Reducing rabbit habitat by ripping warrens has been the focus of our conservation work at Bon Bon Station Reserve over the past two months. Ripping warrens is one of a number of tools being used to reduce rabbit numbers across the reserve because rabbits continue to pose a key threat to the conservation values. Reducing their impact is a priority.
Feral rabbits are Australia’s most widespread and destructive environmental and agricultural vertebrate pest. They not only damage crops and increase grazing competition for livestock; they also damage native plants and directly compete with native wildlife for food and shelter. Their activity in the environment can also cause soil instability and erosion.
Bush Heritage Australia obtained funding through the South Australian Native Vegetation Council (NVC) Significant Environmental Benefit grant program to map and rip rabbit warrens to help reduce the feral rabbit population on Bon Bon.
Rabbit warren ripping is an effective tool in reducing the rabbit’s ability to survive in the environment. The Invasive Animal CRC (Cooperative Research Centre) says a strategic rabbit control program that features warren destruction is the most cost effective way to reduce rabbit populations and prevent on-going damage, particularly when applied over large, semi-arid areas.
The first stage of the NVC funded project was to identify active rabbit habitat by mapping warrens across several land systems. (I wrote about this in an earlier article – 'Where's Warren'). Once the warrens were mapped the next step was to determine where a large wheel loader with rippers could work through the country to destroy the warrens with minimal impact on cultural heritage and environmental values.
After using detailed maps to investigate the mapped warrens and to gain an understanding of where they occur in the environment; we consulted four senior Antakirinja Matu-Yankunytjatjara Aboriginal custodians led by Bill Lennon to assist our understanding of the cultural heritage values. We are now working as a team to complete the warren ripping work in the areas where it is appropriate to take the loader and rippers.
With GPS, electronic and hard copy maps we’ve been working our way through 30,000 hectares of the reserve and so far we’ve ripped about 900 active rabbit warrens.
We’ve found that working in the field with a team of three, we’ve been able to rip the targeted warrens efficiently, while ensuring protection of cultural heritage and environmental values. The large loader (hired from Paul and Louise Simpson) has been working in conjunction with senior Aboriginal custodian, Wayne Willis, who’s driving a support vehicle and providing guidance around cultural heritage clearance. A motorbike that can move faster and more efficiently through the environment, is scouting ahead to locate and check the mapped warrens.
Wayne Willis lived on Bon Bon along with his family when he was a young fella; his father worked on the station for many years, building and repairing fences and yards. Wayne says he's enjoyed working out on the reserve, “Just to be on Bon Bon, to come out here and look at all this country; it’s the most beautiful country and it’s been an honour just to be on Bon Bon helping Mike and Julia.”
We have been pleased to note that about 10% of the warrens that were mapped as active two years ago are now fully collapsed and providing habitat for other animals such as reptiles and native mice. When Lenny Willis and nephew Andy completed the mapping work they did an amazing job tracking down the warrens; as a result we are only finding a small percentage of additional active warrens that were not mapped in the first phase of the project. We were also excited to find a number of active wombat burrows in areas where they hadn’t been previously recorded by Bush Heritage.
At Bon Bon we’re using a number of tools in our strategy to reduce the impact of rabbits on the reserve. In areas where it’s not possible to use a large loader to rip warrens we will be using motorbikes with a support vehicle to fumigate the warrens. Other methods of control include trapping and shooting. In the future we’re also planning to experiment with our tractor with a single tyne ripper (a much smaller and lighter machine) to rip some rabbit warrens that can’t be accessed with the larger machine.
We have also been fortunate to have reduced rabbit numbers across the region due to the on-going effectiveness of the biocontrol, rabbit haemorrhagic virus (RHDV) also known as calicivirus. We’ve observed two outbreaks of the disease in the past three years and we’re hoping the new strain of calicivirus that will be released shortly (RHDV K5) will provide an additional biocontrol tool into the future.
Bush Heritage gratefully acknowledges the South Australian Native Vegetation Council and the Antakirinja Matu-Yankunytjatjara community for their support with this project.