Companion Cats Show No Effect of Trial-and-Error Learning Compared to Dogs in a Transparent-Obstacle Detour Task

We tested companion cats and dogs in similar indoor conditions using identical procedures in the classic detour task around a V-shaped transparent wire-mesh fence. Besides the control group, we used two types of laser light-pointing demonstration (moving around the fence, or pointing straight at the reward). We found that dogs reached the food reward faster than cats; across consecutive trials, only the dogs showed improvement in their speed and dogs continued to use the same side for detouring after a preceding successful attempt, while cats chose the side for detouring irrespective of their previous successful trials. In addition, 'demonstrating' a detour with the laser did not influence the speed or direction of the detour of the subjects; and dogs looked back to their owner more frequently than the cats did. We discuss the possibility that for dogs, detouring along a transparent obstacle represents a more problematic task than for cats; therefore, dogs strongly rely on their previous experiences. This is the first time that cats were successfully tested in this detour paradigm in direct comparison with dogs. The results are relevant from the aspect of testing cognitive performance in companion cats, which are known to be notoriously reluctant to engage with novel experimental situations.

Habitat characteristics around dens in female brown bears with cubs are density dependent

The mechanisms determining habitat use in animal populations have important implications for population dynamics, conservation, and management. Here, we investigated how an increase in annual numbers of brown bear females with cubs of the year (FCOY) in a growing, yet threatened population, could explain differences in the habitat characteristics around reproductive dens. Habitat characteristics around FCOY dens were compared between a low bear density period (1995–2005) and a period when the population was increasing (2006–2016). We also compared the distance to the nearest breeding area and to all other breeding areas observed during the same year. The results suggested that during the second period, breeding areas were closer to rivers, fruit trees, and anthropogenic sources of disturbance (trails, highways) than in 1995–2005. There were also shorter distances to the closest neighboring breeding area, while the mean distance among FCOY breeding areas increased as the population grew and expanded at the landscape level. These changes may reflect that the best den locations were increasingly occupied (i.e., ideal-despotic distribution), and may be further explained by the avoidance of conspecifics by FCOY in a critical time of the year, when newborn cubs are most vulnerable. We suggest that both density-dependent factors and human-related features of the landscape are crucial to understanding long-term dynamics in the habitat use of a threatened species.

Space use and habitat selection of an invasive mesopredator and sympatric, native apex predator

BACKGROUND

Where mesopredators co-exist with dominant apex predators, an understanding of the factors that influence their habitat and space use can provide insights that help guide wildlife conservation and pest management actions. A predator's habitat use is defined by its home range, which is influenced by its selection or avoidance of habitat features and intra- and inter-specific interactions within the landscape. These are driven by both innate and learned behaviour, operating at different spatial scales. We examined the seasonal home ranges and habitat selection of actively-managed populations of a native apex predator (dingo Canis dingo) and invasive mesopredator (feral cat Felis catus) in semi-arid Western Australia to better understanding their sympatric landscape use, potential interactions, and to help guide their management.

METHODS

We used kernel density estimates to characterise the seasonal space use of dingoes and feral cats, investigate inter- and intra-species variation in their home range extent and composition, and examine second-order habitat selection for each predator. Further, we used discrete choice modelling and step selection functions to examine the difference in third-order habitat selection across several habitat features.

RESULTS

The seasonal home ranges of dingoes were on average 19.5 times larger than feral cats. Feral cat seasonal home ranges typically included a larger proportion of grasslands than expected relative to availability in the study site, indicating second-order habitat selection for grasslands. In their fine-scale movements (third-order habitat selection), both predators selected for roads, hydrological features (seasonal intermittent streams, seasonal lakes and wetlands), and high vegetation cover. Dingoes also selected strongly for open woodlands, whereas feral cats used open woodlands and grasslands in proportion to availability.

