When Tibby arrived on her first night with us, we let her out into the fenced backyard. On the steps, she paused for an instant, ears up, nose twitching, poised like an Olympic sprinter in the starting blocks. In the twilight, something caught her eye. Slowly, she stalked, like a panther, into the grass. Then she dashed, disappearing under the arborvitae. In a moment, Tibby emerged, triumphant, shaking a small rabbit between her jaws.