Estimating and indexing feral cat population abundances using camera traps

Context The ability to monitor changes in population abundance is critical to the success of pest animal management and research programs. Feral cats (Felis catus) are an important pest animal, but current monitoring techniques have limited sensitivity or are limited in use to particular circumstances or habitats. Recent advances in camera-trapping methods provide the potential to identify individual feral cats, and to use this information to estimate population abundances using capture–mark–recapture (CMR) methods. Aims Here, we use a manipulative study to test whether camera-trapping and CMR methods can be used to estimate feral cat abundances. Methods We established a grid of infrared cameras and lure stations over three pastoral properties on Kangaroo Island, Australia, for 15 days. We then reduced the population abundance with an intensive trapping program and repeated the camera survey. We estimated population abundances using robust design CMR models, and converted abundance estimates to densities using home-range data from GPS tracking. We also calculated relative abundance indices from the same data. Key results The CMR methods produced credible estimates of the change in population abundance, with useful confidence intervals, showing a statistically identifiable population decline from at least 0.7 cats km–2 before trapping down to 0.4 cats km–2 after trapping. The indexing method also showed a statistically identifiable decrease in abundance. Conclusions Camera-trapping and CMR methods can provide a useful method for monitoring changes in the absolute abundance of feral cat populations. Camera-trap data may also be used to produce indices of relative abundance when the assumptions of CMR models cannot be met. Implications These methods are widely applicable. The ability to reliably estimate feral cat abundances allows for more effective management than is generally available.

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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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Evaluation of risks for two native mammal species from feral cat baiting in monsoonal tropical northern Australia

Wildlife Research ◽

10.1071/wr17171 ◽

2018 ◽

Vol 45 (6) ◽

pp. 518 ◽

Cited By ~ 3

Author(s):

Jaime Heiniger ◽

Skye F. Cameron ◽

Graeme Gillespie

Keyword(s):

Rhodamine B ◽

Native Species ◽

Field Trials ◽

Camera Traps ◽

Northern Australia ◽

Target Species ◽

Mammal Species ◽

Feral Cat ◽

Feral Cats ◽

Dry Tropics

Context Feral cats are a significant threat to native wildlife and broad-scale control is required to reduce their impacts. Two toxic baits developed for feral cats, Curiosity® and Hisstory®, have been designed to reduce the risk of baiting to certain non-target species. These baits involve encapsulating the toxin within a hard-shelled delivery vehicle (HSDV) and placing it within a meat attractant. Native animals that chew their food more thoroughly are predicted to avoid poisoning by eating around the HSDV. This prediction has not been tested on wild native mammals in the monsoonal wet–dry tropics of the Northern Territory. Aim The aim of this research was to determine whether northern quolls (Dasyurus hallucatus) and northern brown bandicoots (Isoodon macrourus) would take feral cat baits and ingest the HSDV under natural conditions on Groote Eylandt. Methods We hand-deployed 120 non-toxic baits with a HSDV that contained a biomarker, Rhodamine B, which stains animal whiskers when ingested. The species responsible for bait removal was determined with camera traps, and HSDV ingestion was measured by evaluating Rhodamine B in whiskers removed from animals trapped after baiting. Key results During field trials, 95% of baits were removed within 5 days. Using camera-trap images, we identified the species responsible for taking baits on 65 occasions. All 65 confirmed takes were by native species, with northern quolls taking 42 baits and northern brown bandicoots taking 17. No quolls and only one bandicoot ingested the HSDV. Conclusion The use of the HSDV reduces the potential for quolls and bandicoots to ingest a toxin when they consume feral cat baits. However, high bait uptake by non-target species may reduce the efficacy of cat baiting in some areas. Implications The present study highlighted that in the monsoonal wet–dry tropics, encapsulated baits are likely to minimise poisoning risk to certain native species that would otherwise eat meat baits. However, further research may be required to evaluate risks to other non-target species. Given the threat to biodiversity from feral cats, we see it as critical to continue testing Hisstory® and Curiosity® in live-baiting trials in northern Australia.

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An evaluation of two methods of assessing feral cat and dingo abundance in central Australia

Wildlife Research ◽

10.1071/wr98067 ◽

2000 ◽

Vol 27 (2) ◽

pp. 143 ◽

Cited By ~ 49

Author(s):

G. P. Edwards ◽

N. D. de Preu ◽

B. J. Shakeshaft ◽

I. V. Crealy

Keyword(s):

Relative Abundance ◽

Population Change ◽

Feral Cat ◽

Feral Cats ◽

Central Australia ◽

Semi Arid ◽

Arid Rangeland

We evaluated the efficacy of spotlight surveys and passive track surveys conducted along roads for assessing the relative abundance of feral cats and dingoes in a semi-arid rangeland environment in central Australia. Track surveys were more time-efficient than spotlight surveys and offered higher precision. We cover a range of issues that need to be considered when using track-based surveys to assess population change. We also discuss the merits of other techniques used to monitor the abundance of mammalian carnivores.