MANAGEMENT RECOMMENDATIONS

Based on these results, and in order to avoid unintended negative ecological consequences (e.g. mesopredator release) that may stem from non-selective predator management, we recommend that feral cat control focuses on techniques such as trapping and shooting that are specific to feral cats in areas where they overlap with apex predators (dingoes), and more general techniques such as poison baiting where they are segregated.

Territoriality drives preemptive habitat selection in recovering wolves: Implications for carnivore conservation

According to the ideal-free distribution (IFD), individuals within a population are free to select habitats that maximize their chances of success. Assuming knowledge of habitat quality, the IFD predicts that average fitness will be approximately equal among individuals and between habitats, while density varies, implying that habitat selection will be density dependent. Populations are often assumed to follow an IFD, although this assumption is rarely tested with empirical data, and may be incorrect when territoriality indicates habitat selection tactics that deviate from the IFD (e.g. ideal-despotic distribution or ideal-preemptive distribution). When territoriality influences habitat selection, species' density will not directly reflect components of fitness such as reproductive success or survival. In such cases, assuming an IFD can lead to false conclusions about habitat quality. We tested theoretical models of density-dependent habitat selection on a species known to exhibit territorial behaviour in order to determine whether commonly applied habitat models are appropriate under these circumstances. We combined long-term radiotelemetry and census data from grey wolves Canis lupus in the Upper Peninsula of Michigan, USA to relate spatiotemporal variability in wolf density to underlying classifications of habitat within a hierarchical state-space modelling framework. We then iteratively applied isodar analysis to evaluate which distribution of habitat selection best described this recolonizing wolf population. The wolf population in our study expanded by >1,000% during our study (~50 to >600 individuals), and density-dependent habitat selection was most consistent with the ideal-preemptive distribution, as opposed to the ideal-free or ideal-despotic alternatives. Population density of terrestrial carnivores may not be positively correlated with the fitness value of their habitats, and density-dependent habitat selection patterns may help to explain complex predator-prey dynamics and cascading indirect effects. Source-sink population dynamics appear likely when species exhibit rapid growth and occupy interspersed habitats of contrasting quality. These conditions are likely and have implications for large carnivores in many systems, such as areas in North America and Europe where large predator species are currently recolonizing their former ranges.

Occupancy and abundance of free-roaming cats in a fragmented agricultural ecosystem

Context Free-roaming domestic cats are a widespread invasive species, occurring throughout the globe in urban and rural environments alike. However, robust estimates of cat occupancy and abundance, especially in rural, agricultural landscapes, are largely unknown. Aims To estimate cat occupancy and abundance within forested habitat in a fragmented agricultural region of Indiana, USA. Methods Free-roaming cats in 55 forest patches were captured from 2004 to 2010 to assess the effects of landscape attributes on cat occupancy probabilities. During 2009–10 abundance of cats in each habitat patch was estimated based on natural markings of captured individuals. Key results Across the entire study (2004–10) cats in 50 of the 55 patches were detected, but detections varied temporally and spatially. Average occupancy probability was estimated at Ψ = 0.773 (s.e. = 0.109), and detection probability was estimated as P = 0.204 (s.e. = 0.012). Distance to human structures and forest patch isolation both were found to negatively influence cat occupancy. In total, 57 individual cats were captured in 2009 and 55 in 2010, when unique individuals were distinguished. Across all forest patches, average cat abundance was n = 1.08 in 2009 and n = 0.91 in 2010, ranging from 0 to 7 among sampled patches. Conclusions Overall, the distribution of free-roaming cats across a rural agricultural landscape varied temporally and was associated with proximity to human structures and the proximity of other forest habitat. Similarly, abundance was found to vary spatially and temporally. Implications The findings suggest free-roaming cats are widespread throughout agricultural ecosystems, but their distribution is dynamic and non-random. Additionally, the potential for cats to impact native fauna inhabiting remnant forest patches is high in fragmented agricultural ecosystems due to the concentration of native species utilising these patches. Further research is needed to determine the effects free-roaming cats are having on native species in human-dominated, rural ecosystems, and what conservation measures might be implemented to best mitigate any impacts.

