Managing feral pigs on Cape York: it’s not a numbers game
About 3000 feral pigs are culled every year in the Archer River Basin on Cape York. But is this helping to protect the things we care about? Together, local people and scientists are building a case for targeted pig management in place of culling programs aimed at killing as many pigs as possible.
Between 2009 and 2013, not a single marine turtle hatchling reached the water’s edge on the beaches of the southern Wik homelands. Every egg was eaten or smashed by the feral pigs that take up residence in the nearby dunes during the turtle nesting season. Despite large-scale culling of pigs on the Cape, the nests of the olive ridley and flatback turtle were being wiped out year after year.
Horace Wikmunea is a senior Aak Puul Ngantam (APN) ranger and elder: “The pigs come around the nesting area where the turtle lay eggs and they start digging – digging, digging around till he finds it and start destroying the eggs. We’re trying to get rid of the pigs but they always hide somewhere. We like to protect the nest because it’s part of our traditional food too.”
Because turtles are long-lived and keep returning to the same beach, the missing generation of turtles can go unnoticed for a time. “You can get complacent because it looks like there are a lot of them”, explains CSIRO scientist Justin Perry. “But as the old ones die, there will be a sudden cut off in numbers. And there will be no turtle memory of that beach. We need to get as many turtle babies in the water as possible – there has already been at least a five-year gap.”
The metrics problem
The problem is one of metrics. Ranger groups and regional organisations receive government funding to control feral pigs. They generally hire contractors to cull the pigs, which are usually shot from a helicopter. They record how many pigs have been killed and, often, they also report the ‘efficiency rates’, or dollars per pig. “Because of the density of pigs on the Cape, you can kill thousands in a couple of days”, says Justin. “But if you kill 2000 pigs, what does that mean for biodiversity? We don’t know how effective this type of culling is.”
And, while the contractors do a great job, he adds, it’s not enough: “Pigs reach a peak level where they use all resources – when you come in and kill 2000 pigs, you’ve created a place where food will grow and the pigs just breed to fill that space. We’ve flown over the area a month following broadscale culling, and still saw hundreds of pigs in the areas of control.”
Effective population control requires around 75% of the population to be culled every year, he says. “Using current estimates of pig numbers for the Archer River Basin, that means that we would need to cull around ten times more pigs in a single year to notice a difference across the landscape”. With limited funding this is not a long-term or sustainable option.
Feral pigs are also an important source of protein for Indigenous people on the Cape, so there’s an immediate conflict with culling programs, which needs to be balanced with conservation.
In 2013, APN rangers and a team of researchers met in Aurukun and together they concluded that the current methods of controlling pigs were doing nothing to save the turtles. With funding from the federal government’s Biodiversity Fund, they decided to make a concerted effort to protect the turtle nesting beach for six weeks.
Along a 10-kilometre stretch behind the beach, they set up bait stations that were accessible only to pigs. The results surprised everyone. In one week, 100–200 pigs were killed and predation on turtle nests fell by 90%. “Our targeted protection method was far more successful than killing thousands of pigs through other methods”, says Justin.
Measure the thing you value
The best way to spend money on managing pigs is to measure the thing you value, claims Justin. So his first step in designing a monitoring program for pig control was to ask the Traditional Owners what they value.
On the eastern edge of the Archer River Basin, the Kantju people are also struggling to control feral pigs. The landscape here is peppered with wetlands, which they value as a source of food. But pig damage, they say, has decimated the harvest over the past 10 years.
“Right now the water’s all dirty and the bank’s all dug up and there’s less lilies now”, says Kalan Ranger and senior Traditional Owner Jennifer Creek. “And there’s hardly any bush tucker. I haven’t eaten the yam in three years.”
Thousands of pigs were being culled and trapped but whether the culling was having any impact on the health of the wetlands was not being monitored.
To gather scientific evidence of what these lagoons would look like without intrusions from feral pigs, Justin and the Kalan rangers are conducting a controlled experiment whereby they have fenced off a number of lagoons.
The rangers are monitoring the sites, which includes taking soil and water samples, collecting data about plant and animal species, and collecting photos from remote sensor cameras. They also use a purpose-designed iPad app for estimating the density of pigs from a helicopter.
Justin explains the approach: “We stood there with Traditional Owners and said, what would you have come here for? What are the things you would’ve collected out of this landscape? And those are the things that we sought to monitor.”
The results of the experiment will indicate whether culling and trapping of feral pigs are control methods worth investing in or whether other forces are at play in disturbing the lagoons.
“Maybe we’ll see more long-neck turtles, more native clams, more plant diversity”, he says. “And if we want the lagoons to look like this, how much are we willing to invest to save it? Maybe we protect our best assets, those we really want to save.”
The value of assets is not necessarily environmental—some of the places where pigs wreak havoc are story places and cultural sites. For Justin, an ecologist, coming to grips with the idea of cultural value was a challenge.
“Toolka, for example, is a special place for the Kantju people”, he says. “It’s basically a pile of rocks in the middle of the savannah and, from a biodiversity perspective, it’s not a big deal. But pigs had been turning over some of the rocks and, for Jenny [Creek], her sacred area is being desecrated. Thinking about this other kind of value has had a huge impact on me.”
The unreported benefits
The benefits of having local people independently control feral pigs go far beyond the cultural and environmental.
Dion Creek is the Chief Operating Officer of Kalan Rangers: “I think it’s good to get some funding to improve the country and to look after the country… But one of the things that isn’t really captured in these reports are some of the social outcomes. That’s probably one of the best things I get out of the job, is actually seeing the changes in people’s lives. You know, coming off the welfare system into fulltime work, using that income to start a business, using that income to put their kids through high school, and to go to university. That’s really important and I think that message should be reported.”
Getting ready to walk away
With two years left before funding runs out, the vision of the Kalan and APN rangers being able to independently use targeted methods of pig management is becoming reality.
“We are getting a handle now on what we need to measure to measure the true impact of the pigs”, says Justin. “For the next two years, we’ll be putting that into place, making work plans with the rangers and setting it up so we can walk away—that’s the dream.”