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Applying home-range and landscape-use data to design effective feral-cat control programs

Wildlife Research ◽

10.1071/wr11097 ◽

2012 ◽

Vol 39 (3) ◽

pp. 258 ◽

Cited By ~ 24

Author(s):

Andrew J. Bengsen ◽

John A. Butler ◽

Pip Masters

Keyword(s):

Home Range ◽

Habitat Preferences ◽

South Australia ◽

Gps Tracking ◽

Feral Cat ◽

Feral Cats ◽

Small Areas ◽

Control Programs ◽

Spatial Coverage ◽

Landscape Use

Context Effective feral-cat (Felis silvestris catus) management requires a sound understanding of the ways cats use their environment. Key characteristics of landscape use by cats vary widely among different regions and different conditions. Aims The present study aimed to describe the most important characteristics of landscape use by feral cats on a large, human-populated island, and to use this information to guide the development of feral-cat management programs. Methods We used GPS tracking collars to record the movements of 13 feral cats at two sites on Kangaroo Island, South Australia, for between 20 and 106 days. We described home-range extents by using local convex hulls, and derived management suggestions from examination of home-range and movement data. Key results Median feral-cat home range was 5.11 km2, and this did not differ between sexes or sites. Cats at a fragmented pastoral site tended to favour woody vegetation over open paddocks, but habitat preferences were less clear at a bushland site. Cats that preferentially used treelines at the pastoral site were almost twice as likely to be recorded close to a tree-line junction as expected. Conclusions Control programs for feral cats on Kangaroo Island should deploy control devices at a density no less than 1.7 devices km–2. Spatial coverage should be as large as practicable or repeated frequently. Infrequent programs covering small areas can be expected only to provide short-term reductions in cat abundance. Implications The information gained from the present study will contribute to the development of strategic sustained management plans for feral cats on Kangaroo Island. The principles from which we inferred management guidelines are applicable to other regions and species.

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Does aerial baiting for controlling feral cats in a heterogeneous landscape confer benefits to a threatened native meso-predator?

PLoS ONE ◽

10.1371/journal.pone.0251304 ◽

2021 ◽

Vol 16 (5) ◽

pp. e0251304

Author(s):

Russell Palmer ◽

Hannah Anderson ◽

Brooke Richards ◽

Michael D. Craig ◽

Lesley Gibson

Keyword(s):

Native Species ◽

Activity Patterns ◽

Camera Traps ◽

Feral Cat ◽

Feral Cats ◽

Gps Collars ◽

Control Programs ◽

Treatment Site ◽

National Priority ◽

Positive Effect

Introduced mammalian predators can have devastating impacts on recipient ecosystems and disrupt native predator–prey relationships. Feral cats (Felis catus) have been implicated in the decline and extinction of many Australian native species and developing effective and affordable methods to control them is a national priority. While there has been considerable progress in the lethal control of feral cats, effective management at landscape scales has proved challenging. Justification of the allocation of resources to feral cat control programs requires demonstration of the conservation benefit baiting provides to native species susceptible to cat predation. Here, we examined the effectiveness of a landscape-scale Eradicat® baiting program to protect threatened northern quolls (Dasyurus hallucatus) from feral cat predation in a heterogeneous rocky landscape in the Pilbara region of Western Australia. We used camera traps and GPS collars fitted to feral cats to monitor changes in activity patterns of feral cats and northern quolls at a baited treatment site and unbaited reference site over four years. Feral cat populations appeared to be naturally sparse in our study area, and camera trap monitoring showed no significant effect of baiting on cat detections. However, mortality rates of collared feral cats ranged from 18–33% after baiting, indicating that the program was reducing cat numbers. Our study demonstrated that feral cat baiting had a positive effect on northern quoll populations, with evidence of range expansion at the treatment site. We suggest that the rugged rocky habitat preferred by northern quolls in the Pilbara buffered them to some extent from feral cat predation, and baiting was sufficient to demonstrate a positive effect in this relatively short-term project. A more strategic approach to feral cat management is likely to be required in the longer-term to maximise the efficacy of control programs and thereby improve the conservation outlook for susceptible threatened fauna.

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Two Methods of Monitoring Cats at a Landscape-Scale

Animals ◽

10.3390/ani11123562 ◽

2021 ◽

Vol 11 (12) ◽

pp. 3562

Author(s):

Cheryl A. Lohr ◽

Kristen Nilsson ◽

Ashleigh Johnson ◽

Neil Hamilton ◽

Mike Onus ◽

...