Differential fitness in field and forest explains density-independent habitat selection by gartersnakes

The ideal free distribution concept predicts that organisms will distribute themselves between habitats in a density-dependent manner so that individuals, on average, achieve the same fitness in each habitat. In ectotherms, environmental temperature has a strong impact on fitness, but temperature is not depletable and thus not density dependent. Can density-dependent habitat selection occur in ectotherms when habitats differ in thermal quality? We used an observational study of habitat selection by small snakes in field and forest, followed by manipulative habitat selection and fitness experiments with common gartersnakes in enclosures in field and forest to test this hypothesis. Snakes were much more abundant in the field, the habitat with superior thermal quality, than in the forest. Gartersnakes in our controlled experiment only used the forest habitat when snake density was highest and when food was more abundant in the forest; habitat selection was largely density independent, although there was weak evidence of density dependence. No female gartersnake gave birth in the forest enclosures, whereas half of the females gave birth in the field enclosures. Growth rates of females were higher in field than in forest enclosures. Overall, our data indicate that temperature appears to be the most important factor driving the habitat selection of gartersnakes, likely because temperature was more limiting than food in our study system. Snakes, or at least temperate snakes, may naturally exist at population densities low enough that they do not exhibit density-dependent habitat selection.

Modeling ecological traps for the control of feral pigs

Ecological traps are habitat sinks that are preferred by dispersing animals but have higher mortality or reduced fecundity compared to source habitats. Theory suggests that if mortality rates are sufficiently high, then ecological traps can result in extinction. An ecological trap may be created when pest animals are controlled in one area, but not in another area of equal habitat quality, and when there is density-dependent immigration from the high-density uncontrolled area to the low-density controlled area. We used a logistic population model to explore how varying the proportion of habitat controlled, control mortality rate, and strength of density-dependent immigration for feral pigs could affect the long-term population abundance and time to extinction. Increasing control mortality, the proportion of habitat controlled and the strength of density-dependent immigration decreased abundance both within and outside the area controlled. At higher levels of these parameters, extinction was achieved for feral pigs. We extended the analysis with a more complex stochastic, interactive model of feral pig dynamics in the Australian rangelands to examine how the same variables as the logistic model affected long-term abundance in the controlled and uncontrolled area and time to extinction. Compared to the logistic model of feral pig dynamics, the stochastic interactive model predicted lower abundances and extinction at lower control mortalities and proportions of habitat controlled. To improve the realism of the stochastic interactive model, we substituted fixed mortality rates with a density-dependent control mortality function, empirically derived from helicopter shooting exercises in Australia. Compared to the stochastic interactive model with fixed mortality rates, the model with the density-dependent control mortality function did not predict as substantial decline in abundance in controlled or uncontrolled areas or extinction for any combination of variables. These models demonstrate that pest eradication is theoretically possible without the pest being controlled throughout its range because of density-dependent immigration into the area controlled. The stronger the density-dependent immigration, the better the overall control in controlled and uncontrolled habitat combined. However, the stronger the density-dependent immigration, the poorer the control in the area controlled. For feral pigs, incorporating environmental stochasticity improves the prospects for eradication, but adding a realistic density-dependent control function eliminates these prospects.

Evaluating and validating abundance monitoring methods in the absence of populations of known size: review and application to a passive tracking index

Rarely is it possible to obtain absolute numbers in free-ranging populations and although various direct and indirect methods are used to estimate abundance, few are validated against populations of known size. In this paper, we apply grounding, calibration and verification methods, used to validate mathematical models, to methods of estimating relative abundance. To illustrate how this might be done, we consider and evaluate the widely applied passive tracking index (PTI) methodology. Using published data, we examine the rationality of PTI methodology, how conceptually animal activity and abundance are related and how alternative methods are subject to similar biases or produce similar abundance estimates and trends. We then attune the method against populations representing a range of densities likely to be encountered in the field. Finally, we compare PTI trends against a prediction that adjacent populations of the same species will have similar abundance values and trends in activity. We show that while PTI abundance estimates are subject to environmental and behavioural stochasticity peculiar to each species, the PTI method and associated variance estimate showed high probability of detection, high precision of abundance values and, generally, low variability between surveys, and suggest that the PTI method applied using this procedure and for these species provides a sensitive and credible index of abundance. This same or similar validation approach can and should be applied to alternative relative abundance methods in order to demonstrate their credibility and justify their use.

