Understanding determinants of home range behaviour of feral cats as introduced apex predators in insular ecosystems: a spatial approach

Home range size and habitat selection of owned outdoor domestic cats (Felis catus) in urban southwestern Ontario

Domestic cats (Felis catus) play a dual role in society as both companion animals and predators. When provided with unsupervised outdoor access, cats can negatively impact native wildlife and create public health and animal welfare challenges. The effective implementation of management strategies, such as buffer zones or curfews, requires an understanding of home range size, the factors that influence their movement, and the types of habitats they use. Here, we used a community/citizen scientist approach to collect movement and habitat use data using GPS collars on owned outdoor cats in the Kitchener-Waterloo-Cambridge-Guelph region, southwestern Ontario, Canada. Mean (± SD) 100% minimum convex polygon home range size was 8 ± 8 ha (range: 0.34-38 ha) and was positively associated with road density but not with intrinsic factors such as boldness, sex, or age. With regards to habitat selection, cats used greenspaces, roads, and agricultural land less often than predicted but strongly selected for impervious surfaces (urban areas other than greenspaces or roads). Our results suggest that wildlife near buildings and residential areas are likely at the greatest risk of cat predation and that a buffer size of 840 m would be needed to restrict cats from entering areas of conservation concern.

Integrating feral cat (Felis catus) control into landscape-scale introduced predator management to improve conservation prospects for threatened fauna: a case study from the south coast of Western Australia

Abstract ContextFeral cat predation has had a significant impact on native Australian fauna in the past 200 years. In the early 2000s, population monitoring of the western ground parrot showed a dramatic decline from the pre-2000 range, with one of three meta-populations declining to very low levels and a second becoming locally extinct. We review 8 years of integrated introduced predator control, which trialled the incorporation of the feral cat bait Eradicat® into existing fox baiting programs. AimsTo test the efficacy of integrating feral cat control into an existing introduced predator control program in an adaptive management framework conducted in response to the decline of native species. The objective was to protect the remaining western ground parrot populations and other threatened fauna on the south coast of Western Australia. MethodsA landscape-scale feral cat and fox baiting program was delivered across south coast reserves that were occupied by western ground parrots in the early 2000s. Up to 500000ha of national parks and natures reserves were baited per annum. Monitoring was established to evaluate both the efficacy of landscape-scale baiting in management of feral cat populations, and the response of several native fauna species, including the western ground parrot, to an integrated introduced predator control program. Key resultsOn average, 28% of radio-collared feral cats died from Eradicat® baiting each year, over a 5-year period. The results varied from 0% to 62% between years. Changes in site occupancy by feral cats, as measured by detection on camera traps, was also variable, with significant declines detected after baiting in some years and sites. Trends in populations of native fauna, including the western ground parrot and chuditch, showed positive responses to integrated control of foxes and cats. ImplicationsLandscape-scale baiting of feral cats in ecosystems on the south coast of Western Australia had varying success when measured by direct knockdown of cats and site occupancy as determined by camera trapping; however, native species appeared to respond favourably to integrated predator control. For the protection of native species, we recommend ongoing baiting for both foxes and feral cats, complemented by post-bait trapping of feral cats. We advocate monitoring baiting efficacy in a well designed adaptive management framework to deliver long-term recovery of threatened species that have been impacted by cats.

Topographic complexity potentially mediates cat predation risk for a critically endangered rodent