Keyword(s):

Protected Area ◽

Landscape Scale ◽

Camera Traps ◽

Feral Cat ◽

Feral Cats ◽

The Cost ◽

Track Counts

Feral cats are difficult to manage and harder to monitor. We analysed the cost and the efficacy of monitoring the pre- and post-bait abundance of feral cats via camera-traps or track counts using four years of data from the Matuwa Indigenous Protected Area. Additionally, we report on the recovery of the feral cat population and the efficacy of subsequent Eradicat® aerial baiting programs following 12 months of intensive feral cat control in 2019. Significantly fewer cats were captured in 2020 (n = 8) compared to 2019 (n = 126). Pre-baiting surveys for 2020 and 2021 suggested that the population of feral cats on Matuwa was very low, at 5.5 and 4.4 cats/100 km, respectively, which is well below our target threshold of 10 cats/100 km. Post-baiting surveys then recorded 3.6 and 3.0 cats/100 km, respectively, which still equates to a 35% and 32% reduction in cat activity. Track counts recorded significantly more feral cats than camera traps and were cheaper to implement. We recommend that at least two methods of monitoring cats be implemented to prevent erroneous conclusions.

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An Evaluation of Systematic Versus Strategically-Placed Camera Traps for Monitoring Feral Cats in New Zealand

Animals ◽

10.3390/ani9090687 ◽

2019 ◽

Vol 9 (9) ◽

pp. 687 ◽

Cited By ~ 2

Author(s):

Margaret Nichols ◽

James Ross ◽

Alistair S. Glen ◽

Adrian M. Paterson

Keyword(s):

New Zealand ◽

Model Selection ◽

Habitat Type ◽

Camera Traps ◽

Type Model ◽

Feral Cat ◽

Feral Cats ◽

Forest Margin ◽

Detection Probabilities ◽

Forest Habitats

We deploy camera traps to monitor feral cat (Felis catus) populations at two pastoral sites in Hawke’s Bay, North Island, New Zealand. At Site 1, cameras are deployed at pre-determined GPS points on a 500-m grid, and at Site 2, cameras are strategically deployed with a bias towards forest and forest margin habitat where possible. A portion of cameras are also deployed in open farmland habitat and mixed scrub. We then use the abundance-induced heterogeneity Royle–Nichols model to estimate mean animal abundance and detection probabilities for cameras in each habitat type. Model selection suggests that only cat abundance varies by habitat type. Mean cat abundance is highest at forest margin cameras for both deployment methods (3 cats [95% CI 1.9–4.5] Site 1, and 1.7 cats [95% CI 1.2–2.4] Site 2) but not substantially higher than in forest habitats (1.7 cats [95% CI 0.8–3.6] Site 1, and 1.5 cats [95% CI 1.1–2.0] Site 2). Model selection shows detection probabilities do not vary substantially by habitat (although they are also higher for cameras in forest margins and forest habitats) and are similar between sites (8.6% [95% CI 5.4–13.4] Site 1, and 8.3% [5.8–11.9] Site 2). Cat detections by camera traps are higher when placed in forests and forest margins; thus, strategic placement may be preferable when monitoring feral cats in a pastoral landscape.

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Feral cat abundance, density and activity in tropical island rainforests

Wildlife Research ◽

10.1071/wr19205 ◽

2020 ◽

Vol 47 (8) ◽

pp. 660

Author(s):

Tyrone H. Lavery ◽

Masaafi Alabai ◽

Piokera Holland ◽

Cornelius Qaqara ◽

Nelson Vatohi

Keyword(s):

Camera Traps ◽

Western Pacific ◽

Tropical Islands ◽

The South ◽

Mammal Species ◽

Bird Abundance ◽

Tropical Island ◽

Study Region ◽

Feral Cat ◽

Feral Cats

Abstract ContextIntroduced predators, especially cats, are a major cause of extinction globally. Accordingly, an extensive body of literature has focussed on the ecology and management of feral cats in continental and island systems alike. However, geographic and climatic gaps remain, with few studies focusing on rainforests or tropical islands of the south-western Pacific. AimsWe aimed to estimate cat densities and elucidate activity patterns of cats and sympatric birds and mammals in tropical island rainforests. We hypothesised that cat activity would be most influenced by the activity of introduced rodents and ground-dwelling birds that are predominant prey on islands. MethodsWe used camera traps to detect feral cats, pigs, rodents and birds on four tropical islands in the south-western Pacific. We used spatial capture–recapture models to estimate the abundance and density of feral cats. Relative abundance indices, and temporal overlaps in activity were calculated for feral cats, pigs, rodents, and birds. We used a generalised linear model to test for the influence of pig, rodent, and bird abundance on feral cat abundance. Key resultsThe species most commonly detected by our camera traps was feral cat, with estimated densities between 0.31 and 2.65 individuals km−2. Pigs and introduced rodents were the second- and third-most commonly detected fauna respectively. Cat activity was bimodal, with peaks in the hours before dawn and after dusk. Cat abundance varied with site and the abundance of rodents. ConclusionsFeral cats are abundant in the tropical rainforests of our study islands, where one bird and two mammal species are now presumed extinct. Introduced rodents possibly amplify the abundance and impacts of feral cats at our sites. Peak cat activity following dusk did not clearly overlap with other species detected by our camera traps. We postulate cats may be partly focussed on hunting frogs during this period. ImplicationsCats are likely to be a major threat to the highly endemic fauna of our study region. Management of feral cats will benefit from further consideration of introduced prey such as rodents, and their role in hyperpredation. Island archipelagos offer suitable opportunities to experimentally test predator–prey dynamics involving feral cats.