Amplified predation after fire suppresses rodent populations in Australia’s tropical savannas

Context Changes in abundance following fire are commonly reported for vertebrate species, but the mechanisms causing these changes are rarely tested. Currently, many species of small mammals are declining in the savannas of northern Australia. These declines have been linked to intense and frequent fires in the late dry season; however, why such fires cause declines of small mammals is unknown. Aims We aimed to discover the mechanisms causing decline in abundance of two species of small mammals, the pale field rat, Rattus tunneyi, and the western chestnut mouse, Pseudomys nanus, in response to fire. Candidate mechanisms were (1) direct mortality because of fire itself, (2) mortality after fire because of removal of food by fire, (3) reduced reproductive success, (4) emigration, and (5) increased mortality because of predation following fire. Methods We used live trapping to monitor populations of these two species under the following three experimental fire treatments: high-intensity fire that removed all ground vegetation, low-intensity fire that produced a patchy burn, and an unburnt control. We also radio-tracked 38 R. tunneyi individuals to discover the fates of individual animals. Key results Abundance of both species declined after fire, and especially following the high-intensity burn. There was no support for any of the first four mechanisms of population decline, but mortality owing to predation increased after fire. This was related to loss of ground cover (which was greater in the high-intensity fire treatment), which evidently left animals exposed to predators. Also, local activity of two predators, feral cats and dingoes, increased after the burns, and we found direct evidence of predation by feral cats and snakes. Conclusions Fire in the northern savannas has little direct effect on populations of these small mammals, but it causes declines by amplifying the impacts of predators. These effects are most severe for high-intensity burns that remove a high proportion of vegetation cover. Implications To prevent further declines in northern Australia, fire should be managed in ways that limit the effects of increased predation. This could be achieved by setting cool fires that produce patchy burns, avoiding hot fires, and minimising the total area burnt.

Population ecology of free-roaming cats and interference competition by coyotes in urban parks

Free-roaming cats are a common element of urban landscapes worldwide, often causing controversy regarding their impacts on ecological systems and public health. We monitored cats within natural habitat fragments in the Chicago metropolitan area to characterize population demographics, disease prevalence, movement patterns and habitat selection, in addition to assessing the possible influence of coyotes on cats. The population was dominated by adults of both sexes, and 24% of adults were in reproductive condition. Annual survival rate was relatively high (S=0.70, SE=0.10), with vehicles and predation the primary causes of death. Size of annual home range varied by sex, but not reproductive status or body weight. We observed partitioning of the landscape by cats and coyotes, with little interspecific overlap between core areas of activity. Coyotes selected for natural habitats whereas cats selected for developed areas such as residences. Free-roaming cats were in better condition than we predicted, but their use of natural habitat fragments, and presumably their ecological impact, appeared to be limited by coyotes through intraguild competition.

