More than 6,000 pigs have been culled in Kakadu National Park in the first aerial shooting operation since a helicopter accident in 2019 that seriously injured two park rangers.
The large numbers of feral pigs, cattle, horses and buffalo in Kakadu sit alongside weeds and fire as its biggest threats.
"Feral animals such as pigs and buffalo do significant damage to wetlands by turning up the ground – damaging habitat for native species such as magpie geese – and spreading weeds throughout the park," park manager Shaun Barclay said.
For the past three years the most effective method of feral control for the park – shooting the animals from helicopters – has not been used.
The park's management stopped aerial culling after a 2019 helicopter accident during a feral control operation.
An Australian Transport Safety Bureau report concluded the activity did not cause the accident, but found a number of issues with Parks Australia's safety procedures.
After an adjustment to the safety protocols, aerial culling resumed in the northern section of the park in May.
"There are certainly a lot of pigs out there," Mr Barclay said.
"They are doing a lot of damage to wetlands, cultural sites and [the culling] is reducing the risk of Japanese encephalitis, which was recently detected in feral pigs in the Northern Territory.
Fear of population boom
In 2018 the Department of Environment estimated there were more than 12,000 feral pigs in the park.
With no aerial culling for the last three years, pig numbers are likely to have increased significantly.
Mr Barclay said he had noticed the impact of the growth in feral numbers over the past three years, "particularly around the waterways where pigs and buffalo have caused a lot of damage".
"We have also seen increased interactions with members of the public and feral animals that have led to some isolated site closures, so we are definitely keen to get numbers back down for safety reasons as well as the environmental damage they cause," he said.
Surveys are being conducted to get an accurate picture of the number of feral animals in Kakadu.
"Once we have that data we'll analyse it, consult with traditional owners to bring together a plan to reduce numbers to a manageable level," Mr Barclay said.
Conservation 'paramount'
Research by Charles Sturt University has found that feral cattle, horses and buffalo – known as ungulates – cause significant damage to waterholes in northern Australia.
PhD candidate Helenna Mihailou completed her honours and PhD research at Limmen National Park, near the Gulf of Carpentaria, which involved fencing 10 waterholes to exclude feral cattle and buffalo.
"I found that there was significantly more bare ground around the edge of waterholes accessible to ungulates," she said.
"Bird diversity was significantly lower as the dry season progressed at waterholes accessible to ungulates, compared to fenced waterholes.
"Overall, this research indicates that even at low densities feral ungulates have significant negative impacts on native flora and fauna communities around savanna waterholes in northern Australia."
Ms Mihailou said the complexities of the ownership of feral cattle made it difficult to control them.
"While ungulates such as horses and cattle may inspire empathy due to their familiarity and magnificence, the conservation of irreplaceable native Australian fauna and their habitats should be paramount, whether that be in NSW, in the NT, or elsewhere," she said.
