Wild pigs may have met their match thanks to eDNA

February 07, 2017

[caption id="attachment_8604" align="alignleft" width="150"] Eurasian wild boar[/caption]

Estimated to be responsible for $1.5 billion in total damage each year, wild pigs, a.k.a., feral swine, are talking a toll on our landscapes and even some livestock. Eating anything in their path from rows of corn to sea turtle eggs, to baby deer and goats, wild pigs are destructive and even responsible for tearing up suburban yards and damaging levees by digging for food.

Researchers at the National Wildlife Research Center in Fort Collins, Colorado, however, have invented a promising new way to track the invasive animals by looking for tiny traces of them in mud and water. With this data they hope to learn more about their travel patterns and eradicate them as quickly as possible.

In the past, this has proven to be a difficult task as one article compares controlling wild pigs to a game of whack-a-mole. This is because wild pigs tend to move a lot, reproduce quickly, and are smart enough to learn to avoid traps and bait. They're also sneaky.

"These things are very secretive," said Jack Mayer, a biologist who has studied wild pigs for 40 years. "A lot of people didn't know about wild pigs until they walked out their front door on Sunday morning and saw that it looked like somebody on drugs had rototilled their yard."

Mayer added these hogs will also run down and kill lambs, sheep, calves, domestic chickens and in some situations even eat humans.  "It's been documented in combat, remote area homicide situations and plane crashes. Pigs will go in and feed on human carcasses."

But these pigs may have met their match. Kelly Williams, a biological science technician at the National Wildlife Research Center, is going high-tech on these hogs without ever even laying eyes on them. All she needs is a scoop of water.

"So, for example, right now in New Mexico the forest service is out collecting water for me," Williams said in the article. "All they have to do is carry around a little Nalgene bottle, scoop up a water sample and ship it back to me."

Pigs love water and mud. They drink it, play in it and roll in it to keep heat and bugs away. When they do, they leave bits of themselves behind — drool, skin cells, hair and urine — like a wildlife crime scene. Each of those bits contains pig DNA.

"We know pigs are pretty messy, dirty animals, so they might shed more DNA than a coyote lapping up water or something," Williams added.

She worked with wild pigs at the National Wildlife Research Center to identify these tiny bits of DNA — called "environmental DNA," or eDNA — which can sometimes be detectable up to a month after a pig has visited a site.

Ecologists have used eDNA to monitor invasive fish in the Great Lakes and endangered whale sharks in the Arabian Gulf. Williams' colleagues even developed a version to track the presence of Burmese pythons in Florida. Now, wild pigs are one of the first land animals to be tracked so extensively using eDNA.

Williams starts with a bottle of dirty water, mixed with a solution to preserve the DNA inside. "Sometimes it looks like chocolate milk," she explained. "Sometimes it looks like lemonade."

Williams then spins down all the solids in the liquid sample, amplifies the DNA inside, and compares what she finds to 125 base pairs of mitochondrial DNA that could only belong to a pig.

At the end, she gets an answer – "Yes, pigs were here," or "No, they weren't." She then passes the results along to people like Brian Archuleta, a wildlife biologist with the U.S. Department of Agriculture's Animal and Plant Health Inspection Service in New Mexico.

Archuleta has a goal for the new year: wild pig annihilation in New Mexico, and says he wants to complete it by this coming September.

To track wild pigs in his region, Archuleta used to have to repeatedly send people out across deserts and mountains to place cameras, use dogs to sniff them out, and bait traps with tubes of corn. But recently, he just had a few people go out and collect water, and then shipped the samples to Kelly Williams. With the results he got back, he was able to narrow the search to about 10 square miles in the desert, and another small area in the mountains.

Next, Archuleta booked a helicopter, hired some sharpshooters and flew over the areas where pig DNA had been found. Sure enough, they found eight hogs in one place and 13 in another.

"There are unknown places in New Mexico that I'm sure have pigs that we just don't know about," he said in the article. Not to mention the other six million wild pigs across the country, with established populations in 35 states.

He's hoping the new eDNA sampler will help him find every last one.

For more information, click here.

Photo credit: http://wildpiginfo.msstate.edu/history-wild-pigs.html