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Enumerating a continental-scale threat: How many feral cats are in Australia?
Abstract
Feral cats (Felis catus) have devastated wildlife globally. In Australia, feral cats are implicated in most recent mammal extinctions and continue to threaten native species. Cat control is a high-profile priority for Australian policy, research and management. To develop the evidence-base to support this priority, we first review information on cat presence/absence on Australian islands and mainland cat-proof exclosures, finding that cats occur across >99.8% of Australia's land area. Next, we collate 91 site-based feral cat density estimates in Australia and examine the influence of environmental and geographic influences on density. We extrapolate from this analysis to estimate that the feral cat population in natural environments fluctuates between 1.4 million (95% confidence interval: 1.0–2.3 million) after continent-wide droughts, to 5.6 million (95% CI: 2.5–11 million) after extensive wet periods. We estimate another 0.7 million feral cats occur in Australia's highly modified environments (urban areas, rubbish dumps, intensive farms). Feral cat densities are higher on small islands than the mainland, but similar inside and outside conservation land. Mainland cats reach highest densities in arid/semi-arid areas after wet periods. Regional variation in cat densities corresponds closely with attrition rates for native mammal fauna. The overall population estimate for Australia's feral cats (in natural and highly modified environments), fluctuating between 2.1 and 6.3 million, is lower than previous estimates, and Australian feral cat densities are lower than reported for North America and Europe. Nevertheless, cats inflict severe impacts on Australian fauna, reflecting the sensitivity of Australia's native species to cats and reinforcing that policy, research and management to reduce their impacts is critical.
... In many situations domestic cats are estimated to occur in much higher numbers than all species of wild cats combined (Hunter, 2015). As a relatively fecund species able to persist under varied climate, habitat, and resource conditions (Lowe et al., 2000;Legge et al., 2017), and which is also regularly given food subsidies by people (Toukhsati et al., 2007;Davey et al., 2019), the domestic cat has some advantage over native predators and prey. Domestic cats (hereafter "cats") impact wildlife via predation, fear effects, competition, and as a vector of diseases and parasites (Beckerman et al., 2007;Dubey and Jones, 2008;Medina et al., 2011;Doherty et al., 2016). ...
... Should the stressors outweigh the rewards then there can be fatal impacts (Fardell et al., 2020). Free-roaming pet and feral cats that are prevalent in urban environments (Legge et al., 2017(Legge et al., , 2020a, could exacerbate stress impacts on urban wildlife through influencing their activity and adversely affecting their health and reproduction capabilities (Preisser et al., 2005), as well as the more obvious direct predation impacts (Murphy et al., 2019). ...
... Offering evidence for the negative nonconsumptive effects of roaming cats could support the need for more consideration in management to be given to the fear and stress impacts that cat presence alone can have on wildlife populations. We, therefore, investigated the fear/stress impacts on wildlife imposed by cat roaming activity, at all hours, in a patchy urban environment in Australia, where pet and feral cats are prevalent across all areas (Legge et al., 2017(Legge et al., , 2020b, to determine if landscapes of fear were evident. To do so, we used infrared motion sensor cameras to observe rates and times of activity of native and introduced wildlife, compared to roaming cat activity within a 24-h period in both yard and green space edge habitats. ...
Roaming domestic cats (Felis catus) are recognised as a threat to wildlife globally. Yet management of pet cats in urbanised areas is not regularly mandated, and management of feral cats in urbanised areas is rarely implemented. Mounting evidence emphasises the value of urban environments as hot spots of wildlife activity, which as the human population continues to grow may become the best or only habitats available to some wildlife species. Wildlife in urban environments must navigate introduced stressors that can compound with natural stressors. Additional, often novel, predators such as free-roaming pet and feral cats that are prevalent in urban environments could have high nonconsumptive fear/stress impacts on urban wildlife that influence their activity and adversely affect their health and reproduction capabilities, possibly more so than direct predation effects do. Cat roaming activity, particularly that of pet cats, could be managed with the support of the community, though motivation needs to be ensured. Understanding if roaming cat activity influences urban wildlife activity via perceived fear/stress impacts will help to build community motivation for the need for domestic cat management in urbanised areas. Using infrared motion sensor cameras positioned in both yards and green space edge habitats, we observed whether the presence and times active of native and introduced small mammals, and native birds, were impacted by domestic cat activity within a 24-h period and by their activity in the prior-24-h period. We found evidence of cat roaming activity during the hours of most wildlife activity, and show that wildlife navigated “landscapes of fear” relative to cat activity, as wildlife observed across a 24-h period increased their activity in the absence of cats in the same 24-h period and in the previous 24-h period. We also tested if cat activity was relative to previous cat activity, or disturbances, and found that cats reduced activity in response to each, but were still consistently present. Our results provide justification for the need to increase management of domestic cats in urbanised areas and offer fear/stress impacts as a novel approach to engender community support of such management.
... To avoid pseudoreplication, density estimates from the same location were averaged, reducing the dataset to 44 spatially distinct density estimates, including six from highly modified environments ( Figure S1b). To analyse the fox density data, we took the same approach as that used by Legge et al. (2017) for modelling cat density across Australia. ...
... The recent analyses of the numbers of animals killed by cats in Australia Woinarski et al., 2018) considered three components of the overall Australian cat population: pet cats, feral cats in highly modified environments (e.g., urban areas) and feral cats in largely natural environments [as defined by Legge et al. (2017)]. A comparable subdivision is not used in our assessment of fox diet because foxes are not kept as pets, and because we included parameters relating to habitat modification in our modelling. ...
... Such tolls help contextualise the relative predation threats imposed by both species (Loss et al., 2012) Note: Values relating to foxes are from this study. Values relating to cats have been sourced from Legge et al. (2017), , Woinarski et al. (2018), Murphy et al. (2019) and Legge et al. (2020). Confidence intervals for the estimated number of animals eaten by cats were not provided by the original sources and therefore have not been provided here. ...
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.
... Sobre todo, hay poca información de lo que ocurre en las zonas urbanas y los hábitats naturales y agrícolas que los rodean, a pesar de la alta densidad que los gatos pueden alcanzar en estos sitios (Hernández-Cortazar et al., 2015;Orduña-Villaseñor, 2015;Ortega-Pacheco et al., 2007;Pacheco, 2003). Por la información existente para otros países podemos suponer que los gatos deben tener importantes efectos sobre diversas especies de reptiles, anfibios, aves y mamíferos (Baker et al., 2008;Barratt, 1997;Legge et al., 2017;Loyd et al., 2013). El impacto por depredación de los gatos en el México continental solo se ha estudiado con gatos domésticos con dueño de vida libre en la ciudad de Morelia, Michoacán (Orduña-Villaseñor, 2015) y Xalapa, Veracruz (Mella-Méndez, 2019). ...
... Dada la información existente, consideramos que gatos y perros deben de ser considerados dentro de planes de manejo a diferentes escalas geográficas para reducir sus efectos ambientales negativos, sobre todo en países megadiversos. Actualmente, ha sucedido solo en Australia (Bellard et al., 2016;Legge et al., 2017;Moseby et al., https://doi.org/10.22201/ib.20078706e.2023.94.4850 2015). En el caso de nuestro país, tanto la alta diversidad β, como el alto número de especies endémicas de diferentes grupos de vertebrados, nos vuelve más susceptibles a los efectos negativos por depredación de ambas especies y nos obliga a considerar acciones de manejo en el corto plazo. ...
Revista Mexicana de Biodiversidad 94 (2023): e944850 Artículo de revisión Tus mejores amigos pueden ser tus peores enemigos: impacto de los gatos y perros domésticos en países megadiversos Recibido: 12 noviembre 2021; aceptado: 23 septiembre 2022 Resumen Los gatos y perros domésticos son las mascotas preferidas del hombre, por lo que se han convertido en especies invasoras y los carnívoros más abundantes del planeta. A pesar de su buena relación con nuestra especie, tienen un impacto ecológico negativo con consecuencias para las políticas de conservación. Los efectos que estos animales tienen sobre la fauna silvestre han sido estudiados principalmente en países con baja biodiversidad de vertebrados (EUA, Nueva Zelanda y Europa), y salvo por algunos trabajos realizados en Australia, Brasil, y México, no contamos con información sobre sus efectos en países con alta biodiversidad. Los efectos negativos que ambas especies tienen sobre la biodiversidad incluyen la depredación y competencia con fauna nativa, su hibridación con especies filogenéticamente cercanas o poblaciones silvestres de su propia especie, y la transmisión de enfermedades a la fauna silvestre y a los humanos. La falta de información sobre los efectos de depredadores introducidos a nivel continental y la falsa idea de que los gatos y perros son ambientalmente inocuos, vuelve crucial aumentar la investigación sobre estas especies en países megadiversos para proponer estrategias de manejo que fomenten la conservación de fauna nativa.
... Oceanic islands are characterised by a high proportion of endemic species (Carlquist 1974;Myers et al. 2000;Kier et al. 2009) contributing to the uniqueness of island communities (see Burlakova et al. 2011). Insular species are particularly naive and vulnerable to the introduction of exotic predators (Moors and Atkinson 1984;Medina et al. 2011;Legge et al. 2017), which are known to be the main drivers of species extinction and biodiversity loss on islands (Moors and Atkinson 1984;Courchamp et al. 2003;Leclerc et al. 2018;Russell and Kueffer 2019). Domestic cats (Felis catus) have established feral populations on many islands worldwide (hereafter referred to as feral cats; Nogales et al. 2013). ...
... The situation is even more complicated by the presence of domestic cats which can be accidentally culled and which permanently supplement the feral cat population through breeding (Choeur et al. 2022). One alternative to eradication is long-term control of feral cats in key areas, in order to maintain the population below a threshold that results in a low and acceptable impact on biodiversity (Doherty et al. 2017;Palmas et al. 2020). However, in most cases, controlled areas are not isolated from nearby uncontrolled areas and are continuously re-invaded by cats (Lazenby et al. 2015;Palmas et al. 2020). ...
Faunas of oceanic islands have a high proportion of endemic species which contribute to the uniqueness of island communities. Island species are particularly naïve and vulnerable to alien predators, such as cats ( Felis catus ). On large, inhabited islands, where the complete eradication of feral cat populations is not considered feasible, control represents the best management option to lower their detrimental effects on native fauna. The first objective of our study was to investigate population genetics of feral cats of Réunion Island. The second objective was to understand the space use of feral cats established near the breeding colonies of the two endemic and endangered seabirds of Réunion Island, the Barau’s Petrel ( Pterodroma baraui ) and the Mascarene Petrel ( Pseudobulweria aterrima ). We evaluated genetic diversity, population structure and gene flow amongst six groups of feral cats located at a maximum of 10 km from known petrel colonies. We also analysed the behaviour and space use of one of these feral cat groups using camera-trap data and Spatially Explicit Capture-Recapture (SECR) models. Genetic analyses revealed that feral cats were structured in three genetic clusters explained mostly by the island topography. Two clusters were observed at five sampled sites, suggesting high connectivity amongst these sites. The last cluster was found in only one site, suggesting high isolation. This site was a remote mountain area located in the vicinity of one of the main Barau’s Petrel colonies. The behavioural study was conducted on this isolated feral cat population. Mark recapture analysis suggested that feral cats were present at low density and had large home ranges, which is probably explained by reduced food availability. Finally, we make several recommendations for refining feral cat management programmes on inhabited islands.
... The European red fox (Vulpes vulpes) and the feral cat (Felis catus) were introduced to the Australian continent following European settlement and have had a devastating impact on the native fauna (Short and Smith 1994;Kinnear et al. 2002;Woinarski et al. 2015). A key conservation response has been to create sanctuaries fenced to exclude these predators for the reintroduction of predator-vulnerable species (Legge et al. 2017). This paper documents the reintroduction and establishment of a critically endangered macropodid to one such sanctuary where predator exclusion was not entirely effective. ...
... The cat density for much of the establishment phase of the woylie population was 0.24 km −2 (a single cat assumed to be resident in 427 ha); comparable to the calculated average across Australia of 0.27 km −2 (Legge et al. 2017). Predator:prey ratios increased from ~1:100 woylies in 2012 to 1:300 in 2018, with new recruits exceeding losses in the years 2011-2016. ...
Abstract
Context.
The fluctuating fortunes of the brush-tailed bettong have seen this species classified as ‘rare or likely to become extinct’ in the 1970s, delisted and hailed as a conservation success in the 1990s, and relisted as ‘critically endangered’ in 2008. Key actions to recover this species, broad-scale fox control and reintroduction to fox-free habitat, have had variable success.
Aims.
To monitor the reintroduction of bettong to fox-free habitat of Wadderin Sanctuary in the eastern wheatbelt of Western Australia.
Methods.
Growth of the population was monitored over a 12 year period by regular trapping throughout the sanctuary.
Key results.