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On the right track: placement of camera traps on roads improves detection of predators and shows non-target impacts of feral cat baiting

Wildlife Research ◽

10.1071/wr19175 ◽

2020 ◽

Vol 47 (8) ◽

pp. 557 ◽

Cited By ~ 1

Author(s):

Michael L. Wysong ◽

Gwenllian D. Iacona ◽

Leonie E. Valentine ◽

Keith Morris ◽

Euan G. Ritchie

Keyword(s):

Survey Design ◽

Camera Traps ◽

Apex Predator ◽

Target Species ◽

Ecological Consequences ◽

Large Herbivores ◽

Feral Cat ◽

Feral Cats ◽

Detection Probabilities ◽

Poison Baiting

Abstract ContextTo understand the ecological consequences of predator management, reliable and accurate methods are needed to survey and detect predators and the species with which they interact. Recently, poison baits have been developed specifically for lethal and broad-scale control of feral cats in Australia. However, the potential non-target effects of these baits on other predators, including native apex predators (dingoes), and, in turn, cascading effects on lower trophic levels (large herbivores), are poorly understood. AimsWe examined the effect that variation in camera trapping-survey design has on detecting dingoes, feral cats and macropodids, and how different habitat types affect species occurrences. We then examined how a feral cat poison baiting event influences the occupancy of these sympatric species. MethodsWe deployed 80 remotely triggered camera traps over the 2410-km2 Matuwa Indigenous Protected Area, in the semiarid rangelands of Western Australia, and used single-season site-occupancy models to calculate detection probabilities and occupancy for our target species before and after baiting. Key resultsCameras placed on roads were ~60 times more likely to detect dingoes and feral cats than were off-road cameras, whereas audio lures designed to attract feral cats had only a slight positive effect on detection for all target species. Habitat was a significant factor affecting the occupancy of dingoes and macropodids, but not feral cats, with both species being positively associated with open woodlands. Poison baiting to control feral cats did not significantly reduce their occupancy but did so for dingoes, whereas macropodid occupancy increased following baiting and reduced dingo occupancy. ConclusionsCamera traps on roads greatly increase the detection probabilities for predators, whereas audio lures appear to add little or no value to increasing detection for any of the species we targeted. Poison baiting of an invasive mesopredator appeared to negatively affect a non-target, native apex predator, and, in turn, may have resulted in increased activity of large herbivores. ImplicationsManagement and monitoring of predators must pay careful attention to survey design, and lethal control of invasive mesopredators should be approached cautiously so as to avoid potential unintended negative ecological consequences (apex-predator suppression and herbivore release).

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Multiple Methods of Monitoring Cats at a Landscape-scale

10.20944/preprints202111.0258.v1 ◽

2021 ◽

Author(s):

Cheryl Lohr ◽

Kristen Nilsson ◽

Ashleigh Johnson ◽

Neil Hamilton ◽

Mike Onus ◽

...

Keyword(s):

Protected Area ◽

Landscape Scale ◽

Camera Traps ◽

Multiple Methods ◽

Feral Cat ◽

Feral Cats ◽

Cost Efficacy ◽

The Cost ◽

Track Counts

Feral cats are both difficult to manage and harder to monitor. We analysed the cost-efficacy of monitoring the pre- and post-bait abundance of feral cats via camera-traps or track counts using four years of data from the Matuwa Indigenous protected Area. Additionally, we report on the recovery of the feral cat population and the efficacy of subsequent Eradicat® aerial baiting programs following 12 months of intensive feral cat control in 2019 that consisted of aerial baiting and leg-hold trapping. Significantly fewer cats were captured in 2020 (n = 8) compared to 2019 (n = 126). Pre-baiting surveys for 2020 and 2021 suggested that the population of feral cats on Matuwa was very low, at 5.5 and 4.4 cats/100 km respectively, which is well below our target threshold of 10 cats/100 km. Post-baiting surveys then recorded 3.6 and 3.0 cats/100 km respectively, which still equates to a 35% and 32% reduction in cat activity. Track counts recorded significantly more feral cats than camera traps and were cheaper to implement. We recommend that at least two methods of monitoring cats be implemented to prevent erroneous conclusions.

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