats and carnivorous species such as quolls and raptors, but no critical evidence has yet been adduced. There is also potential for amensal impacts to occur, either via transmission of the pseudophyllidean tapeworm Spirometra erinacei or of the protozoan parasite Toxoplasma gondii, but evidence for deleterious effects in free-living animals is not compelling. Direct predatory impacts have been inferred from anecdotal and historical evidence, more strongly from failed attempts to reintroduce native species to their former ranges, and most critically from the decimation of island faunas and responses of prey species following experimental removal of cats or reduction of cat numbers. Attributes of the biology of feral cats and their prey species derived from the literature review were used to develop a rank-scoring system to assess the susceptibility of native species to cat predation. Species listed federally as endangered or vulnerable were designated as being at zero, low or high risk of impact from cats according to their attribute scores, and their distributions mapped from primary sources and actual locality data. Based on the number of threatened species they contain, localities and regions within Australia were placed in order of priority for future research to clarify the precise impacts of feral cats. Although difficult and expensive to carry out, controlled and replicated field removal experiments are recommended to elucidate cat impacts in all mainland areas. Removal of cats should take place also on offshore islands and island territories, but only if pilot studies show that this will not release populations of alternative predator species such as introduced rats. If release appears likely, cats should be removed only as a component of an integrated control program that targets all relevant predators.
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The diet of foxes in an arid zone site in western New South Wales was analysed from the contents of scats collected every three months from October 1986 to July 1989. Fox diet comprised 27% invertebrates, 25% carrion, 17% rabbits, 16.5% reptiles, 10% dasyurids and 4.5% ground-dwelling birds after the digestibility of each category had been accounted for. There was no clear seasonal pattern in dietary composition although fewer rabbits were ingested in autumn and winter. Foxes ate rabbits in direct proportion to their availability while the ingestion of ground-dwelling birds and dasyurids was either independent of, or inversely proportional to, their abundance. There were no significant relationships between fox and prey densities. The impact of a decrease in rabbit density on the diet and abundance of foxes was investigated by ripping all rabbit warrens (n = 37) in one site and leaving all warrens (n = 38) undisturbed in an untreated site. Fox density did not change significantly in either site. Foxes significantly increased their ingestion of ground-dwelling birds, dasyurids and invertebrates while decreasing their ingestion of rabbits in the ripped site. The diet of foxes in the untreated site did not change significantly. The ability of foxes to switch their prey preferences while maintaining their density could be highly detrimental for secondary prey species and may be the mechanism by which foxes have contributed to the declines of native fauna in the arid zone.
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The bush stone-curlew (Burhinus grallarius) is a ground-dwelling non-passerine endemic to Australia. The total population is estimated at 15,000 birds (Garnett & Crowley, 2000). The species is listed as ‘Least Concern’ under IUCN criteria. Nevertheless, populations in southern Australia have suffered a marked decline over the past century (Marchant & Higgins 1993; Schodde & Tidemann, 1997). The species is listed as Endangered in the states of New South Wales and Victoria, where populations are estimated at around 1,000 breeding pairs. The key threatening processes are identified as poor recruitment due to predation by feral cats (Felis catus) and foxes (Vulpes vulpes), exacerbated by land clearing and loss of woody debris utilized for camouflage (Schodde & Tidemann, 1997; DEC, 2006). Australian Wildlife Conservancy (AWC), a not-for-profit private conservation organization, is a leading exponent of re-introductions in Australia. Most reintroductions by AWC to date have been native mammals. In 2013, AWC conducted a trial re-introduction of bush stone-curlews to Scotia Sanctuary, southwest New South Wales. Birds were released inside a 4,000 ha fenced enclosure free of feral predators, into which a number of native marsupials had already been re-introduced, and to an adjacent area where foxes and cats were present, but controlled.
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Feral cats are normally territorial in Australia’s tropical savannahs, and hunt intensively with home-ranges only two to three kilometres across. Here we report that they also undertake expeditions of up to 12.5 km from their home ranges to hunt for short periods over recently burned areas. Cats are especially likely to travel to areas burned at high intensity, probably in response to vulnerability of prey soon after such fires. The movements of journeying cats are highly directed to specific destinations. We argue that the effect of this behaviour is to increase the aggregate impact of cats on vulnerable prey. This has profound implications for conservation, considering the ubiquity of feral cats and global trends of intensified fire regimes.