The population increased monotonically to peak at 305 individuals (0.71 ha-1) at 7.5 years following release, before subsequent decline. Population growth was accompanied by a significant decline in mean condition and a reduction in the proportion of females with pouch young or lactating, presumably due to resources per head gradually declining. The proportion of large pouch young relative to total young carried by females declined as woylie numbers increased, suggesting that increasingly pouch young did not go to full term. Declines in population number, condition and reproduction were exacerbated by dry seasons. Bettongs established successfully, despite a succession of single feral cats within the 427-ha Sanctuary. The removal of the last cat, eight years following establishment of bettongs, had no obvious impact on bettong numbers, as at this point their population was stabilising due to declining body condition and reduced reproductive output.
Conclusions.
The observed pattern of population growth of bettongs was consistent with an herbivore irruption consequent of release of a species to new habitat. Decline following peak numbers appeared due to density-dependent resource limitation (declining resources per head with increased abundance) interacting with years of low rainfall.
Implications.
The dynamics of irruption and decline of herbivores are relevant to management of reintroduced populations to fenced predator-free sites and, potentially, to unfenced populations following release from predation.
... 230 years ago) [42] and dispersed rapidly across the continent [43]. It is now present across the entire mainland and about 100 offshore islands [44]. Cats have been linked to the extinction of more than 20 native mammal species [14,45]. ...
... Although cats occur and hunt in all environments or landforms [44,64], we found greater FOO of mammal species occupying more open habitats. Their ambush hunting behaviour is particularly well suited to catching small animals as they emerge from refuges [62,134] or vegetation cover [64]. ...
Introduction of the domestic cat and red fox has devastated Australian native fauna. We synthesized Australian diet analyses to identify traits of prey species in cat, fox and dingo diets, which prey were more frequent or distinctive to the diet of each predator, and quantified dietary overlap. Nearly half (45%) of all Australian terrestrial mammal, bird and reptile species occurred in the diets of one or more predators. Cat and dingo diets overlapped least (0.64 ± 0.27, n = 24 location/time points) and cat diet changed little over 55 years of study. Cats were more likely to have eaten birds, reptiles and small mammals than foxes or dingoes. Dingo diet remained constant over 53 years and constituted the largest mammal, bird and reptile prey species, including more macropods/potoroids, wombats, monotremes and bandicoots/bilbies than cats or foxes. Fox diet had greater overlap with both cats (0.79 ± 0.20, n = 37) and dingoes (0.73 ± 0.21, n = 42), fewer distinctive items (plant material, possums/gliders) and significant spatial and temporal heterogeneity over 69 years, suggesting the opportunity for prey switching (especially of mammal prey) to mitigate competition. Our study reinforced concerns about mesopredator impacts upon scarce/threatened species and the need to control foxes and cats for fauna conservation. However, extensive dietary overlap and opportunism, as well as low incidence of mesopredators in dingo diets, precluded resolution of the debate about possible dingo suppression of foxes and cats.
... However, less is known about the negative and potentially exacerbating, indirect effects of this invasive species, such as disease transmission (Medina et al. 2014). Despite ongoing efforts, complete eradication of feral cats from the Australian mainland is considered highly unlikely in the foreseeable future Legge et al. 2017). Consequently, a more complete understanding of predator-prey interactions is crucial to both the management of feral cats and the successful conservation of threatened native species (Medina et al. 2014). ...
... As well as modulating oocyst survival within the environment, climatic variations can influence transmission by acting on host population composition and interactions (Afonso et al. 2013). For example, expansion of both small mammal and feline populations occurs following increased rainfall (Stenseth et al. 2002;Legge et al. 2017). Such conditions can amplify the parasite in both populations through increased predator-prey interactions (Lélu et al. 2010), vertical transmission (Marshall et al. 2004) and increased environmental burden as young cats are infected and shedding for the first time (Dubey et al. 1977;Dabritz et al. 2007). ...
Toxoplasma gondii is a ubiquitous protozoan transmitted by felids and infection, morbidity, and mortality occur in numerous marsupial species. This study explores the relationship between cat
exposure and Toxoplasma in burrowing bettongs (Bettongia lesueur) in the Arid Recovery
Reserve (ARR), South Australia. We estimated seroprevalence, using a modified agglutination
test for T. gondii-specific immunoglobulins, in cat-free and cat-exposed bettong populations.
Tissue samples collected opportunistically from bettong carcasses and from cats within and
around the reserve were screened for T. gondii DNA using multiplex real-time polymerase chain reaction (M-qPCR). Two cats trapped inside the ARR tested positive (50.0%; 95% CI:
15.0–85.0%). All bettongs tested from the cat-free (n = 48) and cat-exposed (n = 19)
exclosures were seronegative (95% CI: 0–7.41% and 0–16.82% respectively). We found no evidence of fatal toxoplasmosis, with all bettong carcasses negative on M-qPCR (n = 11). We propose that T. gondii was not detected in bettongs coexisting with cats primarily due to low exposure of bettongs at the time of sampling, possibly due to poor oocyst viability in arid conditions or low shedding by cats. Ongoing screening throughout high and low rainfall years should be conducted to better establish the risk of Toxoplasma to bettongs in the ARR.
... Feral cats (Felis catus) are a widespread invasive species that can be found throughout much of the Australian mainland, occupying most habitat types (Legge et al. 2017;West 2018). Due to their estimated large numbers (2.1-6.3 million), their ubiquitous form and ability to prey upon many mammal, bird and reptile species, feral cats are identified as a major threat to many of Australia's native fauna (Legge et al. 2017;Kearney et al. 2018). ...
... Feral cats (Felis catus) are a widespread invasive species that can be found throughout much of the Australian mainland, occupying most habitat types (Legge et al. 2017;West 2018). Due to their estimated large numbers (2.1-6.3 million), their ubiquitous form and ability to prey upon many mammal, bird and reptile species, feral cats are identified as a major threat to many of Australia's native fauna (Legge et al. 2017;Kearney et al. 2018). Consequently, considerable focus has been afforded to the monitoring and management of this pest in recent years. ...
Feral cats are a key threat to many Australian native fauna, with camera traps increasingly used to identify individuals for evaluation of management actions. However, observer bias and camera trap settings can affect individual identification rates. We compared feral cat individual identification by two observers with extremes of experience. Arrays of 39–50 camera traps were deployed continuously for 22 months at four sites in the Western Division of New South Wales. Where possible, feral cats were individually identified from phenotypic characteristics by an expert and naïve lay observer. We obtained 10 465 feral cat images, with 72 cats individually identified across the sites. The experienced observer attributed more feral cat events to a known individual compared with the lay observer (21.3 vs 12.9%, respectively). Forty three percent of cat images were similarly tagged by both observers. Daytime events yielded higher identification rates and match success (28.1 vs 19.5 and 17.9 vs 11.8% for day vs night events for the expert and lay observer, respectively). Lack of congruence between observers, combined with a small number of events where cats could be individually identified, and differences in identification accuracy over time and between sites, makes estimation of detection probabilities and errors difficult.
... 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]. ...
... 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]. ...
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 .
... From analysis of 91 site-based feral cat density estimates in Australia, the mean density of feral cats on the Australian continent is 0.27 cats km −2 (95% confidence interval = 0.18-0.45 cats km −2 ) [47]. Feral cat density varies, however, among habitat types, and estimates suggest that there tend to be more feral cats in the southern half of Australia or in arid areas such as Matuwa (>1.5 cats km −2 after wet periods), and lower numbers in tropical and subtropical areas such as Shamrock Station [47]. ...
... cats km −2 ) [47]. Feral cat density varies, however, among habitat types, and estimates suggest that there tend to be more feral cats in the southern half of Australia or in arid areas such as Matuwa (>1.5 cats km −2 after wet periods), and lower numbers in tropical and subtropical areas such as Shamrock Station [47]. Our estimate of cat abundance on Shamrock Station is in line with the expected density for a non-controlled feral cat population in the region after a wet period. ...
Environmental damage caused by the intensification of agriculture may be compensated by implementing conservation projects directed towards reducing threatening processes and conserving threatened native species. In Australia, feral cats (Felis catus) have been a ubiquitous threatening process to Australian fauna since European colonisation. On Shamrock Station, in the north-west of Western Australia, the Argyle Cattle Company has proposed intensifying agriculture through the installation of irrigation pivots. There is concern that irrigating land and storing agricultural produce may indirectly increase the abundance of feral cats and European red foxes (Vulpes vulpes) on the property, which in turn may negatively impact threatened bilbies (Macrotis lagotis) that also inhabit the property. Feral cat control is required under the approved management plan for this project to mitigate this potential impact. Our baseline study revealed a high density of feral cats on Shamrock Station (0.87 cats km−2) and dietary data that suggest the current native mammal assemblage on Shamrock Station is depauperate. Given the high density of feral cats in this area, the effective control of this introduced predator is likely to confer benefits to the bilby and other native species susceptible to cat predation. We recommend ongoing monitoring of both native species and feral cats to determine if there is a benefit in implementing feral cat control around areas of intensive agriculture and associated cattle production.
... GI is easy to calculate and can be used to monitor variations in feral cat population as an alternative to harder-to-calculate indicators, such as estimated feral cat absolute density (spatially explicit capture-recapture, SECR; Efford 2015). It has been shown to be robust on relative abundance, leading to conclusions that are consistent with those based on other indices (Bengsen et al. 2012;Legge et al. 2017;Palmas et al. 2020a). The GI estimates feral cat activity (relative abundance approximation) by measuring mean camera capture events per camera and per occasion, following the equation of Engeman (2005): ...
... It is also likely that the region supported elevated cat densities following high rainfall during the 2010-11 La Niña event (Wardle et al. 2013;Legge et al. 2017). In this context, with high cat densities and crashing rodent populations triggering cats to seek alternative prey (Letnic and Dickman 2010). ...
Australia’s recent mammal declines have been most severe in the arid regions, with at least 14 species extinctions occurring therein. The common brushtail possum (Trichosurus vulpecula) is a semi-arboreal marsupial that historically occurred widely across arid Australia but has disappeared from much of this region. We surveyed the last known sites for the species in central Australia. In 2012, we detected possum scats from 3 of 19 sites in Tjoritja National Park in the Northern Territory. Presence sites were separated by <4 km and characterised by extreme ruggedness. Further scat surveys in 2016–17, and 10 499 camera-trap nights of targeted survey in 2020–21, resulted in no possum detections. Moreover, no possums were detected during >60 000 camera-trap nights at nearby monitoring sites targeting other species in 2016–22. The contraction of common brushtail possums to rugged refuges by 2012 is consistent with a decline driven by mammalian predators. The possible extirpation also coincided with or followed record years of high temperatures. The culturally significant common brushtail possum is a priority candidate species for reintroduction to parts of central Australia. Reintroduction attempts must manage mammalian predators and consider the suitability of source populations and translocation sites in the face of a rapidly warming climate.
... Cats are putatively the primary threat to savanna mammals in northern Australia (Johnson, 2006;Frank et al., 2014;Ziembicki et al., 2015;Tuft et al., 2021). While feral cats are ubiquitous across the entire study region (Legge et al., 2017), the few survey sites where cats were recorded all had very low mammal abundance and richness compared to sites where cats were not recorded. This suggests a strong local influence of cat activity on mammal populations where cat activity is high. ...
... Higher density cat populations are typically seen in and around urban environments [4]. In Australia, there are approximately 4.09 million owned cats in 30% of households, and approximately 2.8 million feral cats, covering more than 99.8% of Australia's surface area [5][6][7][8]. ...
Free-roaming cats pose a risk to their own health and welfare, as well as to the health and welfare of wildlife and humans. This study aimed to monitor and quantify area-specific free-roaming cat movement. Two local government areas (LGAs) in Greater Sydney were included, Campbelltown (CT) and the Blue Mountains (BM). Motion-capture cameras were installed on 100 volunteer properties (50 per LGA) to indirectly capture animal movements over two months. Transect drives were completed eight times (four per LGA) to directly observe roaming cats in residential areas. The cameras and transects both identified higher free-roaming cat numbers in CT (density of 0.31 cats per ha, resulting in an estimated abundance of 361 cats in the 1604 ha of residential area) than the BM (density of 0.21 cats per ha, resulting in an estimated abundance of 3365 cats in the 10,000 ha of residential area). More wildlife events were captured in the BM (total = 5580) than CT (total = 2697). However, there was no significant difference between CT and the BM for cat events (p = 0.11) or wildlife events (p = 0.32) observed via the cameras. Temporally, cats were observed via the cameras throughout the entire day with peaks at 9:30 am and 8:00 pm in the BM, and 7:00 am and 12:00 pm in CT. Overlaps in activity times were recorded for free-roaming cats with bandicoots (BM), possums (BM), and small mammals (BM and CT). This study demonstrates that camera monitoring on private property and transect drives are useful methods to quantify free-roaming cat abundance to inform cat management interventions.
