Home ranges and use of built resources by feral cats (Felis catus) in Kosciuszko National Park, New South Wales, Australia
Kåren Watson A , Chris R. Dickman
A * and Linda Broome B
A
B
Abstract
We radio-tracked three feral cats (Felis catus) over a period of 15 months in the Perisher Range ski resort area of Kosciuszko National Park, New South Wales, and show that they were active year round above the winter snowline. In winter the home ranges of two adult male feral cats were contracted to built areas of the resorts that provided shelter and possibly opportunities for food scavenging, but the ranges and movements were expanded to exploit additional resources in other seasons. An adult female feral cat made little use of built infrastructure, inhabiting natural habitats throughout the year and denning in winter under the snowpack. Dietary analyses based on microscopic examination of scat and gut contents showed that cats depredated small mammals, including threatened species such as the mountain pygmy-possum (Burramys parvus) and broad-toothed rat (Mastacomys fuscus). Potential cat-impacts on these and other native species may be reduced by focusing management around ski resort buildings and infrastructure, especially in winter, and educating and engaging the public to assist in management activities.
Keywords: Australian alps, Australian snow country, broad-toothed rat, Felis catus, feral cat, mountain pygmy-possum, snowpack, subnivean space.
Introduction
The feral cat (Felis catus) occurs in most parts of the world and often has detrimental impacts on native wildlife. In Australia predation by cats has contributed to the demise of many native species (Woinarski et al. 2019), but further impacts arise from competition and via the introduction of diseases such as toxoplasmosis (Glen and Dickman 2008). Australian studies on the diet of feral cats have been focused largely in the continent’s arid inland regions (Dickman 1996; Doherty et al. 2015), in the northern savannas (Stokeld et al. 2018) or in urban, farm and rural wooded habitats (e.g. Molsher 1999; Denny et al. 2002), and show that cats are carnivorous, with a preference for small mammals. However, knowledge about cats and their impacts on wildlife in colder biomes is limited, especially in seasonally snow-covered environments (Lazenby et al. 2021; Menon et al. 2024). Globally, cats have been recorded using cool-climate habitats in glacial valleys and on subAntarctic islands (Van Aarde 1979; Recio et al. 2015), but appear to be uncommon in alpine and subalpine areas and may not be well adapted to locomotion or hunting in snow (Green and Osborne 2012). Feral cats occupy relatively large home ranges when at low density and in low productivity environments (Bengsen et al. 2016), and also show preferences for built infrastructure and human resource subsidies that may increase their persistence in harsh conditions (Doherty et al. 2014).
In Australia the snow country, using the definition of Slatyer et al. (1984) as averaging 60 days or more of snow cover per winter, that in the Snowy Mountains pertains to areas above 1528 m, covers only 0.02% of the continent (Green 1998). Within this limited biome, Kosciuszko National Park (KNP) has been recognised for its biological significance and is listed by UNESCO as a Biosphere Reserve. The feral cat occurs in KNP, with its establishment likely facilitated by resources provided by the ski industry and, especially, the infrastructure and associated work camps built by the Snowy Hydro Scheme in the mid-twentieth century (Watson 2006; Supplementary Material Table 1). Although cat-impacts here have not been studied, a 77% decline in numbers of the Critically Endangered mountain pygmy-possum (Burramys parvus) between 1997 and 2009 has been linked in part to feral cats; intensive cat control from 2010 allowed numbers of the mountain pygmy-possum to recover to 1997 levels after only 6 years (Broome et al. 2018). Another species potentially preyed upon by feral cats in KNP is the broad-toothed rat (Mastacomys fuscus); this rodent also shows a declining population trend and is listed as Near Threatened by the International Union for Conservation of Nature (https://www.iucnredlist.org/en; accessed 28 June 2025).
Here, we describe the movements, home ranges and prey of feral cats around ski resorts in KNP. We predict that cats will show seasonal variation in home range area, use buildings and infrastructure more than other habitats for shelter and other resource needs, especially in winter when snow covers the ground, and will include small mammals – including threatened species – in their diet. Our results provide preliminary information to help develop management strategies to reduce potential cat-impacts in KNP.
Methods
Study region
At Perisher Valley in KNP, average daily maximum and minimum temperatures peak in February, at 18.3°C and 5.8°C, respectively, descending to 2.4°C and −5.0°C in July. Annual rainfall exceeds 1500 mm, falling mainly as snow in winter (July to September). The snowpack lasts 17–25 weeks/year and varies in depth from 90 to 350 cm. Importantly, the dominant heathland vegetation supports the snowpack, forming a subnivean space above the ground (Costin et al. 2000). Daily temperature variation in this space is ~2°C, whereas variation above the snowpack may be >25°C (Coulianos and Johnels 1962). Some small mammals, such as the broad-toothed rat, are active throughout winter in the subnivean space (Bubela et al. 1991; Happold 2015), although the mountain pygmy-possum hibernates beneath the snowpack (Broome and Geiser 1995).
