It sort of makes sense intuitively. If you really don't understand the ecology and at first light, if you have pigs, people go and shoot pigs, the population goes down. That works for moose, elk, deer, caribou. That has been used for many decades by provinces to regulate the number of tags they allocate to sport hunters and they can have the populations go up or down and the provinces do a remarkable job of sorting all of that out.
That goes out the window with wild pigs. They just reproduce to quickly and they're too hard to find. Sport hunting breaks up groups, unfortunately it makes them more nocturnal so much harder to find. Under any kind of pressure from humans, whether it's being shot at or chased or what ever, those animals will become highly elusive and they'll move into heavy cover.
In the winter they tunnel under the snow to stay warm. They will also tunnel into soil and vegetation so trying to spot them is incredibly challenging. To be honest, most of the time if we find wild pigs, it's not seeing them, it's seeing their tracks. They have shorter legs so you see their belly dragging through the snow.
They also get into these snow caves. We'll fly first thing in the morning and look for steam pouring out of those snow caves or we'll see their nests in cattails. It's rare to see them during the day.
Source : Farmscape