The first time you see wild hogs walking into a corral-type trap, it’s tempting to push the button and release the gate on the trap as soon as they walk in.

Resist the temptation, says Daniel Stanfield, Region 1 game/diversity wildlife manager, with the Tennessee Wildlife Resources Agency and a member of Tennessee’s Wild Hog Eradication Action Team.

“The first night you get a picture of them walking into the trap, and you think, ‘I’ve got to drop it right now,'” says Stanfield. “Don’t do that. Let them come in and get accustomed to the trap, and then drop the gate.”

It wasn’t that long ago wild hogs were confined to two relatively isolated areas in middle and east Tennessee. Now they’re a problem across most of the state, according to Stanfield, who spoke on dealing with wild hogs, high populations of deer and with cougars or mountain lions in a presentation at the Memphis, Tenn., Ag Club.

In some cases, the hogs have simply moved into new territory. In others, they’ve been introduced into areas by landowners and sportsmen so they could be hunted. In either case, the damage to crops caused by the hogs can be catastrophic, reaching as high as $1.5 billion annually across the U.S.

The first step in dealing with the problem is to determine how many hogs are in the area, using research tools, such as game cameras and looking at tracks. The numbers may dictate different approaches.

“Having five hogs versus 500 is two different ball games,” says Stanfield. “If you have two hogs, I’d much rather the landowner get a permit, go in there at night and shoot them than to have to construct and monitor traps. The main thing is to take action early.”

See also: Photos: Huge feral pig killed in Mississippi corn field

Stanfield said when he first began working with wild hogs in west Tennessee in 2011, Shelby Forest State Park, which is located north of Memphis in Shelby County, only had had one siting of a wild hog in 2010. A year later, game cameras were showing a population of 50 to 60 hogs in the area.

“We began working with landowners to try to help solve the problem around the park,” he said. “When they saw how much money they were losing, some of them jumped in and spent $5,000 to $10,000 on traps and surveillance cameras, and they’re able to keep the issue controllable now.”

The first step when you see evidence of a number of wild hogs in an area is to begin baiting an area or putting out corn to get them accustomed to feeding there. Then you build a corral trap with gates at each end so the hogs can enter and leave the trap enclosure.

“When we first started trapping we would build a corral-type enclosure and run a wire from the gate to the feeding area,” says Stanfield. “When a hog started rooting, he would pull on the wire and the gate would fall.

“The problem is wild hogs are some of the most intelligent animals I’ve ever had to deal with. If you have 10 hogs in the trap and 10 outside it, those outside the trap are now educated, and they won’t come anywhere near a trap site.”

Multiple groups of hogs feeding in a trap can also be problematic. “You have a group that comes in at 10 p.m. and another at 12:30 a.m.,” he said. “You don’t want to close the gate on the first group because you won’t have time to eradicate and dispose of those hogs before the other group arrives.”

Remote sensing systems can be helpful. Stanfield has a separate phone that he uses to monitor the trapping sites the Tennessee Wildlife Resources Agency is helping farmers and landowners manage.

“My wife hates that phone because every 30 minutes it pings at night,” he said. “It receives a signal every time a hog enters the trap.”

Drones can also be helpful because a farmer may not be able to see the amount of damage that’s occurring from wild hogs rooting from the edge of a field.

“We’ll go out to a 50-acre field, and we’ll think there’s not much impact from hogs,” he said. “But if you put up a drone or use a helicopter or a plane you can see how much damage they’re doing in the center of it.”