Dirk Hartog Island National Park: Return to 1616

Intensive and systematic eradication and monitoring programs began in 2012 and were completed in October 2018.

Removing Goats

Major destocking efforts began on the island in 2007 when the pastoral leaseholders removed about 4000 sheep by barge. Along with destruction of about 2000 goats during the previous two years, this was in preparation for the change in tenure from pastoral lease to national park. Teams of Parks and Wildlife Service staff then culled the remaining sheep and most of the goats between 2008 and 2013.

Radio collars were fitted to fifteen female goats in order to track their whereabouts on the island. Female goats spend time with other females and attract the more solitary males. The radio collars were used to find the goats and their mobs during monitoring and culling operations.

By November 2017 at total of 5185 sheep and 11,133 goats had been removed from Dirk Hartog Island, with the last of the goats being the most challenging to remove. The final seven goats, all of them female radio collared goats, were removed in November 2017.

Dirk Hartog Island is the largest island in the world from which goats have been eradicated.

Removing feral cats

The feral cat eradication team started work by trapping feral cats, fitting them with satellite collars and tracking their movements. The information gathered helped determine that 1080 poison baiting would be effective on the island.

In 2014 the feral cat team constructed 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 main track.

After baiting, the southern area was intensively monitored from May 2014 until July 2015. Four types of traps were used: automated camera traps, sand pads, soft leghold traps and cage traps. All traps used scent lures to attract feral cats as food lures are more likely to attract other animal species.

Checks south of the fence were done using detector dogs during the winters of 2015 and 2016. Monitoring for feral cats north of the fence began in 2015 and detector dogs checked the northern part of the island in winter 2017. This was followed by two years of systematic 20 day searches covering the whole island four times a year.

The last feral cat detected south of the fence was in August 2015, and the last in the north was in October 2016.

All of this effort has led to the confident declaration in October 2018 that feral cats have been eradicated from Dirk Hartog Island.

Since 2007 the Parks and Wildlife Service has monitored changes to vegetation on Dirk Hartog Island. During this time sheep and goats have been removed, eliminating the only large herbivores on the island.

The vegetation monitoring program uses satellite images along with extensive ground validation to build a picture of how vegetation cover on the island is changing.

Changes were first detected and investigated using satellite imagery. Hundreds of images collected at near monthly intervals since 1988 were analysed to identify where vegetation cover had increased since destocking began in 2008. These areas were then validated on the ground to determine whether the increased ground cover was native vegetation or invasive weeds. Many of the areas shown by satellite imagery to have increased vegetation cover were found to be native species.

Significant vegetation cover change for years 2011, 2013, 2015 and 2018 based on the 1988 to 2008 baseline.

Changes in the extent of sand dunes reflect changes in vegetation cover with reductions in dune cover indicating increases in vegetation cover. The following graph shows sand dune extent changes across Dirk Hartog Island from 1957 to 2018.

Changes in dune cover

Annual field checking continues with a team of Parks and Wildlife staff, including experts in botany and satellite imagery analysis.

Download this poster to find out more about the vegetation monitoring program.