Our study focused on the Perisher Range ski resorts, an area of ~12 km2 that encompasses the villages of Perisher Valley, Guthega, Blue Cow and Smiggin Holes. The base altitude is 1520 m on the Snowy River near Guthega, rising to 2054 m at Mt Perisher. We selected this area because of its human-built infrastructure, proximity to a high quality patch of deep block-stream boulderfield with associated vegetation preferred by mountain pygmy-possums at Mt Blue Cow (Broome 2001), and sightings of feral cats.
Field and laboratory methods
We used live-trapping and radio-telemetry to track cat movements. To capture cats, we set 32 cage traps in the ski resorts and perimeter areas in July 2004, with variable numbers of traps set until September 2004. Captured cats were anaesthetised, weighed, micro-chipped, inspected for sex, body and reproductive condition and fitted with a 2-stage radio-transmitter (Faunatech, Australia). In normal mode the transmitters have a pulse rate of 45 pulses per minute, but emit a mortality mode pulse of 90 pulses per minute if a transmitter remains stationary for 12 h. Transmitters were attached to a leather collar with a 166 mm whip aerial, the top of which was uniquely coloured to assist visual identification of each cat. These units weighed ~40 g, <5% of cats’ body mass. Cats were kept overnight and given food and water before release at their capture location. Supplementary Material Table 2 provides full details of all protocols.
Radio-tracking commenced ≥24 h post-collaring and used an Australis 26 K scanning receiver (Titley Electronics, Australia) with a 3-tiered Yagi antenna, and continued over two winters (July to September) and a spring/summer/autumn season (October to June), from July 2004 to September 2005. During winter, tracking was undertaken opportunistically and mostly by day. We used hand-held GPS units to record exact locations if cats were observed and triangulation if not, attempting to achieve angles of ≥45 degrees between fixes. Spring, summer and autumn tracking methods were similar, but more direct fixes (observations of cats) were achieved due to better access to terrain by roads and on foot. Point locations where cats were located consistently were inspected to determine if these were den sites; although rudimentary, dens could be recognised as sheltered chambers underneath rocks, vegetation or built infrastructure, often with loose cat hairs from grooming, and characteristic cat odour. We defined three broad habitat categories: buildings (e.g. chalets, sheds), tracks and trails, and natural habitats (e.g. boulderfields, grassy woodland, heathland). Feral cats were assigned to one of these habitats if observed there. If cat locations were estimated rather than observed, we assigned habitat only if cats were >25 m distant from the edge of that habitat as we estimated an error radius for radio-fixes during tracking of ~25 m. Home ranges were calculated as 95% kernel densities (KDE) and 100% minimum convex polygons (MCP) encompassing GPS points and initial and final capture sites, with boundaries determined by the ABODE home range package (Laver 2005) and ArcGis/ArcMap software. Comparisons of habitat and home range area were made between winter, when snow covered the ground, and the snow-free seasons of spring, summer and autumn combined.
Live-trapping data were obtained from management operations carried out by the New South Wales National Parks and Wildlife Service (NSW NPWS), and comprised captures of feral cats within the Perisher ski resorts and surrounds between 2002 and 2005, and August 2010 and June 2019 (Supplementary Material Table 3). There was limited information on trap effort, but for cats captured between 2010 and 2019 we categorised trap sites as near buildings, or distant (>1 km) from human-built infrastructure.
To assess cat diet we collected scats from animals captured in cage traps in 2004, and retrieved stomach and gut contents from cats captured and euthanised between July and October 2005 as radio-tracking was concluding. We also collected scats opportunistically in the field and accessed further scats collected by T. Bubela from 1990 to 1993 (Bubela et al. 1998). Scats were dried and stored in paper envelopes after collection; stomach and gut contents were frozen. Mammals were identified by microscopic analysis of hairs in scat and gut contents following Brunner and Coman (1974) and other prey items by reference to their external features, as detailed in Supplementary Material Table 4.
Results
Cat abundance and trapping results
Management operations by NSW NPWS trapped and removed 9–40 feral cats each year between 2002 and 2005 in the Perisher ski resort area, with 84 removed in total. Further operations removed 3–25 cats annually from 2010 to 2019, with 94 captured in total (adults: 48 ♂, 19 ♀, 25 unknown; juveniles: 2; Supplementary Material Table 3). Only three cats were captured away from human-built infrastructure. Although most traps were set near buildings, built infrastructure is clearly frequented by feral cats.