... The impacts of each invasive mammalian predator species can vary with their abundance and behaviour, and with the tolerance of the prey species present, all of which may be dynamic across habitats, landscapes, or seasons. Invasive predators may cause detriment, or may provide ecological benefits, such as controlling potentially damaging native or invasive species (Rayner et al. 2007;Bergstrom et al. 2009;Dowding et al. 2009;Ritchie and Johnson 2009;Glen et al. 2013;Legge et al. 2017;Springer 2018;Ortega et al. 2021), providing food for native species (Carlsson et al. 2009;Travers et al. 2021), or pollination and dispersal for native plants or fungi (Vernes and McGrath 2009;Pattemore and Wilcove 2012;O'Rourke et al. 2020). Given these complexities, understanding the ecological role of invasive predators is critical for informing the need, priority and likely benefits of invasive species management. ...
... Across Australia, the predation impacts of feral cats are thought to be greatest in areas with sparse groundlayer vegetation cover (Lawes et al., 2015). This may be in part because (1) cats are more abundant in these areas (Legge et al., 2017) and/or (2) cats potentially hunt most effectively in open habitats as there may be less cover for prey, making them easier to detect and capture (McGregor, . Therefore, the removal of vegetative cover by fire may advantage feral cats, even if some cats are killed by fire, and even if there is a lower abundance of prey species post-fire. ...
Predation by feral cats ( Felis catus ) has caused the extinction of many native species in Australia and globally. There is growing evidence that the impacts of feral cats can be amplified in post‐fire environments, as cats are drawn to hunt in or around recently burnt areas and are also more effective hunters in open habitats. In 2018–2019, we established arrays of camera traps to estimate the abundance of feral cats on Kangaroo Island, South Australia. Much of the island (including five of our seven survey sites) was subsequently burnt in a severe wildfire (December 2019–February 2020). We re‐sampled the sites 3–8 months post‐fire (seven sites) and 11–12 months post‐fire (three sites). At two unburnt sites sampled post‐fire, it was possible to produce density estimates of cats using a spatially explicit capture–recapture approach. Where estimating density was not possible (due to low detections or individual cats not being distinguishable), the number of individuals and percentage of trap nights with detections was compared between the sampling periods. Some low‐level cat control occurred within 2 km of three of the seven arrays (all within the burn scar) within 3 months of the fire. Across the five burnt sites, there was a decline in cat detections post‐fire (including those without post‐fire cat control). At 3–8 months post‐fire, there was, on average, a 57% reduction in the number of individual cats, and a 65% reduction in the number of nights with cat detections, relative to pre‐fire levels. Although cat detections declined following the fire, reduced population sizes of prey species and reduced cover as a result of the fire might still mean that cat predation is a threat to some surviving prey species. Management that reduces feral cat predation pressure on wildlife following wildfire should enhance the likelihood of post‐fire wildlife persistence and recovery.
... These numbers highlight how little we know about the real magnitude of the predation pressure exerted by domestic cats upon wildlife in Brazil. This becomes even clearer if we consider that the conservative estimate of the cat population in Brazil is 14 million individuals [40], approximately four times larger than the cat population estimated in Australia [41]. Therefore, the low number of species impacted by domestic cats in Brazil is likely due to the lack of systematic studies including long term observations (of this feline and its prey) encompassing different habitats [see 42,43,44]. ...
Domestic cats (Felis catus Linnaeus, 1758) can interact with and cause several negative impacts upon wildlife if unconstrained by their owners. These impacts occur especially because of their innate predatory behavior and, usually the lack of any natural predators, as well as due to their high abundances relative to native carnivores. Although these impacts are well studied in temperate countries, there are but a few records of species used as prey by these carnivores in Brazil. Here, we expand the knowledge of native species preyed upon by domestic cats in Brazil by presenting new records of this predator-prey interaction and reviewing records in the literature. Predation events were recorded through opportunistic encounters between 2016 and 2022. We recorded the predation of 14 native terrestrial vertebrate species (reptiles, amphibians, birds, and mammals) from the Cerrado and Atlantic Forest biomes. Our literature review recovered predation events by cats in the two aforementioned biomes plus in the Amazonia. Our results increase to 48 the number of wild species preyed upon by domestic cats in Brazil, which is probably an underestimation, as this number is much higher in other countries of comparable land size and species diversity. We suggest that cat population control measures should be carried out, especially in protected areas.
... Cats are effective predators and have been implicated in the extinctions of 60+ species in island ecosystems (Doherty et al., 2016;Jones et al., 2016;Nogales et al., 2004) and mainland ecosystems alike (Loss & Marra, 2017). These environmental effects are not restricted to feral cats (e.g., those that have returned to a wild diet independent of humans), but evidence is growing that domestic cats allowed outdoors and those that are fed in communities also contribute to the declines of small mammals, birds, and reptiles at continental scales (Doherty et al., 2015;Kays et al., 2020;Legge et al., 2017;Loss et al., 2013). ...
Free‐roaming cats are a conservation concern in many areas but identifying their impacts and developing mitigation strategies requires a robust understanding of their distribution and density patterns. Urban and residential areas may be especially relevant in this process because free‐roaming cats are abundant in these anthropogenic landscapes. Here, we estimate the occupancy and density of free‐roaming cats in Washington D.C. and relate these metrics to known landscape and social factors. We conducted an extended camera trap survey of public and private spaces across D.C., and analyzed data collected from 1,483 camera deployments from 2018‐2020. We estimated citywide cat distribution by fitting hierarchical occupancy models and further estimated cat abundance using a novel random thinning spatial capture‐recapture model that allows for the use of photos that can and cannot be identified to individual. Within this model, we utilized individual covariates that provided identity exclusions between photos of unidentifiable cats with inconsistent coat patterns, thus increasing the precision of abundance estimates. This combined model also allowed for unbiased estimation of density when animals cannot be identified to individual at the same rate as for free‐roaming cats whose identifiability depended on their coat characteristics. Cat occupancy and abundance declined with increasing distance from residential areas, an effect that was more pronounced in wealthier neighborhoods. There was noteworthy absence of cats detected in larger public spaces and forests. Realized densities ranged from 0.02‐1.75 cats/ha in sampled areas, resulting in a district‐wide estimate of ~ 7,296 free‐roaming cats. Ninety percent of cat detections lacked collars and nearly 35% of known individuals were ear‐tipped, indicative of district Trap‐Neuter‐Return (TNR) programs. These results suggest that we mainly sampled and estimated the unowned cat subpopulation, such that indoor/outdoor housecats were not well represented. The precise estimation of cat population densities is difficult due to the varied behavior of subpopulations within free‐roaming cat populations (housecats, stray and feral cats), but our methods provide a first step in establishing citywide baselines to inform data‐driven management plans for free‐roaming cats in urban environments. This article is protected by copyright. All rights reserved.
... 1. Given fox abundance and occupancy can be negatively affected by lethal fox control (Hunter et al. 2018), we expect that fox reporting rate (i.e. the number of days foxes were detected at a sand pad, divided by total survey days) would decrease in response to increasing spatial and temporal intensity of lethal fox baiting; 2. Some evidence suggests that fox baiting is most effective following periods of low rainfall and prey availability (Short et al. 1997;Burrows et al. 2003;Claridge et al. 2010), so we expect that the effectiveness of baiting at reducing fox reporting rate will be highest during periods of low rainfall; and 3. Because feral cats can increase in abundance as a result of effective fox control (Marlow et al. 2015;Stobo-Wilson et al. 2020) and above average rainfall (Legge et al. 2017), feral cat reporting rate will be positively related to increased fox baiting intensity and/or reduced fox activity, and these relationships will be strongest following periods of low rainfall. ...
Context Invasive predators are major drivers of global biodiversity loss. Red foxes (Vulpes vulpes) and feral cats (Felis catus) have contributed to the decline and extinction of many native species in Australia. The deployment of poison baits to control fox populations is a widespread conservation tool, but the effects of baiting intensity, rainfall and prey abundance on baiting effectiveness remain poorly understood. Aims We aimed to understand what influences the association between fox baiting intensity, red fox activity and feral cat activity, to provide inferences about what might affect the effectiveness of fox baiting in reducing fox activity. Methods We used generalised linear models to assess how fox and cat activity changes in relation to fox baiting intensity, rainfall, native prey availability and distance to agricultural land over a 6-year period (2006–13) in the forest ecosystems of the Upper Warren region of south-western Australia. Key results We found that fox activity was negatively associated with rainfall in the previous 12 months and positively associated with prey abundance and fox baiting intensity. We also found an interaction between fox baiting and prey abundance, with fox activity increasing with prey activity in areas of low and moderate baiting intensity, but remaining constant in areas of high baiting intensity. Feral cat activity was positively associated with prey abundance and fox baiting intensity. We found no clear relationship between fox and cat activity. Conclusions The drivers of the association between fox baiting and fox activity are unclear because intense fox baiting was targeted at areas of known high fox abundance. However, our results indicate that intense fox baiting may be effective at decoupling the positive association between fox activity and prey abundance. Our results also suggest a positive association between fox baiting intensity and feral cat activity, thus supporting the case for integrated fox and cat management. Implications We caution interpretation of our results, but note that management of invasive predators could be improved by adjusting the intensity of management in response to changes in environmental conditions and local context (e.g. strategically conducting intense predator management where prey abundance is highest). Improved understanding of these associations requires a monitoring program with sufficient replication and statistical power to detect any treatment effects.
... Introduced mammalian mesopredators in particular are regarded as "agents of extinction" and "the most damaging group of alien animal species for global biodiversity" (Doherty et al., 2016). They are said to "inflict severe impacts" whether their populations are high or low due to the "sensitivity" of native prey (Legge et al., 2017). There are two main reasons for this dire assessment. ...
Invasion biology is founded on the idea that introduced species cause extinctions because they have not undergone sufficiently long periods of coevolution with native species for more stable relations to develop. The prey naivety hypothesis applies this to predator‐prey interactions, positing that prey are vulnerable to introduced predators because many generations are needed for appropriate avoidance responses to develop. It predicts that prey will be more responsive to native than introduced predators, and least responsive to introduced predators that differ substantially from native predators and to those newly established. To test these predictions, we conducted a global meta‐analysis of studies that measured the wariness responses of small mammals to the scent of sympatric mammalian mesopredators. We identified 26 studies that met our selection criteria, comprised of 134 experiments reporting on the responses of 36 small mammal species to the scent of 6 introduced mesopredators and 12 native mesopredators. Our analysis revealed that, globally, small mammals are similarly wary of the scent of native and introduced mesopredators; that phylogenetic distance and functional dissimilarity between introduced mesopredators and closest native mesopredators has no effect on wariness; and that wariness is unrelated to the number of prey generations, or years, since first contact with introduced mesopredators. Instead, we found that small mammal wariness is responsive to body mass, regardless of nativity. The one thing animals do not seem to recognize is whether their predators are native. This article is protected by copyright. All rights reserved
... The numbers of unowned cats are difficult to quantify, with estimates of their abundance ranging between 30 and 100 million in the USA (Ref. [11] and included references), 700,000 in Australia [12], and 196,000 in New Zealand [13]. Depending on the geographic region, stray cats may suffer from similar poor welfare outcomes to free-ranging owned cats, including road accident trauma [14][15][16][17], poisoning [18], ingestion of hazardous garbage [7], predation by larger carnivores [19], disease [20], and human persecution [21]. ...
Globally, unowned urban cats are a major concern because they may suffer from poor welfare and cause problems, including public health risks, nuisances, and urban wildlife predation. While management options are often presented as a choice between culling or trap–neuter–return (TNR), for 25 years, the Lonely Miaow (Inc.) charity in Auckland, New Zealand (hereafter LM), has used a third strategy—intensive adoption or trap–assess–resolve (TAR). As of 2019, of 14,611 unowned cats trapped, 64.2% were adopted, 22.2% were euthanized if unsocialised or in grave ill-health, 5.7% were neutered and returned to the site, and 7.9% had other outcomes, such as being transferred to other shelters. Adoption rates increased over this time, exceeding 80.0% in 2018 and 2019. The cost of processing each cat from capture to adoption rose from NZD 58 in 1999 to NZD 234 by 2017. Approximately 80% of colonies (sites where cats were trapped) were around residential areas. Approximately 22% of cats required veterinary treatment after capture; common ailments included respiratory infections, ringworm, dental problems, and trauma. Consistently, 52% of cats were young kittens (<10 weeks old), c. 80% of cats were <1 year old, and only c. 2% were estimated to be >5 years old. TAR avoids euthanasia where possible. Its effectiveness would be enhanced by fewer abandonments of owned cats and kittens, fitting within integrated strategies for the control of unowned cats involving community education. Cat adoptions improve the welfare of cats and, with appropriate husbandry, should alleviate concerns about nuisances, public health, and attacks on wildlife or the cats themselves, essentially benefitting the community and the cats. This case study is relevant to other cities around the world that are seeking to manage unowned cats.
... The Australian sea lion inhabits the shores and islands of Australia's southern and south-western coast (Gales et al., 1994), much of which is arid coastline of relatively low human population density. Australia's abundant feral cat population, estimated to be 2.1-6.3 million animals dispersed across 99.8% of the continent (including the arid regions) (Legge et al., 2017) is a likely source of environmental contamination by T. gondii oocysts. Furthermore, while some Australian sea lion colonies exist on felid-free offshore islands (e.g., Olive Island and Dangerous Reef, South Australia), others (e.g., Seal Bay, Kangaroo Island, South Australia) are exposed to a feral cat density estimated to be 10 times greater than that of the adjacent mainland (Taggart et al., 2019a). ...