ContextThe niche reduction hypothesis (NRH) predicts that the realised niche of declining species is reduced by threats that are mediated by environmental, biotic and evolutionary processes, explaining why species decline in some locations but not others. The critically endangered central rock-rat (CRR) survives only in rugged mountain range habitat in central Australia and is highly vulnerable to cat predation. We predicted that cat density and ranging behaviour, and, hence, predation risk, is mediated by habitat complexity, thus explaining the mechanism maintaining the CRR refuge. AimsWe sought to determine whether cat densities were lower in the rugged CRR refuge than in an adjacent valley dominated by less complex rocky habitats and no longer occupied by CRRs. MethodsWe installed arrays of camera traps along two parallel mountain ranges in the refuge and in the intervening valley habitats. We identified uniquely patterned individual cats and compared spatially explicit capture–recapture (SECR) models to evaluate our hypothesis that cat density varies with topographic complexity. Key resultsThe dominant effect in all models was the significant negative relationship between cat detection probability and fine-scale topographic ruggedness. Two of the best three SECR models indicated lower cat densities and relative home-range sizes in the refuge than in the valley. In total, 17% of cats were detected in both habitat types. ConclusionsWe found some evidence that cat density and home-range size were mediated by habitat complexity. Further, the negative relationship between cat detection probability and topographic complexity suggests that cats spend less time foraging in CRR refuge habitat. ImplicationsCat management programs, aimed at reducing predation pressure on the CRR, must include the refuge and surrounding habitats to control cats that pose a threat to CRR subpopulations.

The Significance of Social Perceptions in Implementing Successful Feral Cat Management Strategies: A Global Review

Simple Summary

Feral cats pose a threat to many populations of small- to medium-sized animal species around the world, primarily through predation and disease. For this reason, feral cat management has become a priority in parts of the world where at-risk species are facing high threats of extinction. To implement a successful feral cat management program, there are specific technical and social requirements that need to be met. Most of the recent research conducted around feral cat management has examined the technical aspects, but there is considerably less research around the social aspects that may influence the success of feral cat management in inhabited areas. This review aims to identify and discuss feral cat management from a social perspective, and to highlight potential areas for future research that may aid in building successful campaigns in the future.

Abstract

This review examines the social aspects that influence feral cat management. In particular, it examines definitions and perceptions of feral cats as a species in different countries and across cultures. Using case studies from around the world, we investigate the factors that can influence public perceptions and social acceptance of feral cats and management methods. The review then highlights the importance of social factors in management and suggests the best approach to use in the future to ease the process of gaining a social license for management campaigns. Implications of the influence of education and awareness on public perception and acceptance are further explained, and are suggested to be an essential tool in successfully engaging the community about management in the future.

Modeling habituation of introduced predators to unrewarding bird odors for conservation of ground-nesting shorebirds

Foraging mammalian predators face a myriad of odors from potential prey. To be efficient, they must focus on rewarding odors while ignoring consistently unrewarding ones. This may be exploited as a nonlethal conservation tool if predators can be deceived into ignoring odors of vulnerable secondary prey. To explore critical design components and assess the potential gains to prey survival of this technique, we created an individual-based model that simulated the hunting behavior of three introduced mammalian predators on one of their secondary prey (a migratory shorebird) in the South Island of New Zealand. Within this model, we heuristically assessed the outcome of habituating the predators to human-deployed unrewarding bird odors before the bird's arrival at their breeding grounds, i.e., the predators were "primed." Using known home range sizes and probabilities of predators interacting with food lures, our model suggests that wide-ranging predators should encounter a relatively large number of odor points (between 10 and 115) during 27 d of priming when odor is deployed within high-resolution grids (100-150 m). Using this information, we then modeled the effect of different habituation curves (exponential and sigmoidal) on the probability of predators depredating shorebird nests. Our results show that important gains in nest survival can be achieved regardless of the shape of the habituation curve, but particularly if predators are fast olfactory learners (exponential curve), and even if some level of dishabituation occurs after prey become available. Predictions from our model can inform the amount and pattern in which olfactory stimuli need to be deployed in the field to optimize encounters by predators, and the relative gains that can be expected from reduced predation pressure on secondary prey under different scenarios of predator learning. Habituating predators to odors of threatened secondary prey may have particular efficacy as a conservation tool in areas where lethal predator control is not possible or ethical, or where even low predator densities can be detrimental to prey survival. Our approach is also relevant for determining interaction probabilities for devices other than odor points, such as bait stations and camera traps.

