The tiger masks, one a fierce, ceramic face and one carved of wood, have hung above my desk for several years. They carry memories of an elegant Siberian tiger I met in 1987 on the outskirts of Eugene. Legal issues concerning wild animals kept as pets had spurred an assignment that sent me out that year as a Register-Guard feature writer to interview local wild-animal owners. Standing few feet back from a large, chain-link cage, I watched in uneasy awe as a magnificent, 225-p