Toxoplasma gondii is a ubiquitous parasite increasingly detected in marine mammals and suspected to contribute to limited recovery of endangered populations. This study reports on the exposure of the Australian sea lion ( Neophoca cinerea) to this protozoon using archived adult and pup sera from three island colonies in South Australia. Modified agglutination testing (MAT) detected a seroprevalence of 30.4% (95% CI 13.2-52.9: n = 23) and high antibody titers (512 to > 2048 IU/ml) in adult females (median age 9.5 y, range 5.5-14.5 y) at Dangerous Reef, a felid-free island. Antibodies weren’t detected in any surveyed pup (97.5% CI 0.0-2.0%, n = 184) at two felid-free islands (Dangerous Reef: n = 21; Olive Island: n = 65), nor at Kangaroo Island (n = 98), which has a high-density feral cat population. Kangaroo Island pups of known age were 7-104 d old, while standard length and bodyweight comparison suggested younger and older pup cohorts at Dangerous Reef and Olive Island, respectively. This study provides the first quantification of disease risk in this endangered species from T. gondii exposure. The absence of detectable pup seroconversion supports the lack of detectable congenital transmission, maternal antibody persistence or early post-natal infection in the sampled cohort yet to commence foraging. An extended serosurvey of N. cinerea colonies is recommended to confirm the hypothesis of predominantly forage-associated exposure to T. gondii in this species. Findings have implications for parasitic disease risk in wildlife inhabiting Australia’s islands and for the feral cat control program on Kangaroo Island.
... This is best evidenced in Australia, where disproportionately, feral cats and European red foxes (Vulpes vulpes) present the greatest predatory threat to most endangered Australian mammals. 1 Feral cats and foxes have been implicated as the primary cause of extinction of at least 25 out of 30 endemic land mammal species, which constitutes 30% of modern-day global extinctions. 4,5 Present across >99.8% of Australia's land area, 6 feral cats kill 815 million mammals annually, with the majority (≥56%) being native species. 7 Efforts to mitigate the catastrophic effects of feral cat predation generally involve the attempted removal of feral cats from a target landscape and subsequent attempts to re-establish populations of threatened species through reintroduction (or translocation) programs within the area. ...
Introduced predators are a significant threat to global biodiversity and are responsible for most of all modern bird, reptile, and mammal extinctions. In Australia, the introduced feral cat (Felis catus) kills 459 million mammals annually and leaves many species facing extinction. Attempted reintroductions of threatened mammal species often fail due to the persistence of intractable feral cats-termed "problem individuals"-and the swift depredation of the reintroduced population. Biomaterial implants could hold the key to targeting problem individuals. Herein, we report the development of the population-protecting implant, a subcutaneous implant for native mammals. The implant is intended to be inert within the subcutaneous environment for the life of the native mammal and to release a toxic payload in the gastric environment of a feral cat when ingested during a predation event. By toxifying and causing the death of the feral cat, the problem individual is eliminated, and the remaining population of native mammals is protected from further predation. To achieve this, an innovative reverse enteric coating was developed for use as a biomaterial, which exhibited a previously unreported level of pH selectivity for solubility at gastric pH. Large batches of implants were manufactured via fluidized-bed spray coating with a uniform reverse enteric coating and low intrabatch variability. Implants with a 300 μm coating afforded significant stability and retention of the payload at subcutaneous pH in vitro, with rapid release of the payload observed at gastric pH. In addition, implants exhibited favorable stability in vivo in rats, with no observed difference in biocompatibility compared to conventional radio-frequency identification microchips. This work demonstrates a proof of concept of an innovative type of implant and serves as the basis for its future development and translation into the field.
... The feral cat (Felis catus) is a versatile predator that has established across Australia and most of its offshore islands (Doherty et al. 2014Legge et al. 2017). Feral cats have contributed to most of the 30 native mammal extinctions since European settlement of Australia and are directly contributing to the decline of numerous other populations of small vertebrates (Woinarski et al. 2015;Woinarski 2016;Doherty et al. 2017). ...
Context The Felixer grooming device (‘Felixer’) is a lethal method of feral cat control designed to be cost-effective and target specific. Aims This study aims to test the target specificity of the Felixer in Tasmania, with a particular focus on Tasmanian devil and quoll species due to the overlap in size, habitats and behaviour between these native carnivores and feral cats. Methods Our study deployed Felixer devices set in a non-lethal mode in nine field sites in Tasmania, one field site in New South Wales and two Tasmanian wildlife sanctuaries. Key results Our study recorded 4376 passes by identifiable vertebrate species including 528 Tasmanian devil passes, 507 spotted-tailed quoll passes and 154 eastern quoll passes. Our data showed that the Felixer can successfully differentiate quoll species from feral cats with spotted-tailed quolls and eastern quolls targeted in 0.19% and 0% of passes, respectively. However, Tasmanian devils and common wombats were targeted in 23.10% and 12% of passes, respectively, although sample size was low for common wombats (n = 25). Conclusions The Felixer could not reliably identify Tasmanian devils and possibly common wombats as non-target species. Further data is needed to confirm the potential for impacts on the common wombat and other potential non-target species in Tasmania, and the likelihood of the toxin being ingested by falsely targeted individuals. Implications Our study suggest that the Felixer device is safe for use in the presence of two species of conservation concern, the eastern and spotted-tailed quoll. It also supports evidence from previous studies that the Felixer is unlikely to impact bettongs and potoroos. Use of Felixer devices across much of Tasmania would have to balance the conservation or economic benefits of cat control against potential impacts on Tasmanian devils. We suggest that active Felixer deployments be preceded by surveys to establish the range of species present at the control site, and the season of control considered carefully to minimise potential impacts on more susceptible juvenile animals. In addition, modifications to the Felixer device such as the proposed incorporation of AI technology should be tested against the Tasmanian devil and other non-target species.
... In addition, patterns of connectivity have been altered for some bird species (Cooper and Walters 2002) with likely disruptions to key functional processes such as gene flow (Sunnucks 2016; Radford et al. 2021). Temperate woodland environments are also characterised by relatively large numbers of exotic carnivores (Legge et al. 2017;Lindenmayer et al. 2020b) that can prey on birds as well as exotic herbivores and native herbivores that can degrade bird habitats (Bennett et al. 2020;Lindenmayer et al. 2020b). As a result of major changes in landscapes, bird communities have been substantially altered (Ford et al. 2001;Ford 2011) and are now often dominated by large numbers of hyperaggressive honeyeaters such as the Noisy Miner (Manorina melanocephala) (Montague-Drake et al. 2009;Mac Nally et al. 2012;Maron et al. 2013) which have negative impacts on smaller-bodied bird species (Grey et al. 1997;Westgate et al. 2021b;Hingee et al. 2022). ...
Australia’s temperate woodlands are among the most heavily modified biomes globally. I summarise some of the work on birds in south-eastern Australia that identifies drivers of bird biodiversity loss and the effectiveness of management interventions. I particularly focus on studies by the Sustainable Farms project at The Australian National University which show that: (1) Bird occurrence is associated with the amount of woody vegetation cover at site, farm and landscape scales. (2) Planting to increase woodland cover has greater relative positive effects on birds than grazing control. However, grazing of plantings has inherently negative impacts. (3) There are different broad structural types of woodland (old growth, regrowth and replantings) and each supports different bird assemblages. (4) The highest bird biodiversity occurs on farms which support all three woodland structural types, as well as other natural assets like paddock trees and fallen timber. (5) Long-term data show that while some woodland species are increasing, twice as many species are declining. Despite the body of information on woodland birds, substantial knowledge gaps remain. These include understanding of: (1) the role of fire in woodland bird dynamics and habitat suitability, and (2) demographic processes like bird breeding success and how it affects long-term site occupancy. Bird biodiversity in Australian agricultural landscapes formerly dominated by temperate woodlands will be best supported by: (1) ceasing land clearing, (2) greater woodland regeneration and woodland planting, (3) limiting livestock grazing, and (4) limiting the impacts of the Noisy Miner (Manorina melanocephala).
... Lower detection rates of feral cats, because of closed habitat structure and their cryptic behavior, are thought to have caused underestimations of feral cat abundance in forest environments (Denny & Dickman, 2010). This has led some studies to suggest that rainforests potentially support lower densities of feral cats than more open habitat types, resulting in neglected conservation planning for feral cat management in tropical forests (Dickman, 1996;Legge et al., 2017). ...
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.
... could reflect a shared preference of both species for gardens in which supplementary food is provided, as has been proposed for cat and bird densities (Sims et al., 2008), although we did not find a significant difference in cat activity for gardens with supplemental feeding. Given that there are estimated to be 3.8 million pet cats in Australian residential gardens (Animal Medicines Australia, 2019), in addition to an estimated 0.7 million unowned roaming cats around built up areas (Legge et al., 2017), we support the application of a precautionary principle regarding the impacts of pet cats on wildlife (Calver et al., 2011). There was no support for a relationship between quenda activity on camera trap and dog activity in residential gardens surveyed in the present study. ...
Residential gardens can provide essential opportunities for native wildlife and represent a valuable way of creating new habitats. Bandicoots (marsupial family Peramelidae) are medium-sized digging mammals that play a valuable role in maintaining ecosystem health; retaining these important ecosystem engineers across urban landscapes, including in private gardens, can have enormous conservation benefits. Urbanisation is a significant threat for some bandicoot species, and therefore understanding the factors associated with their activity can help guide urban landscape and garden design. To identify key features associated with the activity of a local endemic bandicoot species, the quenda (Isoodon fusciventer), we carried out a camera trap survey of front and back yards for 65 residential properties in the City of Mandurah, Western Australia. We compared quenda activity with biotic and abiotic factors that could indicate potential predation risk (activity of domestic dogs Canis familiaris and cats Felis catus, and the presence of artificial or natural protective cover), food availability (including deliberate or inadvertent supplementary feeding, provision of water, and diggable surfaces) and garden accessibility (distance to bushland, permeability of boundary fencing, and garden position). Supplementary feeding was strongly associated with quenda activity. Quenda were also more active in back yards, and in gardens where there was greater vegetation cover. Of concern, quenda activity was positively associated with cat activity, which could reflect that straying pet cats are attracted to gardens that harbour wildlife populations, including quenda. Furthermore, almost half of the gardens showed cat activity despite only a small sample of the surveyed residents owning a pet cat. Results of this study can help guide the design of residential gardens to increase useful habitat for these important digging mammals. Vegetation, wood mulch and semi-permeable fencing can provide valuable resources needed to support the persistence of quendas across the rapidly changing urban landscape mosaic, where natural and managed (e.g., gardens and parks) green spaces are becoming less common and more isolated.
... On a global scale, invasive generalist predators have caused extensive biodiversity loss (Medina et al. 2011;Doherty et al. 2016). In Australia, feral cats (Felis catus) are distributed right across the continent (Legge et al. 2017), have caused the extinction of at least 22 mammalian species, and are thought to have contributed to the extinction of many others (Woinarski et al. 2014). Cats negatively impact native wildlife through predation and competition, and also through their role in transmitting parasites and disease (Nishimura et al. 1999;Veitch 2001;Medway 2004;Phillips et al. 2007). ...
Across Australia, feral cat (Felis catus) control and eradication programs are conducted to conserve threatened and vulnerable species. Controlling feral cats effectively at a landscape scale, particularly in remote woodland habitats, remains a significant challenge. Unfortunately, some standard feral cat control methods, such as shooting and cage trapping, require road access. Poison baiting is one of the few methods available to control feral cat populations in remote and inaccessable areas. We aimed to examine the impact of a Curiosity ® (Scientec Research PTY LTD, Melbourne, Australia) baiting program on the feral cat population found in continuous woodland habitat of the Dudley Peninsula, on Kangaroo Island, South Australia. The density of cats was monitored using camera traps set up across both treatment and control sites using a before-after control-impact approach. Feral cat density was calculated using a spatially explicit capture-recapture framework. In addition, 14 feral cats were GPS collared at the treatment site, and their status and location, before and after baiting, was monitored. At the treatment site after baiting, feral cat density fell from 1.18 ± 0.51 to 0.58 ± 0.22 cats km −2. In total, 14 feral cats were GPS collared, and of those, eight were detected within the treatment zone during and after bait deployment. Six of those eight cats died shortly after baiting, likely from bait consumption. A new individual cat was detected in the treatment zone within 10 days of baiting, and within 20 days, four new individuals were detected. Both before and after baiting, the number of feral cat detections was highest on roads, suggesting cat recolonisation of baited areas may be assisted by roads. Curiosity baiting was found to be an effective method for reducing the density of feral cats in continuous woodland habitats of Kangaroo Island. Roads may act as access routes aiding cat recolonisation. Curiosity baiting programs on Kangaroo Island (and elsewhere) would benefit from incorporating follow-up control, particularly along roads, to target feral cats re-colonising the area.
