Bruce Means first came to Florida by way of Alaska in the late 1960s. His doctoral research with Florida State University focused on salamanders in the U.S. Coastal Plain. At the time, Means witnessed hog damage in the wetlands he was studying, but the damage was not so severe that it alarmed him.

Twenty-five years later, Means went back to survey salamander populations in their more than 250 localities in Florida. He found that one salamander species in particular, the Southern Dusky Salamander, was nearly extinct aside from a small group of populations in the Apalachicola National Forest.

Another species, the Spotted Dusky Salamander, also decreased in abundance by 68% during that same period.

So what had happened in the 25 years since his original research? One possible factor: the wild hog populations in the Panhandle had increased and with that came more rooting damage in the salamanders’ larval habitat.

“They’d increased so thoroughly that there was outrageous evidence of their destroying the breeding habitat for several salamanders that live in the ravine heads over there,” Means said.

Means has seen the damage in many different kinds of wetland areas, but the salamander’s habitat is concentrated in special ravines called steep heads. Salamanders live in this interface, but so do big earthworms, and the area is filled with fine rootlets from nearby trees and shrubs. All of these elements create a rich buffet for the hogs to feed on.

“There’s a bunch of stuff for them to eat,” Means said. “No one is going to waste time digging around somewhere where it’s not going to get something to feed on.”

Feral hogs compete with native bear, deer and turkey for space. They prey on native birds, reptiles and amphibians. When they get hot, they dig muddy wallows to relax. These shallow holes are prime mosquito breeding grounds, and in large numbers, can change the hydrology of the landscape. The wallow puddles also breed bacteria and parasites that can be passed on to other wildlife who need a place to quench their thirst.

Invasive plants favor the torn up earth that pigs leave in their wake. The swine can also transport seeds of these plants in their fur or feces.

Wild pigs eat seeds like acorns and beech nuts. By interfering with seed dispersal, they have the ability to shift the species diversity and density in forests, and reduce the number of large seed-producing trees.

“They’re quite destructive,” said Raoul Boughton, a wildlife biologist in the University of Florida Department of Wildlife Ecology and Conservation. “And the problem is most of these things haven’t been really well quantified in terms of how much they cost to repair.”

A Perfect Host

Feral hogs are also the perfect host for at least 30 viral and bacterial diseases and nearly 40 parasites that can be passed on not only to humans, but also pets, livestock and other wildlife.

Means believes he, his graduate students and his son may have all been infected with diseases from hogs after conducting field work in areas where they were present.

“I crawl around looking for these salamanders on my hands and knees,” he said. “I crawl around in hog wallow and hog excrement, not realizing I’m doing it. So I’ve been exposed.”

Means experienced over six months of joint pain, swollen legs and other symptoms that could have been explained by a case of leptospirosis, a rare bacterial infection that can pass from animals to humans when an open wound comes in contact with water or soil that contains animal urine. Though rare, the severe form of this infection can lead to serious consequences such as meningitis.

At 79 years old, Means thought the pain he was experiencing was simply the product of aging, so he never had his symptoms diagnosed by a doctor. But after several months, he got better.

“It was scary,” he said. “I’ll never know what it was or if it was a disease situation. At least I’m better now anyway.”

Another common pathogen carried by pigs is a herpes virus called pseudorabies, or PRV. The virus has been in the U.S. for more than 150 years and can lead to abortions, stillbirths and respiratory problems in pigs, and death in piglets. When pigs are actively shedding the virus, they can spread it to other species, like dogs, panthers, cattle or sheep. Rabies-like frothing at the mouth, loss of muscular control and erratic behavior will kill the victim within 48 hours.

Pseudorabies is the third leading cause of death to the endangered Florida panther. The fleeting species relies on wild pigs as a staple of its diet. One study suggests that 40 to 50% of wild boars are infected in South Florida.

Samantha Wisely, an assistant professor in the UF Department of Wildlife Ecology and Conservation wanted to know what factors might cause a higher prevalence of pseudorabies in wild hog populations. After analyzing eight years’ worth of blood samples collected as part of the USDA’s national wild pig disease monitoring effort, the team found that higher rates of the virus were found in areas where dog hunting was allowed.

