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Covering about 4350 km2, Kangaroo Island is the third-largest offshore island in Australia and lies 15 km off the South Australian coast. With nearly half of the native vegetation still remaining, Kangaroo Island is nationally important for biodiversity conservation, primary production and tourism. The island is free of foxes and rabbits, but has other feral pests including pigs, goats1, deer and cats.
Feral cats pose a direct threat to native fauna on Kangaroo Island, including endangered species such as the southern brown bandicoot and Kangaroo Island dunnart2. They also have an impact on the island’s primary producers, as carriers of parasitic diseases2,3,4. The cost to island sheep graziers is estimated between $2–4 million annually due to lost meat production from the muscle cyst-causing disease sarcocystosis5.
On Kangaroo Island there is strong community support for feral cat management, but efforts have been hampered by a lack of effective control tools and monitoring techniques. Feral cats tend to be difficult pests to control in the wild. They have a preference for live prey and a natural wariness that makes them difficult to bait and trap. In 2010, a year-long project examined a new type of control tool for feral cats known as the ‘cat spray tunnel’, which sprays toxin (see below). This project also collected information on the cat population that would be needed to effectively control feral cats in the future.
The project aimed to:
The project was a collaboration between the Kangaroo Island Natural Resources Management Board (KINRMB), Department of Environment and Natural Resources (South Australia) and the Invasive Animals Cooperative Research Centre (IA CRC). Feral cat prototype spray tunnels were provided by two companies: Connovation — New Zealand, and Ecological Horizons — South Australia.
Spray tunnel technology is an innovative and target-specific approach to feral cat control that exploits a cat’s automatic response to groom itself when sprayed with a foreign substance6. These devices use motion sensors to detect the presence of a feral cat and then deliver a toxin (eg PAPP) in gel form to the coat of the animal.
Kangaroo Island was a well-suited location to trial feral cat control strategies because:
Landscape use by feral cats was investigated by capturing and fitting 13 feral cats with VHF/GPS-tracking collars to record their movements over several months7. Only cats large enough to support a tracking collar (ie cats weighing at least 2.5 kg) were fitted. Collared feral cats were monitored at two sites on the Dudley Peninsula — one being a bushland habitat and the other located on sheep farming country.
A method to estimate feral cat abundance was tested using a manipulative experiment that combined remote camera-trapping techniques with capture-mark-recapture (CMR) models. Camera traps (36 in total) monitored fresh chicken lures in cages, across a 4 x 4 km sampling grid that covered several pastoral leases. The camera traps were operated for 15 days of sampling, researchers then removed feral cats by intensive trapping for 15 days, and then repeated the camera sampling protocol8.
A range of feral cat lures were trialled to identify the most effective means of attracting cats to bait stations or devices such as traps and tunnels. Feral cats were exposed to scent, sound and food-based lures in traps and on tracking boards, assessing (i) the capacity to draw feral cats to a site and (ii) the ability to entice them into a cage trap. The lures included ‘Rudducks catnip spray’ (Rudducks Pty Ltd, Dandenong Vic), ‘Cats me dead’ anal gland lure (Outfox pest control, Ivanhoe Vic), ‘Feralmone’ synthetic fermented egg (Pestat Pty Ltd, Canberra ACT), fresh chicken wing or drumstick, tinned sardines, water, and the auditory felid-attracting phonic (Westcare Electronics, WA). Feral cat visitations were detected by remote camera, plot tracks and/or trapping.
Two prototype versions of cat spray tunnel — ‘Cat Assassin’ tunnels (Ecological Horizons, Figure 1) and ‘Spitfire’ tunnels (Connovation, Figure 2) — were tested at farm and bushland sites on the island. Prototype Spitfire tunnels were trialled for 169 effective tunnel nights during winter and 168 tunnel nights in summer. Spitfire prototypes available for the study were not fitted with gel-dispensing mechanisms, but they were able to count the number of times that the sensors were triggered.
Prototype Cat Assassin tunnels were trialled during spring of 2010 for 136 tunnel nights and then 168 tunnel nights in summer. Cat Assassin tunnels were of two sizes: one with a large internal diameter (27 cm) and one of smaller diameter (20 cm). Cat Assassin tunnels were fitted with an overhead gel-dispensing mechanism.
To stop feral cats from investigating lures from the outside without entering the tunnels, one end was covered with vegetation or masonite board.
Tunnels were baited with fresh chicken wired to a mesh panel at one end, or chicken lure plus audio lure. Cat Assassin tunnels were also tested using only an auditory–visual lure consisting of a small plastic bird spinning above a chirping box (Prowler Bait and Digital Caller, Edge by Expedite, Hudson USA). Tunnels were monitored using remote cameras and were left in position for 6–8 days at a time.
It was found that feral cats spent most of their time in structurally complex vegetation such as bushland and woodland areas. GPS-tracking specifically showed that feral cats had average home ranges of about 5.1 km2, and traversed up to 32 different properties6. Camera-trapping and CMR modelling techniques were successful in monitoring changes in feral cat abundance. For example, intensive trapping was shown to reduce cat densities from 0.7 cats per km2 to 0.4 cats per km2 after control7.
No lure tested worked better for feral cats than the control (water), and none were more attractive to non-target animals than any other. Scent lures were also ineffective at attracting cats. Sites with auditory lures were more attractive (1.96 times) than those without, but trapping success was not significantly improved.
Together, the two prototype cat spray tunnels were approached by up to 10 vertebrate species during winter and spring trials, but feral cats tended to be the only animal to enter and activate tunnels. Summer trials had more non-target species investigations (goannas and birds) and very few feral cat visits. It was determined that cat control tools, such as traps or tunnels, should be spaced no farther than 800m apart to ensure that all cats in the area are exposed to control.
Feral cats appeared more likely to enter larger tunnel designs, which didn’t require the cat to crouch. The taller box shape of the Spitfire design maintained better cat shape and size for sensor recognition. Both prototype designs needed substantial work before they could achieve effective control. The best features of both designs have now been combined for further pen and field testing.
The two prototype feral cat spray tunnels trialled showed promise as novel cat control tools.
The tunnels were mostly target-specific to feral cats, and relatively easy to use over large areas. The design changes recommended from this study will shape the next generation of tunnels towards greater specificity and effectiveness against feral cat populations. Improved versions of the tunnels will be trialled soon in further pen and field tests.
This study will also help develop strategic programs for feral cat control for Kangaroo Island and other regions. Results on feral cat habitat use and estimating cat population abundance suggest that control action will need to be taken over large spatial scales or at frequent intervals to achieve useful population reductions. This highlights the importance of coordinated control activities across adjacent properties, and the need for a low-effort cat control technology.
Pestsmart Toolkit for Feral cats
Invasive Animals Ltd has taken care to validate the accuracy of the information at the date of publication [November 2013]. This information has been prepared with care but it is provided “as is”, without warranty of any kind, to the extent permitted by law.