Living with the enemy: a threatened prey species coexisting with feral cats on a fox-free island

Abstract ContextFeral domestic cats (Felis catus) have contributed to substantial loss of Australian wildlife, particularly small- and medium-sized terrestrial mammals. However, mitigating cat impacts remains challenging. Understanding the factors that facilitate coexistence between native prey and their alien predators could aid better pest management and conservation actions. AimsWe estimated feral cat density, examined the impact of habitat cover on long-nosed potoroos (Potorous tridactylus tridactylus), and assessed the spatial and temporal interactions between cats and potoroos in the ‘Bluegums’ area of French Island, south-eastern Australia. Materials and methodsWe operated 31 camera stations across Bluegums for 99 consecutive nights in each of winter 2018 and summer 2018/19. We used a spatially explicit capture–recapture model to estimate cat density, and two-species single-season occupancy models to assess spatial co-occurrence of cats and potoroos. We assessed the influence of vegetation cover and cat activity on potoroo activity by using a dynamic occupancy model. We also used image timestamps to describe and compare the temporal activities of the two species. Key resultsBluegums had a density of 0.77 cats per km2 across both seasons, although this is a conservative estimate because of the presence of unidentified cats. Cats and long-nosed potoroos were detected at 94% and 77% of camera stations, respectively. Long-nosed potoroo detectability was higher in denser vegetation and this pattern was stronger at sites with high cat activity. Cats and potoroos overlapped in their temporal activity, but their peak activity times differed. Conclusions Feral cat density at Bluegums, French Island, is higher than has been reported for mainland Australian sites, but generally lower than in other islands. Long-nosed potoroos were positively associated with cats, potentially indicating cats tracking potoroos as prey or other prey species that co-occur with potoroos. Temporal activity of each species differed, and potoroos sought more complex habitat, highlighting possible mechanisms potoroos may use to reduce their predation risk when co-occurring with cats. ImplicationsOur study highlighted how predator and prey spatial and temporal interactions, and habitat cover and complexity (ecological refuges), may influence the ability for native prey to coexist with invasive predators. We encourage more consideration and investigation of these factors, with the aim of facilitating more native species to persist with invasive predators or be reintroduced outside of predator-free sanctuaries, exclosures and island safe havens.

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Seasonal and spatial shifts in feral cat predation on native seabirds vs. non-native rats on Mikura Island, Japan

Mammal Research ◽

10.1007/s13364-020-00544-5 ◽

2020 ◽

Author(s):

Sarara Azumi ◽

Yuya Watari ◽

Nariko Oka ◽

Tadashi Miyashita

Keyword(s):

Native Species ◽

Control Strategies ◽

Interspecific Interactions ◽

Rattus Rattus ◽

Large Body ◽

Effective Control ◽

Alternative Prey ◽

Feral Cat ◽

Feral Cats ◽

Invasive Predators

Abstract Understanding how invasive predators impact native species is essential for the development of effective control strategies, especially in insular environments where alternative non-native prey species exist. We examined seasonal and spatial shifts in diet of feral cat Felis silvestris catus focusing on the predation on native streaked shearwaters, Calonectris leucomelas, and introduced rats, Rattus rattus and R. norvegicus, which are alternative prey to shearwaters, on Mikura Island, Japan. Streaked shearwaters breed at low elevations on the island from spring to autumn, whereas rats inhabit the island throughout the year, which makes them an alternative prey when native shearwaters are absent. Fecal analysis revealed that feral cats dramatically shifted their diets from introduced rats in winter to streaked shearwaters in seabird-season in low elevation areas of the island, while cats preyed on rats throughout the year at high altitudes on the island. This finding suggests that feral cats selectively prey on shearwaters. This is probably because of their large body size and less cautious behavior, and because introduced rats sustain the cat population when shearwaters are absent. The number of streaked shearwaters killed was estimated to be 313 individuals per cat per year, which represents an indication of top-down effects of feral cats on streaked shearwaters. Further studies on the demographic parameters and interspecific interactions of the three species are required to enable effective cat management for the conservation of streaked shearwaters on this island.

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Evidence of significantly higher island feral cat abundance compared with the adjacent mainland

Wildlife Research ◽

10.1071/wr18118 ◽

2019 ◽

Vol 46 (5) ◽

pp. 378 ◽

Cited By ~ 9

Author(s):

Patrick L. Taggart ◽

Bronwyn A. Fancourt ◽

Andrew J. Bengsen ◽

David E. Peacock ◽

Patrick Hodgens ◽

...