Sniffing out the stakes: hair-snares for wild cats in arid environments

Context Wild cats (Felis spp.) are difficult to monitor because of their cryptic lifestyle and usually low numbers. Hair-snaring is a promising non-invasive method being used increasingly to estimate mammal populations. Aims Our aim was to carry out pilot trials of a simple hair-snare designed to capture hair from wild cats in arid environments. Methods Roughened wooden stakes were set at multiple sites on the crests of sand dunes and in swales in western Queensland, Australia, and in mostly sandy habitats of the Namib and Kalahari Deserts, Namibia. In Australia, stakes were sprayed with cat urine, extracts of catnip or valerian herbs as lures, or left untreated; in Namibia, alternate stakes were sprayed with a food lure of tuna emulsion oil. The stakes were checked for hair, usually daily, for 2–14 days, and the surrounding ground was inspected for tracks. Remote cameras also were used at some sites to confirm the identity of visitors to stakes. Key results In Australia, feral cats (Felis catus) were attracted to, and left hairs on, stakes sprayed with cat urine six times more frequently than to unsprayed stakes irrespective of whether snares were on dune crests or in swales, and showed no response to catnip or valerian. Tracks and photos showed that cats, dingoes or wild dogs (Canis lupus ssp.) and foxes (Vulpes vulpes) also approached and sniffed the stakes. In Namibia, F. catus, F. lybica and F. nigripes left hair on stakes, with deposition rates two and a half-fold higher at stakes with the food lure than without it. At least five other species of predators visited the hair-snare sites. Conclusions Simple wooden stakes provide a cheap and simple method of snaring hairs from wild cats, especially if used in conjunction with appropriate lures. Our results broadly support previous work, and extend the utility of the method to different Felis spp. in arid habitats. Implications Further research is needed on snares to investigate the seasonal efficiency of different lures. If DNA also is to be extracted to identify individuals, more work is needed to confirm that snares yield hair of sufficient quality to allow this.

The diet of the dingo (Canis lupus dingo) in north-eastern Australia with comments on its conservation implications

The dingo (Canis lupus dingo and hybrids) is the top mammalian predator on the Australian mainland and is thought to control and suppress populations of native herbivores and smaller mesopredators, including the introduced feral cat (Felis catus). Dingoes have been persecuted as a threat to domestic livestock, and local population decreases have been linked to increasing mesopredator populations, which in turn may cause the decline of small native mammals. There is little data on the dingo’s dietary composition in northern Australia. We examined the diet of dingoes in north-eastern Queensland via scat collection and analysis. A total of 178 scats were examined between 1994 and 2000, comprised of 185 prey items and representing 21 discrete prey types. Native mammal prey was the most frequent dietary component (69.7%), with large- to medium-sized macropods (Macropus spp. and Wallabia bicolor) present in the majority of samples (51.1%). Critical Weight Range species were found in 18.0% of the records. Introduced species such as the European hare/rabbit (Lepus capensis/Oryctolagus cuniculus) and cattle (Bos taurus) were found in smaller amounts (14.6 and 10.1%, respectively). These results suggest that dingoes prey considerably on large- to medium-sized macropods in our study area (north-eastern Australia). Dingo diet tends to differ regionally where dingoes prey on native species that are locally common or abundant. Finally, the diets of the dingo and feral cat do not appear to considerably overlap in our study area, which may have implications for mesopredator suppression.

Is water the key? Dingo management, intraguild interactions and predator distribution around water points in arid Australia

Context Predators are major beneficiaries of artificial water points in arid environments, yet little is known of the effects of water on the distribution of many sympatric species. Intraguild interactions around water points in arid Australia may play a significant role in structuring mammalian predator assemblages and influence spatial predation on some native prey species. Aims We examined how management of an apex predator, the dingo (Canis lupus dingo), influenced the distribution of two introduced mesopredators, foxes (Vulpes vulpes) and feral cats (Felis catus), around water points in arid Australia. Methods The spatial activity of dingoes, foxes and feral cats was assessed at five study sites with varying dingo management regimes. Sampling of predator activity was monitored using track counts at measured proximity to water points. Key results At sites where dingoes were uncontrolled, foxes were less likely to be found within 5 km of water points; conversely, where dingoes were controlled using exclusion fencing, fox activity was highest near water. Where dingo activity was reduced using 1080 baiting, feral cats were found closer to water. Conclusions These patterns suggest that the presence of dingoes instigates avoidance behaviour by foxes and feral cats, and through doing so may limit the use of artificial waters by these mesopredators. Through limiting access to such an essential resource in arid environments, dingoes may reduce mesopredator populations and minimise their impact on native prey. Implications For the conservation of native biodiversity, it may prove beneficial to maintain intact dingo populations due to their suppressive effect on mesopredators.

