Invasive wild pigs are generally known to be bad for deer. Most hunters in the Southeast have a story of wild pigs destroying food plots or chasing deer away from food sources like acorns near their tree stand. But what is the impact of wild pigs on deer? Does the impact vary throughout the year as deer and pigs key in on different resources in different seasons?
These are the questions the Carnivore-Ungulate Team at Clemson University tried to answer during a multi-year study of white-tailed deer in the piedmont of South Carolina. This cooperative study with the South Carolina Department of Natural Resources used nearly 100 trail-cameras along roads and trails spaced in a grid across 15,000-acres of private land to assess where pigs, deer and other wildlife occurred and when they were most active throughout each season.
Deer Avoided Pigs… Sometimes
In our recently published scientific study we found the impacts of wild pigs on deer varied across seasons. During the spring and summer we didn’t see deer avoiding the places or times pigs were most active. Deer and pigs occurred in most habitat types and their only preferences seemed to be for areas away from people and near water sources.
By contrast, during the fall, deer became much more selective about where to spend time. Deer liked to use food plots, preferred to be near water and away from roads, and spend time in forests with canopy cover but little understory cover. Basically, the places deer hunters know to focus on. But deer also responded to something else – they started to avoid areas frequented by pigs. Putting this all together, our findings suggest pigs could be pushing deer out of areas most hunters like to target.
Why were pigs impacting where deer are in the fall but not in the other seasons? We don’t know the answer but think the timing of when deer were active provides a clue. During most times of the year, deer preferred to be active in the hours around sunrise and sunset, tending to avoid being active in the middle of the night, which is when pigs were most active. But in the fall, deer increased their nighttime activity level compared to other seasons.
A New Player on the Stage in Fall
What happened in fall that caused deer to shift when they were most active? Coyotes are known to be most active in the morning and evening, but they primarily eat small fawns in our study area, and so we would expect the shift in activity to occur in the summer rather than fall. The other player inspiring fear in deer across the country in the fall is, of course, humans.
The private land where we conducted our study is closed to the public, but there is a pulse of hunter activity during fall deer season. And the timing works out: hunters are typically most active in the early morning and evening, and those are the times we saw deer shift their activity to avoid.
Our working hypothesis is that in the fall hunters go out to areas deer like to be in in the early morning and late evening – like food plots and hardwoods – and deer respond by trying to visit those areas later in the night under the cover of darkness when hunters are gone. However, nighttime is when pigs are most active, so deer can no longer avoid pigs in time and have to vacate the places pigs are most active. In other words, deer are being forced out of areas they like to normally be in because of the combined disturbance of hunters and pigs.
Further supporting the idea that hunting could be impacting deer-pig interactions is that once winter rolled around and the hunting season closed, everything shifted. Deer seemed to be able to go back to being more active during the morning and evening and were active in areas with high pig activity. In fact, winter was the only season where we observed deer frequenting areas commonly used by pigs. This is likely in large part due to both pigs and deer trying to key in the same habitats that have a combination of shelter from the elements and food resources during winter when food and cover are otherwise scarce.
This brings up a whole suite of additional questions about the extent to which competition with pigs for food in the winter is impacting the health of the deer herd. Also, if deer are not able to forage optimally in the fall leading up to winter, how does that compound with winter competition for limited food to influence herd health? Recent research out of northern Virginia closely links fawn survival to red oak acorn availability the previous fall and winter during gestation. For does, could balancing the risk of encountering humans and pigs in fall result in decreased reproductive output the following spring?
More broadly, we want to know if hunting activity causes deer to shift their activity periods and alters how they use pig-frequented areas in other places. And if so, what level of human disturbance triggers deer to shift their activity periods and decide to avoid pig-frequented areas?
Deer hunters know that by venturing out and taking an animal they are part of the ecosystem, and our findings hint that hunting could have more subtle impacts on deer behavior and how they avoid wild pigs. Hunting isn’t alone, as activity of mountain bikers, hikers and even bird watchers have been shown to impact wildlife behavior. What we are learning now is that even small changes in deer behavior could have impacts on how they avoid increasingly prevalent wild pigs on the landscape.
Advice for Deer Hunters in Wild Pig Country
While more research is needed, we have two pieces of advice for hunters going out this fall where wild pigs roam.
First, consider mixing up your hunting strategy such that you don’t consistently disturb deer in a particular place (which is good advice even in areas without pigs). Our research suggests that when hunters push deer into being more active at night around preferred areas like food plots, they come into contact with wild pigs and move away from those areas entirely.
Second, hunters might need to look for deer in other areas that aren’t traditionally thought of as “prime” fall deer habitat. Wild pigs are changing how deer behave, so if you aren’t seeing deer in familiar spots, try putting up some trail-cameras and checking out other areas. You might be surprised by what you find.
About the Authors: This research was conducted by the Carnivore-Ungulate Team at Clemson University, led by Dr. Mike Muthersbaugh, Dr. Alex Jensen and Elizabeth Saldo who focused their graduate research on deer, coyotes and pigs respectively. Oversight of this project was provided by Dr. David Jachowski of Clemson University, Dr. John Kilgo of the U.S. Forest Service, and Charles Ruth and Jay Cantrell of the South Carolina Department of Natural Resources.