Radio-tracking
We captured and radio-collared six feral cats between July and September 2004, five in or near built infrastructure (Guthega Village, n = 3; Pleasant Valley ski run at Perisher Blue, n = 1; Kahane lodge, Perisher, n = 1) and one away from it, with trap success of 2.8%. Three cats provided too few fixes (<10) to be useful; three cats (1 ♀, 2 ♂) provided sufficient data for analysis, with 93, 40 and 58 fixes, respectively.
Two male cats – Blackie (3.5 kg, black) and Garfield (3.4 kg, ginger tabby) – used more human-built infrastructure during the snow-covered months compared with the snow-free months (Table 1), and reduced their 100% MCP home range areas by 61–73% and 95% KDE ranges by 40–74% in winter compared with the other seasons (Table 2, Fig. 1). However, the female cat – Felix (3.0 kg, tabby) – concentrated her activity away from human infrastructure and showed little seasonal variation in habitat use or home range size (Table 1, Fig. 1). The female’s home range was at least 30% smaller than that of the males in summer but 5% (95% KDE) to 60% (100% MCP) larger, on average, in winter (Table 2). Each cat appeared to use core areas, with movements that extended from these sites from time to time, especially in the absence of snow cover (Fig. 1, Supplementary Material Figs 1–4). Inspections of these sites post-thaw revealed dens in built infrastructure (aqueduct pipes, woodpiles, around lodges and ski lift infrastructure), and under boulders, along creek lines and within the subnivean space at altitudes of 1600–1800 m.
| Cat | Sex | Winter: snow covered period A | Non-snow covered period | |||||
|---|---|---|---|---|---|---|---|---|
| Buildings | Tracks and trails | Natural habitats | Buildings | Tracks and trails | Natural habitats | |||
| Felix | ♀ | 2.3 | 16.3 | 81.4 | 2.0 | 16.0 | 82.0 | |
| Blackie | ♂ | 62.5 | 12.5 | 25.0 | 0 | 56.2 | 43.8 | |
| Garfield | ♂ | 66.7 | 11.1 | 22.2 | 34.7 | 28.6 | 36.7 | |
| Cat | Sex | Season A | Number of fixes | 100 MCP (ha) | 95 KDE (ha) | |
|---|---|---|---|---|---|---|
| Felix | ♀ | Winter 2004 | 25 | 350.4 | 192.7 | |
| Winter 2005 | 18 | 428.4 | 291.1 | |||
| October 2004–June 2005 | 50 | 450.7 | 315.5 | |||
| Mean | 409.8 | 266.4 | ||||
| Blackie | ♂ | Winter 2004 | 8 | 288.4 | 115.4 | |
| October 2004–June 2005 | 32 | 745.6 | 447.4 | |||
| Mean | 517.0 | 281.4 | ||||
| Garfield | ♂ | Winter 2005 | 9 | 315.9 | 346.5 | |
| October 2004–June 2005 | 49 | 1161.7 | 580.9 | |||
| Mean | 738.8 | 463.7 |
Home ranges (100% minimum convex polygons) of three feral cats radio-tracked in the Perisher ski resorts area of Kosciuszko National Park from winter 2004 to winter 2005. The shaded polygons represent the ranges of these cats when snow covered the landscape, and the broken lines represent the larger ranges of these cats during the snow-free period between October 2004 and June 2005. The numbers of fixes used to estimate the home ranges are shown in Table 2. All three cats overlapped at the creek line below the Pleasant Valley chairlift.
Diet
Two of the twenty-two feral cat scats collected between 1990 and 1993 contained hair from the mountain pygmy-possum and three from broad-toothed rats. One of the seventeen scat and gut samples collected in 2004 and 2005 contained hair from the mountain pygmy-possum and six from broad-toothed rats. Other mammals recorded in both temporal samples of cat diet included rats Rattus spp., mainland dusky antechinus (Antechinus mimetes), and rabbit Oryctolagus cuniculus. Birds, reptiles, invertebrates, plant material and anthropogenic items indicative of scavenging comprised other components of the diet (Supplementary Tables 4a and 4b).