... Na primeira delas, exponho meus dados de campo a respeito dos cães ferais na Terra do Fogo, de forma a preparar o terreno, por assim dizer, para as reflexões que pretendo tecer ao longo do restante do texto. A partir do 13 Sobre cães e gatos "invadindo" ambientes "selvagens" e ameaçando espécies "nativas", ver também Legge et al. (2017) e Doherty et al. (2017). que pude ver e ouvir na Argentina e do pensar com autores como Anderson (2014), Anderson e colaboradores (2017), Osório (2013Osório ( , 2019, Sordi (2015Sordi ( , 2017Sordi ( , 2019, entre outros, bem como de discussões a respeito de "invasores biológicos" no campo do preservacionismo (Paschoal et al. 2012;Silva-Rodríguez et al. 2010;Silva-Rodríguez & Sieving 2011), buscarei, na seção subsequentededicada a contextos brasileiros e chilenos -, apontar para a amplitude da interação desses animais com os ambientes que co-constituem com outros humanos e outros não humanos. ...
Busco, neste artigo, refletir a respeito dos denominados cães “ferais”, ou “selvagens”, a partir de seu papel ativo na construção, alteração e co-constituição de paisagens – argentinas, brasileiras e chilenas. Mobilizo, principalmente, o conceito de “arquiteturas da domesticação”, e proponho que também pensemos tais arquiteturas como infraestruturas “contra a invasão”. Se, por um lado, cercas, correntes e outros artefatos criam relações de domesticidade, por outro eles também podem vir a desvelar outras formas de interação – cercas também são sobre evitar a entrada de outrem, e, portanto, manter a divisão dentro x fora. A partir de etnografia realizada na Província da Terra do Fogo (Argentina), onde me deparei pela primeira vez com os tais dos perros salvajes, tenciono, nas páginas que se seguem, discutir e tecer conexões com outros contextos nos quais cães feralizados também tomam parte: as reservas florestais brasileiras e certas zonas rurais no Chile. Tais conexões, a meu ver, importam no sentido de que podem, quiçá, ajudar a suprimir lacunas nos estudos animais a respeito da convivência humano-animal com as tais das “espécies exóticas invasoras”, e, por conseguinte, do que estes animais estão fazendo e podem fazer. Tendo em conta que o selvagem e o feral são segmentos de um sistema de relações mais amplo, minhas intenções, aqui, são apontar para a amplitude da interação desses animais com os ambientes que co-constituem e continuamente reconfiguram com humanos e outros não humanos. Sugiro, neste artigo, que os processos de constituição de paisagens multiespécies não são somente sobre inclusão, mas, também, sobre exclusão.
... Free-roaming domestic cats (Felis catus; hereafter 'cats') are both common and found at high densities in urban areas worldwide (Hansen et al., 2018;Legge et al., 2016;Gehrt et al., 2013). Cats with outdoor access are subjected to numerous risks, including possible vehicle collisions (Rochlitz, 2003), heightened exposure to zoonotic disease (Gehrt et al., 2013;Roseveare et al., 2009), exposure to toxins (Tan et al., 2020;Berny et al., 2010), increased potential for abuse (Bonela Gomes et al., 2021), and possible predation by native predator species (Larson et al., 2020;Tan et al., 2020;Kays et al., 2015). ...
The ecological impact of free-roaming domestic cats (Felis catus) is well-studied. However, despite receiving considerable attention in both the scientific and popular literature, predation behavior is rarely an explicit consideration when developing cat population management plans. We used motion-activated wildlife cameras to document predation events by cats in Washington, D.C. (U.S.A), and assessed the relationships between predation and local environmental characteristics. Our analyses reveal that predation by cats is greatest where supplemental food is most abundant, and that the probability of a cat preying upon a native species increases closer to forest edges. Conversely, we found that the probability of a cat depredating a non-native brown rat increases with increasing distance from forest edges. Therefore, we recommend the implementation of cat exclusionary buffer zones around urban forests and that free-roaming domestic cat management policies explicitly consider the spatial location of cat-feeding sites. Our findings provide a data-driven approach to free-roaming cat management.
... Between 25-85% of owned cats are kept indoors in the United States and Canada (25, 28) and >80% are sterilized (29), suggesting that while management strategies must account for both groups, unowned cats likely contribute the most to cat population replenishment and account for the majority of concerns. Unowned cats will also generally be found at higher density in modified environments where shelter-based programs tend to predominate, vs. natural habitats in which other methods may be deployed (30). Importantly, although public and published debate has tended to center on cat "colonies" (cats living in large aggregates around a food source), such groups account for <5% of unowned cats (31)(32)(33)(34)(35). Scattered individual cats accessing multiple food sources are difficult to detect compared to the more visible and troublesome groups. ...
Substantial societal investment is made in the management of free-roaming cats by various methods, with goals of such programs commonly including wildlife conservation, public health protection, nuisance abatement, and/or promotion of cat health and welfare. While there has been a degree of controversy over some of the tactics employed, there is widespread agreement that any method must be scientifically based and sufficiently focused, intensive and sustained in order to succeed. The vast majority of free-roaming cat management in communities takes place through local animal shelters. Throughout the 20th century and into the 21st, this consisted primarily of ad hoc admission of cats captured by members of the public, with euthanasia being the most common outcome. In North America alone, hundreds of millions of cats have been impounded and euthanized and billions of dollars invested in such programs. Given the reliance on this model to achieve important societal goals, it is surprising that there has been an almost complete lack of published research evaluating its success. Wildlife conservation and public health protection will be better served when debate about the merits and pitfalls of methods such as Trap-Neuter-Return is grounded in the context of realistically achievable alternatives. Where no perfect answer exists, an understanding of the potential strengths and shortcomings of each available strategy will support the greatest possible mitigation of harm—the best, if still imperfect, solution. Animal shelter function will also benefit by discontinuing investment in methods that are ineffective as well as potentially ethically problematic. This will allow the redirection of resources to more promising strategies for management of cats as well as investment in other important animal shelter functions. To this end, this article reviews evidence regarding the potential effectiveness of the three possible shelter-based strategies for free-roaming cat management: the traditional approach of ad hoc removal by admission to the shelter; admission to the shelter followed by sterilization and return to the location found; and leaving cats in place with or without referral to mitigation strategies or services provided by other agencies.
... Le site de Grande Anse abrite plusieurs espèces indigènes et endémiques insulaires avec des densités de chats élevées comparables à des zones urbaines(Legge et al. 2017). Au regard des impacts désastreux des chats sur la biodiversité native insulaire(Medina et al. 2011), Grande Anse représente un enjeu de conservation important où la gestion des chats errants doit être une des priorités. ...
The southern coastal cliffs of Reunion Island (tropical island in the Western Indian Ocean) host a unique flora and fauna: the last populations of Manapany day gecko (Phelsuma inexpectata, an endemic reptile in critically endangered), relics of indigenous vegetation including endemic and/or threatened species (e.g.: Euphorbia viridula, Psiadia retusa, Latania lontaroides) and breeding colonies of three native seabirds (white-tailed tropicbirds, Phaethon lepturus ; brown noddies, Anous stolidus and wedge-tailed shearwaters, Ardenna pacifica). This biodiversity is threatened by habitat transformations due to invasive plants, human activities (urbanization and culture) and invasive mammals (especially cats, felis catus, and rodents). Moreover, little is known about biology and ecology of the native species, which does not allow the implementation of effective conservation strategy. Based on hand-in-hand collaboration between researchers (UMR ENTROPIE) and managers (CDL, NOI, AVE2M) working on different taxa, the aim of this thesis was to provide multispecies conservation prescriptions on cliffs study for the Manapany day gecko and the wedge-tailed shearwater. We undertook a progressive approach from describing of species conservation states through understanding threatening processes to the prescription and monitoring of management actions. Three research topics were targeted: (i) demography and reproductive biology, (ii) terrestrial habitat requirements, and (iii) impacts and management of invasive mammals (especially cats). Our results highlighted the critical conservation state of Manapany day geckos and wedge-tailed shearwaters populations. Invasive plants and mammals (especially cats) are threats to the conservation of native biodiversity. We provide several local and general conservation prescriptions, including management of invasive species, multispecies terrestrial habitat restoration and captive head-start program of Manapany day geckos. Several of these prescriptions were implemented during this thesis (invasive species management and captive breeding program) and monitored as part of active adaptive management approach. This multispecies study at the interface between research and management must be continued and supported by a strong federating regulatory tool as a National Nature Reserve (NNR).
Keywords: Ardenna pacifica, biological invasions, captive head-start program, Capture-Mark-Recapture, cat control, cat tracking, conservation biology, Felis catus, habitat selection, multispecies management, Phelsuma inexpectata, population dynamics, Population Viability Analyses, Reunion Island, Spatial Mark-Resight, tropical island
Stray animals are unowned free roaming, homeless, abandoned, street or sheltered animals, particularly dogs, cats and cattle. They could act as carrier of several zoonotic pathogens such as rabies virus, Mycobacterium and Brucella species. However, comprehensive information on the prevalence of zoonotic pathogens in stray animals is very limited. We conducted a systematic review as per Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) 2020 guidelines to estimate the prevalence of brucellosis in stray dogs, cats and cattle. Eligibility criteria for the study were determined using the PECOS classification (population, exposure, comparison, outcome, study design) as a tool to guide the research and adjust the search strategy. Major bibliographic databases [Web of Science, Medline, Scopus, ScienceDirect, Google Scholar and PubMed] were searched using predefined keywords for published epidemiological studies on brucellosis in stray animals (dogs, cats and cattle). Systematic assessments of all the studies since 1990-2022 were conducted and those reporting the prevalence of brucellosis in stray dogs, cats and cattle using appropriate diagnostic tests (culture, molecular, serological) were included. Studies reporting prevalence of brucellosis (Brucella infection or exposure) in kennel dogs, dairy herds, livestock farms, humans or marine species were excluded. The apparent individual test- wise prevalence along with 95% confidence intervals (CI) was estimated using Epitools. Out of 2689 studies, 37 met the inclusion criteria and were included in the systematic review. Of 37 studies, 28 (75.7%) were conducted in stray dogs, 7 (18.9%) in cattle and 2 (5.4%) in cats. Furthermore, only 21.62% studies (8/37) used probabilistic random sampling approaches and 13.51% studies (5/37) explained and justified the study sample size using appropriate methods for estimation of disease prevalence in the study populations. Higher sero-prevalence in stray dogs has been reported in studies conducted in Jordan (38.0% (95% CI: 24.0-54.0) and Pakistan (38.0% (95% CI: 31.0-45.0) whereas no sero-positivity was recorded in the studies conducted in Brazil, North Colombia, Cyprus, South Korea and USA. All studies on brucellosis (n = 7) in stray cattle were from India; conducted in stray cattle reared in cow-shelters. Sero-prevalence in the range of 4.3%- 64.3% was reported in stray cattle. Differences in diagnostic tests and host species, as well as limited number and non-randomized studies and high statistical heterogeneity did not allow us to determine combined meta-analysed prevalence estimates. Stray animals are likely to pose a zoonotic and disease spillover risk to human and livestock populations.
Control of invasive predators is a priority to protect island biodiversity. Understanding the responses of other species in multi-species invaded food webs is important to avoid unintended consequences. We use an intensive 2-year cat-trapping program in the vicinity of seabird colonies on Bruny Island, Tasmania, to investigate its effectiveness in reducing feral cat density and whether cat control influenced the behaviour and abundance of native and invasive mammal species. Cat density before control was extremely high around this seasonally rich food resource, much higher than on mainlands. Cat density was reduced 5.4-fold by control showing that trapping is effective in reducing cat density in this focussed landscape context. We found no direct effect of cat reduction on the abundance or behaviour of native or invasive mammalian prey species. Recruitment of invasive black rats and native swamp rats increased on the seabird colonies after the shearwater breeding season, and cats responded by increasing their presence on the colonies relative to surrounding areas. This suggests cascading bottom-up effects from a lagged productivity pulse provided by breeding seabirds which would require nutrient sampling to confirm. Our results highlight the complexity of subsequent effects of an invasive predator control on the broader ecosystem.
Australia's biota is species rich, with high rates of endemism. This natural legacy has rapidly diminished since European colonization. The impacts of invasive species, habitat loss, altered fire regimes, and changed water flows are now compounded by climate change, particularly through extreme drought, heat, wildfire, and flooding. Extinction rates, already far exceeding the global average for mammals, are predicted to escalate across all taxa, and ecosystems are collapsing. These losses are symptomatic of shortcomings in resourcing, law, policy, and management. Informed by examples of advances in conservation practice from invasive species control, Indigenous land management, and citizen science, we describe interventions needed to enhance future resilience. Many characteristics of Australian biodiversity loss are globally relevant, with recovery requiring society to reframe its relationship with the environment.
This report reviews valuation methods with potential to include the non-market values associated with alien invasive species in benefit-cost analysis. It illustrates non-market impacts using the examples of the feral cat (Felix catus) and buffel grass (Cenchrus ciliaris). It then summarises the results of a survey of environmental managers that provides insights into factors influencing the use of non-market valuation methods. The report concludes with practical strategies that decision makers can use to improve the consideration of non-market values when managing AIS.
