The cat eradication and bilby recovery program at Astrebla Downs is an inspirational example of an effective management response to invasive species.
Astrebla Downs National Park (Astrebla Downs) was declared in 1996 to protect Queensland’s most significant population of the endangered greater bilby (Macrotis lagotis). In 2011, the bilby population at Astrebla Downs was estimated to be 700.
High rainfall on the Mitchell grass plains from 2009 to 2011 resulted in a plague of native long-haired rats (Rattus villosissimus), which provided an abundant food source and resulted in a feral cat population boom. In April 2012, a sudden influx of feral cats was reported at Astrebla Downs. Analysis of feral cat diets found that they were almost 100 per cent long-haired rat.
Queensland Parks and Wildlife Service rangers immediately implemented actions to control the cats, with some support from the Sporting Shooters Association of Australia.
In March 2013, the rat populations crashed, and cats were driven to switch to alternative food sources. Cats were observed hunting bilbies in April and May 2013, and analysis of the cats’ diets found that bilbies were a significant food source.
The primary control method was shooting, augmented by 1080 baiting. Approximately 3000 feral cats were shot from May 2012 to late 2015 (with an additional number eradicated by baiting). These controls, along with the depletion of virtually all food sources, led to a significant decline in cat numbers by June 2013.
Regular spotlighting has continued at Astrebla Downs since 2012. There was an 18-month period when diggings and scratchings were the only evidence of bilbies, and there was great concern for the survival of the species. Since May 2014, bilby activity and the number of bilby sightings have increased. Preliminary results of an aerial survey conducted in September 2015 indicate that the bilby population on Astrebla Downs is now around 1000 animals.
Queensland Parks and Wildlife rangers monitor cat numbers approximately every 6 weeks from April to September every year, and continue to implement control methods and investigation of cats’ diets.
Source: Marty McLaughlin, Principal Ranger Central Region, Queensland Parks and Wildlife Service