Keyword(s):

Relative Abundance ◽

Spatial Model ◽

Native Species ◽

Prey Species ◽

South Australia ◽

Camera Trap ◽

Feral Cat ◽

Feral Cats ◽

Continental Scale ◽

Scale Models

Context Feral cats (Felis catus) impact the health and welfare of wildlife, livestock and humans worldwide. They are particularly damaging where they have been introduced into island countries such as Australia and New Zealand, where native prey species evolved without feline predators. Kangaroo Island, in South Australia, is Australia’s third largest island and supports several threatened and endemic species. Cat densities on Kangaroo Island are thought to be greater than those on the adjacent South Australian mainland, based on one cat density estimate on the island that is higher than most estimates from the mainland. The prevalence of cat-borne disease in cats and sheep is also higher on Kangaroo Island than the mainland, suggesting higher cat densities. A recent continental-scale spatial model of cat density predicted that cat density on Kangaroo Island should be about double that of the adjacent mainland. However, although cats are believed to have severe impacts on some native species on the island, other species that are generally considered vulnerable to cat predation have relatively secure populations on the island compared with the mainland. Aims The present study aimed to compare feral cat abundance between Kangaroo Island and the adjacent South Australian mainland using simultaneous standardised methods. Based on previous findings, we predicted that the relative abundance of feral cats on Kangaroo Island would be approximately double that on the South Australian mainland. Methods Standardised camera trap surveys were used to simultaneously estimate the relative abundance of feral cats on Kangaroo Island and the adjacent South Australian mainland. Survey data were analysed using the Royle–Nichols abundance-induced heterogeneity model to estimate feral cat relative abundance at each site. Key results Cat abundance on the island was estimated to be over 10 times greater than that on the adjacent mainland. Conclusions Consistent with predictions, cat abundance on the island was greater than on the adjacent mainland. However, the magnitude of this difference was much greater than expected. Implications The findings show that the actual densities of cats at local sites can vary substantially from predictions generated by continental-scale models. The study also demonstrates the value of estimating abundance or density simultaneously across sites using standardised methods.

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Influence of fragmentation and disturbance on the potential impact of feral predators on native fauna in Australian forest ecosystems

Wildlife Research ◽

10.1071/wr9960387 ◽

1996 ◽

Vol 23 (4) ◽

pp. 387 ◽

Cited By ~ 79

Author(s):

S. A. May ◽

T. W. Norton

Keyword(s):

Forest Ecosystems ◽

Prey Species ◽

Prey Availability ◽

Current Knowledge ◽

Native Forest ◽

Feral Cat ◽

Predator Prey ◽

Small Prey ◽

Potential Impact ◽

The Impact

The current knowledge is reviewed of the diet and predator–prey relationships of the feral cat (Felis catus), fox (Vulpes vulpes) and dingo (Canis familiaris dingo) (including wild dogs). The effect of forest fragmentation by roads on the use of native forest ecosystems by these species and the significance of this for native fauna is considered. The cat, fox and dingo are significant predators in Australia that interact with native fauna in various ways, including predation, competition for resources, and transmission of disease. On the basis of current knowledge, it is clear that the nature and impact of predation by the cat, fox and dingo on native fauna are primarily determined by prey availability, although there are exceptions to this rule. Generally, dingoes prey upon large to medium-sized prey species (e.g. wallabies, common wombats, and possums), foxes prey upon medium-sized to small prey (e.g. possums and rats) and consume a significant component of scavenged material and vegetation, while cats also prey upon medium-sized to small prey, but may have a greater proportion of reptiles and birds in their diet. The cat is generally considered to be an opportunistic predator and to have contributed to the demise of a number of mammals. The fox is considered more of a threat to small native mammals and it has been asserted that all species of mammals that fall within the critical weight range (CWR) of 120–5000 g are at risk of local extinction when the fox is present. The severity of the impact of the dingo upon the native fauna is considered to be minimal, at least in comparison with the impact that the cat and fox can have on populations. The dingo is not considered a threat to CWR mammals in undisturbed environments. The fox, feral cat and dingo are all considered to have the ability to selectivity prey upon species and, to some extent, individual sexes and age-classes of a number of larger prey species. Although many of Australia's forested areas are relatively heavily fragmented by roads, there are no published studies specifically investigating the use of roads by feral predators. Information on the distribution and abundance of foxes, cats and dingoes in these ecosystems, their ecology and their impact on native fauna is particularly limited. Further, the extent to which roads influence the distribution and abundance of these species and the consequences of these for native fauna are poorly known. One of the most important research needs is to establish the relative impact that exotic predators may have on native fauna under varying degrees of road construction within native forests. For example, are areas with and without roads in forests used differently by exotic predators and what is the significance of this in terms of the potential impact on fauna? The extent to which feral predators forage away from roads needs further investigation, as does the rates of predation within edges, because this may have several consequences for the design, location and size of retained strips and wildlife corridors as well as restoration programmes. Further observations on regional differences influencing predator–prey interactions are required, as is research on the potential impacts on native fauna resulting from prey selection in forests subjected to various degrees of fragmentation and modification.