A critical review of habitat use by feral cats and key directions for future research and management

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 and unowned cats in the context of applicable 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 habitat use by cats 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.

Weighed down by science: do collar-mounted devices affect domestic cat behaviour and movement?

Context Animals carrying tracking and logging devices are subject to a range of instrument effects that negatively affect survival, reproduction and behaviour. The common recommendation is that device weight should not exceed 5% body mass (BM) for terrestrial species; however, this rule-of-thumb has little empirical basis. Modelling indicates that devices weighing less than 3% BM may still have impacts. Several studies have used telemetry and data loggers on domestic cats (Felis catus) with instruments ranging in weight from 30 g to 125 g, but there has been no quantitative evaluation of instrument effects. In addition, inexpensive GPS tags such as iGotU are increasingly being used to track domestic cats, but often with little acknowledgement of habitat-related location error. Aims We evaluated the impact of wearing devices of different weights on domestic cat movements, and quantified location error across typical suburban habitats. Methods We recorded movements of cats wearing three different GPS collar weights for a week at a time: light, 30 g (<1% BM); medium, 80 g (~2% BM); and heavy, 130 g (~3% BM). Location error (LE) and fix success rates (FSR) were compared between backyard habitats and up- or downward orientation of the GPS tags on collars. Key results Home-range size and distance travelled from home were smaller when cats wore the heaviest collar. LE was lower and FSR higher for GPS tags with direct-line-of-sight to satellites (e.g. on lawns), but there was no difference between tags placed in dense vegetation (hedges) or more open vegetation (trees), or tags oriented up or down. Conclusions Collars carrying instruments on cats should be no more than 2% BM (medium-weight collar). LE was large relative to typical urban habitat size, indicating that misclassification of locations into habitats could easily occur in habitat-selection studies. Implications Some published accounts of cat home-range sizes may be underestimates, resulting in underestimates of the extent of impacts on prey species. Habitat-use studies should acknowledge the error associated with GPS tags and incorporate it into analyses using techniques such as Brownian Bridges.

Seasonal and individual variation in selection by feral cats for areas with widespread primary prey and localised alternative prey

Context Seasonal and individual variation in predator selection for primary and alternative prey can affect predator–prey dynamics, which can further influence invasive-predator impacts on rare prey. Aims We evaluated individual and seasonal variation in resource selection by feral cats (Felis silvestris catus) for areas with European rabbits (Oryctolagus cuniculus) around a breeding colony of endangered black-fronted terns (Chlidonias albostriatus) in the Upper Ohau River, within the Mackenzie Basin of New Zealand. Methods Within a feral cat population subject to localised control (within a 1-km area surrounding the tern colony), we mapped the movements of 17 individuals using GPS collars, and evaluated individual and seasonal variation in third-order resource selection (i.e. within home ranges) by using resource-selection functions with mixed effects. The year was divided into breeding and non-breeding seasons for terns. Key results Three of the eight feral cats monitored during the breeding season used the colony in proportion to availability and one selected it. These four individuals therefore pose a threat to the tern colony despite ongoing predator control. Selection by feral cats for areas with high relative rabbit abundance was not ubiquitous year-round, despite previous research showing that rabbits are their primary prey in the Mackenzie Basin. Conclusions Results suggest that rabbit control around the colony should reduce use by feral cats that select areas with high relative rabbit abundance (less than half the individuals monitored), but is unlikely to alleviate the impacts of those that select areas with low relative rabbit abundance. Hence, predator control is also required to target these individuals. Results thus support the current coupled-control of feral cats and rabbits within a 1-km buffer surrounding the tern colony. Future research should determine what scale of coupled-control yields the greatest benefits to localised prey, such as the tern colony, and whether rabbits aid hyperpredation of terns by feral cats via landscape supplementation. Implications The present study has highlighted the importance of considering seasonal and individual effects in resource selection by predators, and the role of primary prey, when designing management programs to protect rare prey.