Cat-exclusion zones in rural and urban-fringe landscapes: how large would they have to be?

Context. The process of urban sprawl brings the human population and their domestic cats (Felis catus) in close contact with wildlife in areas that were previously remote, including reserves and conservation areas created to protect populations of vulnerable or threatened species. Various mitigation measures have been proposed, including devices designed to hinder cat hunting ability, desexing to reduce wandering and nuisance behaviours, containment at night or at all times and regulations governing cat ownership. Such regulations may aim to reduce cat densities by limiting the number of cats per household, or they may define zones around sensitive conservation areas where cat ownership is prohibited. Aims. The present study sought to establish the necessary size of cat-exclusion zones in rural and urban-fringe landscapes where vulnerable prey species may also reside. Methods. With GPS collars, we tracked 38 domestic cats at three sites (one rural, two urban fringe) where small reserves contained threatened lizard species. Key results. Home ranges (95% kernel density estimates) were considerably larger for cats at the rural site (0.3–69 ha) than at urban-fringe sites (0.35–19 ha at Kaitorete Spit and 0.2–9 ha at Otago Peninsula), and were larger at night than day. Resource selection ratios indicated avoidance of open areas with little cover, such as cultivated areas (farmland), tussock grassland and duneland, whereas sources of cover such as trees and buildings were preferred. Maximum distances moved and large variability between individual cats suggest buffers in rural landscapes would need to be at least 2.4 km wide, whereas those in urban-fringe habitat could be half as large. Conclusions. Despite significant home-range size differences exhibited by cats living in rural v. urban-fringe habitats, exclusion zones would need to be wide to account for considerable inter-cat variation in movement behaviour. Implications. The size of an effective cat-exclusion zone should represent the specific landscape, amount of residential development and substantial variability between individual cats.

Movement patterns of feral predators in an arid environment – implications for control through poison baiting

Control of introduced predators is critical to both protection and successful reintroduction of threatened prey species. Efficiency of control is improved if it takes into account habitat use, home range and the activity patterns of the predator. These characteristics were studied in feral cats (Felis catus) and red foxes (Vulpes vulpes) in arid South Australia, and results are used to suggest improvements in control methods. In addition, mortality and movement patterns of cats before and after a poison-baiting event were compared. Thirteen cats and four foxes were successfully fitted with GPS data-logger radio-collars and tracked 4-hourly for several months. High intra-specific variation in cat home-range size was recorded, with 95% minimum convex polygon (MCP) home ranges varying from 0.5 km2 to 132 km2. Cat home-range size was not significantly different from that of foxes, nor was there a significant difference related to sex or age. Cats preferred habitat types that support thicker vegetation cover, including creeklines and sand dunes, whereas foxes preferred sand dunes. Cats used temporary focal points (areas used intensively over short time periods and then vacated) for periods of up to 2 weeks and continually moved throughout their home range. Aerial baiting at a density of 10 baits per km2 was ineffective for cats because similar high mortality rates were recorded for cats in both baited and unbaited areas. Mortality was highest in young male cats. Long-range movements of up to 45 km in 2 days were recorded in male feral cats and movement into the baited zone occurred within 2 days of baiting. Movement patterns of radio-collared animals and inferred bait detection distances were used to suggest optimum baiting densities of ~30 baits per km2 for feral cats and 5 per km2 for foxes. Feral cats exhibited much higher intra-specific variation in activity patterns and home-range size than did foxes, rendering them a potentially difficult species to control by a single method. Control of cats and foxes in arid Australia should target habitats with thick vegetation cover and aerial baiting should ideally occur over areas of several thousand square kilometres because of large home ranges and long-range movements increasing the chance of fast reinvasion. The use of temporary focal points suggested that it may take several days or even weeks for a cat to encounter a fixed trap site within their home range, whereas foxes should encounter them more quickly as they move further each day although they have a similar home-range size. Because of high intra-specific variability in activity patterns and home-range size, control of feral cats in inland Australia may be best achieved through a combination of control techniques.

