Climate change and parks

Wild boar in Cades Cove, Great Smoky Mountains National Park. / Meredith Boatman

Editor's note: This is the latest installment in a series of articles about invasive species and the threats they pose in the national park system.

Wow. Great Smoky Mountains National Park is a warm, sunny autumn day, and I am standing on the side of the park’s main road. The leaves were just beginning to turn golden, amber, and red, so the park was crowded with people peeping at the leaves. A steady stream of cars galloped past. Wow. I tried to ignore the traffic and pay attention to what the park wildlife biologist Ryan Williamson showed me: a piece of grass on the side of the road was rutted and uprooted, like someone carrying a miniature all-terrain vehicle off-road.

The culprit? Wild boar. In this case, Williamson believed that a wild boar caused the damage along the road and cited a report of a lone pig seen near the road a few days ago. After a while, Williamson led me deep into the woods to a larger, muddy ground disturbance area, this time I could see standing water. This is undeniable evidence of the destruction of the park landscape by wild boars-uprooting native vegetation, creating new wet areas, and competing with local park wildlife for food and shelter.

"They almost just follow their noses and turn the soil over, a bit like cleaning up all edible things," Williamson said. "They almost directly compete with all our native wild animals, so they eat a lot of acorns, a lot of seeds, a lot of nuts, and a lot of tubers. Pigs directly compete with them for everything our native wild animals eat."

Biologist Ryan Williamson traps wild boars in Great Smoky Mountains National Park. / Kim O'Connell

Wild boars are just one of several invasive mammals that pose a huge challenge to national park managers. Unlike invasive insects or reptiles, invasive mammals are usually larger and more "charming" animals, and parks are difficult to eradicate from a logistical, financial, and emotional perspective. As familiar furry mammals, these invasive animals often have a common attraction with iconic park creatures such as bears, bighorn sheep, deer and wolves. However, the problems they cause are multifaceted-destroying and changing the ecosystem, competing with native wild animals or predating directly, or carrying diseases.

Invasive or non-native mammals in national parks include goats in Grand Teton National Park, meerkats in Hawaiian volcanoes, donkeys in Death Valley National Park, rats in the Channel Islands, and cattle in Glen Canyon National Recreation Area. Wild boars (also called pigs or pigs) can be found in parks from coast to coast, from the Great Smoky Mountains, Cumberland Island National Coast and Congari National Park in the southeast, to the Great Jungle Country in Texas Sanctuary and Pinnacles National Park. West, wait.

According to a 2018 National Park Service report "Biodiversity, Invasive Animals and National Park Service under Siege", more than half of national parks contain invasive animal species, including mammals, and only a small part of these animals Considered to be suppressed, contained, or eliminated. In 2016, NPS counted 37 invasive mammal species in the national park system, distributed in each region, representing nearly 350 known populations. The report states, “When it comes to attractive species (for example, goats, wildcats, wild horses) or the visitor experience is affected (including public health or safety issues), the public will have greater interest and pressure on how they will live. .manage."

Methods of controlling invasive mammals vary from place to place, depending on the dynamics and biology of the particular species, funding, resources, and public opinion—but usually include some combination of hunting, fencing, sterilization, and resettlement.

"Wild boar is one of the biggest problems in the park," said Jennifer Sieracki, NPS National Invasive Species Coordinator. "Many of the affected parks have trapping programs to control this species. Free-range cats have also caused problems in dozens of parks. They are efficient hunters and also bring disease problems. They can be very difficult to manage, so We ask people to help us keep their cats indoors, and if they can no longer take care of them, give them to shelters instead of throwing them outdoors and avoid feeding cats that are outdoors."

Sieracki added that wild horses and donkeys appear in fewer parks and are often managed by individual parks as needed. “Parks usually work with partners to remove animals from the park and then adopt them,” she said, “and may also build fences around sensitive spring areas to protect them from grazing and trampling.”

However, even if the park succeeds in eradicating invasive species—which is a big “if” in most places—you need to be vigilant. For the last time an organization knew about a maintenance backlog of approximately US$12 billion, continued vigilance was often too costly to achieve.