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Understanding Australia’s national feral cat control effort

Wildlife Research ◽

10.1071/wr19216 ◽

2020 ◽

Vol 47 (8) ◽

pp. 698

Author(s):

Georgia E. Garrard ◽

Alexander M. Kusmanoff ◽

Richard Faulkner ◽

Chathuri L. Samarasekara ◽

Ascelin Gordon ◽

...

Keyword(s):

Threatened Species ◽

Native Species ◽

Control Effort ◽

Data Repositories ◽

Feral Cat ◽

Feral Cats ◽

Mixed Methods Approach ◽

Qualitative Responses ◽

The Impact ◽

Combining Estimates

Abstract Context. Feral cats (Felis catus) pose a significant threat to Australia’s native species and feral cat control is, therefore, an important component of threatened species management and policy. Australia’s Threatened Species Strategy articulates defined targets for feral cat control. Yet, currently, little is known about who is engaged in feral cat control in Australia, what motivates them, and at what rate they are removing feral cats from the environment. Aims. We aim to document who is engaging in feral cat control in Australia, how many cats they remove and to estimate the number of feral cats killed in a single year. Furthermore, we seek to better understand attitudes towards feral cat control in Australia. Methods. We used a mixed methods approach combining quantitative and qualitative techniques. Feral cat control data were obtained from existing data repositories and via surveys targeting relevant organisations and individuals. A bounded national estimate of the number of feral cats killed was produced by combining estimates obtained from data repositories and surveys with modelled predictions for key audience segments. Attitudes towards feral cat control were assessed by exploring qualitative responses to relevant survey questions. Key results. We received information on feral cat control from three central repositories, 134 organisations and 2618 individuals, together removing more than 35000 feral cats per year. When including projections to national populations of key groups, the estimated number of feral cats removed from the environment in the 2017–2018 financial year was 316030 (95% CI: 297742–334318). Conclusions. Individuals and organisations make a significant, and largely unrecorded, contribution to feral cat control. Among individuals, there is a strong awareness of the impact of feral cats on Australia’s biodiversity. Opposition to feral cat control focussed largely on ethical concerns and doubts about its efficacy. Implications. There is significant interest in, and commitment to, feral cat control among some groups of Australian society, beyond the traditional conservation community. Yet more information is needed about control methods and their effectiveness to better understand how these efforts are linked to threatened species outcomes.

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The impact of bush-rock removal on an endangered snake species, Hoplocephalus bungaroides (Serpentes : Elapidae)

Wildlife Research ◽

10.1071/wr97022 ◽

1998 ◽

Vol 25 (3) ◽

pp. 285 ◽

Cited By ~ 60

Author(s):

Richard Shine ◽

Jonathan K. Webb ◽

Mark Fitzgerald ◽

Joanna Sumner

Keyword(s):

Path Analysis ◽

Survey Data ◽

Anthropogenic Disturbance ◽

Prey Species ◽

Habitat Degradation ◽

Population Densities ◽

Snake Species ◽

Eastern Australia ◽

The Impact ◽

Capture Rates

We examined the impact of habitat degradation (removal of surface rocks) on an endangered snake species (Hoplocephalus bungaroides, Elapidae) at 23 sites in south-eastern Australia, by quantifying the impact of rock removal on (i) the availability of suitable shelter-sites for the snakes and their major prey species (the velvet gecko, Oedura lesueurii), and (ii) the numbers of snakes and geckos. Our survey showed that both the snakes and the geckos prefer rocks lying on other rocks, rather than on soil, and select rocks of particular sizes. The rocks removed by bush-rock collectors overlap considerably in size (diameter and thickness) and substrate (rock on rock) with those used by broad-headed snakes and velvet geckos. Multivariate path analysis suggests that population densities of broad-headed snakes (as measured by capture rates) may be determined primarily by gecko numbers, which in turn depend upon availability of suitable rocks. In some sites, rock numbers were substantially reduced by anthropogenic disturbance. Thus, our survey data suggest that bush-rock removal has contributed to the endangerment of H. bungaroides.