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Understanding and reversing the widespread population declines of birds require estimating the magnitude of all mortality sources. Numerous anthropogenic mortality sources directly kill birds. Cause-specific annual mortality in the United States varies from billions (cat predation) to hundreds of millions (building and automobile collisions), tens of millions (power line collisions), millions (power line electrocutions, communication tower collisions), and hundreds of thousands (wind turbine collisions). However, great uncertainty exists about the independent and cumulative impacts of this mortality on avian populations. To facilitate this understanding, additional research is needed to estimate mortality for individual bird species and affected populations, to sample mortality throughout the annual cycle to inform full life-cycle population models, and to develop models that clarify the degree to which multiple mortality sources are additive or compensatory. We review sources of direct anthropogenic mortality in relation to the fundamental ecological objective of disentangling how mortality sources affect animal populations.
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The 'Alala (Corvus hawaiiensis) is the most endangered corvid in the world, and intensive efforts are being made to reintroduce it to its former native range in Hawaii. We diagnosed Toxoplasma gondii infection in five free-ranging 'Alala. One 'Alala, recaptured from the wild because it was underweight and depressed, was treated with diclazuril (10 mg/kg) orally for 10 days. Antibodies were measured before and after treatment by the modified agglutination test (MAT) using whole T. gondii tachyzoites fixed in formalin and mercaptoethanol. The MAT titer decreased four-fold from an initial titer of 1:1,600 with remarkable improvement in physical condition. Lesions of toxoplasmosis also were seen in two partially scavenged carcasses and in a third fresh intact carcass. Toxoplasma gondii was confirmed immunohistochemically by using anti-T. gondii specific serum. The organism was also cultured by bioassay in mice from tissues of one of these birds and the brain of a fifth 'Alala that did not exhibit lesions. The life cycle of the parasite was experimentally completed in cats. This is the first record of toxoplasmosis in 'Alala, and the parasite appears to pose a significant threat and management challenge to reintroduction programs for 'Alala in Hawaii.
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Introduced predators have been implicated in the decline of many fauna populations around the world and are the main factor responsible for the failure of numerous fauna reintroduction programs. As a result, control of introduced predators is a significant management action implemented in wildlife protection programs, particularly in Australia, New Zealand and on islands. Individual predators are seldom targeted in conservation programs, which usually conduct broad-scale, non-specific predator control based on the assumption that the removal of each individual predator is equally important. In contrast, predator management programs initiated by human–wildlife conflict typically use profiling or specific control techniques to target ‘problem’ predators.
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Predators are often classed as prey specialists if they eat a narrow range of prey types, or as generalists if they hunt multiple prey types. Yet, individual predators often exhibit sex, size, age or personality-related differences in their diets that may alter the impacts of predation on different prey groups. In this study, we ask whether the house cat Felis catus shows individuality and specialisation in its hunting behaviour and discuss the implications of such specialisation for prey conservation and management. We first examine the prey types killed by cats using information obtained from cat owners, and then present data on cat hunting efficiency on different prey types from direct observations. Finally, we quantify dietary shifts in cats when densities of their preferred prey vary. Our results suggest that cats can exhibit individual, or between-phenotype, variation in hunting behaviour, and continue to hunt specific prey types even when these prey become scarce. From a conservation perspective, these findings have important implications, particularly if cats preferentially select rare or threatened species at times when populations of these species are low. Determining whether prey specialisation exists within a given cat population should therefore be useful for assessing the likely risk of localised prey extinctions. If risks are high, conservation managers may need to use targeted measures to control the impacts of specialist individual cats by using specific baits or lures to attract them. We conclude that individuality in hunting behaviour and prey preference may contribute to the predatory efficiency of the house cat, and suggest that studies of the ontogeny and maintenance of specialist behaviours be priorities for future research.