Williamson told me that in the Great Smoky Mountains, the park has accepted that some wild boar resident population may continue into the foreseeable future, mainly because the park does not have enough staff or funds to initiate a complete eradication plan. Around 1,500 pigs are believed to live within the boundaries of the park. This means culling is carried out every year to control the current population and collect tissue samples for ongoing scientific research.

Biologist Ryan Williamson checks a motion-sensing camera near a wild boar den in the Great Smoky Mountains. / Kim O'Connell

Williamson said that the wild boar population in the park dates back to around 1912, when wild boars were taken from Russia to a private (presumably fenced) hunting reserve south of the present-day national park. At some point, the pigs escaped and mingled with domestic pigs on the local farmland, creating a hybrid population with Russian and domestic genetics, the offspring of which are still roaming in the park to this day. The national park has been trapping and shooting invading wild boars for decades, and an estimated 13,000 wild boars have been cleared so far. Currently, the park eliminates approximately 250 to 300 pigs each year.

But there are several factors that make management difficult: First, most of the more than 800 square miles of parks are remote areas covered by forests. In the summer, wild boars tend to look for highlands that are cooler but more difficult for park biologists to reach, so most cullings occur in the fall and winter, when wild boars feed in low-altitude areas close to park roads, access points. 

Wild boars are also regarded as valuable creatures by hunters and other stakeholders. Dr. Becky Epchin-Neil, a senior researcher at the non-profit think tank Future Resources, said that he conducts research on various invasive species issues. 

“The fact that some people take their presence in the landscape very seriously may hinder control plans,” Epanchin-Niell said, “because people can maintain populations on their land, and these populations can be used as a source for other parts of the landscape, thereby It’s more difficult to prevent damage elsewhere. What’s more challenging is that some people may even purposefully introduce species to new locations to establish new hunting populations."

Another problem is the prolific reproductive cycle of pigs. "A group of pigs is called a sounder, and usually in the sounder it is almost a matrilineal clan," Williamson said. "This is a herd of young females, and then you will occasionally show up boars. They have an incredible gestation period. Three months, three weeks, three days. So if your adult pig goes through pregnancy , And then give birth to a litter, then she can have up to three litters a year. A litter usually has 8 to 12 pigs; sometimes we see four to six. In addition, once she has that litter, that litter has It may start to multiply at six months of age. Therefore, if it is not regulated, it will be an exponential growth curve."

Williamson and I quickly trudged to another area of ​​the park, where a few pigs were rolling. Here, a large area of ​​low-lying land was completely turned over and covered with ruts, and the pit was full of water.

Biologists said: "Due to wet spots or leakage, they are very destructive to many plant species, especially endangered plant species. This is the most limited ecosystem in our park because we are on the mountain. So It is very rare to find wetlands here. Our pigs really focus on these places because it is easy to tear up, they can flip the soil and grab those tubers and roots. They really pay attention to those areas, which is for those wetland animal species It’s destructive."

Williamson pointed to a camouflage camera installed on a nearby tree. He and his colleagues posted several such cameras in strategic areas of the park. They believed that the pigs were always there as a means of collecting animal activity data, and also allowed them to open remote trapdoors to catch pigs. To eradicate. Williamson took me to a single box trap that could only catch one pig at a time. After sprinkling some corn kernels in the trap and covering the floor of the trap with dirt, he triggered the trap door to close. Grand Slam! The sound echoed on the nearby tree.

Other national parks have their own systems to deal with invasive mammals, which usually involves coordination with other land management agencies, law enforcement agencies, non-profit organizations, and ordinary citizens. For example, in Smokies, the park cooperates with the Wildlife Service of the U.S. Department of Agriculture to conduct scientific research to determine whether there are any diseases. Wild boars are related to pseudorabies. Pseudorabies does not infect humans, but it affects other animals, such as domestic pigs and other livestock, as well as brucellosis that humans can infect.

A wild boar tissue sample from the Great Smoky Mountains. / Kim O'Connell

"We try to cooperate on any type of disease surveillance and any [similar] aspects that anyone is willing to participate in with us," Bill Stiver, a supervising biologist in the Great Smoky Mountains, told me, like a Pile of tissue samples from Little Manila envelopes full of pigs are stacked on his desk. "We are also a partner of WHEAT (Wild Boar Eradication Action Group)." This is a multi-agency partnership that focuses on parks, public lands, and communities in Tennessee.