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The impact of fox control on the relative abundance of forest mammals in East Gippsland, Victoria

Wildlife Research ◽

10.1071/wr08135 ◽

2009 ◽

Vol 36 (3) ◽

pp. 252 ◽

Cited By ~ 64

Author(s):

Nick Dexter ◽

Andy Murray

Keyword(s):

Relative Abundance ◽

Ecological Trap ◽

Red Foxes ◽

Significant Treatment ◽

Terrestrial Mammals ◽

Treatment Site ◽

Eastern Australia ◽

Significant Difference ◽

The Impact ◽

Fox Control

Predation by European red foxes is believed to be the major cause of the extinction and decline of a large number of native medium-sized terrestrial mammals in Australia. We examined the impact of poisoning of foxes on the relative abundance of a group of medium-sized mammals in an experiment conducted in three large forest blocks in south-eastern Australia. The blocks consisted of paired sites, as follows: one site where poison baiting was used to control foxes (treatment site) and one where foxes were not controlled (non-treatment site). At all six sites, the population responses of a range of mammals were measured, and compared between treatment and non-treatment sites. The relative fox abundance, as indexed by bait-take, declined during the course of the study at treatment sites and to a lesser extent at non-treatment sites. The decline in bait-take at non-treatment sites was most likely due to treatment sites acting as ecological traps, so that reduced intra-specific competition attracted foxes from non-treatment to treatment sites, where they were subsequently poisoned. There was a significant treatment effect for the abundances of total mammals, long-nosed potoroos, southern brown bandicoots and common brushtail possums, with higher abundances at treatment sites than at non-treatment sites. Common ringtail possums increased in abundance during the course of the study, with no significant difference between treatment and non-treatment sites. There was no significant effect of time or treatment on the abundance of long-nosed bandicoots. The increase in the abundance of native mammals at treatment sites was most likely due to a lower predation pressure by foxes brought about by fox control, and the smaller increase in abundance in non-treatment blocks was likely due to the ecological-trap effect because of fox baiting at treatment sites. The present study demonstrated that broad-scale fox control can lead to increases in the abundance of native mammals in forested habitats, without recourse to aerial baiting or fences. The study also demonstrated that the influence of fox control on the fox abundance can extend well beyond the perimeter of the area baited.

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

The Rangeland Journal ◽

10.1071/rj10052 ◽

2011 ◽

Vol 33 (1) ◽

pp. 79 ◽

Cited By ~ 19

Author(s):

L. A. Brook ◽

A. S. Kutt

Keyword(s):

Canis Lupus ◽

Native Species ◽

Bos Taurus ◽

Local Population ◽

European Hare ◽

Feral Cat ◽

Critical Weight ◽

Conservation Implications ◽

Eastern Australia ◽

North Eastern

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.

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Management of invasive mesopredators in the Flinders Ranges, South Australia: effectiveness and implications

Wildlife Research ◽

10.1071/wr19237 ◽

2020 ◽

Vol 47 (8) ◽

pp. 720

Author(s):

Alyson M. Stobo-Wilson ◽

Robert Brandle ◽

Christopher N. Johnson ◽

Menna E. Jones

Keyword(s):

Prey Species ◽

South Australia ◽

Short Time Period ◽

Short Term ◽

Feral Cat ◽

Feral Cats ◽

Flinders Ranges ◽

Time Period ◽

Short Time ◽

The Impact

Abstract ContextSignificant resources have been devoted to the control of introduced mesopredators in Australia. However, the control or removal of one pest species, such as, for example, the red fox (Vulpes vulpes), may inadvertently benefit other invasive species, namely feral cats (Felis catus) and rabbits (Oryctolagus cuniculus), potentially jeopardising native-species recovery. AimsTo (1) investigate the impact of a large-scale, long-term fox-baiting program on the abundance of foxes, feral cats and introduced and native prey species in the Flinders Ranges, South Australia, and (2) determine the effectiveness of a short time period of cat removal in immediately reducing feral cat abundance where foxes are absent. MethodsWe conducted an initial camera-trap survey in fox-baited and unbaited sites in the Flinders Ranges, to quantify the impact of fox baiting on the relative abundance of foxes, feral cats and their prey. We then conducted a secondary survey in sites where foxes were absent, following an intensive, but short, time period of cat removal, in which 40 cats were shot and killed. Key resultsNo foxes were detected within baited sites, but were frequently detected in unbaited sites. We found a corresponding and significant increase in several native prey species in fox-baited sites where foxes were absent. Feral cats and rabbits were also more frequently detected within baited sites, but fox baiting did not singularly predict the abundance of either species. Rather, feral cats were less abundant in open habitat where foxes were present (unbaited), and rabbits were more abundant within one predominantly open-habitat site, where foxes were absent (fox-baited). We found no effect of short-term cat removal in reducing the local abundance of feral cats. In both camera-trap surveys, feral cat detections were positively associated with rabbits. ConclusionsLong-term fox baiting was effective in fox removal and was associated with a greater abundance of native and introduced prey species in the Flinders Ranges. To continue to recover and conserve regional biodiversity, effective cat control is required. ImplicationsOur study showed fox removal has likely resulted in the local release of rabbits and an associated increase in cats. Because feral cat abundance seemingly fluctuated with rabbits, we suggest rabbit control may provide an alternative and more effective means to reduce local feral cat populations than short-term removal programs.

