Return to 1616
|The western barred bandicoot is one of the animals that will be returned to Dirk Hartog Island
Return to 1616 is a project that aims to restore the vegetation and habitats of Dirk Hartog Island National Park to how Dirk Hartog would have seen them in 1616.
The island has experienced significant changes since Dirk Hartog landed there on 25 October 1616. Sheep and goats changed the vegetation, their grazing habits and trampling reducing the food and shelter available for native species. Efficient new predators, feral cats, added to the pressures on native species, making it impossible for some to survive.
Ten species of small mammals and marsupials did not survive the changes to the island’s ecology - the western barred bandicoot, chuditch, mulgara, dibbler, greater stick-nest rat, desert mouse, Shark Bay mouse, heath mouse, woylie and boodie. Find out more about some of these animals here.
But Return to 1616 brings hope. With the sheep believed removed and most of the goats now gone, habitats are returning to how they would have appeared to Dirk Hartog in 1616. A cat eradication program is also underway to restore the natural balance of predators to how it was in 1616. When the cats are gone, ten animals that couldn’t survive the changes brought by introduced species since 1616 will be returned.
Two extra marsupials will join the reintroduced species. No evidence has yet been found of the rufous hare-wallaby and banded hare-wallaby previously occupying Dirk Hartog Island but, since they have become extinct on the mainland and now only occur on other nearby islands, Dirk Hartog Island will increase their chance of survival.
|To help maintain successful shoots, Judas collars have been fitted to female goats
Plants and habitats must be restored before small mammals can be returned to Dirk Hartog Island National Park. To do this introduced herbivores, goats and sheep, must be removed.
Major destocking efforts began on the island in 2007 when the pastoral leaseholders removed about 4,000 sheep and 750 goats from the island by barge. This was in preparation for the change in tenure from pastoral lease to national park. Teams of Parks and Wildlife staff then culled the remaining sheep and most of the goats between 2008 and 2013.
To maintain successful shoots as numbers decrease, Parks and Wildlife staff fitted Judas collars to goats. Goats wearing these radio collars can always be tracked during the collars’ four year battery life.
By collaring only females, the goat eradication team makes the most of the female goats’ social nature. Female goats spend time with other females and attract males. The males are more solitary. The Judas collars are used to find the goats during monitoring and culling operations. Goats with Judas collars are not shot during these operations as they must live to gather and betray another mob.
Although it is estimated that less than 100 goats remain on the island in 2014, the goat eradication team cannot afford to become complacent. Goats have two breeding seasons each year. In each season a goat can produce two or three young so the population will quickly explode if there is a lessening of effort before all goats are eradicated.
While over 10,000 goats and 5,000 sheep have been removed from Dirk Hartog Island since 2007, the last of the goats will be the most challenging to remove. In 2014 the eradication team are incorporating new methods into their operations and are systematically surveying the entire island twice a year.
When this project is complete, Dirk Hartog Island will be the largest island in the world from which goats have been eradicated.
|Cats have a devastating impact on native animals.
Removing feral cats
Cats are efficient predators that have devastating impacts on native animal populations. The ten species of small mammals planned for reintroduction cannot be brought onto Dirk Hartog Island National Park while cats remain.
The cat eradication team started work by radio collaring cats, tracking their movements and researching the effectiveness of baiting, the main control technique.
In 2014 the team set up temporary camps and a network of sand pads and camera traps for monitoring cats before and after baiting on the southern part of the island. This is important for making sure all cats have been eliminated. They are also constructing a fence to divide the island into two sections to make monitoring more efficient and effective.
Located at the northern end of Herald Bay and extending nearly 13 km to the west coast, the 1.8 metre high fence is made of rabbit netting with an overhang at the top and three electric wires. A gate allows vehicles to continue travelling north-south along the existing track.
The first baiting operation in May 2014 covered the whole of Dirk Hartog Island National Park, with monitoring south of the cat-proof fence to find and remove any surviving cats. The next baiting and monitoring operations will be done north of the fence in 2015.
Once each section is deemed cat-free, success will be verified by an independent team with detector dogs. The dogs will be trained to react only to cats. They will be muzzled and will follow scents to cats, stopping and pointing if they find one. This will be followed by two years of surveill ance in both sections of the island for any sign of cat presence. If there is no evidence of cats following the checks with dogs, and after two years of surveillance, the island will be declared free of cats and safe for the return of native mammals.
| This map shows the location of the cat-proof fence dividing the island and the network of monitoring sites and tracks.
Invasive weeds threaten natural ecosystems by displacing native species. When weeds displace native plants, animals are left without their natural homes and food. Consequently managing weeds is an important part of land management and ecological restoration.
High risk species are those that are most likely to adversely affect an area so priority is given to managing high risk species. The Dirk Hartog Island Weed Management Plan recommends management of the following weed species on Dirk Hartog Island:
The ‘high risk alert species’ listed below have been recorded in Shark Bay but are not currently known on Dirk Hartog Island. It is important that any sightings of these species on the island are reported so they can be checked and dealt with promptly.
Visitors coming from an area where any of these weeds are prevalent should thoroughly inspect their vehicles prior to going onto the island.
Keeping Dirk Hartog Island free of pests
Keeping exotic plants and animals off Dirk Hartog Island is crucial to the success of the Return to 1616 project. All visitors to Dirk Hartog Island are encouraged to follow the example of Parks & Wildlife in making sure their vehicles, trailers, boats and equipment are clean and free from soil, weeds and animals. See Island protection for more about how you can help keep the island free of pests.
Gorgon Barrow Island Net Conservation Benefits program
The Dirk Hartog Island Ecological Restoration Project is mostly funded through the Gorgon Barrow Island Net Conservation Benefits (NCB) program with additional funding from the Department of Parks and Wildlife. The NCB program aims to deliver long term conservation benefits to places in Western Australia with similar values to Barrow Island. The Department of Parks and Wildlife received $11.5 million to deliver the first stage of the Return to 1616 project over seven years to June 2018.
A pilot study for the proposed eradication of feral cats on Dirk Hartog Island, Western Australia. Algar et al.
A bait efficacy trial for the management of feral cats on Dirk Hartog Island. Johnston et al.
Field efficacy of the Curiosity feral cat bait on three Australian islands. Johnston et al.
Population Structure and Management of Invasive Cats on an Australian Island. Koch et al.
Interim report A survey for black rats (Rattus rattus) in the Shark Bay communities of Denham, Monkey Mia and Useless Loop. Palmer, R & Morris, K.
Program to restore historic WA Island (Northern Guardian)
Turning back the clock on feral island (Australian)
Clock turned back 400 years on Dirk Hartog Island (Ministerial media statement)