Similar work is being done elsewhere. For example, in Glen Canyon, the park is working with the Bureau of Land Management and local officials to remove as many as 50 non-local maverick cattle from the Escalante River canyon through rounds, believing that these animals can be pushed. To the market and sell.

In Pu'uhonua o Hōnaunau National Historical Park, the NPS and other agencies successfully cleared 458 invasive goats this summer and used directional fences to enclose these animals in an area where they were allowed to be distributed to interested parties and taken To other places.

On the Cape Hatteras National Seashore in North Carolina, there are an estimated 3,000 wildcats roaming Hatteras Island. About two-thirds of them are managed by the federal government and pose a threat to nesting shorebirds and other native animals. According to Debbie Martin, the founder of Cape Hatteras, a non-profit feline friend, feeding cats by the sea is an ongoing problem. Although visitors to Yellowstone Park may know better than feeding a grizzly bear (people hope so), wild cats look like family pets and are irresistible to some park visitors. Although not an official partner of the park, Friends of the Feline-Cape Hatteras Island has launched a trap-neutral return program that helps to control the number of cats in a humane way described by Martin, and It is the corresponding method of NPS culling measures.

In Grand Teton National Park, park officials are continuing a qualified volunteer culling program to help eradicate non-native goats, which threaten the park’s single native bighorn sheep population and are considered vulnerable in the Teton Mountains .

An image of a pig in a corral trap taken by a remotely installed camera in the Great Smoky Mountains. / Ryan Williamson

In December 2019, a group of park researchers published a study in Biological Invasion that investigated the problem of invasive species in national parks. In other findings, the team determined that concerted action is needed to adequately respond to invasive species, and acknowledged that lack of leadership may be a factor hindering progress (although the lead author of the study, Dr. Ashley Dayer, pointed out that NPS has taken steps to bring Sieracki Named the National Invasive Animal Coordinator). The recent confirmation by NPS director Charles "Chuck" Sams can also promote invasive species projects, and perhaps more partnerships and public participation on this issue-both deemed necessary in the research. 

"The park will jointly develop tools to help them manage invasive animals, but in most cases, the park has achieved great success in cooperation with local partners on the issue of cross-border invasive species," Sieracki said. "At the national level, we are working to establish partnerships with park staff that can be implemented at the local level. We also often work with other federal agencies to solve national problems by setting priorities, formulating policies, and developing innovative tools. And share information."

When resources are dispersed, it is essential to have efficient technology. "We wear a lot of hats," Ryan Williamson said. "This is almost to the point where you can do a lot of things well, but when you can't focus on one thing and do so many things, it hinders what we can accomplish. If I have a group of 25 pigs doing bait, And I encountered the bear problem, so I had to deal with the bear problem."

In a quiet area of ​​the park, Williamson showed me a corral-style pigpen, which was designed to stay in the landscape for a period of time to let the pigs get used to it. Once a group of people enters, a motion detection camera will transmit images via a mobile phone application, allowing the park biologist to open the trapdoor remotely. Once, the park caught nearly two dozen pigs at once with this trap. Large net traps can also catch many pigs at the same time, although they are difficult to install in densely forested environments.

Once the pig is killed, the park will allow the carcass to be left on the ground to feed on scavengers. In this biodiversity-rich landscape, the natural recovery of a 200-pound pig carcass takes only a few hours.

"The life cycle in the park," Williamson said, "is very short."

The previous installments of this series:

Traveler Special Report: Invasion of the National Park System

Traveler Special Report: Invasive Fishes in National Parks

Audio postcard from the park | Battle of Russian olives at Glen Canyon NRA

Traveler Special Report: Plant Invaders in National Parks

Charity funds help fight intruders in the national park system

Special Report for Travellers: The Cost of Invasive Species in the National Park System

Traveler Special Report: Fighting invaders with fire on the national battlefield

Special Traveler Report: Measuring the success rate of invasive species

Audio postcard for travelers from the park: Wild Boar

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