Wisely has a hypothesis for this.

The pigs’ stress levels spike as they are being pursued in the hunt, causing the virus to shed. Wisely and the other study authors recommend management agencies prohibit dog hunting where panthers and hogs share a common habitat. And, this may prove more difficult as panthers creep north into the Kissimmee River Valley where several public lands allow dog hunts.

Wisely said examples like these are why more research is needed into how land use policy affects feral hog management.

“There’s not a lot of management that goes on right now for feral swine other than as a game species,” Wisely said.

If it gets into feral pigs, we will never get rid of it.”

Sam wisely

Pseudorabies isn’t the only pathogen Wisely and her colleagues worry about. Another threat is marching steadily west from Eastern Europe — African Swine Fever, a deadly virus affecting wild and domesticated pigs.

“If it gets into feral pigs, we will never get rid of it.”

“ASF is a devastating, deadly disease that would have a significant impact on U.S. livestock producers, their communities and the economy if it were found here,” reads the USDA website. “There is no treatment or vaccine available for this disease. The only way to stop this disease is to depopulate all affected or exposed swine herds.”

At a recent U.S. Animal Health Association Meeting, veterinarians convened to talk about emerging diseases that pose a risk to livestock.

“They were not talking about if [ASF] was going to hit the United States, they were talking about when.”

In China, roughly one quarter of the country’s four billion pigs have been culled due to ASF. If it made its way into domestic pig populations in the United States, our $20 billion U.S. pork industry that provides nearly half a million jobs would be at stake.

“If it gets into feral pigs, we will never get rid of it,” Wisely said.

‘They’re Here Forever’

In 2018, more than $1.3 million was spent on feral swine management in Florida.

Jeremy Butts, assistant state director in the Wildlife Services Program with the USDA Animal and Plant Health Inspection Service, said trapping is his team’s most effective management tool. The USDA uses a variety of trap types, depending on the situation, including cages, corrals, traps that are tripped with a string and traps that can be closed with cellular technology.

But other methods are used as well.

It’s not like a do it for a year and walk away from it kind of thing.”

Jeremy Butts

“It’s not like a do it for a year and walk away from it kind of thing.”

In 2018, over 100 hours of helicopter flights were logged by the USDA in Florida for feral swine management through aerial gunnery. Though costly, Butts said this method works particularly well in South Florida ranchlands and wetland prairies.

“It is a pretty interesting experience,” Butts said. “Removing upwards of 100 hogs in about six hours, it can be a very effective method.”

In 2018, over 100 hours of helicopter flights were logged by the USDA in Florida for feral swine management through aerial gunnery.

One novel method that is still undergoing research is the use of sodium nitrite–a common food preservative that is lethal to pigs but safe for humans and wildlife in small amounts.

When feral swine eat sodium nitrite, they become lethargic, pass out and then pass away within a matter of hours.

Butts said the substance is still being tested, but it shows potential, especially because it is believed to have limited impacts on humans and other wildlife.

“Pigs are the ones that really can’t take it even though, if you look at it, it’s in every type of hotdog,” Butts said.

Management has seen some successes in Florida, especially in island habitats. In 2018, feral swine were completely eliminated from Cayo Costa State Park, and Butts said swine were removed from St. Vincent Island this year as well.

“It’s just something that when someone decides to make an effort, it’s not like a do it for a year and walk away from it kind of thing,” he said. “It’s a long-term investment of saying, ‘I want to control these swine and keep my natural ecosystem the way it is.’”

The tug of war between the idea of wild hogs as both a beloved game species and an invasive pest is why managing the species isn’t so black and white. Wisely empathizes. Although she’s well aware of their impacts, she’s hunted and eaten wild pigs before.

“There is always going to have to be this balance,” Wisely said. “Wild pigs have this sort of dual citizenship as it were. Florida will never be pig-free. They’re here forever.”

Credits:

Photo Credits Hannah Brown, Steve Hillebrand/USFWS, Noah J Mueller