A mining company owner who put up a fence to keep out rattlesnakes tore it down at the demand of environmental officials after being threatened with contempt. The state had accused Jay Montfort of failing to obey a judge's order to tear down the wire-mesh fence by April 3. Montfort built the fence this year around a parcel of Hudson Valley property near Fishkill, N.Y., that he has been seeking permission to mine. The fence was about 250 feet from a den of Eastern timber rattlesnakes, which are listed as threatened under New York's Endangered Species Act. The state claimed the fence would disrupt the snakes' migration patterns.