AgBioResearch

Michigan residents take full advantage of the abundance of natural resources at their fingertips, especially in terms of hunting. According to the Michigan Department of Natural Resources (MDNR), Michigan ranks third in the U.S. in hunter participation. Hunters contribute more than $2 billion to the state’s economy through trip-related expenditures and equipment purchases.

But the picture isn’t entirely rosy. A plethora of wildlife pressures – from disease and climate change to illegal hunting – have created a situation that has captured the interest of scientists.

“There is a rich history of hunting and overall enjoyment of the outdoors in Michigan, something we want to preserve for generations to come,” said Gary Roloff, an associate professor in the Department of Fisheries and Wildlife at Michigan State University (MSU). “Wildlife in our state is threatened by a number of things, and it’s our responsibility as scientists to understand more about how we can minimize the impacts of negative environmental stressors.”

Researchers at MSU want to conserve the animals, the environment and the multibillion-dollar industries utilized by many. Sometimes that means removing an invasive species from the equation.

A PIG PROBLEM

Researchers from MSU, MDNR, U.S Department of Agriculture Wildlife Services and the University of Michigan-Flint are roughly midway through a five-year project in which they aim to learn about the ecology of feral swine. They want to develop management recommendations and, ultimately, eradicate feral swine from the state.

Most feral swine belong to the category of Russian boar, also known as the Eurasian boar, although some are domesticated pig escapees. Pigs were first introduced to the U.S. in the 1500s as a game animal and food source for European explorers. Over time, wild pigs — which can grow to well over 300 pounds — have become a favorite target for hunters, particularly in southern states where the population has exploded. More than five million now inhabit the country, causing more than $1.5 billion in damage to agricultural lands and forests.

The animals also carry various diseases that can spread to humans, pets and domestic livestock. Harm to the pork industry, a $500 million per year business in Michigan, is a major concern.

Controlling feral swine populations is difficult due to the rapid rate of reproduction. Both genders become sexually mature as young as six months, and females can have multiple litters of four to six piglets or more per year.

“The good news is that there are likely less than 1,000 feral swine in Michigan,” Roloff said. “The bad news is that they reproduce quickly, are extremely adaptable and can have significant detrimental effects on crops and the environment. They root around in the soil and can destroy vegetation and crops, eat food that native species rely on, and they can threaten domestic pork operations. However, Michigan is in a good position to remove this threat from the state.”

While researchers believe Michigan is ahead of the eradication curve nationally, little is known about how feral swine interact with the environment in the upper Midwest. Roloff’s team is actively capturing pigs in cooperation with property owners, primarily in the hotbed counties of Gladwin, Midland, Ogemaw and Arenac. The pigs are fitted with collars that use wireless monitoring and are then released. Via satellites, the collar records the animal’s location every 30 minutes, and users are able to view maps that show how many times each location has been visited.

Steven Gray, a graduate student of Roloff’s, has been reviewing data and conducting field work to assess environmental damage from the swine.

"What we’re seeing is that feral swine have a larger home range than we anticipated,” Gray said. “Michigan doesn’t have a lot of pigs relative to other states, so they have more room to roam. They like woody wetland areas where they can wallow in the mud, and we see large spots where they’ve rooted for grubs or other food. Just a few pigs can do a massive amount of damage, and we’re trying to quantify that.”

To further track feral swine locations, University of Michigan-Flint scientists are using environmental DNA. The technology allows researchers to take samples of water or soil, for example, and test for the presence of feces, urine or other traces of the pigs. This will help researchers determine if feral swine have been truly removed from a given location.

In addition to funding research, Michigan has taken steps to curb the feral swine population with assistance from the public. The state enacted an invasive species order in 2011 that prohibits the possession of Russian boar. Furthermore, residents with a valid hunting license are allowed to shoot feral pigs on sight while hunting. Also, private property owners don’t need a license if shooting on their property.

“Pig hunting is engrained in the culture of many southern states, but in Michigan we already have a variety of larger game animals for hunting such as turkey, deer and bear,” Roloff said. “With feral swine, we run the risk of upsetting the balance of our ecosystems and potentially causing a lot of environmental damage, while also presenting health risks. Great progress has already been made to get rid of feral swine in Michigan, so we need to continue that momentum.”

ENSURING SUCCESS FOR AN ICONIC SPECIES

Wild turkeys are one of the most revered birds in North America and a common spectacle for nature lovers throughout the Great Lakes region. But not long ago, turkey sightings in Michigan were relatively rare. Populations were wiped out in the late 19th century due to habitat destruction and unregulated hunting, leading to a reintroduction effort that began in the 1950s.

Populations of the large bird increased steadily in Michigan from the 1950s through the 1990s, when wild turkeys expanded to occupy nearly all available habitat in Michigan. Since the early 2000s, the numbers have begun to stabilize.

A team led by William Porter, the Boone and Crockett Chair of Wildlife Conservation at MSU, sought to determine if the current level of turkey harvest by hunters is sustainable.

“Historically, a rule of thumb has been that the wild turkey population could withstand just shy of 10 percent harvest each year,” Porter said. “But we saw that this recommendation was based on conditions that were extremely favorable for turkey nesting and raising young. When we looked at more average conditions, it turns out that close to 10 percent harvest may be too much.”

The wild turkey is the second most popular hunted animal in Michigan behind deer, with roughly 100,000 hunters taking to the woods each year. Hunters harvest more than 30,000 turkeys annually, putting Michigan No. 7 in the U.S. Numbers of wild turkeys have grown robust enough to support two hunting seasons in Michigan. A fall season allows hunters to take a turkey of either sex, but it’s spring hunting that generates the most interest. Spring is mating season for turkeys, and hunters go afield to lure gobblers by imitating the call of hens.

“Those who hunt turkeys in the spring will say that matching wits with a gobbler is like no other outdoor experience,” Porter said. “As the interest in hunting grows, we have to make sure that the wild turkey population can sustain the annual harvest.”

Hunting representatives have been involved throughout the project, an aspect Porter believes has been essential.

“Over the last 30 years, Michigan hunters and the MDNR have created one of the best records of information on turkey populations that exists anywhere,” Porter said. “Because of that, we have a really good idea of where the population stands. We’ve only been able to achieve this because of a strong partnership with the hunting community.”

The project began with an analysis of factors that likely drive change in turkey populations. Potential options for management were then incorporated to be assessed. As the process moved forward, researchers drew on the knowledge of wildlife managers, hunters, farmers and other stakeholders to build sophisticated statistical models that predict responses of turkey populations to potential management options.

Currently, findings are being used to develop recommendations for future management programs. Porter foresees little change in hunting regulations in the immediate future. Traditionally, regulations in Michigan have been focused on protecting populations from over-harvest and ensuring a high-quality hunting experience. The research shows that Michigan has been wise to sell hunting licenses through a quota system similar to the one used for deer, as opposed to open-ended sales of licenses for small game such as rabbits. License quotas allow for careful management of the number of turkey hunters and consequently control the harvest each year.

“The system has produced some of the most abundant wild turkey populations and the highest-quality hunting anywhere in the country,” Porter said. “The research identifies the pressure points that are likely to be important in the future. We’ll keep monitoring the situation, and the findings from the research will allow Michigan to be prepared to deal with those pressures should they arise.”

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