With each extension of the traps, the pigs here have grown wary, staying away for a couple of nights before returning to nibble the bait. Officials hope that by the end of March, the pens will be finished and the pigs sufficiently acclimated to allow technicians to set trip wires closing the gates. The traps are circular because feral pigs have been known to crowd into the corners of other traps and climb atop one another to escape.

Last year, the state set a similar corral trap too soon, catching only three pigs. After that, none of the others returned to the area, even after the trap was dismantled. “I’ve never worked with an animal this smart,” Mr. Reed said.

Farmers in the region are nervously following the clash between the boars and the bureaucrats. “With all the agriculture here, the pigs have plenty of food,” said Peter Glushko, supervisor of Peru, a town of 7,000 on Lake Champlain, nine miles south of Plattsburgh. “Who knows where they’ll end up? Other farms should be concerned.”

The growing population has a number of origins: domestic livestock and pet pigs that were either released or escaped captivity; Eurasian boars imported for use on hunting ranches; and a hybrid between the two. Some researchers believe that pigs were most likely introduced to North America by Christopher Columbus in the West Indies; American settlers later brought more pigs as livestock. The practice by farmers of allowing pigs to roam on open ranges continued in some states until the 1960s, furthering their expansion into the wild. So far, feral pigs have infiltrated 5 of 62 counties in New York State. They first showed up about a decade ago in neighboring Onondaga and Cortland Counties, and the statewide population is estimated to be a few hundred, according to Justin Gansowski, a wildlife disease biologist with the United States Department of Agriculture in Castleton, N.Y.