Feral cats are a significant pest in all parts of Australia. They have helped kill off dozens of small mammal species, and are getting bigger and more numerous by the year. But some places are fighting back against the pussycat peril. One of the success stories comes from tiny Bruny Island, off the coast of Tasmania. By Jeremy Torr.

Tasmania, 4 August 2021. As early as 1773, ships cats were used to keep rats and mice numbers down on exploratory voyages sent to Tasmania. When the cats inevitably escaped onto land, they found a feline paradise. Small, tasty, unafraid wildlife was everywhere – and there were no predators to stop their kitty colonisation. Since then, estimates put the number of feral cats today at up to 6 million across Australia. They have contributed to the extinction of at least 22 Australian mammal species. And they continue to thrive and kill other animals, both directly and indirectly.

As well as killing and eliminating small mammals and birds, feral and stray cats can also spread diseases that impact livestock. “Toxoplasmosis (a disease partly spread by stray cats) can cause significant lamb losses during pregnancy,” says Dr. Bruce Jackson, a local vet. “A reduction in numbers of feral and stray cats on Bruny Island will mitigate this risk, and will bring benefits both for animal welfare and farming.”

Bruny Island, a 362 km2 sized lump of land off the south-east coast of Tasmania, was being severely impacted by cat impact on both fronts. Its population of the endangered Eastern Quoll, critically endangered Swift Parrots, Forty-spotted Pardalotes, Little Penguins and Short-tailed Shearwaters were all under threat.

But removing cats on a significant scale remains an ongoing challenge. As a result, islands like Bruny are increasingly being valued as potential safe havens for biodiversity. Island based cat management programs that work towards eradication can have lasting positive outcomes for wildlife in these landscapes say conservation mangers.

“We saw a lot of devastation in the island’s shearwater colonies, which was because of feral cats, and we wanted to see things change and to remove them from that area,” says Conrad Daniels, one of the island’s farmers and a participant in the cat reduction program.

Daniels has managed the cat-reduction programs control work since 2017 and says he has already seen the positive outcomes of large-scale feral cat control efforts. “We’re hoping to see a rapid decline in younger cats once this round of trapping starts as they’re easier to catch,” he adds.

Daniels is working with several other agencies including Tonia Cochran and her team at Inala, as well as researcher Cyril Scomparin from the University of Tasmania who is researching how indigenous carnivores such as the native eastern quoll and the introduced cat and black rat, interact. Local council Kingborough Council is looking at community engagement and the management of domestic and stray cats, and the local weetapoona Aboriginal Corporation is also bringing traditional expertise to the project.

The Bruny programme is now one year into a three year project which will be coordinated through NRM South (Natural Resource Management south). It is using multiple strategies to maintain cat control, from camera monitoring to cage trapping, shooting and luring. This multi-faceted approach is time-consuming, say the NRM team, but it ensures the project is getting a broad picture of the behaviours, success rate and demographics of Bruny Island’s feral and stray cat population.

“We are doing lure trials to see what will give us the best success for catching cats,” explains Daniels. “The quolls seem less likely to go for tuna, but if we bait with fried chicken or put the trap under a tree, we’re almost certain to get a brush-tailed possum.” Daniels says that trap placement is also important; if they put a trap anywhere near an ant trail, they will be more likely to get an echidna. “We’re mindful to be sensitive to other wildlife with our approach – as well as tourists and to the general population,” he adds.

The use of cameras is integral to the project, say the co-ordinators, as it helps to build a picture of the success rate of cage trapping or shooting. Whenever a cat is recorded on camera, they can be individually identified from their fur patterns, and the information added to a database. This is critical in helping track cat movements and population estimates.

The word is spreading in the community too. Over the last few years, domestic cat owners on Bruny have benefitted from technical advice, assistance with materials and construction of enclosures, as well as help to install enclosures, netting, cat doors and tunnels – to help keep cats from straying. Bruny looks like it is inching towards a feral-cat-free environment; Daniels is confident they will see a sharp decline in the feral and stray cay population on the island.

“After the first round (of trapping), there was a significant dent in the cat population,” he says. “We saw a definite change for the better in shearwater colonies.” Cat free soon? We can only hope so.