Summary of preliminary findings of the Kangaroo Island Feral Cat Eradication Program

Phase one of the Kangaroo Island Feral Cat Eradication Project is nearing completion and has included an evaluation of current and emerging feral cat control techniques while undertaking detailed studies into feral cat ecology on the Island.

The data obtained from this part of the program will be used to inform the feral cat eradication plan for the Dudley Peninsula.

The focus areas and major preliminary findings are detailed below.

Non-toxic baiting trials:

Camera trap non-toxic bait trials revealed a high rate of bait uptake from feral cats and low rate of uptake from non-target species. Uptake by feral cats was consistently very high when they encountered the baits and in two of the trials showed greater than 90% uptake.

Non-toxic Felixer Grooming trap trials

Non-toxic trials of the Felixer grooming trap revealed that the traps are successful at identifying feral cats as targets 72% of the time. Refinements of the traps software and algorithms during these initial trials has improved target specificity. 

Lure trials

Camera traps were used to assess the effectiveness of three potential cat lures. The trials revealed that olfactory (smell) lures are the most successful at attracting cats, followed closely by visual lures, with audio lures being the least successful method of attracting cats to a desired location. This information is critical for the eradication program which will now use the olfactory lure to guide targeted grooming trapping, cage trapping and leg hold trapping and in monitoring programs.

Cage trapping trials 

The effectiveness of cage trapping was evaluated through various field trials throughout the project. Camera trapping used in conjunction with cage trapping revealed that at best, only 41% of feral cats that encounter a trap enter it and at its lowest, only 16% of feral cats and trap encounters are successful.

Detection dog trials

A detector dog was trained and trialled during the project. During training the detector dog was able to locate its target in over 90% of the trials. The training of a local detection dog has been cost-effective, useful and embraced by the local community. It is anticipated that detection dogs will be a very useful eradication tool in a variety of habitats on the island.

Feral cat ecology studies

Throughout this project, the ecology of feral cats was studied in detail through a variety of means:

Radio telemetry:

Thirty-three feral cats were captured and fitted with a combination of GPS and VHF radio collars and then tracked. This information provided in-depth and up-to-date knowledge of feral cat ecology and home range data. Ten female and five male cats of various ages were studied through radio telemetry in the Dudley Peninsula Isthmus Management Zone.

The results of these studies revised the previous size of feral cat home ranges, contrasting with previous feral cat telemetry work which found the average home range of feral cats was 5.11 km² and that it didn’t differ between sexes. The current research revealed the average home range of male cats is 6.3 km² and 2.3 km² for female cats.

The radio telemetry data has also provided knowledge of feral cat habitat use, including the maternal dens sites of all the ten female GPS collared cats and information on diurnal shelter sites for all collared cats.

The methods used are appropriate to gather the key information on feral cat ecology required to guide the development of the Dudley Peninsula Eradication Plan.

Stomach content analysis:

The stomach contents of eighty-two feral cats were analysed to gain an insight into the impact of feral cats on native fauna. This data revealed feral cats are predominantly feeding on birds and small mammals across the island, while also preying on free range poultry.

Extensive camera trapping throughout the Dudley Peninsula Isthmus Management Zone has also provided insight into the impacts of feral cats on native fauna, with several feral cats photographed carrying freshly killed waterbirds, small mammals, small birds and even a wallaby.

Camera trapping:

A camera trapping array was established within the Dudley Peninsular Isthmus Management Zone consisting of 69 cameras at 23 sites. Data from the array was used to obtain a density estimate of 0.52 cats per km² in the study area, which is consistent with previous studies. The images from the cameras have been used to build a library of all identifiable feral cats within the area. This library was used to plot approximate home ranges of un-collared cats within the study area. The images also identified the impacts that feral cats are having on native animals, with several images capturing feral cats hunting and consuming native species.

Fauna monitoring

The project undertook extensive fauna surveys across the Dudley Peninsula and western Kangaroo Island on either side of the proposed feral cat barrier fence. The fauna surveys used a before-after-control-impact (BACI) design and will provide a benchmark from which to monitor the changes in feral cat prey abundance as the Dudley Peninsula feral cat eradication is undertaken.

The surveys were undertaken in spring and autumn to detect any seasonal variance. Seventy-seven fauna species, comprising 954 individuals, were caught in spring 2016 and 861 individuals were caught in autumn 2017.

The camera trapping array in the Dudley Peninsula Isthmus Management Zone detected 36 different fauna species. Cameras recorded 44 images of the EPBC Act listed Kangaroo Island short-beaked echidna and 63 records of the SA threatened species the Rosenberg’s goanna. Of particular significance was the detection of the EPBC Act listed southern brown bandicoot, which is believed to be in rapid decline across the island. This record is the first solid evidence of the species persistence on the Dudley Peninsula for several years.

 

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