Complex interactions among mammalian carnivores in Australia, and their implications for wildlife management

Mammalian carnivore populations are often intensively managed, either because the carnivore in question is endangered, or because it is viewed as a pest and is subjected to control measures, or both. Most management programmes treat carnivore species in isolation. However, there is a large and emerging body of evidence to demonstrate that populations of different carnivores interact with each other in a variety of complex ways. Thus, the removal or introduction of predators to or from a system can often affect other species in ways that are difficult to predict. Wildlife managers must consider such interactions when planning predator control programmes. Integrated predator control will require a greater understanding of the complex relationships between species. In many parts of the world, sympatric species of carnivores have coexisted over an evolutionary time scale so that niche differentiation has occurred, and competition is difficult to observe. Australia has experienced numerous introductions during the past 200 years, including those of the red fox (Vulpes vulpes) and the feral cat (Felis catus). These species now exist in sympatry with native mammalian predators, providing ecologists with the opportunity to study their interactions without the confounding effects of coevolution. Despite an increasing body of observational evidence for complex interactions among native and introduced predators in Australia, few studies have attempted to clarify these relationships experimentally, and the interactions remain largely unacknowledged. A greater understanding of these interactions would provide ecologists and wildlife managers world-wide with the ability to construct robust predictive models of carnivore communities, and to identify their broader effects on ecosystem functioning. We suggest that future research should focus on controlled and replicated predator removal or addition experiments. The dingo (Canis lupus dingo), as a likely keystone species, should be a particular focus of attention.

Home ranges of feral cats (Felis catus) in central-western New South Wales, Australia

Twenty-one feral cats were radio-tracked using direct sighting and triangulation techniques (amassing 730 location fixes) during winter in an agricultural landscape in central-western New South Wales. Factors affecting home-range size, home-range overlap and habitat use were assessed. Mean home-range size was 248 ha (s.e. = 34.9, n = 15 cats, 598 location fixes). Home-range size and habitat use were not influenced by sex or age of adult cats, prey abundance or time of day. However, cat weight significantly influenced range size, with heavier cats having larger ranges than smaller cats. Although the cats are apparently solitary, their home ranges overlapped considerably, particularly between young adults and old adult cats. Cats were active both by day and night and did not occupy permanent dens. Home ranges encompassed mixed habitat types that provided both shelter and prey. Open woodland and open forest were the main habitat types covered by home ranges, but within these areas cats showed a preference for grassland, where rabbits were more abundant. The results recorded in this study indicate that cat-control programs should concentrate in mixed habitat areas, where both shelter and food are available, and over widely dispersed areas. The absence of group living suggests that the effectiveness of virally vectored fertility or biological control agents would be limited.

An evaluation of transect, plot and aerial survey techniques to monitor the spatial pattern and status of the bilby (Macrotis lagotis) in the Tanami Desert

We evaluated three monitoring techniques to determine the spatial pattern and relative abundance of the bilby (Macrotis lagotis) in the Tanami Desert, Northern Territory. All the methods examined relied on the identification of animal sign (foot imprints or diggings) to indicate the presence of a species. With fixed transects, a 10-km prepared tracking surface was monitored regularly using an all-terrain vehicle. With random plots, an unprepared tracking surface within a 200 × 300 m area was searched on foot for sign of the species. A helicopter was used in an aerial survey to identify bilby diggings from an altitude of 15–20 m while travelling at a speed of 30–40 knots along a predefined transect. The results for each method were stratified in relation to latitude and substrate to facilitate comparison of the efficacy of each technique. The fixed transects returned the least number of bilby records for most effort. The aerial transect technique resulted in few (<4%) false negative records but a sizeable (42%) number of false positive records. It is suggested that the aerial survey technique combined with ground-truth survey plots would provide reliable information on the extent of occurrence and status of the bilby in the remote spinifex deserts of central Australia.