Discussion
Our results provide broad support for our initial predictions and confirm that feral cats persist year-round in ski resorts of the Australian high country, exploiting habitats above 1528 m where the annual duration of snow cover averages 60 days (Slatyer et al. 1984), and depredating small mammals, including threatened species. Northern hemisphere studies have suggested that cats avoid snowy conditions because they are poorly equipped to move on powdery snow (Formazov 1946). In Australia, however, the incidence of powdery snow is sporadic as snowfalls are usually followed by clear days above zero degrees and nights of sub-zero temperatures that melt and freeze the snowpack (Sanecki et al. 2006); these conditions quickly form a surface crust on which animals can move. Indeed, observations by Watson (2006) of a cat hunting by night on the snowpack and our observations of cat den sites in the subnivean space confirm that cat activity occurs both on and below the snowpack. Feral cats have also been captured on camera traps set over winter when snow is present at 1200–1600 m in remote parts of KNP, and continued collection of scats and records of paw prints on snow from various locations show that cats are resident and widespread throughout the region (LB, unpubl. data). Post-thaw, cats have also been sighted close to the highest elevations of Mt Kosciuszko (2228 m) and Muellers Peak (2129 m) (Bates 2017; LB, unpubl. data).
As expected, we found that cats use built infrastructure around ski resorts, although there is individual variation. The two male cats sheltered in the resort area extensively during winter, denning in and near buildings to avoid the inclement conditions outside, and perhaps also exploiting anthropogenic food resources. These cats made more use of tracks and natural habitats during non-snow periods, with home range increases likely facilitating access to additional resources and mates. In contrast, the female cat seldom used and never denned in buildings, instead denning under boulders and deep heath vegetation. She was found in the latter habitat during periods of snow cover, also using the subnivean space, accessed through breaks in the snow pack along streams or melt rings around the boles of snowgums (Eucalyptus pauciflora). Many of her winter locations were at the lower, west-facing elevations, along the Snowy River near Guthega Dam, where snow accumulation was less than at the higher elevation sites used during summer. This cat was euthanised by managers in 2011 following capture in the same boulderfield habitat at Mount Blue Cow that she had used in 2004–05; this habitat is also used by mountain pygmy-possums.
The mean home range areas we estimated exceed those of male feral cats by >5% and of females by >40% described in other Australian studies that have used comparable methods (Jones and Coman 1982; Schwarz 1995; Molsher 1999; Molsher et al. 2005; Buckmaster and Dickman 2012). Home ranges of the cats in this study may have been affected by the success of cat management over the previous two winters, when 50 cats were trapped and removed from the Perisher Range area. Previous studies indicate that cat home ranges are generally smaller where cats are at high density (Denny et al. 2002; Molsher et al. 2005). It is also possible that high activity of the European red fox (Vulpes vulpes) in the study region was influential (Bubela et al. 1998; Green and Osborne 2012). Red foxes can suppress both the abundance and range of habitats used by feral cats (Molsher et al. 2017; Rees et al. 2023); if such suppression occurred in the study region, cats may have increased their movements and areas traversed to obtain sufficient food resources. The prey of feral cats was likely scarce in 2004–2005 due to the effects of the Millenium Drought (Van Dijk et al. 2013), with low numbers of small mammals trapped at Mt Blue Cow in November 2004 (LB, unpubl. data).
We note that our use of radio-collars rather than GPS trackers likely underestimated home ranges (White and Garrott 1990), with the feral cats ranging further than we recorded. We observed that cats used ski runs, tracks and roads as travel routes, that likely facilitated movement across the landscape. Underestimation was likely greater during winter as fewer fixes could be obtained in this season than at other times (Table 2). Despite our small sample size of cats (n = 3), these observations suggest that the home ranges of feral cats in the study area could have been considerably greater than we have estimated.
Conclusion and implications for management
Despite small sample sizes, our results show that feral cats use natural habitats and especially human-built infrastructure throughout the year in Australia’s snow country and depredate small mammals such as mountain pygmy-possums and broad-toothed rats that are of conservation concern. The association of feral cats with ski resort buildings and infrastructure, which becomes more focused during winter, provides an opportunity for targeted cat control. A ‘see a cat catch a cat’ program is currently implemented in the resorts, whereby cage traps are deployed during winter in response to cat sightings reported by visitors and staff (Broome et al. 2018, M. Schroder, pers. comm.). We suggest that this program continues and is monitored to assess its efficacy, and also that care is taken to minimise cat-access to edible rubbish by using sealed bins at commercial premises and on streets in the resorts. A public education campaign using social media and traditional materials (e.g. brochures, information sheets) distributed within lodges and restaurants could further warn visitors of the perils to native wildlife from feral cats.
Acknowledgements
We thank David Woods and Mellesa Schroder, NSW NPWS, Jindabyne, for facilitating cat control in KNP, Fred Ford for assistance with radio-tracking, and Fred Ford and Hayley Bates for providing observations of cats and their footprints in snow. Fieldwork was permitted under licence and ethical approval from the (then) NSW Department of Environment and Conservation Animal Care and Ethics Committee (ACEC) in June, 2004. This research was undertaken in conjunction with NSW NPWS in-kind support.
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