Feral pigs are known for breeding like rabbits, damaging crops and being notoriously difficult to control - and they will stop at nothing to score a free meal from farmers.
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More than 2500 feral pigs were culled in 42 hours across the northern agricultural zone last month, as part of an annual aerial shoot program led by the Northern Biosecurity Group (NBG) and Department of Primary Industries and Regional Development (DPIRD).
Since the program started in 2018, the destructive pest has continued to wreak havoc in the Northampton, Chapman Valley and Greenough areas - eating and trampling grain and legume crops, and leaving some farmers tens of thousands of dollars out of pocket.
"They aren't fussy - they will take whatever they can get," said Bowes mixed farmer Ben McCartney.
"They love anything that is cropped and will strip the heads off wheat, eat the pods and seed heads of lupins, and knee-high canola once it starts to flower."
Despite containment efforts, including trapping, baiting and aerial shooting, numbers have continued to rise steadily in the northern agricultural region.
For farmers like Mr McCartney, controlling feral pigs has become another job to add to the list.
Situated about 25 kilometres north of Geraldton, Mr McCartney runs an 80:20 mixed cropping and sheep operation, with 1450 hectares of wheat, canola and lupins and 600 Merino ewes.
He purchased the coastal blocks in the Bowes-Howatharra areas about five years ago, and feral pigs have been a problem ever since.
Resting by water and in bushland during the day, the pest usually strikes over a few nights - and by the time farmers realise it is too late.
As well as eating crops, they uproot mature plants, disrupt seedlings and facilitate weed establishment, ploughing through the soil.
From 2022-23, Mr McCartney removed more than 300 feral pigs from his property, with damages in that time reaching $30,000.
Already this year-to-date, numbers have reached similar levels to those culled annually in previous years.
Mr McCartney's main problem area is on the north western side of his property where there is thick bushland.
"They rest during the day and come out at night when you aren't even aware of it," he said.
"They could take out 20-30ha of wheat in a hit, but initially it just looks like a mob of sheep have been in the paddock."
Mr McCartney started using his own control measures, to coincide with NBG and DPIRD's aerial shoot, which has proven effective.
The aim is to remove as many feral pigs out of the system before August-October, when crops have built up and the pest can do the most damage.
As part of this and about three years ago, Mr McCartney invested several thousands of dollars in his own Matlock trapping system and is now able to trap all year round.
While it was costly, the system paid for itself within the first couple of weeks of trapping, when compared to what would normally have been destroyed.
The Matlock trap has a remotely operated door and is supported by a surveillance camera connected to the mobile network.
It allows landholders to monitor feral pig numbers in and around the trap via remote real-time video link.
Mr McCartney keeps an eye out for tracks or activity in paddocks, before throwing out grain as bait and putting out a surveillance camera.
By using the camera he is able to watch what feral pigs are coming through the area and in what numbers.
"We continue feeding them over a couple of weeks until they are comfortable and we have big enough numbers - then we set the trap off," he said.
"The most we have caught in the Matlock trap at any one time is about 60 feral pigs.
"It all depends on how big, small and smart they are, and if they have been in a trap situation before.
"If a feral pig has been outside a trap when the gate has closed it is usually pretty onto it."
Not relying on just one control method, Mr McCartney also does a small amount of baiting, with 1080, later on in the season and closer to harvest.
He said best results were achieved by using a combination of trapping, baiting and aerial shooting, and also when landholders, biosecurity groups and government departments worked together.
"You can't just rely on a chopper being used once a year to fix the problem," Mr McCartney said.
"Controlling feral pigs is part of farming here, we have to do it and we have to keep at it because they breed so quickly."
By staying on top of the problem as best he can, Mr McCartney has reduced crop damage by about 15ha.
He has also noticed the size of pigs entering his property has decreased, reporting a large number of younger and smaller pigs compared to older and bigger bores.
Over the past six years, the NBG has worked with landholders in northern WA to reduce the abundance of feral pigs and their impacts on agricultural, biodiversity and social assets.
In that time, a total of 13,012 feral pigs have been shot across three control blocks, Northampton, Chapman Valley and Greenough, in 280 hours of flying.
The first aerial shoot included seven properties in the Hutt River area, within Northampton.
NBG co-ordinator Marieke Jansen said it was initially held as a trial, however the success of the program saw the shoot area expand and the duration increase.
"Over two days we shot 512 pigs," Ms Jansen said.
"We realised we could shoot all day and in some areas twice a day because of the number of pigs that were in those areas."
In 2019, the aerial shoot was conducted over three days and resulted in a total of 1067 pigs being shot.
From 2020, properties in the Chapman Valley and Greenough were included and numbers doubled from 1141 head in 2021 to 2282 head in 2022.
The combined total numbers for all three areas has continued to steadily rise since 2022 and this year peaked at 2777 head.
This equates to 1.1 pigs shot per minute and is up on the 2598 head accounted for the year prior.
Ms Jansen said it was disappointing that numbers had increased over the past 12 months, but believed that - unlike previous bumper seasons - the dry period provided a good opportunity to locate feral pigs in known areas.
According to a 2018-24 aerial shooting program review, conducted by DPIRD, the abundance and rate of feral pig production is likely to vary over time based on food availability - in cropping regions this is likely to depend on rainfall.
The review showed that during the first four years (2018-21) of the program rainfall in the previous 12 months was below average.
However in 2021-22, the region recorded above average rainfall, which resulted in exceptionally productive conditions.
"It is highly likely the wet conditions over the 2021 and 2022 growing seasons contributed to the high catch per unit effort (a proxy for density) of feral pigs in the 2022 and 2023 aerial shoots," the DPIRD review stated.
"While the 2023 rainfall was well below average, feral pig density remained high, likely a delayed effect of the previous two years of optimal conditions."
As well as aerial control, the NBG uses netting, trap door and Matlock system trapping methods, and 1080 baiting.
From 2021-22, the group also funded 200 days of contracted trapping services by a licensed pest technician.
This was done to support landholders who lacked time or struggled to conduct on ground management activities.
Over the years, carcases have been collected and dissected by a necropsy team, typically within 24 hours of being killed.
The carcases are weighed and sexed, different measurements are taken, reproductive status is determined and stomach contents identified.
Ms Jansen said feral pigs from this year's shoot weighed in at a 40kg average, calculated from small piglets through to 100kg bores.
She said they predominantly consumed a grain-based diet.
Furthermore, the average rate of pregnancy of those dissected was 51pc, with about five young produced per sow.
"Pigs are prolific breeders and are pregnant for three months, three weeks and three days from the first day of mating," Ms Jansen said.
"Some pigs produce at least 10 piglets and may have two litters each year, which is significant."
Reports have suggested that 55-70pc of feral pigs need to be culled each year to prevent the population size from expanding.
However, Ms Jansen believes to keep numbers below pre-control levels this figure would need to be at least 70-80pc.
"We have not been able to achieve this, even with our efforts in aerial shooting, baiting and trapping," she said.
"Feral pigs breed so fast - we would have to significantly increase our management efforts to see a dramatic change in numbers, which would cost significant time and money."