An evidence-based approach to the conservation management of a species requires knowledge of that species' status, distribution, ecology, and threats. Coupled with budgets for specific conservation strategies, this knowledge allows prioritisation of funding toward activities that maximise benefit for the species. However, many threatened species are poorly known, and determining which conservation strategies will achieve this is difficult. Such cases require approaches that allow decision-making under uncertainty. Here we used structured expert elicitation to estimate the likely benefit of potential management strategies for the Critically Endangered and, until recently, poorly known Night Parrot (Pezoporus occidentalis). Experts considered cat management the single most effective management strategy for the Night Parrot. However, a combination of protecting and actively managing existing intact Night Parrot habitat through management of grazing, controlling feral cats, and managing fire specifically to maintain Night Parrot habitat was thought to result in the greatest conservation gains. The most cost-effective strategies were thought to be fire management to maintain Night Parrot habitat, and intensive cat management using control methods that exploit local knowledge of cat movements and ecology. Protecting and restoring potentially suitable, but degraded, Night Parrot habitat was considered the least effective and least cost-effective strategy. These expert judgements provide an informed starting point for land managers implementing on-ground programs targeting the Night Parrot, and those developing policy aimed at the species' longer-term conservation. As a set of hypotheses, they should be implemented, assessed, and improved within an adaptive management framework that also considers the likely co-benefits of these strategies for other species and ecosystems. The broader methodology is applicable 1 3 Biodiversity and Conservation to conservation planning for the management and conservation of other poorly known threatened species.
Despite the importance of safeguarding forests and woodlands for achieving global climate and biodiversity agendas, logging continues across most forested countries. Forestry advocates often claim logging has minimal impacts, but rarely consider the cumulative threat deforestation and degradation has had, and continue to have, on species. Using New South Wales (Australia) as a case study, we quantify the extent of deforestation and degradation from 1750 – current. Using these estimates of overall loss as a baseline, we then quantify the relative extent of contemporary (2000 – 2022) logging and the condition of the remaining native forest and woodland (quantified by measuring the similarity of a current ecosystem to a historical reference state with high ecological integrity). Using these data, we measure the impacts on distinct vegetation types and on 484 terrestrial forest-dependent now-threatened species. We show that more than half (29 million ha) of pre-1750 (pre-European colonization of Australia) native forest and woodland vegetation in NSW has been lost. Of the remaining 25 million ha, 9 million ha is degraded. We found contemporary degradation from logging affected 244 forest-dependent now-threatened species that had already been affected by this historical deforestation and degradation, but the impacts varied across species and vegetation types. We found that 70 now-threatened species that were impacted by historical deforestation and degradation and continue to be impacted by logging, now have ≤50% of their pre-1750 extent remaining that is intact (with three species now having <20%). By quantifying the historical impacts of deforestation and degradation, our research sets the impact of contemporary degradation from logging in perspective and highlights shortfalls in current environmental assessments that fail to consider appropriate baselines when reporting on overall impact. Future land management decisions need to consider not only the extent of remaining habitat based on pre-1750 extents, but also its condition.
Article impact statement
The impact of logging needs to be placed in perspective by considering past losses and degradation due to human land use decisions.
The Australian marsupial fauna has been devastated in the past 250 years, mainly due to impacts from invasive mammalian predators (cats and foxes), although other threats such as invasive herbivores, habitat loss and fragmentation, changes to fire regimes, and now climate change have played a role. The profound and ongoing impact of invasive predators has driven substantial research and management innovation. Australia has been at the forefront of developing approaches to reduce the density and impacts of introduced predators and implementing novel and ambitious species conservation programs. A large and growing network of islands and mainland fenced areas, free of introduced predators (“havens”), has been critical for avoiding further species extinctions. Outside these havens, advances in toxin presentation and deployment have enabled cat and fox densities to be reduced over large areas. Substantial research and field trials have been carried out to understand how predator-prey interactions, and habitat quality management, can be used to reduce predation impacts on susceptible native species. Synthetic biology offers new opportunities to manage introduced predators, including potentially by using gene drives. Finally, the attenuation of the formerly large continuous ranges of many species to small, isolated population remnants (because of predation or other reasons) has also driven research and improvements in genetic and metapopulation management that will increase the chance of population persistence in the longer term. However, unless Australia continues to invest in research and innovative conservation actions, the plight of its priceless marsupial fauna will remain perilous.
The 'Compassionate Conservation' movement is gaining momentum through its promotion of 'ethical' conservation practices based on self-proclaimed principles of 'first-do-no-harm' and 'individuals matter'. We argue that the tenets of 'Compassionate Conservation' are ideological-that is, they are not scientifically proven to improve conservation outcomes, yet are critical of the current methods that do. In this paper we envision a future with 'Compassionate Conservation' and predict how this might affect global biodiversity conservation. Taken
Australia was isolated for approximately 40 million years from the presence of eutherian predation until the introduction of the dingo (Canis familiaris; 4000 years ago), foxes (Vulpes vulpes; 1871) and feral cats (Felis catus; post-1788). The arrival of these invasive species coincides with the decline and extinction of many native mammals, specifically within the critical weight range (35–5500 g). These extinctions are likely a result of competition and predation, where locomotor performance and the associated behaviours contribute largely to overall fitness. We used the population responses of native fauna in the presence of introduced predators to establish a research framework. Introduction/extinction timelines, predator diets, and prey occurrence were used to identify invasive/native relationships where predation may define the population outcome. We then examined the locomotor performance of these species using current data (maximum speeds). Consumption of prey items does not seem to be associated with the probability of the predator encountering the prey. Dingoes had the most variable mammalian prey of all invasive predators, likely due to higher maximal speeds. Feral cats favour Dasyuridae and smaller species, preying upon these prey groups more than dingoes and foxes. The role of locomotor performance in invasive ecology is not well understood; we identified relationships for further exploration.
Monitoring trends in animal populations in arid regions is challenging due to remoteness and low population densities. However, detecting species' tracks or sign is an effective survey technique for monitoring population trends across large spatial and temporal scales. In this study, we developed a simulation framework to evaluate the performance of alternative track-based monitoring designs at detecting change in species distributions in arid Australia. We collated presence-absence records from 550 2-ha track-based plots for 11 vertebrates over 13 years and fitted ensemble species distribution models to predict occupancy in 2018. We simulated plausible changes in species' distributions over the next 15 years, and with estimates of detectability, simulated monitoring to evaluate the statistical power of three alternative monitoring scenarios: 1) when surveys were restricted to existing 2-ha plots; 2) when surveys were optimised to target all species equally; 3) when surveys were optimised to target two species of conservation concern. Across all monitoring designs and scenarios, we found that power was higher when detecting increasing occupancy trends compared to decreasing trends due to relatively low levels of initial occupancy. Our results suggest that surveying 200 of the existing plots annually (with a small subset re-surveyed twice within a year) will have at least an 80% chance at detecting 30% declines in occupancy for 4 of the 5 invasive species modelled and 1 of the 6 native species. This increased to 10 of the 11 species assuming larger (50%) declines. When plots were positioned to target all species equally, power improved slightly for most compared to the existing survey network. When plots were positioned to target two species of conservation concern (crest-tailed mulgara and dusky hopping mouse), power to detect 30% declines increased by 29% and 31% for these species, respectively, at the cost of reduced power for remaining species. The effect of varying survey frequency depended on its trade-off with the number of sites sampled and requires further consideration. Nonetheless, our research suggests that track-based surveying is an effective and logistically feasible approach for monitoring broad-scale occupancy trends in desert species with both widespread and restricted distributions.
CRISPR-based gene drives offer novel solutions for controlling invasive alien species, which could ultimately extend eradication efforts to continental scales. Gene drives for suppressing invasive alien vertebrates are now under development. Using a landscape-scale individual-based model, we present the first estimates of times to eradication for long-lived alien mammals. We show that demography and life-history traits interact to determine the scalability of gene drives for vertebrate pest eradication. Notably, optimism around eradicating smaller-bodied pests (rodents and rabbits) with gene-drive technologies does not easily translate into eradication of larger-bodied alien species (cats and foxes).
Accurate information about the number of cats living outdoors and how they respond to different kinds of management are necessary to quell debates about outdoor cat policy. The DC Cat Count will develop the tools and methodologies needed to realize this possibility and make them available for broader use. This three-year initiative represents a major collaboration between animal welfare organizations and wildlife scientists. Its unique and innovative approach is to use the best scientific methods to quantify all subpopulations of cats in the District of Columbia (outdoor, owned, and shelter cats), concurrently test and optimize simpler methods that can be used to measure cat populations by diverse users at scale, and identify the types of interventions that are likely to accomplish desired outcomes most efficiently. Ultimately, we believe that this approach is more likely to improve outcomes for both cats and wildlife than a continuation of the status quo.
Many threatened species depend on climatic microrefugia, but places with harsh climates for predators may also play a refugial role. Feral cats threaten many native species in arid Australia. Although cats can persist in regions with no free water, their abundance should depend on the availability of microclimates that protect them from harsh environmental conditions. We developed a biophysical model of feral cat heat stress and used it to explore how behavior and microhabitat features influence water requirements and activity. Tests of model predictions against fine‐scale GPS and microclimate data highlight the importance of refuges, particularly rabbit burrows. Continent‐wide simulations show large but temporally varying areas of the arid zone that would be lethal for cats without access to deep or shaded burrows. Our approach can identify locations that may act as natural refuges for native prey, and where habitat management strategies may be effective in controlling cat abundance.
Control of invasive predators is a priority to protect island biodiversity. Understanding the responses of other species in multi-species invaded food webs is important to avoid unintended consequences. We use an intensive two-year cat-trapping program in the vicinity of seabird colonies on Bruny Island, Tasmania, to estimate the change in densities of feral cats and investigate the effect of control on the behaviour and abundance of native and invasive mammal species. Cat density before control was extremely high then reduced by 5.4-fold consequent to control. We show a complex but subtle cascade of ecological effects among mesopredator and prey species, with a lagged response to a pulse of bottom-up productivity provided by breeding seabirds. Our study demonstrates that cat density on islands, particularly around seasonally rich food resources such as seabird colonies, can be very high, much higher than on mainland areas, and that control using trapping is effective reducing cat density in this focussed landscape context. Our results highlight the complexity of effects of control of an invasive predator on the broader ecosystem. The top-down effect of cats on the ecosystem was limited but the response of prey indicates a predator effect conditioned by temporal change in bottom-up productivity.
The choice of words we use often conveys specific meanings and tone to a topic. Hence, the words that we use in conservation science often have important ramifications in scientific, legal, and social contexts. The management of free-ranging cats is an important example, because of the animal welfare, predation, and public health implications. In this context, one set of words that has recently arisen outside of conservation but has particular relevance for it and many other fields is ‘community cat.’ As we note, through an evaluation of the literature, ‘community cat’ is almost always used as a synonym for unowned, free-ranging cats. Such rebranding is significant for conservation, policy, and management because it implies community ownership of animals without, in many cases, explicit agreement from the community. As such, there is a need to understand the history of the term, what it really means, and its implications for the advancement of conservation biology, natural resource management, veterinary medicine, and animal welfare.
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.
The domestic cat (Felis catus) is an invasive exotic in many locations around the world and is thought to be a key factor driving recent mammal declines across northern Australia. Many mammal species native to this region now persist only in areas with high topographic complexity, provided by features such as gorges or escarpments. Do mammals persist in these habitats because cats occupy them less, or despite high cat occupancy? We show that occupancy of feral cats was lower in mammal-rich habitats of high topographic complexity. These results support the idea that predation pressure by feral cats is a factor contributing to the collapse of mammal communities across northern Australia. Managing impacts of feral cats is a global conservation challenge. Conservation actions such as choosing sites for small mammal reintroductions may be more successful if variation in cat occupancy with landscape features is taken into account.
Felis catus, the domestic cat, occurs throughout the Australian mainland as well as on more than 40 islands off the Australian coast. Cats exploit diverse habitats, including deserts, forests, woodlands, grasslands, towns and cities, and occur from sea level to altitudes above 2000 m. The classification of cats as domestic, stray or feral (Moodie 1995) reflects the varied ecology of cats and their dichotomous status in Australia — as both a valued pet species and an introduced feral predator.
Impacts
Feral cats are carnivorous hunters that depredate animals up to 2 kg, but more often take prey under 200 g. The feral cat is linked to the early continental extinctions of up to seven species of mammals. They are also linked to island and regional extinctions of native mammals and birds and have caused the failure of reintroduction attempts aimed at re-establishing threatened species. Today, 35 vulnerable and endangered bird species, 36 mammal species, seven reptile species and three amphibian species are thought to be adversely affected by feral cats. Other species are potentially affected by infectious diseases transmitted by cats. The true environmental and economic impact of feral cats has not been calculated.
