Karen Krebbs had an armed escort while she was out nights last week at Organ Pipe Cactus National Monument. She's not a law-enforcement agent and she doesn't dabble in anything illegal. She's a conservation biologist with the Arizona-Sonora Desert Museum, studying an endangered population of nectar-feeding bats. Researchers along Arizona's border these days must balance their desire to study wildlife in the Sonoran Desert - where the chance to observe long-protected desert-dwelling populations proves an irresistible lure - with a growing fear of theft by desperate border crossers or violence from drug and people smugglers. The fears are fueled by...