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The diets of predators and their selection of prey often shape prey community dynamics. Understanding how different predators select their prey could enable ecologists to predict their impact on specific prey populations. Here, we investigate the diets of the feral cat (Felis catus), red fox (Vulpes vulpes), and dingo (Canis dingo) in the Simpson Desert of central Australia, over a 1-year period between 2011 and 2012, and compare the selectivity of these predators for small mammalian prey. We found that cats showed the greatest consumption of small mammals, whereas dingoes consumed larger prey, thus indicating preferences for different prey sizes. High occurrence of small mammals in the diets of all predators probably reflected high abundances of small mammals in the environment; rodents declined after an irruption, but were still abundant at the time of sampling. The cat exercised greatest selectivity for small mammal species, whereas the dingo did not positively select for any species. Positive selection by predators for the long-haired rat (Rattus villosissimus) and negative selection for the spinifex hopping-mouse (Notomys alexis) may reflect inefficient and well-developed escape strategies by these 2 prey species, respectively. High selectivity by the cat for Forrest's mouse (Leggadina forresti) suggests that conservation of this rare rodent may depend on effective cat management.
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The highly distinctive and mostly endemic Australian land mammal fauna has suffered an extraordinary rate of extinction (>10% of the 273 endemic terrestrial species) over the last ∼200 y: in comparison, only one native land mammal from continental North America became extinct since European settlement. A further 21% of Australian endemic land mammal species are now assessed to be threatened, indicating that the rate of loss (of one to two extinctions per decade) is likely to continue. Australia's marine mammals have fared better overall, but status assessment for them is seriously impeded by lack of information. Much of the loss of Australian land mammal fauna (particularly in the vast deserts and tropical savannas) has been in areas that are remote from human population centers and recognized as relatively unmodified at global scale. In contrast to general patterns of extinction on other continents where the main cause is habitat loss, hunting, and impacts of human development, particularly in areas of high and increasing human population pressures, the loss of Australian land mammals is most likely due primarily to predation by introduced species, particularly the feral cat, Felis catus, and European red fox, Vulpes vulpes, and changed fire regimes.
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Context. Invasive mammalian predators are often associated with fragmented landscapes, and can compound the impacts of habitat loss and fragmentation on native fauna. Knowledge of how invasive predators are influenced by different landscape structures can assist in the mitigation of their impacts. Aims. The aim of the present study was to investigate the influence of landscape structure and site-scale habitat attributes on the frequency of feral-cat and red-fox detections in fragmented agricultural landscapes. Methods. Field surveys of the frequency of red-fox and feral-cat visitation at a site scale were stratified for six different habitat types in six study subregions. The habitat types were large remnant patch interior, large remnant patch edge, small remnant patch, roadside verge, regrowth patch and open agricultural land adjacent to a remnant patch. Sites were centred in a 1-km buffer area from which landscape composition and configuration were calculated. We applied a generalised linear model and an information-theoretic approach to determine the effect size and importance and rank of the explanatory variables on red-fox, feral-cat and pooled cat and fox detection rates. Key results. The most important factors influencing detection rates had a positive effect and included: the dominance of cropping in the landscape (cat, fox, pooled cat and fox); and the density of vegetation at a site scale (fox, pooled cat and fox). The number of native habitat patches was also an important factor in the models of red foxes and pooled invasive predators. Conclusion. Spatially heterogeneous cropping landscapes incur higher rates of invasive-predator detections than do intact native-woodland and pasture landscapes at the 1-km scale. At a site scale, elevated invasive-predator detections occurred at sites with dense vegetation, characteristic of narrow woodland and the edges of large woodland patches. Implications. The research findings highlight that vertebrate pest management needs to target highly fragmented agricultural landscapes that are more likely to have elevated levels of invasive-predator activity. Landscape restoration efforts need to consider the redesign of landscapes to make them less suitable for predators and more hospitable for native wildlife.
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Reducing the impacts of feral cats (Felis catus) is a priority for conservation managers across the globe, and success in achieving this aim requires a detailed understanding of the species’ ecology across a broad spectrum of climatic and environmental conditions. We reviewed the diet of the feral cat across Australia and on Australian territorial islands, seeking to identify biogeographical patterns in dietary composition and diversity, and use the results to consider how feral cats may best be managed. Australia and its territorial islands. Using 49 published and unpublished data sets, we modelled trophic diversity and the consumption of eight food groups against latitude, longitude, mean temperature, precipitation, environmental productivity and climate-habitat regions. We recorded 400 vertebrate species that feral cats feed on or kill in Australia, including 28 IUCN Red List species. We found evidence of continental-scale prey-switching from rabbits to small mammals, previously recorded only at the local scale. The consumption of arthropods, reptiles, rabbits, rodents and medium-sized native mammals varied with different combinations of latitude, longitude, mean annual precipitation, temperature and environmental productivity. The frequency of rodents and dasyurids in cats’ diets increased as rabbit consumption decreased. The feral cat is an opportunistic, generalist carnivore that consumes a diverse suite of vertebrate prey across Australia. It uses a facultative feeding strategy, feeding mainly on rabbits when they are available, but switching to other food groups when they are not. Control programmes aimed at culling rabbits could potentially decrease the availability of a preferred food source for cats and then lead to greater predation pressure on native mammals. The interplay between cat diet and prey species diversity at a continental scale is complex, and thus cat management is likely to be necessary and most effective at the local landscape level.