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Prevalence of threatened native species in canid scats from coastal and near-coastal landscapes in south-eastern Australia

Australian Mammalogy ◽

10.1071/am09038 ◽

2010 ◽

Vol 32 (2) ◽

pp. 117 ◽

Cited By ~ 12

Author(s):

Andrew W. Claridge ◽

Douglas J. Mills ◽

Simon C. Barry

Keyword(s):

Native Species ◽

Mammal Species ◽

Study Region ◽

Terrestrial Mammals ◽

South Eastern ◽

Eastern Australia ◽

Coastal Landscapes ◽

Wild Dog ◽

Wild Dogs ◽

Prey Items

Predator scat analysis was used to infer the potential impact of wild dogs (Canis lupus dingo, C. l. familiaris and hybrids of the two) on threatened native terrestrial mammals in coastal and near-coastal southern New South Wales, Australia. Prey items recorded in wild dog scats were compared with those occurring in scats of the red fox collected at the same study sites. Six threatened mammal species were recorded in either wild dog or fox scats: eastern pygmy possum, grey-headed flying fox, long-nosed potoroo, southern brown bandicoot, white-footed dunnart and yellow-bellied glider. The prevalence of these threatened species in fox scats was significantly higher than in wild dog scats. Otherwise, wild dogs mostly consumed larger prey items such as swamp wallabies and wombats whereas foxes more heavily preyed on small mammals such as antechinus and rats. Our results suggest that foxes are the major threat to threatened mammal species in the study region. Land management agencies in south-eastern mainland Australia should therefore focus on controlling foxes for biodiversity gain.

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The Impact of Ultraviolet Radiation on Barrier Function in Human Skin: Molecular Mechanisms and Topical Therapeutics

Current Medicinal Chemistry ◽

10.2174/0929867324666171106164916 ◽

2019 ◽

Vol 25 (40) ◽

pp. 5503-5511 ◽

Cited By ~ 5

Author(s):

Abdulaziz Alhasaniah ◽

Michael J. Sherratt ◽

Catherine A. O'Neill

Keyword(s):

Ultraviolet Radiation ◽

Barrier Function ◽

Molecular Mechanisms ◽

Transepidermal Water Loss ◽

Protective Effects ◽

Barrier Dysfunction ◽

Epidermal Barrier ◽

Positive Effects ◽

Terrestrial Mammals ◽

The Impact

A competent epidermal barrier is crucial for terrestrial mammals. This barrier must keep in water and prevent entry of noxious stimuli. Most importantly, the epidermis must also be a barrier to ultraviolet radiation (UVR) from the sunlight. Currently, the effects of ultraviolet radiation on epidermal barrier function are poorly understood. However, studies in mice and more limited work in humans suggest that the epidermal barrier becomes more permeable, as measured by increased transepidermal water loss, in response UVR, at doses sufficiently high to induce erythema. The mechanisms may include disturbance in the organisation of lipids in the stratum corneum (the outermost layer of the epidermis) and reduction in tight junction function in the granular layer (the first living layer of the skin). By contrast, suberythemal doses of UVR appear to have positive effects on epidermal barrier function. Topical sunscreens have direct and indirect protective effects on the barrier through their ability to block UV and also due to their moisturising or occlusive effects, which trap water in the skin, respectively. Some topical agents such as specific botanical extracts have been shown to prevent the loss of water associated with high doses of UVR. In this review, we discuss the current literature and suggest that the biology of UVR-induced barrier dysfunction, and the use of topical products to protect the barrier, are areas worthy of further investigation.

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