Legislation
In most Australian states and territories, legislation has been introduced to restrict the reproductive and predation potential of owned domestic cats. Many local government areas have introduced cat-specific legislation, with restrictions including the banning of cats as pets in some communities, compulsory neutering, individual identification, and containment of pet cats. Predation by feral cats was listed as a Key Threatening Process under the Federal Endangered Species Protection Act 1992 (now incorporated in the Environment Protection and Biodiversity Conservation Act 1999). A Threat Abatement Plan for Predation by Feral Cats was produced in 1999 and amended in 2008 to promote the recovery of vulnerable and endangered native species and threatened ecological communities (Environment Australia 1999 and DEWHA 2008).
Estimating abundance
The three most common techniques for estimating cat abundance in Australia are spotlighting, counting tracks, and bait uptake estimates. The accuracy of spotlighting is dependent upon the density of vegetative cover and cat behaviour; the accuracy of track counts depends upon where track pads are set and the competence of the operative in recognising tracks; and most bait uptake studies provide data on cat activity rather than relative abundance or densities. All three techniques are best suited to open, dry habitats with low vegetative cover. In wetter, more closed and productive habitats with high vegetative cover, techniques such as remote photography and the analysis of DNA extracted from scats or hairs provide alternatives for estimating abundance or density. Such estimates are a necessary prerequisite for the implementation of control or eradication programs to avoid over- or under-commitment of labour, time and money, and are also necessary to measure the efficacy of management programs.
Techniques for control or eradication
A nationally co-ordinated program of feral cat control across Australia is not feasible, as it is with other introduced species, and control efforts are best targeted at protecting threatened species or habitats. All successful cat eradication programs in Australia have been conducted on islands or within areas bounded by predator-proof fencing, and most have required the use of more than one control method. Successful techniques for the control or eradication of cats on islands have proved largely impractical on the mainland. Hunting, trapping and shooting are time and labour intensive and not economically viable over large areas. Trap-neuter-return is unsuccessful in open populations and not practical over large areas. The introduction of disease (e.g. panleucopaenia) is restricted by the probable impact on owned domestic cats and the low transmission rate amongst widely dispersed feral cats. Toxins presently registered for cat baiting may have unacceptable environmental impacts on many habitats. Research into more felid-specific toxins, cat attracting baits and lures and cat-specific toxin delivery systems may lead to the adoption of poisoning as the most widely used technique for the control or eradication of feral cats.
Management at the regional and local level
Management of feral cats requires reliable data on the density or relative abundance of cats in targeted areas, and analysis of the cost effectiveness and efficacy of the various control measures that may be implemented. At the regional and local level, eradication of cat colonies and the management of resource-rich artificial habitats to discourage colonisation by cats should be an adjunct to any feral cat control program. Implementation of companion animal legislation that requires firmer controls on the owned, domestic cat population is also an important consideration for the longer-term reduction of the feral cat population in Australia.
Factors limiting effective management
Although adequate legislation is in place in some jurisdictions, the problems associated with cat control programs in Australia include: the time, cost and social impacts associated with enforcing companion animal legislation; the acceptance in some states of cats as pest control agents; variable cat densities between habitats; relatively low bait acceptance by feral cats; a lack of programs aimed specifically at stray cat colonies exploiting highly modified habitats; little data on the impact of cat removal on populations of introduced rodents and rabbits; and few accurate estimates of the density or relative abundance of feral cats. Research is needed to define the most successful methods for gaining public acceptance of the importance of maintaining effective companion animal legislation; estimating densities of cats in various habitats; the cost effectiveness of control techniques including broadscale baiting; assessing the impact of the removal of colony-forming cats in resource-rich artificial habitats on the broader feral cat population; and assessing the impact of cat removal on both native and introduced small mammal populations and the further indirect effects of removal on other components of the biota.
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.
As evidence mounts that the feral Cat (Felis catus) is a significant threat to endemic Australian biodiversity and impedes reintroduction attempts, uncertainty remains about the impact a residual population of cats following control will have on a mammal reintroduction programme. Also, behavioural interactions between cats and their prey continue to be an area of interest. Within the framework of an ecosystem restoration project, we tested the hypotheses that successful reintroductions of some medium-sized mammals are possible in locations where feral cats are controlled (but not eradicated) in the absence of European Red Fox (Vulpes vulpes), and that hare-wallabies that dispersed from their release area are more vulnerable to cat predation compared with those that remain at the release site. We used radiotelemetry to monitor the survivorship and dispersal of 16 Rufous Hare-wallabies (Lagorchestes hirsutus spp.) and 18 Banded Hare-wallabies (Lagostrophus fasciatus fasciatus) reintroduced to four sites within Shark Bay, Western Australia. Nearly all foxes were removed and feral cats were subject to ongoing control that kept their indices low relative to prerelease levels. All monitored hare-wallabies were killed by cats within eight and 10 months following release. Significant predation by feral cats was not immediate: most kills occurred in clusters, with periods of several months where no mortalities occurred. Once a hare-wallaby was killed, however, predation continued until each population was eliminated. Animals remaining near their release site survived longer than those that dispersed. The aetiology of predation events observed offers new insights into patterns of feral cat behaviour and mammal releases. We propose a hypothesis that these intense per capita predation events may reflect a targeted hunting behaviour in individual feral cats. Even where feral cats are controlled, the outcome from consistent predation events will result in reintroduction failures. Managers considering the reintroduction of medium-sized mammals in the presence of feral cats should, irrespective of concurrent cat control, consider the low probability of success. We advocate alternative approaches to cat-baiting alone for the recovery of cat-vulnerable mammals such as hare-wallabies.
Invasive mammalian predators are major drivers of species extinctions globally. To protect native prey, lethal control is often used with the aim of reducing or exterminating invasive predator populations. The efficacy of this practice, however, is often not considered despite multiple practical and ecological factors that can limit success. Here, we summarize contemporary knowledge regarding the use and challenges of both lethal control and alternative approaches for reducing invasive predator impacts. As the prevailing management approach, we outline four key issues that can compromise the effectiveness of lethal control: release of herbivore and mesopredator populations, disruption of predator social systems, compensatory predator immigration, and ethical concerns. We then discuss the relative merits and limitations of four alternative approaches that may enhance conservation practitioner's ability to effectively manage invasive predators: top-predator conservation or reintroduction, maintaining habitat complexity, exclusion fencing, and behavioral and evolutionary ecology. Considerable uncertainty remains regarding the effectiveness of management approaches in different environmental contexts. We propose that the deficiencies and uncertainties outlined here can be addressed through a combination of adaptive management, expert elicitation, and cost-benefit analyses. Improved management of invasive predators requires greater consideration and assessment of the full range of management approaches available.
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.
The ecology of a feral cat population in an intensively cultivated region of northern Italy was studied. The study area is a land accretion territory, reclaimed in the early 1970s, characterised by the absence of any food source of human origin (e.g. garbage dumps, farms, houses) and surrounded by a continuous irrigation channel that is likely to limit immigration/emigration of cats. The cat population was censused for two successive years using the sighting-resighting method; spacing patterns were studied by means of radio-telemetry; hunting behaviour was assessed by observation. Feral cats avoided any direct contact with humans, and reproduced in the wild. The density of the population remained stable throughout the study period. Turnover appeared very high, and was remarkably higher than that of cats regularly fed by humans. Very low densities, large home range sizes, solitary habits, territorial patterns similar to those of the wildcat, seasonal parturition, and prevalence of hunting activity were found. We speculate that these patterns are related to the peculiar conditions of resource availability and dispersion in the study area. Our results indicate that feral cats, even in agricultural areas and in the absence of any food provided by humans, have solitary habits and low densities, thus confirming a key role of resource availability and dispersion on the ecology of carnivores.
Context Feral cats are a major cause of mammal declines and extinctions in Australia. However, cats are elusive and obtaining reliable ecological data is challenging. Although camera traps are increasingly being used to study feral cats, their successful use in northern Australia has been limited. Aims We evaluated the efficacy of camera-trap sampling designs for detecting cats in the tropical savanna of northern Australia. We aimed to develop a camera-trapping method that would yield detection probabilities adequate for precise occupancy estimates. Methods First, we assessed the influence of two micro-habitat placements and three lure types on camera-trap detection rates of feral cats. Second, using multiple camera traps at each site, we examined the relationship between sampling effort and detection probability by using a multi-method occupancy model. Key results We found no significant difference in detection rates of feral cats using a variety of lures and micro-habitat placement. The mean probability of detecting a cat on one camera during one week of sampling was very low (p≤0.15) and had high uncertainty. However, the probability of detecting a cat on at least one of five cameras deployed concurrently on a site was 48% higher (p≤0.22) and had a greater precision. Conclusions The sampling effort required to achieve detection rates adequate to infer occupancy of feral cats by camera trap is considerably higher in northern Australia than has been observed elsewhere in Australia. Adequate detection of feral cats in the tropical savanna of northern Australia will necessitate inclusion of more camera traps and a longer survey duration. Implications Sampling designs using camera traps need to be rigorously trialled and assessed to optimise detection of the target species for different Australian biomes. A standard approach is suggested for detecting feral cats in northern Australian savannas.
One of the key gaps in understanding the impacts of predation by small mammalian predators on prey is how habitat structure affects the hunting success of small predators, such as feral cats. These effects are poorly understood due to the difficulty of observing actual hunting behaviours. We attached collar-mounted video cameras to feral cats living in a tropical savanna environment in northern Australia, and measured variation in hunting success among different microhabitats (open areas, dense grass and complex rocks). From 89 hours of footage, we recorded 101 hunting events, of which 32 were successful. Of these kills, 28% were not eaten. Hunting success was highly dependent on microhabitat structure surrounding prey, increasing from 17% in habitats with dense grass or complex rocks to 70% in open areas. This research shows that habitat structure has a profound influence on the impacts of small predators on their prey. This has broad implications for management of vegetation and disturbance processes (like fire and grazing) in areas where feral cats threaten native fauna. Maintaining complex vegetation cover can reduce predation rates of small prey species from feral cat predation.
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.
A quantitative review was conducted of the effects of cattle grazing in arid systems on 16 response variables ranging from soil bulk density to total vegetative cover to rodent species diversity. Various studies from North American arid environments that used similar measures for assessing grazing effects on the same response variables were used for the review; each study was assigned to serve as a single data point in paired comparisons of grazed versus ungrazed sites. All analyses tested the 1-tailed null hypothesis that grazing has no effect on the measured variable. Eleven of 16 analyses (69%) revealed significant detrimental effects of cattle grazing, suggesting that cattle can have a negative impact on North American xeric ecosystems. Soil-related variables were most negatively impacted by grazing (3 of 4 categories tested were significantly impacted), followed by litter cover and biomass (2 of 2 categories tested), and rodent diversity and richness (2 of 2 categories tested). Vegetative variables showed more variability in terms of quantifiable grazing effects, with 4 of 8 categories testing significantly. Overall, these findings could shed light on which suites of variables may be effectively used by land managers to measure ecosystem integrity and rangeland health in grazed systems.
Context Feral cats (Felis catus) pose a significant threat to biodiversity in Australia, and are implicated in current declines of small mammals in the savannas of northern Australia. Basic information on population density and ranging behaviour is essential to understand and manage threats from feral cats. Aims In this study, we provide robust estimates of density and home range of feral cats in the central Kimberley region of north-western Australia, and we test whether population density is affected by livestock grazing, small mammal abundance and other environmental factors. Methods Densities were measured at six transects sampled between 2011 and 2013 using arrays of infrared cameras. Cats were individually identified, and densities estimated using spatially explicit capture-recapture analysis. Home range was measured from GPS tracking of 32 cats. Key results Densities were similar across all transects and deployments, with a mean of 0.18 cats km-2 (range≤0.09-0.34km-2). We found no evidence that population density was related to livestock grazing or abundance of small mammals. Home ranges of males were, on average, 855ha (±156ha (95% CI), n≤25), and those of females were half the size at 397ha (±275ha (95% CI), n≤7). There was little overlap in ranges of cats of the same sex. Conclusions Compared with elsewhere in Australia outside of semiarid regions, feral cats occur at low density and have large home ranges in the central Kimberley. However, other evidence shows that despite this low density, cats are contributing to declines of small mammal populations across northern Australia. Implications It will be very difficult to reduce these already-sparse populations by direct control. Instead, land-management practices that reduce the impacts of cats on prey should be investigated.
Predation by house cats (Felis catus) is one of the largest human-related sources of mortality for wild birds in the United States and elsewhere, and has been implicated in extinctions and population declines of several species. However, relatively little is known about this topic in Canada. The objectives of this study were to provide plausible estimates for the number of birds killed by house cats in Canada, identify information that would help improve those estimates, and identify species potentially vulnerable to population impacts.
In total, cats are estimated to kill between 100 and 350 million birds per year in Canada (> 95% of estimates were in this range), with the majority likely to be killed by feral cats. This range of estimates is based on surveys indicating that Canadians own about 8.5 million pet cats, a rough approximation of 1.4 to 4.2 million feral cats, and literature values of predation rates from studies conducted elsewhere. Reliability of the total kill estimate would be improved most by better knowledge of feral cat numbers and diet in Canada, though any data on birds killed by cats in Canada would be helpful.