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Foraging theory predicts that animals should forage so as to maximize their net rate of energy gain or to minimize their risk of starvation. In situations where prey numbers fluctuate dramatically, theory predicts further that foragers will eat ‘optimal’ prey when it is abundant but expand their diet to include other prey types when the optimal prey is scarce; this is the alternative prey hypothesis. Here, we test this prediction by analyzing the diet of a mammalian predator, the feral house cat Felis catus, during periods of scarcity and abundance of the long-haired rat Rattus villosissimus. We also investigate whether the body condition of feral cats differs during different stages of the prey population cycle. Feral cats were shot during culling operations in semi-arid grassland habitats in central Queensland, Australia, and the stomach contents later identified. We found that the body condition of feral cats did not differ between phases of the prey population cycle, but the diets of cats culled when long-haired rats were scarce were significantly more diverse than when this rodent was abundant. Rats comprised about 80 % of cats’ diet by volume and frequency of occurrence when they were present, whereas birds, reptiles and invertebrates comprised the bulk of the diet when rats were not available. We conclude that, whilst feral cats are often thought to be specialist predators, they may be better considered as facultative specialists that will shift their diet in predictable ways in response to changes in the abundance of primary prey.
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Intensification of fires and grazing by large herbivores has caused population declines in small vertebrates in many ecosystems worldwide. Impacts are rarely direct, and usually appear driven via indirect pathways, such as changes to predator-prey dynamics. Fire events and grazing may improve habitat and/or hunting success for the predators of small mammals, however, such impacts have not been documented. To test for such an interaction, we investigated fine-scale habitat selection by feral cats in relation to fire, grazing and small-mammal abundance. Our study was conducted in north-western Australia, where small mammal populations are sensitive to changes in fire and grazing management. We deployed GPS collars on 32 cats in landscapes with contrasting fire and grazing treatments. Fine-scale habitat selection was determined using discrete choice modelling of cat movements. We found that cats selected areas with open grass cover, including heavily-grazed areas. They strongly selected for areas recently burnt by intense fires, but only in habitats that typically support high abundance of small mammals. Intense fires and grazing by introduced herbivores created conditions that are favoured by cats, probably because their hunting success is improved. This mechanism could explain why, in northern Australia, impacts of feral cats on small mammals might have increased. Our results suggest the impact of feral cats could be reduced in most ecosystems by maximising grass cover, minimising the incidence of intense fires, and reducing grazing by large herbivores.
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Predators are often classed as prey specialists if they eat a narrow range of prey types, or as generalists if they hunt multiple prey types. Yet, individual predators often exhibit sex, size, age or personality-related differences in their diets that may alter the impacts of predation on different prey groups. In this study, we ask whether the house cat Felis catus shows individuality and specialisation in its hunting behaviour and discuss the implications of such specialisation for prey conservation and management. We first examine the prey types killed by cats using information obtained from cat owners, and then present data on cat hunting efficiency on different prey types from direct observations. Finally, we quantify dietary shifts in cats when densities of their preferred prey vary. Our results suggest that cats can exhibit individual, or between-phenotype, variation in hunting behaviour, and continue to hunt specific prey types even when these prey become scarce. From a conservation perspective, these findings have important implications, particularly if cats preferentially select rare or threatened species at times when populations of these species are low. Determining whether prey specialisation exists within a given cat population should therefore be useful for assessing the likely risk of localised prey extinctions. If risks are high, conservation managers may need to use targeted measures to control the impacts of specialist individual cats by using specific baits or lures to attract them. We conclude that individuality in hunting behaviour and prey preference may contribute to the predatory efficiency of the house cat, and suggest that studies of the ontogeny and maintenance of specialist behaviours be priorities for future research.
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