These estimates suggest that 2-7% of birds in southern Canada are killed by cats per year. Even at the low end, predation by house cats is probably the largest human-related source of bird mortality in Canada. Many species of birds are potentially vulnerable to at least local population impacts in southern Canada, by virtue of nesting or feeding on or near ground level, and habitat choices that bring them into contact with human-dominated landscapes where cats are abundant. Because cat predation is likely to remain a primary source of bird mortality in Canada for some time, this issue needs more scientific attention in Canada.
The number of individuals in a wildlife population is often estimated and the estimates used for wildlife management. The scientific basis of published continental-scale estimates of individuals in Australia of feral cats and feral pigs is reviewed and contrasted with estimation of red kangaroo abundance and the usage of the estimates. We reviewed all papers on feral cats, feral pigs and red kangaroos found in a Web of Science search and in Australian Wildlife Research and Wildlife Research, and related Australian and overseas scientific and 'grey' literature. The estimated number of feral cats in Australia has often been repeated without rigorous evaluation of the origin of the estimate. We propose an origin. The number of feral pigs in Australia was estimated and since then has sometimes been quoted correctly and sometimes misquoted. In contrast, red kangaroo numbers in Australia have been estimated by more rigorous methods and the relevant literature demonstrates active refining and reviewing of estimation procedures and management usage. We propose four criteria for acceptable use of wildlife abundance estimates in wildlife management. The criteria are: use of appropriate statistical or mathematical analysis; precision estimated; original source cited; and age (current or out-of-date) of an estimate evaluated. The criteria are then used here to assess the strength of evidence of the abundance estimates and each has at least one deficiency (being out-of-date). We do know feral cats, feral pigs and red kangaroos occur in Australia but we do not know currently how many feral cats or feral pigs are in Australia. Our knowledge of red kangaroo abundance is stronger at the state than the continental scale, and is also out-of-date at the continental scale. We recommend greater consideration be given to whether abundance estimates at the continental scale are needed and to their use, and not misuse, in wildlife management.
Introduction: Recent studies at sites in northern Australia have reported severe and rapid decline of several native mammal species, notwithstanding an environmental context (small human population size, limited habitat loss, substantial reservation extent) that should provide relative conservation security. All of the more speciose taxonomic groups of mammals in northern Australia have some species for which their conservation status has been assessed as threatened, with 53 % of dasyurid, 47 % of macropod and potoroid, 33 % of bandicoot and bilby, 33 % of possum, 30 % of rodent, and 24 % of bat species being assessed as extinct, threatened or near threatened. However, the geographical extent and timing of declines, and their causes, remain poorly resolved, limiting the application of remedial management actions.
Introduction: Recent studies at sites in northern Australia have reported severe and rapid decline of several native mammal species, notwithstanding an environmental context (small human population size, limited habitat loss, substantial reservation extent) that should provide relative conservation security. All of the more speciose taxonomic groups of mammals in northern Australia have some species for which their conservation status has been assessed as threatened, with 53 % of dasyurid, 47 % of macropod and potoroid, 33 % of bandicoot and bilby, 33 % of possum, 30 % of rodent, and 24 % of bat species being assessed as extinct, threatened or near threatened. However, the geographical extent and timing of declines, and their causes, remain poorly resolved, limiting the application of remedial management actions.
Material and methods: Focusing on the tropical savannas of northern Australia, this paper reviews disparate recent and ongoing studies that provide information on population trends across a broader geographic scope than the previously reported sites, and examines the conservation status and trends for mammal groups (bats, macropods) not well sampled in previous monitoring studies. It describes some diverse approaches of studies seeking to document conservation status and trends, and of the factors that may be contributing to observed patterns of decline.
Results and Discussion: Current trends and potential causal factors for declines. The studies reported demonstrate that the extent and timing of impacts and threats have been variable across the region, although there is a general gradational pattern of earlier and more severe decline from inland lower rainfall areas to higher rainfall coastal regions. Some small isolated areas appear to have retained their mammal species, as have many islands which remain critical refuges. There is now some compelling evidence that predation by feral cats is implicated in the observed decline, with those impacts likely to be exacerbated by prevailing fire regimes (frequent, extensive and intense fire), by reduction in ground vegetation cover due to livestock and, in some areas, by ‘control’ of dingoes. However the impacts of dingoes may be complex, and are not yet well resolved in this area. The relative impacts of these individual factors vary spatially (with most severe impacts in higher rainfall and more rugged areas) and between different mammal species, with some species responding idiosyncratically: the most notable example is the rapid decline of the northern quoll (Dasyurus hallucatus) due to poisoning by the introduced cane toad (Rhinella marina), which continues to spread extensively across northern Australia. The impact of disease, if any, remains unresolved.
Conservation Management Responses. Recovery of the native mammal fauna may be impossible in some areas. However, there are now examples of rapid recovery following threat management. Priority conservation actions include: enhanced biosecurity for important islands, establishment of a network of feral predator exclosures, intensive fire management (aimed at increasing the extent of longer-unburnt habitat and in delivering fine scale patch burning), reduction in feral stock in conservation reserves, and acquisition
Significance
The island continent of Australia harbors much of the world’s most distinctive biodiversity, but this review describes an extent of recent and ongoing loss of its mammal fauna that is exceptionally high and appreciably greater than previously recognized. The causes of loss are dissimilar to those responsible for most biodiversity decline elsewhere in the world.
Understanding the impact of habitat fragmentation, roads, and other anthropogenic influences on cougars (Puma concolor) requires quantitative assessment of habitat selection at multiple scales. We calculated annual and multiyear home ranges using a fixed-kernel (FK) estimator of home range for 13 adult female and 2 adult male radiotagged cougars that were monitored October 1986 through December 1992 in the Santa Ana Mountain Range of southern California, USA. Using compositional analysis, we assessed diurnal use of vegetation types and areas near roads at 2 orders of selection (second- and third-order; Johnson 1980). Mean annual and multiyear 85% FK home ranges for males were larger than those reported by previous studies in California. Mean wet-season 85% FK home ranges were significantly larger than those of the dry season. At both scales of selection and across seasons, cougars preferred riparian habitats and avoided human-dominated habitats. Grasslands were the most avoided natural vegetation type at both scales of selection. Although cougar home ranges tended to be located away from high- and low-speed 2-lane paved roads (second-order avoidance), cougars did not avoid roads within their home range, especially when roads were in preferred riparian areas. Protection of habitat mosaics that include unroaded riparian areas is critical to the conservation of this cougar population.
Feral cats (Felis catus) have a wide global distribution and cause significant damage to native fauna. Reducing their impacts requires an understanding of how they use habitat and which parts of the landscape should be the focus of management. We reviewed 27 experimental and observational studies conducted around the world over the last 35 years that aimed to examine habitat use by feral and unowned cats. Our aims were to: (1) summarise the current body of literature on habitat use by feral cats, in the context of existing ecological theory (i.e. habitat selection, foraging theory); (2) develop testable hypotheses to help fill important knowledge gaps in the current body of knowledge on this topic; and (3) build a conceptual framework that will guide the activities of researchers and managers in reducing feral cat impacts. We found that feral cats exploit a diverse range of habitats including arid deserts, shrublands and grasslands, fragmented agricultural landscapes, urban areas, glacial valleys, equatorial to sub-Antarctic islands and a range of forest and woodland types. Factors invoked to explain cat habitat use included prey availability, predation/competition, shelter availability and human resource subsidies, but the strength of evidence used to support these assertions was low, with most studies being observational or correlative. We therefore provide a list of key directions that will assist conservation managers and researchers in better understanding and ameliorating the impact of feral cats at a scale appropriate for useful management and research. Future studies will benefit from employing an experimental approach and collecting data on the relative abundance and activity of prey and other predators. This might include landscape-scale experiments where the densities of predators, prey or competitors are manipulated and then the response in cat habitat use is measured. Effective management of feral cat populations could target high-use areas, such as linear features and structurally complex habitat. Since our review shows often-divergent outcomes in the use of the same habitat components and vegetation types worldwide, local knowledge and active monitoring of management actions is essential when deciding on control programs.
We studied the response of vegetation and vertebrate assemblages to fire and grazing, and their interacting effects, in Eucalyptus woodland in north-eastern Australia. In this vegetation type, many pastures remain free of cattle grazing due to the occurrence of a native shrub poisonous to livestock. Vegetation (floristic data and 22 habitat variables) and vertebrate fauna (birds, mammals, reptiles) were sampled in 29 standardized 50 × 50-m quadrats in the 2001 wet season, representing four treatments: sites burnt recently (within 2 y) and grazed by cattle (423%, fire in ungrazed sites 68–39%) and increased the cover of forbs (8% in burnt and grazed sites, 3% if ungrazed) and tussock grasses (20% in grazed and unburnt sites and 5% when ungrazed). Grazing caused a shift in floristic composition from the perennial hummock grass Triodapungens to tussock grasses (e.g. Aristida spp., Enneapogon spp.), forbs (e.g. Phyllanthus spp.) and shrubs (e.g. Acacia spp.). Of the vertebrate groups, birds responded more to fire effects (9 species), reptiles to grazing effects (6 species) and mammals to the interaction (2 species). Species reacted to increases in bare ground (e.g. crested pigeon Ocyphapslophotes, hooded robin Melanodryascucullatus, Ctenophorusnuchalis) and to the dominant ground cover (e.g. Ctenotuspantherinus) or change in vegetation architecture (e.g. singing honeyeater Lichenostomusvirescens, variegated fairy-wren Maluruslamberti). The clearest example of an interacting effect was the cycle of complementary dominance between the rodents Pseudomysdelicatulus and P.desertor, the latter's post-fire recovery becoming more muted in sites where cattle grazed (modelled time for population recovery twice as long as in ungrazed sites).
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.
Two models to predict the food of predators are proposed. They assume that prey size and prey abundance are the only availability factors of importance to predators. One model assumes that the predator consumes prey as they are encountered and the other that predators feed to maximize their energy intake. Previous work, principally from aquatic
situations is examined to test the models. It is concluded that many invertebrates and larval vertebrates eat prey as they are encountered while adult vertebrates feed as energy maximizers. The limitations of the models are discussed and their relation to models of optimal diet examined.
Animals commonly choose among habitats that differ both in foraging return and mortality hazard. However, no experimental study has attempted to predict the level of increase in resources, or the decrease in mortality hazard, which will induce a forager to shift from a safer to a more hazardous (but richer) foraging area. Here we present and test a model that specifies the choice of foraging areas ("habitats") that would minimize total mortality risk while allowing collection of some arbitrary net energy gain. We tested the model with juvenile creek chubs (Semotilus atromaculatus) in an experimental field stream in which the foragers could utilize a foodless refuge and choose between two foraging areas that differed in experimentally manipulated resource densities (Tubifex spp. worms in sediments) and mortality hazard (adult creek chubs). For the case tested, the model specified a simple rule: "use the refuge plus the site with the lowest ratio of mortality rate (μ) to gross foraging rat (f)," i.e., "minimize μ./f." Independent prior measurements of mortality hazard (as a function of predator density) and gross foraging rate (as a function of resource density) allowed us to predict the resource level in the more hazardous foraging site that should induce a shift from the safer to the more hazardous site. The chubs' preferences in subsequent choice experiments agreed well with the theoretical predictions. The "minimize μ/f" rule (deaths per unit energy), perhaps in modified form, provides a simple alternative to the "maximize f" (energy per unit time) criterion that applies to long-term rate maximization when predation hazard does not differ among choices.
Small mammal species are declining across northern Australia. Predation by feral cats Felis sylvestris catus is one hypothesised cause. Most evidence of cat impacts on native prey comes from islands, where cat densities are often high, but cats typically occur at low densities on mainland Australia.We conducted a field experiment to measure the effect of predation by low-density cat populations on the demography of a native small mammal. We established two 12·5-ha enclosures in tropical savanna in the Northern Territory. Each enclosure was divided in half, with cats allowed access to one half but not the other. We introduced about 20 individuals of a native rodent, Rattus villosissimus, into each of the four compartments (two enclosures × two predator-access treatments). We monitored rat demography by mark-recapture analysis and radiotracking, and predator incursions by camera surveillance and track and scat searches.Rat populations persisted over the duration of the study (18 months) in the predator-proof treatment, where we detected no predator incursions, but declined to extinction in both predator-accessible compartments. In one case, cat incursions were frequently detected and the rat population was rapidly extirpated (<3 months); in the other, cat incursions were infrequent, and the population declined more gradually (c. 16 months) due to low recruitment. We detected no incursions by dingoes Canis dingo, the other mammalian predator in the area.Synthesis and applications. This is the first study to provide direct evidence that cats are capable of extirpating small mammals in a continental setting, in spite of their low population densities. This finding supports the hypothesis that predation by feral cats is contributing to declines of small mammals in northern Australia. The conservation management of native small mammals in northern Australia may require intensive control of cat populations, including large cat-free enclosures.